Blumea 62, 2017: 125 –156
www.ingentaconnect.com/content/nhn/blumea
RESEARCH ARTICLE
ISSN (Online) 2212-1676
https://doi.org/10.3767/blumea.2017.62.02.07
A synoptic revision of Inversodicraea (Podostemaceae)
M. Cheek1, A. Feika 2, A. Lebbie 2, D. Goyder 1, B.Tchiengue 3, O. Sene 3,
P. Tchouto 4, X. van der Burgt 1
Key words
conservation
extinction risk
hybridisation
hydroelectric dam projects
rheophytes
stage-dependent heteromorphy
Abstract Six new species of Inversodicraea (I. feika from Sierra Leone, I. liberia from Liberia, and I. ebo, I. eladii,
I. tchoutoi, and I. xanderi from Cameroon) are described as new to science in the context of a synoptic revision of
this African genus, now comprising 30 species, including I. cussetiana comb. nov., newly transferred from Macro
podiella. Inversodicraea is now equal in number of species to Ledermanniella (as redefined), as the largest genus of
the family in Africa. Terete or slightly dorsiventrally flattened leaf petioles (not sheathing and/or stipulate) are newly
discovered to distinguish the genus from Ledermanniella, in addition to the presence of scale-leaves. Inversodicraea
boumiensis, I. annithomae, and I. bosii are redelimited in this paper. Examples of species hybrids are discussed.
Eighteen species are point endemics. A key and IUCN 2012 standard conservation assessments for all species are
included. 28 of the 30 species have been assessed as Threatened or Near Threatened. Hydroelectric projects are
the biggest source of extinction risk to species of the genus, threatening 19 of the 30 species.
Published on 13 September 2017
INTRODUCTION
Podostemaceae are a pantropical family of annual or perennial herbs placed in Malpighiales in a sister relationship with
Hypericaceae. There are about 300 species globally, in c. 54
genera (Koi et al. 2012, Kato 2016). Species numbers are
highest in tropical America, followed by Asia, with Africa having
c. 80 species. All species of the family are restricted to rocks
in rapids and waterfalls of clear-water rivers, and are therefore
rheophytes (torrenticolous). However, this very habitat is being
increasingly exploited for hydropower at some risk to the survival of the Podostemaceae they contain (Schenk et al. 2015,
Cheek et al. 2015, Cheek & Ameka 2016). Most of the African
species of Podostemaceae are narrow endemics, many being
species known from only a single waterfall. New discoveries
of species are still being made frequently (Rial 2002, Cheek
2003, Schenk & Thomas 2004, Beentje 2005, Kita et al. 2008,
Schenk et al. 2015, Cheek et al. 2015, Cheek & Ameka 2016,
Cheek & Haba 2016a). Important characters in defining African
genera in Podostemaceae are the position of the flower in the
unruptured spathellum, and the shape and sculpture of the
ovary. At species level, important characters are the shape and
relative proportions of spathellae, stigmas, anthers, filaments,
gynophores, pedicels, and leaves.
The current generic classification of African Podostemaceae is
based on the framework established by Cusset (1973, 1974,
1978, 1983, 1984, 1987, 1997). This work has been compiled
and updated by Rutishauser et al. (2004) who recognise c. 85
species in 16 genera. Recently, combined morphological and
molecular phylogenetic studies of African Podostemaceae have
shown that Ledermanniella (as delimited by Cusset) is paraphyletic, including all other sampled genera of Podostemaceae
1
2
3
4
Science, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AE, United
Kingdom; corresponding author e-mail: m.cheek@kew.org.
National Herbarium, University of Sierra Leone, Njala, Private Mail Bag,
Sierra Leone.
IRAD-Herbier National du Cameroun, Yaoundé, BP 1601, Cameroun.
Programme for the Sustainable Management of Natural Resources, Buea,
P.O. Box 417, South West Region, Cameroon.
recognised in Africa (Thiv et al. 2009, employing plastid markers
matK, trnD-trnT, rpoB-trnC in sampling 9 genera and 17 species
of African Podostemaceae, and Schenk et al. (2015), employing
plastid markers matK, trnL, rpoB-trnC, ndhF, rbcL and matR in
sampling 10 genera and 27 species of African Podostemaceae).
Molecular phylogenetic sampling of African Podostemaceae
has been only c. 30 % complete at species level (Schenk et al.
2015). Thiv et al. (2009) and Schenk et al. (2015), have convincingly shown that Ledermanniella subg. Phyllosoma C.Cusset
forms a well-supported clade of species that are sister to the
rest of all other African Podostemaceae sampled, comprising
Ledermanniella subg. Ledermanniella and, embedded within it,
9 smaller genera: Macropodiella, Winklerella, Djinga, Monandri
ella, Dicraeanthus, Leiothylax, Letestuella, and Stonesia. Thiv et
al. (2009) and Schenk et al. (2015) both advocate resurrecting
the generic name Inversodicraea Engl., as the oldest generic
name for the species of Ledermanniella subg. Phyllosoma and
both transfer species formerly included under the last taxon to
Inversodicraea. The last 7 remaining species names of subg.
Phyllosoma for which formal transfer was necessary were
placed into Inversodicraea in Cheek & Haba (2016a).
Thus Inversodicraea has been resurrected to accommodate
those species previously included in Ledermanniella subg.
Phyllosoma (Thiv et al. 2009, Schenk et al. 2015, Cheek & Haba
2016a). Material has come to light representing new species
which are published here together with a synoptic account and
a key to all the species currently recognised.
MATERIALS & METHODS
Nomenclatural changes and lectotypifications were made according to the Code (McNeil et al. 2012). Names of species
and authors follow IPNI (continuously updated). Herbarium
material was examined with a Leica Wild M8 dissecting binocular microscope fitted with an eyepiece graticule measuring
in units of 0.025 mm at maximum magnification. The drawings
(Fig. 2–8) were made with the same equipment with a Leica
308700 camera lucida attachment. Pollen grains were exam-
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126
ined from macerated single stamens mounted in a water drop
on a slide with coverslip and examined with a compound light
microscope using a × 40 objective lens fitted with a calibrated
eyepiece graticule for measurements.
Species are recognised on the basis of being separated from all
other species of the genus by three or more disjunct morphological characters, ideally qualitative, and with no intermediate
specimens being present. These characters are presented in
the key to the species, and in the cases of new species described in this paper, in tables of characters and in the species
diagnosis, being further discussed in the notes. In four species
at two sites intermediate specimens have been found which
we ascribe to hybridisation.
The arrangement of species in the taxonomic treatment follows
that of Cusset (1983), with modifications. All specimens known
are cited except for the most common and widespread species
I. ledermannii and I. tenax, where only representative specimens are cited for each country in which that species occurs.
Specimens were inspected from the following herbaria: BM,
FHO, HNG, K, P, WAG, and YA. BR and COI specimens were
not accessible since they were being digitised during the period
of study. Where altitudes at which specimens were collected
were not recorded on specimen labels, specimen sites were
traced using Google Earth and altitudes read from that source.
Field observations and collections of Inversodicraea were
made by the authors in West and Central Africa in the period
1995 –2016, in Guinea, Sierra Leone, and Cameroon.
The format of the description follows Cusset (1983), e.g., in
referring to the specialized ribbon-like roots as ‘thallus’, and
long, subfiliform, to narrowly ribbon-like dichotomously branched leaves as ‘leaves’. However, we do not refer to the scaleleaves as ‘leaflets’ (‘feuillettes’) since, as an anonymous reviewer has pointed out, a leaflet is technically one element of
a compound leaf, and this is not the case with these structures.
All specimens marked have been seen except those marked
‘n.v.’. The conservation assessment follows the IUCN (2012)
standard, using the IUCN-preferred grid cell size of 1 km 2 for
riverine organisms unless noted otherwise. The main online
search address used for retrieving specimen data from labels at
P was https://science.mnhn.fr/institution/mnhn/collection/p/item/
p00179355?listIndex=128&listCount=610. However, resolution
of images of herbarium specimens was insufficient in all cases
to confirm specimen identification. Herbarium codes follow
Index Herbariorum (Thiers, continuously updated).
MORPHOLOGY
The morphology and anatomy of three species of Inversodic
raea, I. ledermannii, I. cf. bosii, and I. cristata, have been presented in detail by Moline et al. (2007) and Thiv et al. (2009).
This information was part of their wider study of about ten
species of African Podostemoideae. Here we give an overview
of the different structures found in the genus Inversodicraea,
and their range in variation across the 30 currently known
species of the genus. The overview is based on morphological
observations made when researching this paper, combined with
data from Cusset (1983) and the excellent in-depth studies of
the three species reported by Moline et al. (2007) and Thiv et
al. (2009).
Root
The root (Thiv et al. 2009), also known as the thallus (Cusset
1983), is narrowly ribbon-like, that is dorsiventrally compressed,
usually about three times wider than thick, and adheres to
the substrate by numerous short adhesive hairs (root hairs or
rhizoids) that depend from the lower (ventral) surface, except-
Blumea – Volume 62 / 2, 2017
ing from the midline (see Moline et al. 2007: f. 2B). A single
dorsiventrally flattened vascular bundle is present. A rootcap
is lacking (Moline et al. (2007) and Thiv et al. (2009)). Disc-like
hold fasts are produced where leaves arise from the margin of
the root (I. ledermannii: Moline et al. 2007: f. 2C).
The root (thallus) is described by Cusset (1983) as 1 mm wide
in almost every species, except in I. ledermannii (2–3 mm),
I. mortonii (0.5 mm), I. warmingiana (1–1.5 mm), I. feika (0.6–1
mm, this paper). The root is not recorded in the following species: I. boumiensis, I. digitata, I. harrisii, I. abbayesii, I. bosii,
I. kamerunensis, I. torrei, and I. pepehabai. Thalli are often
not collected because they can be so difficult to remove intact
from the rock substrate in contrast to the remainder of the plant
(Cheek pers. obs). Foliaceous thalli (implying that they are much
broader) are recorded for I. gabonensis and I. thollonii but their
width is not given (Cusset 1983).
Branching of the root-thallus occurs endogenously (arising from
the interior, not budding off from the exterior) where it has been
recorded (Moline et al. (2007) and Thiv et al. (2009)). This has
been confirmed in I. achoundongii (Schenk et al. 2015: 542),
and we have observed this also, e.g., in I. feika (Fig. 2, 3),
I. xanderi (Fig. 5).
Stems
Stems subtended by leaves, arise from both margins of the
root, either alternating (I. ledermannii, Moline et al. 2007:
f. 2C) or opposite to each other as in I. feika (Fig. 2) and
I. achoundongii (Schenk et al. 2015), but for most species these
data are either not preserved or not recorded.
Stems also arise endogenously where recorded (I. feika, Fig. 2
and I. achoundongii Schenk et al. 2015).
Stems can be either erect, self-supporting and short-lived (annual), when usually only 2–5 cm tall (e.g., I. ledermannii) or
erect, self-supporting, and seemingly long-lived (apparently
growing for more than one season, e.g., in I. ebo, I. cristata,
I. tchoutoi), or with an elongate principle stem of 20–80 cm or
more (80 cm in I. feika and I. warmingiana), which flows in the
current, carries few scale-leaves, or none (e.g., I. annithomae,
I. paulsitae), but which bears either long lateral branches bearing leaves only and/or shorter spur-branches bearing flowers
(e.g., I. adamesii) or is unbranched apart from the short, regular, densely leaflet-clad spur-branches (e.g., I. annithomae,
I. paulsitae).
Pseudo-dichotomous stem branching is conspicuous in some
species, such as I. cristata, I. ebo, I. tchoutoi, I. ntemensis,
presumably due to these species having determinate stems
which terminate in a flower or a leaf, the stems continuing to
grow through new shoots that can arise on both sides so that
the stems appear to fork dichotomously with the leaf or flower
in the fork of the dichotomy. Should a new shoot develop on
one side only, the leaves and flowers will appear lateral. This
is explained by ‘double-sheathing leaves’ (Moline et al. (2007)
and Thiv et al. (2009)). These references should be consulted
for a detailed explanation of this remarkable phenomenon.
Leaf phyllotaxy
The leaf phyllotaxy on stems appears spiral, rarely distichous
(I. annithomae, I. paulsitae), never opposite. In some species
the leaves appear in the axils of stem pseudo-dichotomies (see
I. tchoutoi Fig. 5b), as a result of the ‘double-sheathed stems’
referred to above. The leaves are elongate and (pseudo-)
dichotomously branched, the ultimate segments terete or flattened (ribbon-like). They contain vascular bundles that extend
to the ultimate segments (Thiv et al. 2009). The petiole is terete.
Sheathing leaf bases and stipules have never been recorded
in Inversodicraea as delimited in this paper except in I. kamer
M. Cheek et al.: A synoptic revision of Inversodicraea
unensis fide Cusset (1983: 386). However, since this species
is known from the single specimen Ledermann 440A, that we
believe was not seen by Cusset, this statement is likely to be
an error since we were unable to detect these features in the
specimen ourselves. Despite searching for these features in
every species of the genus included in this paper, we have not
been able to detect them and conclude that they do not occur.
Thiv et al. (2009), also state that they had not observed these
features in Inversodicraea although they could not be sure of
their absence due to the leaflets that interfere with observation
of leaf bases in many species.
Leaves are probably the main photosynthetic and also the main
absorbitive structures since they have a large surface relative
to their volume and a thin cuticle (in contrast the root hairs or
rhizoids which have a much lower surface area and primarily
seem to function as anchoring structures). The leaves are only
present when the plants are under water or continually sprayed
by water droplets from a waterfall. Once plants are exposed
by falling water levels in the dry season, the leaves fall rapidly,
usually before the flowers open. We postulate that since the
leaves have very thin cuticle, this leaf-drop mechanism reduces
the loss of water from the plant as a whole that might otherwise
compromise seed production, and in long-lived species, their
perenniality. An abscission zone has not been observed. Since
plants are usually collected only when in flower, the leaves are
often not collected. For those several species where leaves
have not been recorded, it is not known whether it is because
they are not produced (as claimed of I. boumiensis by Schenk
et al. 2015) or simply because they have not been collected
before the leaves have fallen.
Scale-leaves
Scale-leaves (‘feuillettes’, meaning leaflets, of Cusset 1983) are
present in all species. They lack vascular bundles (Thiv et al.
2009). Insertion is spiral, rarely in loose whorls of three (e.g.,
I. adamesii (Taylor 1953: f. 9/2) and I. ntemensis (Kita et al.
2008: f. 1)), never opposite. Files of scale-leaves (i.e. scaleleaves appearing to be in longitudinal lines down the stem)
can be observed in some species with spirally inserted leaves,
such as I. eladii (c. 5 leaf files) and less usually, with only c. 3
files, I. liberia.
The scale-leaves of Inversodicraea appear to be a unique synapomorphy, certainly within African Podostemoideae. However,
in Tristicha (Tristichoideae, sister to all other Podostemaceae)
scale-leaves are also developed. The leaflet-clad stems of
I. liberia, being tristichous, resemble those of Tristicha. Perhaps expression of scale-leaves in Inversodicraea arose from
‘switching-on’ genes that had long lain dormant in the Podo
stemoideae genome. However, it is not known that the scaleleaves of Inversodicraea are homologous with those of Tristicha.
Katayama et al. (2010) have shown that shoot apical meristems
(SAMs) while present in Tristichoideae are lacking in Podoste
moideae, and that organogenesis is therefore different.
Scale-leaves either:
1. completely cover the entire stem(s) as in I. ledermannii;
2. cover completely the distal 50 –80 % of the stems
(e.g., I. ebo);
3. cover densely only the spur shoots bearing the flowers,
and then are absent or are only very sparsely covering the
principal axes (e.g., I. paulsitae); or
4. are not present immediately below the flowers but are
scattered along the main axis (I. achoundongii, Schenk et
al. 2015).
The precise shape, and especially the marginal ornamentation of the scale-leaves, is the single most important source
of characters for species delimitation in Inversodicraea. The
127
overall shape varies from needle-like (I. mortonii) to orbicular
(I. boumiensis), through equilaterally triangular, ovate, and
oblong. While the first mentioned species have entire margins,
some have one or two irregular lateral lobes (e.g., I. pepehabai)
or an erose, erratically minutely lobed margin (I. kamerunensis).
More usually, the margins are regularly toothed, the shape,
depth, and number of teeth being characteristic of the species.
The scale-leaves are always either flat, concave, or acicular.
Rarely do they bear projections from their abaxial surface
(I. harrisii, I. xanderi, I tenax, and I. congolana).
While in some species the scale-leaves are monomorphic, in
others they are more or less dimorphic, as in I. cristata, I. tchou
toi, I. xanderi. In these cases the scale-leaves on the branches
differ from those on the main stems (I. cristata, I. tchoutoi), or
those subtending the spathellae differ from those on the stems
below (e.g., I. xanderi ). This equates to stage-dependent heteromorphy. In these cases, generally speaking, scale-leaves
subtending the spathellae are more slender and have fewer
lobes than those on the main body of the stems below.
Scale-leaves appear to function as armature in most Inver
sodicraea. The scale-leaves, especially the epidermal cells,
are filled with silica bodies, unlike the leaves (Thiv et al. 2009).
These silica bodies are uniform between species, being more
or less isodiametric, apart from the outer face which is convex
and has a median line of pits. Thiv et al. (2009) speculated that
the silica bodies protect the plants against bombardment from
current-borne pebbles and other projectiles. Yet, we consider
it as or more likely that they have a probably more important
function: protection against herbivores. Just as silica bodies in
grasses help to protect them from grazing animals, we postulate
that so do the silica bodies in the epidermis of Inversodicraea
species protect them from underwater herbivores, both fish
and invertebrates. When growing underwater, Podostemaceae
populations are inhabited by numerous animal species, often
preserved accidentally in herbarium specimens. While some
of these animals may use the plants for shelter and reproduction, others appear to graze the plants, chewing away their
leaves and scale-leaves, which likely reduce their ability to
photosynthesise and so to reproduce. An anonymous reviewer
pointed out that the bracts of some Asian Podostemoideae,
e.g., Cladopus, also have dense silica bodies on the surface
which render the bracts harder and which may play a role in
the protection of flowers.
Inflorescences
Inflorescences in most species are borne terminally on long or
short stems densely clad in scale-leaves and leaves. These
last two structures often form a cup inside which the spathellum is developed and partly protected (Thiv et al. 2009). In a
few species the stems immediately below the flower have only
(short) dichotomous leaves (e.g., I. achoundongii, I. adamesii )
and the scale-leaves are placed further down the stem.
Inflorescences appear to arise as single flowers in the axils of
the pseudo-dichotomous forks, e.g., in I. ntemensis, or they
can be multi-flowered fascicles as in I. feika and I. cussetiana.
In species such as I. feika, few-flowered inflorescences arise
directly from the thallus-root on shoots only 1–2 mm long. These
shoots are clad in scale-leaves and subtended by a reduced
leaf (Fig. 2, 3).
The spathellum varies from globose (I. tenax) to narrowly obovoid and stipitate (e.g., I. thollonii). An apical rostrum is developed in I. cristata. In herbarium specimens, spathellae are
concolorous with the leaves and stems, except in I. tenax where
the spathellum dries purple.
The flower is inverted within the spathellum, rupturing the apex
to achieve anthesis as the pedicel expands and the flower
128
rotates to the vertical position (Moline et al. 2007: f. 2E). This
is triggered when plants are exposed to air. Plants growing
under the water surface that have fully formed spathellae can
be triggered into anthesis overnight within 12 hours by exposing
them to air inside a plastic bag (Cheek pers. obs. 1995 –2016).
The pattern of spathellae rupturing can vary from one species to
another, some species tending to have a single lateral longitudinal split, others three more or less equal apical triangular lobes,
but there is variation within species, and within specimens,
reducing the taxonomic value of this character.
Tepals
The tepals are two, except in very rare monstrous flowers that
have three. Tepals are concolorous with the pedicel and gynophore and appear to have no attractive or other functional value.
In c. 90 % of the species they are subulate and their length
ranges from 0.3–0.8 mm. In I. annithomae, I. adamesii, and
I. torrei they can reach 1 mm long. The longest tepals are recorded by us in I. thollonii (1.2–1.5 mm) and the shortest are noted in
I. warmingiana (0.2 mm). Exceptionally, in I. feika, the apex of
the tepal is slightly spatulate.
Androecium
The androecium has either one or two stamens. In some species both three and two stamened androecia occur in some
populations (I. tchoutoi pers. obs., I. annithomae: Cusset 1983:
f. 6: 8). The number of stamens, proportions and length of the
androphore and its branches, all have some taxonomic value
at the species level. The pedicels are reported as pink in
I. tchoutoi (Letouzey 15539), and in other species the staminal
filaments and/or ovary are described as red, and the anthers
white. Flower colour may thus have a role in attracting pollinating insects. No direct observations of pollination are recorded
for Inversodicraea, but we contend that Apis mellifera, the
honey-bee, is likely to be the main pollinator, since this species
has been observed to visit flowers of Ledermanniella on several
occasions and at several locations (Cheek pers. obs.). Pollen
is produced as either dyads or monads, depending on species;
but otherwise no systematic study of pollen has been made
for Inversodicraea. Monads are more or less spherical and
tricolpate. Among the six species of Podostemaceae studied
in detail by Lobreau-Callen et al. (1998) was Inversodicraea
(Ledermanniella) ledermannii, which they illustrate in their
f. 2F–I. They describe the mesocolpial tectum as echinulate
and continuous, its thickness equal to that of the average of
the infratectum and of homogenous texture, with imperfectly
compacted sporopollenin. The infratectum is stated to be of
large irregular lumps united to the tectum or elongated radially,
resembling irregular columns, resting on a foot-layer which is
very thin and discontinuous. The endexine is thick, in two layers
and weakly sculpted. On the lateral faces at the periphery of
the areas united in dyads, the tectum is thinner and continuous,
forming ectexine bridges between the monads.
Gynoecium
The gynoecium, produced on an erect gynophore, is usually ellipsoid, oblong-ellipsoid or fusiform, and terete in transverse
section, when alive or preserved in spirit. Laterally compressed
or flattened ovaries and fruits occur in I. feika and I. cussetiana.
The compression occurs in the plane intersecting the commissural ribs. These species would have been referred to the genus
Macropodiella in previous classifications (Cusset 1983, 1987).
Locule number, placentation, ovules, and seeds
Thiv et al. (2009) found that the fruit and ovary appear to have a
single locule with free axile placentation (the placenta attached
Blumea – Volume 62 / 2, 2017
at base and apex only). However, Engler (1915) depicts, e.g.,
I. cristata as being bilocular, the septa occurring in the plane
connecting the commissural ribs. We assume that Engler’s
depiction is an error since our own observations (this paper Fig.
1–8) confirm those of Thiv et al. (2009). The placenta appears to
be ellipsoid in shape, but the careful study by Kita et al. (2008)
of I. ntemensis showed the presence of an incomplete septum,
suggesting that two locular ovaries may have been ancestral.
Such detailed studies of placentation are rare in Inversodicraea
and study of the other species might reveal additional cases.
Detailed comparative studies are lacking on the ovules and
seeds. About 50–150 ovules and seeds are developed, the
seeds being approximately ellipsoid and having a mucilaginous
outer coat, as usual in African Podostemaceae.
Stigmas
Stigmas number is generally two, but in I. ntemensis and
I. tchoutoi, three stigmas are present. Three stigmas occur in the
Tristichoideae which are sister to all other Podostemaceae (Koi
et al. 2012). It is possible that the three stigma character-state
arose from ‘switching-on’ genes that had long lain dormant in
the Podostemoideae genome. However, it is more likely that
this is simply an aberrant form of the 2-merous flower usual in
Podostemoideae since the rest of the flowers of the species
concerned remain bimerous and not trimerous. It is difficult to
explain how this unique synapomorphy occurs in such otherwise
morphologically dissimilar species that co-occur at the same
site unless one invokes horizontal gene transfer.
Generally the stigmas are filiform or linear and about 0.7–0.8
mm long, but in I. fluitans and I. tenax they are 1.2 mm long
(Cusset 1983). In I. gabonensis, I. congolana, I. pygmaea
they are 0.3 mm long, and in I. harrisii 0.2 mm. The stigmas
are thicker, c. 0.15 mm wide, approaching botuliform in I. ebo.
In I. feika the stigmas resemble those of Dicraeanthus being
narrowly triangular and erect, tapering from a broad base to
an acute apex.
Fruit
On drying, longitudinal ribs are visible in the developing fruits.
These correspond with vascular bundles within the pericarp.
As the fruit develops, these bundles are exposed at the surface
by shedding of the ovary epidermis (Thiv et al. 2009) making
the ribs more pronounced. Most Inversodicraea appear to have
eight equally developed ribs. Two of these, on opposite sides
of the fruit, the commissural ribs, are longitudinally bisected by
lines of dehiscence, allowing the fruit to split on drying into two
more or less equal valves. In some species the commissural
ribs are barely thickened in comparison with the remaining
ribs, and the fruits then appear 6-ribbed (e.g., I. adamesii,
I. liberia). In I. congolana, I. eladii, I. ebo and I. digitata, either the
median or all the non-commissural ribs are winged in the distal
part of the fruit.
Fruit dehiscence, we postulate, is due to differential effects of
drying on the ribs. The non-commissural ribs tend to contract
and straighten on drying more than do the commissural ribs.
We postulate that this is due to the non-commissural rib bundles
being longer, extending down the pedicel (see below) while
those of the commissural ribs do not. In fact the commissural
ribs may lack vascular bundles, as is indicated in a transverse
section of the ovary of I. cristata (Engler 1915: f. 180K). The
results are visible in the deformed shape of the valves postdehiscence when they are longer along the axis of the median
non-commissural rib than in the undehisced fruit. The drying
stresses rupture the fruit along the preformed lines inside the
commissural ribs. In several species (e.g., I. feika) only one of
the two suture lines opens, but in most species the fruit splits
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M. Cheek et al.: A synoptic revision of Inversodicraea
into 2 valves which remain joined only at the gynophore. In
several species, e.g., I. xanderi, loss of epidermis and cortical
tissue extends down the gynophore, exposing the 6 vascular
bundles that descend down the pedicel from the fruit valves
where they form the non-commissural ribs.
HYBRIDISATION
Species hybridisation is reported here for the first time in Podo
stemaceae. Intermediate specimens between co-occurring
species have been observed by us at two locations, involving
a total of four species:
1. at the Seli/Rokel river near Bumbuna in Sierra Leone, intermediates and so potential hybridisation between I. leder
mannii and I. harrisii;
2. at the Lobé Falls in Cameroon where intermediates are
present between I. ledermannii and both I. eladii and I. bosii.
The specimens and characters evidencing this phenomenon are
detailed below under the accounts of the species concerned.
We conjecture that while hybridisation may be breaking down
the barriers between species and allowing gene-flow, it may
also support speciation.
ECOLOGY
Inversodicraea, as with most Podostemaceae, only grow at
sites with permanent, or more usually seasonally, fast flowing,
silt-free water, or with water spray and splashes. They are always associated with waterfalls and rapids, apparently requiring
highly aerated water and a rock substrate. Additionally, Inver
sodicraea occur mainly where such sites occur in lowland rainforest (below 800 m alt.). At the Lobé Falls in Cameroon, three
species occur just above sea-level. Inversodicraea are usually
absent from waterfalls and rapids in woodland (savannah)
habitat. Exceptionally, I. fluitans, I. digitata, and I. warmingiana
of Angola occur in rapids in woodland habitat at high altitude,
above 1 000 m. The second of these species occurs at 1 640 m,
the upper altitudinal limit of the genus. Inversodicraea species are completely absent from the main watercourses of the
large rivers of the Nile, the Niger, and the Congo, although
one species is present in the Zambesi, e.g., at the Victoria
Falls. We conjecture that this is because where falls exist in
these rivers the water is too turbid to support Inversodicraea,
although Ledermanniella is present abundantly in the falls of
the Congo River at and below Brazzaville and Kinshasa. Support for the argument that Inversodicraea cannot grow in turbid
water can be found at Kisangani where the clear-water Tshopo
joins the Congo River. Immediately above the confluence, the
Tshopo drops over two small sets of falls a few metres high,
and about 800 m apart. Here occurred both I. congolana and
Leiothylax quangensis (Léonard 1993). In contrast, the Boyama
or Wagenya Falls which start at Kisangani on the Congo and
continue upstream over a stretch of c. 100 km, with six sets
of falls, each of c. 5 m height, lack Podostemoideae, and both
aforementioned genera have not been recorded, despite the
falls being in every other way conducive to the growth of Podo
stemaceae. The difference in turbidity levels between the
Tshopo and Congo at the confluence can be easily detected
by eye when viewing Google Earth imagery, the first appearing
black (silt absent), the second brown (silt abundant) (see Fig. 1
caption for georeference).
Most falls at which species of the genus have been recorded are
open to full sunlight, being in large, broad, sometimes braided,
rocky, river beds. At these sites they are sometimes associated
with other rheophytic species from diverse families and genera,
e.g., Karima (Euphorbiaceae), Cheek et al. (2016).
Although Podostemaceae can also occur in diverse rheophytic communities in shaded sites, generally Inversodicraea
species tend to be absent (e.g., Cheek in Cheek et al. 2004:
49). Inversodicraea pepehabai is thought to be an exception
in occurring in shaded sites. Where more than one species
of Podostemaceae occur at a site, they can be partitioned
by lighting and/or by depth in the watercourse (Cheek et al.
2004: 49) or by the amount of aeration (‘violence’) of the water
(Léonard 1993). Generally short-lived, annual species such as
I. ledermannii occur highest up the river bank. These areas are
the last to be inundated when the wet season begins, and the
first to be exposed when levels begin to drop as the dry season
begins. Long-lived, probably perennial, larger species with
rubbery stems generally occur at lower points in the river bed.
Habitat partitioning
At most sites from which Inversodicraea has been recorded,
only a single species of the genus is known, but at several
sites, two or even three species have been recorded. At three
such sites there is some evidence of habitat partitioning within
the genus, while for a fourth, the available evidence does not
support this.
1. Port Loko, Sierra Leone.
At this site I. ledermannii, a small erect, 2–4 cm tall annual
species, is abundantly present on the upper part of the rocky
banks of the river. It is exposed, flowers, then fruits and dies
early in the dry season, in October– November as water levels fall. In contrast, I. feika, a large, up to 80 cm long, flowing
stemmed, apparently perennial species remains submerged in
deeper parts of the river, only beginning to flower when exposed
in December and continuing at least until March, towards the
end of the dry season when water levels are lowest (observations by Ben Pollard, Sue Frisby, and Xander van der Burgt).
2. Memv’ele Falls, Bongola, Cameroon.
The three species of Inversodicraea at this site differ radically from each other in form and size, suggesting that they fill
different niches.
Inversodicraea achoundongii plants are < 1 cm tall (exceptionally 2 cm) with minute stems.
Inversodicraea tchoutoi plants are stout-stemmed, erect, subshrubby plants 10–15 cm tall. The plants are gregarious forming
carpets over the rock. It is possible that they and I. achoundongii
are sustained in growth by spray for most of the year, rather
than being submerged.
Inversodicraea ntemensis has long stems c. 20 cm long that
appear to flow in the current. We conjecture that it remains submerged in deeper parts of the watercourse, as is usual, in our
Fig. 1 The hydroelectric power plant at Tshopo River Falls, Kisangani, DRC,
N0°32’17.03” E25°11’14.29”. Showing layout of 1950s constructed ROR
hydropower installation which preceded the local extinction of I. congolana
at one of its only two global sites. From Google Earth imagery dated 11 Jan.
2016 (Digital Globe). — Drawn by Martin Cheek.
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Blumea – Volume 62 / 2, 2017
experience, with species of this habit. Additional Podostema
ceae present at this location are: Macropodiella heteromorpha,
Ledermanniella pusilla, Tristicha trifaria, Ledermanniella sp.
3. Rapids on Ogooué, near Booué, above Lopé, Gabon.
Here I. thollonii (N. Hallé & Le Thomas 206), a small, apparently annual plant with slender erect stems c. 1–2 cm tall, appears with the larger, more robust I. annithomae, which has
long stems up to c. 25 cm long that flower while floating on the
water (N. Hallé & Le Thomas 202b). Other species of Podo
stemaceae that were collected at this site by the same collectors at the same day in July in successive collecting numbers
were: Macropodiella heteromorpha (Baill.) C.Cusset (201, 204),
M. hallaei C.Cusset (203), Ledermanniella pusilla (202) and
L. nicolasii C.Cusset (205).
4. The Lobé Falls near Kribi, Cameroon are a touristic attraction, with waterfalls tumbling in a series directly into the sea,
across a sandy beach. They have also been an attraction to
podostemologists, since ten species of Podostemaceae (including I. eladii, published in this paper) have been documented at
this locality, a record for Africa:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Dicraeanthus africanus
Inversodicraea bosii
Inversodicraea eladii
Inversodicraea ledermannii
Ledermanniella batangensis
Ledermanniella bifurcata
Ledermanniella linearifolia
Ledermanniella pusilla
Ledermanniella variabilis
Tristicha trifaria
There is no data to suggest that the three species of Inversodi
craea at this site are separated by habitat partitioning. All three
are small erect annual herbs it appears. All three species have
been found in mixed collections with other Inversodicraea at
this site, and hybrids between I. bosii and I. ledermannii have
been suggested (this paper).
This location was first collected for Podostemaceae more than
100 years ago. Karl Ledermann was among the first botanists
to visit the locality. After landing at Grand Batanga as part of the
German colonial mission to explore and document the hinterland of their new colony, Kamerun, he began his mission of
botanical prospection into the interior when he collected many
Podostemaceae (Ledermann 1912). Ledermanniella Engl.,
named in his honour (Engler 1909), although now diminished
by the resurrection of Inversodicraea, is still probably the most
species-diverse genus of the family in Africa.
It is generally only possible to study Podostemaceae in their
natural habitat when the water level drops seasonally, at which
time they are exposed to air and triggered into flowering. Seedling establishment, and their development into adult plants,
have not been recorded in Inversodicraea, and neither have
observations been recorded on pollination or seed dispersal.
A detailed phytosociological study has been completed at only
one site at which Inversodicraea occurred. This was completed
in June–July 1947 and May and August 1948, before a hydroelectric dam was installed, but the study was not reported until
45 years later (Léonard 1993). By this time a second study at
the site, Nyakabwa (1982) failed to refind the Inversodicraea
and other associated rare and specialized waterfall species,
leading Léonard (1993) to conclude that they had become locally extinct. The study site is at N0°32'17.03" E25°11'14.29",
at an altitude of 400 m where the clear water of the Tshopo
River flows in rapids and falls over micaceous sandstone rock
into the turbid water of the Congo River at Kisangani in Democratic Republic of Congo (DRC). The flow rate of the Tshopo
at this point is given as 100–700 m 3 per second, at a velocity
of 5–6 m per second at the falls. The water is pH 6.6–6.8, at a
temperature of 26–28 °C when measured in January and June
in 1987. Mineralization of the water was reported to be weak,
below that of the Congo itself. The dominant cation is Ca 2 +,
the anion HCO 3. The annual fluctuation in water level is 4–5 m,
with high water periods occurring twice per year, April–May and
October–December. The junction of the rivers is marked by the
great falls, which vary from 11.2–13.8 m high depending on the
height of the Congo River. About 120 m further upstream, over
a section of rapids in the Tshopo, are the small falls, 3.2 m high.
In this study area 36 different transects were placed, analysis
of which showed 6 different communities, each equating to a
habitat. Two of these communities contained Podostemaceae:
1. ‘Tristicha and Philonotis’ (the globally most widespread
Podostemaceae, and a moss) occurs on rocks which are
not violently battered by water, but which are periodically
inundated and under spray at low water periods.
2. ‘Leiothylax and Ledermanniella’ (Leiothylax quangensis and
Inversodicraea congolana, both Podostemaceae) occurs on
rocks which are violently hit by water, and underwater all
year or more usually exposed at low water. This community
is only present at the large and small falls, or in portions of
the rapids.
Inversodicraea congolana was recorded in four of the eight
transects of the second vegetation type. It occurred in each
transect with 2 –7 other species, most frequently Leiothylax
quangensis which occurred in all eight transects. In two of
the four I. congolana plots, cyanobacteria Pleurocapsa minor
occurred, and in one also Tolypothrix sp. The moss Philonotis
hastata also occurred in two of the transects, while Fissidens
bessouensis, F. sylvaticus, Philonotis brevicuspes, Hyophila
involuta, and Glossadelphus congolensis each also occurred
in one of the Inversodicraea transects.
GEOGRAPHY
Inversodicraea species occur from Guinea-Bissau in West
Africa to Tanzania in East Africa, and as far south as Namibia.
They are absent from the Sahel and North Africa. However,
although the 30 species of the genus occur in 17 countries,
species densities and endemism are highest in West-Central
Africa. East and south of DRC, apart from Angola (5 species, of
which 2 are endemic), no country has more than one species
of the genus. Cameroon has the highest number of both total
species (11) and endemic species (8), followed by Gabon (7/2),
Sierra Leone, and Guinea-Conakry (both 5/3). The Dahomey
Gap (White 1983) is evident for the genus, since no species are
recorded at present for the four countries between Ivory Coast
and Cameroon. Upper Guinea (sensu White 1983 (west of the
Dahomey Gap)), with 9 endemic and 1 widespread species is
the second most important centre of diversity for the genus,
following Lower Guinea with 14 endemic and 1 widespread
species. Within Lower Guinea, the Cross-Sanaga interval
(Cheek et al. 2001) is evident, since within the interval itself,
only 1 species is recorded, while between the Sanaga and
Congo Rivers occur 13 endemic and 1 widespread species.
Of the 30 known species, 18 are point endemics, at once placing them at high risk of extinction from development, and
also indicating areas important for plant conservation. The
resurgence of interest in the concept and move to implementation of Important Plant Areas in the Tropics (IPAs or TIPAs)
has provided impetus to the authors for this study (Darbyshire,
continuously updated, Darbyshire et al. 2017).
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M. Cheek et al.: A synoptic revision of Inversodicraea
THREATS
Threats to Inversodicraea species
The principal threats to Inversodicraea species apply equally
to Podostemaceae as a whole. Being restricted to habitats with
clean, non-turbid, aerated water, with a rock substrate, degradation of these environmental factors pose threats. Because
so many Podostemaceae species, including Inversodicraea,
are restricted to only one or two locations, they are especially
vulnerable. A threat at even one location is likely to pose a high
extinction risk for any Inversodicraea present.
Turbidity and eutrophication threats
Turbidity in the water, indicating that silt is present, can reduce
establishment of seedlings (Philbrick & Novelo 1995). It can also
reduce photosynthesis during the main growth period, when
plants are under water in the wet season. (Cheek et al. 2015).
Algal growth can blanket Podostemaceae plants at some
sites and reduce their ability to photosynthesise. Such growth
appears to be associated with nutrient addition to rivers from
human populations that may use water courses for processing
crops, cleaning, and removal of waste-products. Inversodicraea
feika (this paper) appears to be threatened in this way.
Hydroelectric Power Project threats
The greatest threats to Podostemaceae are from hydroelectric
projects which have been growing rapidly in number in recent
years as a source of cheap, greener energy. While hydroelectric projects have many environmental benefits compared with
alternative options, all too often they threaten Podostemaceae
species with extinction. In many cases dams are constructed
just above rapids or falls so as to benefit from the vertical drop
in water levels (the ‘head’) at these sites (Fig. 1). Construction
of dams may directly impact upon the falls and the species that
they contain. More usually dams negatively affect populations
of Podostemaceae through changes in water flow by four different threats:
Threat 1 — Reduction of water flowing over falls at the dam
site. Water is rerouted in penstocks, which are canals or
pipes around the falls, feeding turbines below, before the
water re-enters the watercourse below the falls (Fig.1). In
extreme situations this can result in the prevention of 95 %
of the former discharge water flowing over the falls. Without
adequate water flow every year, Podostemaceae cannot
survive. More usually, water flow over the falls can be expected to continue via spillways when the dam reservoir is
full, typically in the second half of the rainy season, but flow
is stopped or reduced at the beginning of the rainy season,
so that the number of months for which the flow of water
over the falls is continuous, that is, the growing season for
Podostemaceae, is reduced, and may be insufficient to allow them to reach reproductive size before the water level
drops at the beginning of the dry season. This is thought to
have been a factor in the likely extinction of Ledermanniella
lunda at the Dundo dam in Lunda Norte, Angola (Cheek et
al. 2015).
Threat 2 — Impounding of water by the dam creates a large
reservoir of motionless, non-aerated water in which Podo
stemaceae cannot survive. When the reservoir covers rapids
or falls upstream of the dam, any Podostemaceae at these
sites will be killed as is predicted at the Bumbuna phase 2
dam in Sierra Leone (Cheek et al. 2017), which threatens
Ledermanniella yiben Cheek, an endemic Podostemaceae.
Run-of-the-River (ROR) hydroelectric projects (such as the
Tshopo project, Fig. 1), do not create large reservoirs and
are feasible where river water flows are aseasonal, or in
cascade systems (Threat 4 below).
Threat 3 — Disruption downstream of natural season fluctua
tions in flow. The purpose of a dam is usually twofold:
a. to raise the head of water available to generate electricity;
and
b. to produce a reservoir (except in ROR projects) so that
water is in place to generate electricity even in the dry
season when natural water flow drops below that which
is needed to operate the turbines.
With the reservoir in operation, water can re-enter the watercourse below the dam, through the turbines in the dry
season. This can result in preventing the usual dry season
drop in water level which is necessary to trigger flowering
and subsequent seed production, compromising the maintenance of Podostemaceae at rapids and falls downstream of
the dam. An example of this is the effect of the Lom Pangar
dam on the Sanaga River of Cameroon which has resulted
in the global population of Ledermanniella sanagensis (situated downstream at the Nachtigal Falls – themselves the
subject of a proposed hydroelectric project by EDF) being
kept underwater, and so not producing seed, throughout the
dry season of 2015 and 2016 (Ghogue pers. comm. 2017).
Threat 4 — Annihilation of all Podostemaceae habitat. Cascade
projects are designed to harness the potential hydropower of
entire river systems so as to convert it into electricity through
a series of dams along the length of a river, potentially submerging permanently all rapids and falls, and so destroying
all Podostemaceae present. Effectively such systems extend
and intensify Threat 3). In comparison, the other threats
above are modest. An example of a completed dam cascade
is that of the Lancang River of China, where a cascade of
nine dams has been constructed (Wang et al. 2013).
Cascade systems are under development along the Sanaga
River of Cameroon, of which the Lom Pangar dam is potentially the first of several dams, and also the Ogooué River
of Gabon, of which the Grand Poubara is again only the
first element. The Kwanza of Angola and the Cunene of the
Angolan/Namibian border, are set to be the first completed
cascade systems in Africa.
In this paper we expose the threats to numerous species of
Inversodicraea from dams, mainly through paths 1) and 3):
Path 1 — At the Memv’ele Falls dam nearing completion in
S. Region, Cameroon, three Inversodicraea species, each
recently discovered and globally unique to the falls, are
threatened by reduction of water flow over the original falls.
These are I. ntemensis (Kita et al. 2008), I. achoundongii
(Schenk et al. 2015) and I. tchoutoi (this paper). In the same
way, I. congolana is thought to be extinct at the Tshopo Falls
in DRC due to the construction of a dam on one of the falls,
and the reduction of water flow over the main falls.
Path 3 — Along the length of Kwanza (Cuanza) River in Angola, multiple hydroelectric projects threaten I. warmingiana,
I. fluitans, and I. digitata. On the Ogooué River of Gabon,
I. annithomae and I. thollonii are considered to be at risk
from the Grand Poubara project upstream.
DISCOVERY
The first published species of the genus that would come to
be known as Inversodicraea was Podostemum thollonii collected in 1887 by Thollon in present day Gabon (Baillon 1890).
This was followed by Sphaerothylax warmingiana collected in
Namibia by Baum in 1900 (Gilg 1901). Kolbe then collected
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Blumea – Volume 62 / 2, 2017
I. tenax at Victoria Falls in 1906 (Wright 1909). Inversodicraea
cristata, I. kamerunensis, and I. ledermannii were all published
by Engler (1915) from collections in Cameroon made by Ledermann in 1908. In 1944 I. congolana was published from DRC
(Haumann 1944).
and minutely papillate, rarely triangular or slightly botuliform.
Fruit dry, dehiscent by (1–)2 valves. Seeds numerous ellipsoid,
released dry, epidermis mucilaginous and adhesive on wetting.
Distribution — Tropical Africa, Guinea-Bissau to Tanzania
and South to Botswana, 30 species.
Hess’s collections from Angola in the 1940s and 1950s, combined with those of Gossweiler, resulted in the publication of
I. digitata and I. fluitans (Hess 1953). Inversodicraea abbayesii,
I. pygmaea, I. adamesii were collected in the 1940s and 1950s
mainly by Prof. des Abbayes and Peter Adames in Guinea and/
or Sierra Leone (Taylor 1953).
Note — Engler coined the name Inversodicraea and formally
published it as a new name, giving himself as author (Engler
1915). However, he appears to have been pre-empted in use
of his name by Fries (1914) who while attributing it to Engler
used the name first, to accommodate Dicraea tenax of Wright
(1909). Thus Fries’ use of the name has priority over that of Engler according to the Code. The type species of Inversodicraea
is thus I. tenax (C.H.Wright) R.E.Fr., being the only species on
which Fries (inadvertently) based the new genus.
Georges Le Testu collected specimens in 1925 –1928 from
Gabon and Congo-Brazzaville that were, together with collections by Nicholas Hallé, Annique Le Thomas, Paul Sita, Claude
Farron, and others later to be published as I. gabonensis,
I. boumiensis, I. paulsitae by Cusset (1983). At the same time
she published I. bosii, I. torrei, I. mortonii, and I. harrisii, all
named for their principal collectors, and made respectively in
Cameroon, Mozambique and Sierra Leone and Guinea. Her
publication, with eight new species, was the greatest increase
in numbers of species of the genus, then formulated as Leder
manniella subg. Phyllosoma (Cusset 1983). Inversodicraea
ntemensis and I. achoundongii (Kita et al. (2008), Schenk et
al. (2015)) were the only two new species to science published
in the subsequent 30 years.
The six new species to science added to this genus will not
be the last. It is expected that botanical surveys of the many
rapids and waterfalls of Africa that have never been inspected
for Podostemaceae will produce additional new species to
science. Revision of the few widespread and variable species
may also result in discovery of additional new species.
The application of Inversodicraea
Inversodicraea was used by Engler (1915) to include many
African taxa which were thought to have inverted flowers in
their spathellum. These included taxa currently treated as
Ledermanniella thalloidea, Macropodiella pellucida, L. aloides,
L. batangensis, L. minima, etc., as well as I. cristata, I. kamerun
ensis. Thus Engler’s concept for Inversodicraea was broad. This
use was continued with some adjustments until Cusset (1974)
pointed out that Ledermaniella Engl. (1909) was the earlier
name. She then transferred most names from Inversodicraea
into Ledermanniella (Cusset 1974).
TAXONOMY
With the discovery through molecular phylogenetic research
(Moline et al. 2007, Thiv et al. 2009, and Schenk et al. 2015)
that Cusset’s Ledermanniella subg. Phyllosoma was both coherent and not immediately connected phylogenetically with
Ledermanniella subg. Ledermanniella sensu Cusset (1983),
the decision was made to elevate it to generic rank, for which
the earliest available name was Inversodicraea.
Inversodicraea Engl. ex R.E.Fr.
Generic delimitation
Rheophytic, hermaphroditic, annual and probably perennial
herbs with narrowly ribbon-like, endogenously branching roots,
gripping the substrate with adhesive root hairs (also known as
rhizoids), distinct haptera (marginal disc-like holdfasts) rarely
observed and not well-developed. Stems < 1 cm to 80 cm long,
branched or unbranched, erect and free-standing in absence of
water, or horizontal, flowing in the current. Scale-leaves more
or less spirally inserted, rarely in loose whorls, more or less
covering the stems, dorsiventrally flattened, about as long as
wide, appressed to stem or spreading, margin entire or variously toothed or lobed, rarely the scale-leaves long and awnlike (I. mortonii). Leaves deciduous (shed before flowering as
plants are exposed by falling water levels), alternate, appearing
1–5 times dichotomously branched, blade and petiole terete
or dorsiventrally compressed, petiole not sheathing, stipules
absent. Spathellae single, terminal, rarely appearing axillary,
containing a single, inverted flower, rupturing before anthesis.
Pedicel expanding to lift the flower from the spathellum. Tepals
2, usually filiform, inconspicuous at junction of androphore (or
united staminal filaments) and gynophore. Stamens two (rarely
three as monstrosities), with filaments more or less united at
the base into the androphore, sometimes with a single stamen
only, anthers tetrasporangiate, connective inconspicuous, pollen in dyads or monads, tricolpate. Ovary with short gynophore,
unilocular with axile placentation (attached at base and apex
only), ellipsoid to oblong-ellipsoid in side view, cylindrical or
laterally compressed in the plane of the two sutures, becoming
6–8-ribbed longitudinally in fruit (the sutures with or without
ribs), the ribs sometimes distally produced as wings. Ovules numerous, anatropous, completely covering the placenta. Styles
2 (3 in I. ntemensis and I. tchoutoi), filiform with acute apex
Species of the resurrected Inversodicraea (Ledermanniella
subg. Phyllosoma as erected, delimited and revised by Cusset
(1983)) are easily recognised due to the unique synapomorphy
(derived feature) in having their stems more or less densely
covered in (usually) spirally inserted, dorsiventrally flattened,
often lobed, rarely needle-like, scale-leaves or ‘leaflets’ or
‘feuillettes’, often in addition to larger, but caducous, branched,
filiform dichotomous leaves which are also commonly seen in
other African Podostemaceae. Such scale-leaves are otherwise
absent in African Podostemaceae–Podostemoideae. Inversodi
craea are also distinct from, e.g., Ledermanniella, in having
terete or slightly flattened petioles and lacking sheathing stem
bases and stipules (see Morphology section).
The key to species below is based on that of Cusset (1983) with
modifications. In the course of constructing the key, it became
necessary to incorporate two newly described species from
Cameroon, I. ntemensis Y.Kita, Koi, Rutish. & M.Kato (2008)
and I. achoundongii J.J.Schenk, Herschlag & D.W.Thomas
(2015). These two species share an architecture unexpected
in Inversodicraea. The scale-leaves neither a) densely clad
the entire stem, as in I. cristata group, nor b) densely clad the
spathellae-bearing spur shoots but are absent or only sparsely
scattered on the main stems as in the I. annithomae group.
Instead these species show a third pattern, c) the spathellae are
surrounded by dichotomously branched leaves while the scaleleaves occur thinly scattered on the main axis only. Placement
inside Inversodicraea of I. ntemensis and I. achoundongii has
been confirmed by molecular phylogenetic analysis (Schenk et
al. 2015). Pattern c) appears to be shared by the little known
I. thollonii (Baill.) C.Cusset from Gabon.
M. Cheek et al.: A synoptic revision of Inversodicraea
These three species are additionally unusual in the unspecialised shape and margin of their scale-leaves which are triangular,
or triangular-ovate with an irregular margin. In contrast, most
Inversodicraea have scale-leaves which are often diagnostic
of the individual species, having species-specific shape and
marginal lobing or other ornamentation. Only I. bosii C.Cusset
seems to come close to these group c) species in having scaleleaves lacking marginal ornamentation, although they have a
species distinctive ovate-oblong shape.
Observations that species with only a few, sparse, sometimes
inconspicuous scale-leaves can be placed in Inversodicraea
prompted a reassessment of the recently described Macro
podiella cussetiana Cheek & Ameka. This species, clearly a
Macropodiella sensu C.Cusset (1978) since it has laterally
compressed ovaries and fruits, also had puzzling unspecialised
leafy scale structures discussed in Cheek & Ameka (2016).
One of the new species in this paper, I. feika also has strongly
laterally flattened ovaries and fruit (and so initially was to have
been described as a Macropodiella) yet is undoubtedly an
Inversodicraea due to its typically shaped scale-leaves which
are arranged in pattern b). It became clear in preparing this
paper that Cusset’s (1978) concept of Macropodiella, based
solely on the laterally flattened ovary feature (in separating it
from Ledermanniella s.lat.) was flawed. Cusset’s concept had
been questioned already in Cheek & Ameka (2016) when three
groups of Macropodiella species each with their own different
architectures were posited to have closer affinities to species
in other genera than to each other.
Macropodiella cussetiana had been placed in one of these
groups together with M. garrettii (C.H.Wright) C.Cusset and
M. macrothyrsa (G.Taylor) C.Cusset. All three species have
anomalous small unspecialised leafy structures that were
characterised as ‘bracts’ by Cusset (1978), presumably since
they are associated with the spathellae. However, bracts have
not been convincingly demonstrated in African podostemoids
apart from the spathellum itself. We postulate that these leafy
structures are in fact scale-leaves homologous with those that
uniquely characterise Inversodicraea in Africa. Accordingly,
Macropodiella cussetiana is here transferred to Inversodicraea.
We hesitate from reinstating the remaining two species there,
where they had earlier been placed by Taylor (1953), because
their ‘bracts’ differ from those known so far in Inversodicraea.
In M. garrettii they are dichotomous, and in M. macrothyrsa
they are stem-sheathing and only present as single structures
subtending a spathellum. Their homology with the scale-leaves
of Inversodicraea remains to be confirmed.
133
5. Scale-leaves ± patent or spreading, covering c. 50 % of
the stem, sometimes with 1– 2 side lobes . . . . . . . . . . . 6
5. Scale-leaves ± appressed to the stem, covering 70–100 %
of the stem, lacking side lobes . . . . . . . . . . . . . . . . . . . 7
6. Flowers with 1 stamen, fruit with 8 ribs. — Guinea . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23. I. pepehabai
6. Flowers with 2 stamens, fruit with 6 ribs. — Liberia . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30. I. liberia
7. Scale-leaves broadest in the distal half, apex broadly
convex. — Cameroon . . . . . . . . . . . 17. I. kamerunensis
7. Scale-leaves broadest in the proximal half, tapering towards
a slender apex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8. Flower with 1 stamen; scale-leaves on proximal third of
principal stem more than twice as long as broad. — Gabon,
Congo . . . . . . . . . . . . . . . . . . . . . . . . . . 2. I. gabonensis
8. Flower with 2 stamens; scale-leaves on proximal third of
the stem more than twice as long as broad. — Gabon . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19. I. thollonii
9. Scale-leaves digitately 5 –15-lobed or toothed . . . . . . 10
9. Scale-leaves 3(–4)-lobed . . . . . . . . . . . . . . . . . . . . . . 14
10. Apex of leaflet lobes rounded; stamen 1. — Angola . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. I. digitata
10. Apex of leaflet lobes acute; stamens 2 (where known) 11
11. Scale-leaves, in addition to the marginal teeth or lobes
bearing 4–10 spines on abaxial surfaces. — Cameroon
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26. I. xanderi
11. Scale-leaves teeth or lobes on margin only, projections
absent from abaxial surfaces . . . . . . . . . . . . . . . . . . . 12
12. Leaflet lobes 8–14, tine-like; ovary and fruit apex winged.
— Cameroon . . . . . . . . . . . . . . . . . . . . . . . . . . 25. I. ebo
12. Leaflet lobes 5–11, triangular; ovary and fruit without wings
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
13. Scale-leaves about as long as wide, scale-leaves at stem
base tridentate, pedicels 5–10 mm long in fruit. — Cameroon, C.A.R. . . . . . . . . . . . . . . . . . . . . . . . . . 5. I. cristata
13. Scale-leaves twice as long as wide, scale-leaves at the
stem base entire, rounded; pedicels 14–15 mm long in
fruit. — Cameroon . . . . . . . . . . . . . . . . . . . 28. I. tchoutoi
14. Scale-leaves flat with only 3 straight lobes at apex . . . 15
14. Scale-leaves not flat, the 3 apical lobes curved inwards,
and a fourth curved, reflexed lobe on the abaxial surface. — Guinea, Sierra Leone . . . . . . . . . . . . 7. I. harrisii
15. The three lobes triangular, subequal . . . . . . . . . . . . . . 16
15. The three lobes linear, the central lobe twice as long as
the two lateral lobes. — Guinea. . . . . . . . . 8. I. pygmaea
1. Scale-leaves densely covering (by 50 % or more) both the
principal stems and the side-branches (if any) . . . . . . . . 2
1. Scale-leaves only on the side-branches and/or absent to
sparsely covering (< 40 % cover) the principal stems . . 17
16. Leaflet oblong, the lobes minute, apical, occupying only
c. 10 % of the length of the leaflet and shorter than the
width of the unlobed part of the leaflet . . 6. I. congolana
16. Leaflet palmate in outline, the lobes occupying 40–50 %
of the length of the leaflet, and longer than the width of the
unlobed part of the leaflet. — Guinea to Angola . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9. I. ledermannii
2. Scale-leaves entire or sometimes with 1(–2) shallow lateral
lobes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Scale-leaves always 3–15-lobed or toothed, lobes usually
deep (but covering < 10 % of the leaflet length in I. congo
lana) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
17. Principal stems > 20 cm long, lax, flowing in the water and
lacking scale-leaves; scale-leaves dense on spur shoots
< 1 cm long . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
17. Principal stems either < 20 cm, and/or erect, and/or with
at least some scale-leaves present . . . . . . . . . . . . . . . 21
3. Scale-leaves linear-subulate. — Sierra Leone 1. I. mortonii
3. Scale-leaves ovate, orbicular, or obovate, apex dentate,
lobed or rounded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
18. Principal stems unbranched along their length . . . . . . 19
18. Principal stems with several major branches along their
length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4. Scale-leaves longer than wide, often with 1–2 shallow lateral
lobes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Scale-leaves orbicular or ovate, unlobed. — Gabon . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. I. boumiensis
19. Scale-leaves broadly elliptic, finely denticulate. — Gabon
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10. I. annithomae
19. Scale-leaves with three equal lobes. — Gabon, Congo
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11. I. paulsitae
KEY TO SPECIES OF INVERSODICRAEA
134
20. Apex of ovary and fruit with 6 short wings. — Angola . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12. I. warmingiana
20. Apex of ovary and fruit lacking wings. — Angola . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13. I. fluitans
21. Principal stems > 20 cm long, flowing in water . . . . . . 22
21. Principal stems < 20 cm long, usually 1–12 cm long, erect
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
22. Fruits and ovary strongly laterally compressed, usually not
in axils of pseudo-dichotomies . . . . . . . . . . . . . . . . . . 23
22. Fruits and ovary terete (not compressed), usually single
in axils of pseudo-dichotomies. — Cameroon . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21. I. ntemensis
23. Scale-leaves subtending each spathellum c. 10, often with
a lateral lobe; stigmas triangular. — Sierra Leone . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24. I. feika
23. Scale-leaves subtending each spathellum 1– 2, entire,
stigmas linear. — Ivory Coast . . . . . . . . 27. I. cussetiana
24. Scale-leaves with projections on the abaxial surface. —
Tanzania to Botswana . . . . . . . . . . . . . . . . . . 14. I. tenax
24. Scale-leaves without projections on the abaxial surface
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
25. Scale-leaves needle-like, not lobed (but with two short lateral lobes at stem apex with spathellae). — Guinea . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15. I. abbayesii
25. Scale-leaves triangular, ovate, or oblong, apex entire or
lobed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
26. Plants 1(–2) cm tall, scale-leaves ± uniformly equilaterally
triangular, not lobed. — Cameroon . . 22. I. achoundongii
26. Plants > 2 cm tall, scale-leaves ovate, oblong, sometimes
lobed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
27. Scale-leaves mostly (90 %) ovate, entire (near spathellae
slightly lobed). — Cameroon . . . . . . . . . . . . . . 16. I. bosii
27. Scale-leaves not ovate, but oblong, broadly or narrowly,
and lobed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
28. Scale-leaves as long as broad, or slightly longer (near
spathellae needle-like), ovary apex winged. — Cameroon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29. I. eladii
28. Scale-leaves twice to four times longer than broad, ovary
apex unwinged . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
29. Scale-leaves about twice as long as broad, ovary and fruit
6-ribbed. — Guinea, Sierra Leone. . . . . . 20. I. adamesii
29. Scale-leaves about four times as long as broad, ovary and
fruit 8-ribbed. — Mozambique . . . . . . . . . . . . .18. I. torrei
SYNOPTIC SPECIES TREATMENTS
1. Inversodicraea mortonii (C.Cusset) Cheek
Inversodicraea mortonii (C.Cusset) Cheek in Cheek & Haba (2016a) 2. —
Ledermaniella mortonii C.Cusset (1983) 368, f. 1. — Type: Morton in SL
2899 (holotype WAG n.v.; isotype K), Sierra Leone, Gbenge Hills, opposite
Bumban School, fl., fr., 28 Nov. 1965.
Etymology. Named for the collector of the type specimen, Prof. Morton,
botanist, specialist in West African Labiatae, Compositae, and Commelina
ceae who was based in Sierra Leone and Ghana in the 1960s and 1970s,
concluding his career at the University of Waterloo in Canada.
Distribution — Sierra Leone.
Habitat & Ecology — ‘Stem creeping over wet smooth rocks
of drying-out stream’; 5 –225 m altitude.
Conservation — Inversodicraea mortonii is not listed on
www.iucnredlist.org. Two locations only are known for this species. Despite targeted searches for Podostemaceae in Sierra
Leone 2009 –2016 for the Bumbuna and Yiben hydroelectric
projects, and for the Tonkolili iron project, I. mortonii has not
Blumea – Volume 62 / 2, 2017
yet been rediscovered. Inversodicraea mortonii has not been
seen for over 35 years. However, neither of the two known
localities for this species are known to have been searched
at the correct season. Since we know of no immediate direct
threats at either of the two localities, the species is here assessed as Near Threatened. Given that the area of occupancy
can be estimated as 2 km 2 using the preferred IUCN cell size
of 1 km 2, I. mortonii should be reassessed as Endangered, EN
B2 ab(iii) should any threat materialise, such as a hydroelectric
or mining project.
Additional specimen. Sierra Leone, Rapids, 4.2 km downstream of Mano,
Taia River (River Jong, River Pampam), N8°01' W12°07', fr., 28 Feb. 1981,
P.J.C.Harris 12 (P00179338 image).
Note — Remarkable for the uniformly subulate (awl-like),
linear-conical scale-leaves with rounded apices. Unlikely to be
confused with any other species.
2. Inversodicraea gabonensis (C.Cusset) Cheek
Inversodicraea gabonensis (C.Cusset) Cheek in Cheek & Haba (2016a) 2.
— Ledermanniella gabonensis C.Cusset (1983) 368, f. 2. — Type: Le Testu
6017 (holotype P00179287 image), Gabon, Haut Ngounyé (now Ngounié
Province), ‘rapides de l’Ogoulou à Mitingo’, fl., fr., 19 July 1926.
Etymology. Named for Gabon, the home of the type specimen.
Distribution — Congo-Brazzaville, Gabon.
Habitat & Ecology — In the spray of waterfalls in small rivers
or streams in the evergreen forest zone; 200 –600 m altitude.
Conservation — Inversodicraea gabonensis is not listed on
www.iucnredlist.org. The only known location is upstream of the
nearly completed hydroelectric dam at the Imperatrice Falls on
the Ngounié so is expected not to be affected. Two other locations occur in the Republic of Congo. The first at Foulakari is a
local tourist destination near Brazzaville. The second remote in
the upper headwaters of the Nyanga in Massif du Chaillu near
the Gabonese border. No threats have been detected by us at
these locations. However, we have made no direct observations. Given an area of occupation of 3 km 2, this species would
be assessed as Endangered, EN B2 ab(iii) if any threat were
known. Since we know of no threats at these localities, the
species is here assessed as Near Threatened. Given that the
number of hydroelectric projects in Africa is increasing rapidly,
such threats might materialise at any time.
Additional specimens. Gabon (type), Congo-Brazzaville (Republic of
Congo), Chutes de Foulakari, fl., fr., 13 Aug. 1969, Attims 202 (P00179288
image); ibid., fr., 13 Oct. 1968, F. Hallé 1467 (IEC, P00179289 image); ibid.,
fr., 6 Sept. 1972, Sita 3448 (IEC, P00179291 image); Chutes de la Nyanga
à Mouvoungou, fl., 18 May 1925, Le Testu 5459 (P00179290 image).
Note — Similar to I. tholloni, I. kamerunensis, I. boumiensis
(also C. Africa), I. pepehabai and I. liberia (W. Africa) in having
scale-leaves membranous, irregularly or not lobed, loosely held
or spreading (not appressed) on slender, sparsely branched,
short (2–5 cm long) more or less erect stems. Distinct for the
lanceolate scale-leaves often with a side lobe, apices rounded,
flowers 1-anthered, pollen in monads.
3. Inversodicraea boumiensis (C.Cusset) Cheek
Inversodicraea boumiensis (C.Cusset) Cheek in Cheek & Haba (2016a) 2.
— Ledermanniella boumiensis C.Cusset (1983) 370. — Type: Le Testu
6536 (holotype P00179270 image; isotype P00179271 image), Gabon,
Mbigou, Chutes de Boumi, fl., fr., 5 July 1927.
Etymology. Named for the Boumi Falls of Gabon, only known location for
the species.
Distribution — Gabon. Known only from the type.
Habitat & Ecology — Rapids; 600–700 m altitude.
135
M. Cheek et al.: A synoptic revision of Inversodicraea
Conservation — Inversodicraea boumiensis is listed on
www.iucnredlist.org as VU D2 (Vulnerable). It was assessed
in 2007 (Ghogue 2010c). Cheek (Onana & Cheek 2011) assesses it as EN B2 ab(iii), that is Endangered. However, both
assessments follow the protologue (Cusset 1983) which asserts that the species occurs at the Ntem Falls of Cameroon
as well as the type locality in Gabon. Yet, the plants at Ntem
ascribed to this species are shown in this paper to be I. tchoutoi
(see that species). Currently the species is known only from
the type locality, falls near Mbigou on the Boumi, a tributary
of the Ngounié River in the Province of that name. Assigning
an area of occupancy to this species of 1 km 2 would result in
an assessment of Critically Endangered, CR B2 ab(iii) if any
threat were known or to appear. Since we know of no threats
at either of these two localities, the species is here assessed
as Near Threatened.
Notes — In describing this species, Cusset (1983) cited
Letouzey 15339 from the Ntem River in Cameroon in addition
to the type from Gabon. Examination of this Letouzey specimen at YA showed it to be I. tchoutoi (see discussion under that
species). Therefore, I. boumiensis is known only from Gabon.
Inversodicrea boumiensis resembles I. gabonensis, the type
of which was collected within some tens of kilometres. They
differ in that the first has pollen in dyads from flowers with two
stamens, while I. gabonensis has monads and one stamen.
4. Inversodicraea digitata H.Hess
Inversodicraea digitata H.Hess (1953) 363, t. 8/3. — Ledermanniella digitata
(H.Hess) Cusset (1974) 273; (1983) 372. — Type: Hess 50/239 (lectotype
ZT n.v., isolectotype BM), Angola, Benguela, ‘In einem Seitenfluss des Rio
Catumbela, dem Rio Cubal da Hanha, zirka 50 km südlich Vila Mariano
Machado [Ganda], auf zirka 1400 m Höhe gefunden. Der Cubal bildet dort
Falle von etwa 2 m Höhe. Die Pflanze wurde erst am Ende der Trockenzeit
gesammelt’, fl., fr., 29 Aug. 1950.
Etymology. Named for the shape of the leaflet lobes which resemble the
fingers of a hand, with rounded tips.
Distribution — Angola.
Habitat & Ecology — Waterfalls with Hydrostachys polymor
pha Klotzsch (Hess 50/232); 1000–1642 m altitude.
Conservation — Inversodicraea digitata is not listed on www.
iucnredlist.org. Since three locations are known, and the area
of occupancy can be calculated as 3 km 2, and since two of
those two locations are in the Cuanza (Kwanza) drainage, we
here assess the species as EN B2 ab(iii). Podostemaceae on
the Cuanza are threatened (where they still exist) by the four
hydroelectric dams which have changed the natural annual
fluctuation of water levels. In 2014 (http://www.hydroworld.
com/articles/2014/09/angola-plans-five-hydroelectric-projectson-middle-cuanza-river.html accessed 17 Feb. 2017) it was
announced that five new, additional dams are to be constructed
on the Cuanza.
Additional specimens. anGoLa, Cuanza Sul, Mussende, R. GangoCuanza, 1000 m, fr., 13 June 1930, Gossweiler 9291 (BM, COI n.v., K, ZT
n.v.); Bié Province, Cuquema River (Kwanza drainage), 13 km WSW of Kuito,
S12°25'32" E16°49'6", 1642 m, fl., 19 May 2015, Goyder 8001 (K); ibid., st.,
8 Feb. 2016, Goyder 8203 (K).
Notes — Although Cusset (1983) stated that the holotypes
of Hess’s 1953 names are at ZT, specimen locations are not
given in the protologue, so lectotypification is needed. The ZT
duplicate is therefore formally selected as lectotype since Hess
is believed to have been based there.
Gossweiler 9291 (BM), previously cited by Cusset (1983) as
I. cristata, is here recognised as a second record of I. digitata in
view of the single stamen. This specimen was compared with
the type of I. digitata at BM.
This species is similar to I. warmingiana and I. fluitans, also in
Angola. It differs in that the leaflet lobes are finger-shaped: each
is parallel-sided with round apices (not acute) according to the
figure in Cusset (1983). The flowers have 1, not 2 stamens,
and the stems are short, not more than 20 cm long. However,
the leaflet lobes in the specimens seen are acute. Either the
Cusset figure is misleading or the unseen type number at ZT
differs from the remaining material in this respect.
The two Goyder specimens (8001 and 8203) represent the
highest altitudinal record for the genus at 1642 m above sealevel. The first is in full flower but lacks leaves, while the second,
from the identical spot but collected in the wet season while
under water, has both fully developed and unfolding leaves but
is sterile. Unusually in the genus, the ovaries dry red, and are
reported as being red in life.
5. Inversodicraea cristata Engl.
Inversodicraea cristata Engl. (1915) 276, f. 180A–M; (1926) 462; (1930)
58. — Ledermanniella cristata (Engl.) C.Cusset (1974) 273; (1983) 372;
(1987) 74. — Type: Ledermann 1173 (B holotype destroyed, lectotype
selected here BM; isotype U n.v.), Cameroon, ‘Makaka’ (Makaka Station),
‘gr. Steine & Felsen in reissendem Bach im gebirgigen Walde’. ‘Podostem.
mit grünlichen Bl. und rosaroten Blütenstielen’, fl., fr., 21 Nov. 1908, 500 m.
Etymology. Cristata meaning ‘crest’ may refer to the crest-like arrangement of tine-like divisions along the apex of the scale-leaves.
Distribution — Cameroon.
Habitat & Ecology — Rapids; 520–780 m altitude.
Conservation — Inversodicraea cristata is listed (as Leder
manniella) on www.iucnredlist.org as VU B2 ab(iii) in 2007 by
Ghogue (2010d). That assessment follows the protologue of
Cusset (1983) which recognises the species as extending to Angola, C.A.R., Equatorial Guinea, and Gabon, as well as Cameroon. Yet, in studying these specimens for this paper, it was
discovered that the only authentic records of this plant appear
to be from Cameroon alone (see above). However, at the time
of writing, not all of the specimens attributed by Cusset to I. cris
tata have been viewed and identified and therefore a formal
reassessment of its conservation assessment cannot yet be
made. However, the species is very likely threatened.
Additional specimens. Cameroon, Maan (24 km ESE Nyabesan), rochers
du lit du R. Mvigili, dans la NW du village, fl., fr., 6 Mar. 1963, J.& A. Raynal
10263 (P00179279 image; P00179280 image, YA); Mali, R. Fall, c. 8 km N.
Bétaré Oya. fl., 5 Feb. 1966, Leeuwenberg 7761 (P00179278 image, WAG
n.v., YA).
Notes — Ledermanniella cristata is the type of Lederman
niella subg. Phyllosoma C.Cusset (1983). Cusset’s delimitation
of this subgenus is followed here, albeit elevated to generic
level, as Inversodicraea, for which the type selected is I. tenax.
The protologue of I. cristata Engl. (1915) cites no specimen but
the figure is a good match for the BM sheet of Ledermann 1173,
the number generally understood to be its basis (e.g., cited in
Engler (1926) and cited as type by Cusset (1974) and so is
selected as lectotype here. Cusset’s (1983) concept of I. cris
tata was broad, including discordant elements. For example,
Gossweiler 9291 (Angola) is in fact I. digitata (see under that
species), while Tisserant 3210 (C.A.R., ‘Riv. Koyali, Bozoum’,
7 Jan. 1933, P00179281 image; P00179282 image) has an
uncertain placement, needing further research. Neither of these
specimens matches the illustration in the protologue, nor the
type specimen itself, which has 9–12 long, slender, tine-like
scale-leaf lobes. Therefore the material assigned to this species requires reassessment since more than one species is
probably involved.
136
6. Inversodicraea congolana Hauman
Inversodicraea congolana Hauman (1944) 179; (1948) 244. — Lederman
niella congolana (Hauman) C.Cusset (1974) 273; (1983) 374. — Type:
Vanderijst 21682 (BR n.v.), Congo-Kinshasa (DRC), Chutes de Luilu,
Thielen St. Jacques, fr.
Etymology. Named for the Congo (now DRC) to which this species is
endemic.
Distribution — DRC.
Habitat & Ecology — Rapids; 300–775 m altitude.
Conservation — Inversodicraea congolana is not listed in
www.iucnredlist.org. It was only known from two falls. The first
was at the set of falls on the Tshopo where a hydroelectric dam
has been installed since the species was collected. Here the
Tshopo joins the Congo near Kisangani, DRC’s third largest
city. It is notable that there are no records of Inversodicraea
from the vastly more extensive Wagenya (Boyama) Falls, also
at Kisangani, but on the Congo River itself. These falls extend
upriver for about 100 km in a series of step falls none more
than 5 m vertically. This absence is probably due to the high
silt levels of the water of the Congo River, which viewed on
Google Earth are brown, unlike the clear water of the smaller
Tshopo River.
The second location for the species was also recorded in the
grasslands of the Kasai at Thielen St Jacques, now MweneDitu, specifically at Chutes de Luilu on a braided river where
no obvious threats are visible on Google Earth. Accordingly
we calculate the area of occupancy as 2 km 2. Construction of
the dam at the Tshopo Falls is thought to have impacted on
the species, principally by reducing the total volume of water
flowing over the falls (much has now been diverted around the
falls via a penstock) and also by disrupting the natural seasonal
water flow regime at the falls, constituting threats. According to
Léonard (1993), citing Nyakabwa (1982), I. congolana, which he
discovered and surveyed at the site in 1947, no longer occurs
there and is locally extinct. Therefore we assess the species
as Endangered, EN B2 ab(iii). A survey for the species at the
Tshopo site is still advisable to determine whether or not some
last few plants might still survive there.
Additional specimen. DRC, Kisangani, Chutes de Tshopo, fr., July 1947,
Léonard 1346 (BR n.v.).
Note — This is the sole member of the genus known from
DRC apart from I. tenax towards the southern border. Inver
sodicraea congolana occurred at two isolated locations: 1) in
the forest belt almost within the city limits of Kisangani; and 2)
in the Kasai grasslands towards the border with Angola. These
two locations are so far apart, and in such different vegetation
types that both specimens deserve comparison to confirm that
they are indeed conspecific. Neither specimen has been examined in this study since BR specimens were not accessible in
2016/2017 owing to a digitisation programme. Inversodicraea
congolana is distinctive for its pair of ovary apical wings, derived from the two median longitudinal ovary ribs. The same
character occurs in I. warmingiana of Angola (but on all six
longitudinal ribs) and in I. feika of Sierra Leone, I. eladii and
I. ebo of Cameroon. Inversodicraea congolana is also unusual
in having dorsal protuberances on its leaflet. It is unique in the
genus in combining this character with winged ovaries.
7. Inversodicraea harrisii (C.Cusset) Cheek
Inversodicraea harrisii (C.Cusset) Cheek in Cheek & Haba (2016a) 2. —
Ledermanniella harrisii C.Cusset (1983) 374, f. 5. — Type: Harris 41
(P00179305 image holotype), Sierra Leone, rapids at Dodo ferry crossing
to Magbwema, river Sewa, N7°50" W11°44", fl., fr., 8 Dec. 1981.
Etymology. Named for Prof. P.J.C. Harris, Agricultural Scientist, University
of Coventry, United Kingdom, the collector of the type specimen and most
of the original material.
Blumea – Volume 62 / 2, 2017
Distribution — Guinea-Conakry (Republic of Guinea) and
Sierra Leone.
Habitat & Ecology — Rapids in rivers of evergreen forest
areas; 60–280 m altitude.
Conservation — Inversodicraea harrisii is not listed on www.
iucnredlist.org. Five locations are known (above), equating to
an area of occupancy of 5 km 2. Its location in Guinea on the
Bafing River is threatened by the planned Koukoutamba dam
for which construction bids were sought in 2016 (https://www.
africa-energy.com/article/guinea-omvs-develop-koukoutambahydro-scheme accessed 17 Feb. 2017). This threatens the species through both permanent flooding and arresting of the flow
of water in the reservoir part of the project, and the disruption
of the natural cycle of water levels below the dam. The second
location, on the Sewa River, is thought to be threatened by high
levels of diamond extraction upriver, which places silt into the
water, reducing both seedling establishment and photosynthesis for Podostemaceae downstream. Finally, the location at the
site of the Bumbuna-Yiben hydroelectric dam is thought to be
in the process of being lost. Accordingly the species is here
assessed as Endangered, EN B2 ab(iii).
Additional specimens. Guinea-Conakry, Haut Bafing, près Socotoro, fr.,
Apr. 1905, Chevalier s.n. (holotype P00179299 image). – Sierra Leone, rapids
of the river Sewa at Dodo to Magbwema, N7°50" W11°44", fl., fr., 8 Dec.
1981, Harris 41 (P00179305 image holotype); ibid., Harris 37 (P00179301
image); ibid., Harris 38 (P00179302 image); rapids near Mofwe, River Sewa,
N7°40" W11°58", 8 Dec. 1981, Harris 34 (P00179300 image); River bridge
near Baiima, River Tabe N8°06" W11°51", 8 Dec. 1981, Harris 46 (P00179303
image); Road bridge 2 miles SW of Lengkoro, River Mawaloko, N9°27"
W11°42.4", 10 Dec. 1981, Harris 71 (P00179304 image); Koinadugu District,
SE of Fadugu, along Seli (Rokel) river east of Fadugu, upstream of the village
of Yiben, to be flooded by proposed dam N9°18'52.2" W11°39'27.5", 260 m
alt., old fr., 31 May 2014, van der Burgt 1840 (BR n.v., K, MO n.v., P n.v., SL
n.v., WAG n.v.).
Notes — Unique in West African species of the genus in the
single dorsal tooth of the leaflet, more or less equal in size to
the lateral teeth-lobes. Those few other species with dorsal projections have much smaller and more irregular protuberances,
and none occur in West Africa.
The figure in the protologue (Cusset 1983) shows all of the
scale-leaves with the distinctive dorsal spine. However, recent
specimens from the Bumbuna area of Sierra Leone such as
van der Burgt 1840 (initially identified as L. ledermannii ) have
only one in five, or one in ten scale-leaves with the spine. It
is not clear whether this is because of variation in the frequency of expression through the population, or whether another explanation, such as hybridisation and introgression with
I. ledermannii, which also occurs at this location, might be the
cause. Alternatively the figure in Cusset (1983) may be erroneous, but this cannot be checked against the original material,
all at P, without a physical visit, since resolution of the online
digital images is too low for this purpose.
8. Inversodicraea pygmaea G.Taylor
Inversodicraea pygmaea G.Taylor (1953) 72, f. 10; (1954) 127. — Leder
manniella taylorii C.Cusset (1983) 376, f. 5 — Ledermanniella pygmaea
(G.Taylor) C.Cusset, non L. pygmaea (Pellegr.) C.Cusset (1974) 274. — In
versodicraea ledermannii auct. non. Engl., sensu A.Chev. p.p. (Chevalier
1938: 297). — Type: H. des Abbayes 353/1951 (holotype BM), GuineaConakry, ‘cercle de Kindia, Grandes-Chûtes, Rochers plats au bord de la
rivière au niveau des basses-eaux, parmi les Dicreanthus parmelioides,
4-12-1951’.
Etymology. Named for the diminutive stature of the species (‘the pygmy
Inversodicraea’).
Distribution — Guinea-Conakry.
Habitat & Ecology — On flat rocks at the edge of the river
at low water, among ‘Dicraeanthus parmelioides A.Chev.’ (=
Stonesia) rapids; 230 m altitude.
M. Cheek et al.: A synoptic revision of Inversodicraea
Conservation — Known only from the Grandes-Chûtes of
Kindia, which falls give their name to a Forêt-Classé, in the
centre of which is a large and expanding bauxite mine operated
by Russal (Cheek 2016 pers. obs.). The falls themselves have
had their seasonal flow modified by a series of hydroelectric
dams upstream, the Baneah and Donkeah dams. These developments are likely to have negatively impacted the Podo
stemaceae at the falls. However, I. pygmaea may have become
extinct after the first hydroelectric project on the river, which was
constructed at Grandes-Chûtes, in 1962–1963 by Hidrotehnika
of the former Yugoslavia.
Here I. pygmaea is assessed as Critically Endangered, CR B2
ab(iii), given the single location and threats stated above. The
area of occupancy is 1 km 2. Inversodicraea pygmaea is not
listed on www.iucnredlist.org.
Additional specimen. Guinea-Conakry, cercle de Kindia, Grand-Chûtes,
chemin de fer, km 107, fl., 19 Dec. 1908, Chevalier 20232 (P00179378 image).
Notes — Although the trifid leaves are unremarkable, the
species is distinctive for its very short (3(–5) mm tall) erect,
stout, stems which are thickly and densely clad in uniformly
shaped scale-leaves, from the 0.2 mm wide ribbon-like root
to the terminal spathellae. The spathellae often ruptures into
3 or 4 equal triangular lobes but this varies, with sometimes
one large and one small lobe, for example.
The fruits lack commissural ribs, resembling I. adamesii in this,
but the species differs in gross morphology, stamen number,
and other features. The non-commissural ribs project so far
that they are narrowly wing-like.
9. Inversodicraea ledermannii (Engl.) Engl.
Inversodicraea ledermannii (Engl.) Engl. (1915) 274; (1926) 463; (1930) 58;
Taylor (1954) 127. — Dicraea ledermannii Engl. (1909) 381. — Lederman
niella ledermannii (Engl.) C.Cusset (1974) 274; (1983) 377; (1987) 72. —
Type: Ledermann 225 (holo B destroyed; isotype BM, U n.v.), Cameroon,
S. Region, ‘Wasserfall, Gross-Batanga station, 10–12 m, auf Felsen unter
wasser oberhalb der Fälle im ‘Lobe’. Podostem. Kleines Pflänzchen in
Wasser. Blüht weiss-grün, konnt in ganzen kolonien vor.’ fl., 10 Aug. 1908.
Etymology. Named for Karl Ledermann the collector of the type specimen, and of specimens that became the types of many other new species
of Podostemaceae and other families which were published by Engler.
Distribution — Angola, Cameroon, Gabon, Guinea, Ivory Coast,
Sierra Leone.
Habitat & Ecology — The upper banks of rapids, first to be
exposed as the water levels drop at the end of the wet season,
in full sun; 0–400 m altitude.
Conservation — Inversodicraea ledermannii (as Lederman
niella) was listed on www.iucnredlist.org as Least Concern in
2009 (Diop 2010c). However, the species is not in fact recorded
from some of the countries in which it is claimed to occur in that
publication, such as Ghana, Senegal, Niger, Togo, etc. Despite
this it is probably, with I. tenax, the most common and widespread species of the genus and therefore we do not contest
this assessment.
Additional specimens. anGoLa, Bengo, River at Bela Vista, Exp. Zool.
Staat. 1959 (HBG n.v.). – Cameroon, SW Region, Korup National Park, N5°01'
E8°50', 50 m alt., 5–15 Dec. 1984, D. Thomas 4135A (K, P00179325 image). – DRC, N. Lukafu, valley of Lofoi R., Schmitz 1833 (BR n.v.). – Gabon,
Rapides de l’Ogooué au passage de la route de Mimongo à Koula Moutou,
fr., 25 June 1926, Le Testu 5983 (P00179326 image). – Guinea, GuinéeForestière, Beyla Prefecture, Mts Bèro, fl., 22 Nov. 2008, P.M. Haba 242
(BR, G, HNG, K, MO, P, SERG, WAG). – ivory CoaSt, Mt Cavally, Pays de
Dyolas, au pied de Mt Dô, 750 m alt., prés Gouékangouine, st., 2 May 1909,
Chevalier 21421 (P00179316 image). – Sierra Leone, small waterfall in Rokel
River; Kabala to Makeni, Northern province, 22 Mar. 1971, P.W. Richards
7320 (K, P00179375 image).
137
Notes — This, with I. tenax, is the most widespread and
frequent species of the genus. There is a large geographic
disjunction between the populations in Guinea-Ivory Coast
and those in Cameroon-Angola, and it is possible that these
correspond with two different taxa. It is not yet clear how much
morphological support there is for this idea. The matter was
first discussed by Taylor (1953). Those specimens above not
seen by us were studied and cited by Cusset (1983).
The isotype of I. bosii at K appears to be I. ledermannii. Hybridisation and possibly introgression, is suspected to have occurred
between I. ledermannii and I. bosii in Cameroon, and with I. har
risii in Sierra Leone (this paper).
Inversodicraea ledermannii is distinctive for the three, more
or less triangular, equal, lobes, each of which is about half the
length of the entire leaflet and has an acute apex.
Caution should be used before identifying material as this species in West Africa, since material originally identified thus later
proved to be separate species, e.g., I. pygmaea and I. harrisii.
10. Inversodicraea annithomae (C.Cusset) Rutish. & Thiv
Inversodicraea annithomae (C.Cusset) Rutish. & Thiv (Thiv et al. (2009) 72).
— Ledermanniella annithomae C.Cusset (1983) 377, f. 6; (1987) 76. —
Type: N. Hallé & A. Le Thomas 206 (holotype P00179254 image), Gabon,
Booué, lit de l’Ogooué, fl., 29 July 1966.
Etymology. Named for Annique Le Thomas co-collector of the type specimen and a noted specialist of Annonaceae and a palynologist at P.
Distribution — Gabon. Only known from the type specimen
at Booué.
Habitat & Ecology — River rapids of the Ogooué R. ‘4 espèces en mélange sur rochers’ (type, N. Hallé & A. Le Thomas
206) with Ledermanniella nicolasii C.Cusset (205), L. pusilla
(Warm.) C.Cusset (202), Macropodiella hallaei C.Cusset (203),
M. heteromorpha (Baill.) C.Cusset (201, 204), I. annithomae,
and I. thollonii (202bis) at c. 200 m altitude.
Conservation — Inversodicraea annithomae (as Lederman
niella) was assessed in www.iucnredlist.org as Endangered
(EN B2 ab(iii) in 2007 (Ghogue 2010a), and also by Cheek (in
Onana & Cheek 2011), citing only two known locations, one in
Cameroon and one (the type) location in Gabon. In this paper,
the population in Cameroon is shown to be a misidentification
for I. tchoutoi (see above, and under that species). This leaves
only a single location, the type, for I. annithomae. The area of
occupancy is therefore estimated as 1 km 2. Given threats from
hydroelectric dams on the Ogooué River, of which the Grand
Poubara, upstream, that opened in 2013, is the first, the future
for this species is bleak.
Since such dams moderate the natural seasonal fluctuation of
water levels downstream, they can deprive Podostemaceae of
the drop in water level needed to expose plants and so allow
flowering and seed production, and thus regeneration. Accordingly, we here reassess the threat to this species as CR B2
ab(iii), that is Critically Endangered.
Notes — The sterile paratype cited in the protologue,
Letouzey 10299, ‘Chutes du Ntem ou de Memve’ele, près
Nyabessan, 60 km E Campo (st. avr.)’ is a different taxon to
that of the type, and is described, with several new, fertile
specimens from the same location, as I. tchoutoi in this paper.
Inversodicraea annithomae itself, appears to be confined to
Gabon and is only known from the type collection. References
to I. annithomae from the Ntem River of Cameroon, and its
appearance in phylogenetic analyses (e.g., Thiv et al. 2009,
Schenk et al. 2015) probably refer to I. tchoutoi. The differences
between the taxa are given in a table in the account for the last
species.
138
Blumea – Volume 62 / 2, 2017
The Paris website lists under this species Sita 5856 (P00179255
image), from Congo, Chaillu, Rapide de Mandoro, 3 ponts,
6 June 1985, identified by C.Cusset in 1998. Since the specimen shown is highly branched, we consider this determination
to be unlikely, but image resolution was insufficient to provide
an alternative determination.
The thick main axes are 10–12 cm long, unbranched except at
the base. At anthesis they lack leaves, and bear flowers only
from short, 2 mm long erect, densely leaflet-clad stems which
are held in clusters of 4–12, the clusters are 5–10 mm diam
on the upper side of the main axis.
Inversodicraea annithomae is one of the most distinctive
members of the genus. Together with I. paulsitae it is unique
in having long (5–25 cm), flexible, unbranched floating stems,
with regular internodes, each node with a short, densely leafletclad flowering stem opposite to a long, dichotomously branched
leaf. While the last species has deeply 3-lobed scale-leaves,
I. annithomae has almost entire scale-leaves.
12. Inversodicraea warmingiana (Gilg) Engl.
In fact, at the type location near Booué, six species of Podo
stemaceae were collected by N. Hallé & A. Le Thomas when
collecting the type specimen, and probably there are seven
since Tristicha trifaria is very likely to be present, being ubiquitous.
11. Inversodicraea paulsitae (C.Cusset) Cheek
Inversodicraea paulsitae (C.Cusset) Cheek in Cheek & Haba (2016a) 2. —
Ledermanniella paulsitae C.Cusset (1983) 378, f. 7. — Type: Le Testu 6510
(holotype P00179346 image; isotype BM), Gabon, ‘Moupoundi, rapide
Litsila de la Ngounye’, fl., fr., 20 June 1927.
Etymology. Named for Paul Sita, pioneering Congolian forest botanist
based at IEC, the National Herbarium of Congo-Brazzaville. He is the author
of the first checklist of Congo Plants. He collected one of the original specimens of this species.
Distribution — Gabon, Congo-Brazzaville.
Habitat & Ecology — Dans les embruns, waterfalls; 350–
780 m altitude.
Conservation — Inversodicraea paulsitae is not listed on
www.iucnredlist.org. It is known from only four locations (see
above), equating to an area of occupancy of 4 km 2. The Moukoukoulou dam at Mindouli represents a threat to the location
on the Bouenza. This dam provides power to Pointe Noire.
Constructed in the 1970s, it is possible that the specimen
collected at this site (Farron 4581) was made before the dam
was constructed and that the species is now extinct at the site,
since a survey mission there led by one of us (XVDB) in 2011
failed to find the species.
The location of the Sita 3581 seems to be in the region of the
upper reaches of the Nyang at Niari in the Massif du Chaillu.
The location of the Beckendorff s.n. location in Gabon, is equally
uncertain. The type location, of Le Testu 6510, is on a tributary
of the Ngounie. Since all three of these locations are not affected immediately by any known hydroelectric project that we
have discovered, the species is probably extant, and possibly
secure. However, as micro-hydroelectric projects expand in their
geographic range, there is a distinct possibility that more of the
locations for I. paulsitae may become threatened. The species
is here assessed as Endangered, EN B2 ab(iii).
Additional specimens. ConGo-brazzaviLLe, Mouyondzi, chutes de la
Bouenza S3°53' E13°42', fr., 2 Aug.1965, Farron 4581 (P00179347 image);
ibid., Divenié, Mission Catholique, sur rochers immergés dans la Bibaka, fr.,
28 Jan. 1975, Sita 3581 (IRSC n.v., P00179348 image). – Gabon, Riviere
Louetoie, Chutes Byoko, 1933, J.J. Eckendorff s.a. (BM).
Notes — Similar and perhaps closely related to I. anni
thomae, the two being unusual in sharing long (5 – 25 cm),
flexible, unbranched floating stems, with regular internodes,
each node with a short, densely leaflet-clad flowering stem opposite to a long, dichotomously branched leaf. Inversodicraea
paulsitae is easily separated from I. annithomae by the deeply
trifid (not entire or with shallow, irregular, marginal teeth) scaleleaves.
Inversodicraea warmingiana (Gilg) Engl. (1915) 274; (1926) 462; H.Hess
(1953) 365; Obermeyer (1970) 208. — Sphaerothylax warmingiana Gilg
(1901) 17; Warm. & Gilg (1903) 240; Baker & C.H.Wright (1909) 128; Engl.
(1930) 58. — Ledermanniella warmingiana (Gilg) C.Cusset (1974) 275;
(1983) 380. — Type: Baum 904 (B destroyed; BM, C n.v., COI n.v., G n.v.,
K, L n.v., M n.v., U n.v., Z n.v.), Angola, Huíla/Cuando Cubango, Menempremp, near Wolombo, Cubango River, ‘Im Kubango bei Menempremp
1300 m (Wolombo). Abschüssige Stellen des Kutsi (Cuchi) und Kubango
(Cubango) ….’, fl., 11 May 1900, alt. 1300 m.
Etymology. Named for Johannes Eugen(ius) Bülow Warming 1841–1924,
a Danish botanist who wrote the first textbook and gave the first lectures on
the subject of ecology. Podostemaceae was reputed to be his favourite plant
family, which he researched and published upon in Brazil.
Distribution — Angola and possibly just over the border into
Namibia.
Habitat & Ecology — Waterfalls; 940–1500 m altitude.
Conservation — Inversodicraea warmingiana was listed on
www.iucnredlist.org as Vulnerable A3c after an assessment in
2006 (Sieben 2010) which states “a planned dam in the Okovango River will seriously impact the population in Namibia
with an estimated 30–50 % of the population that could be
lost”. This assessment was based on the assumption that the
species occurs in Namibia which is unproven (see below),
and also the mistaken assumption that “the species is only
found in two sites”. The first of these two sites is the Ruacana
Falls on the border of Angola and Namibia. And there is now
indeed a hydro plant on the river there. However, the dam is
on the Angolan side, and it looks from Google Earth that the
(formerly) suitable territory for the species would also have
been on that side. It is expected that both Hess and Exell &
Mendonça collections came from the Angolan side. The second
site is in S. Angola, cited as being the Kubango River. However,
I. warmingiana is the most commonly collected Inversodicraea
in Angola. Apart from the Cubango River, it is known also from
the Cunene, Cuanza, Cuchi, and Cutata Rivers, occurring in
four provinces of Angola. Yet, since we have not mapped this
species, nor collected the data on threats, we do not reassess
the species here. Given the number of locations and threats
from hydroelectric projects in Angola it is likely that it would be
rated as Vulnerable under Criterion B if reassessed.
Additional specimens. anGoLa, Cunene, ‘Prov. Huila. Schnellen von
Lacavala (Rio Cunene) 40 km oberhalb’, 9 June 1952, Hess 52/1966 (BM,
ZT n.v.); ibid., Ruàcanà, c. 1000 m, 8 June 1937, Exell & Mendonça 2740
(BM, COI n.v); Malanje/Cuanza Sul, Prov. Malange, R. Cuanza, Condo
Falls, c. 1000 m, stems fleshy, as thick as a finger, brownish green, fl., 29
Mar. 1937, Exell & Mendonça 137 (BM, COI); R. Cuanza, bridge between
Cabuta and Cassoque, fl., 25 June 1937, Exell & Mendonça 3085 (BM, COI);
R. Cuanza, Port Condo, Gossweiler 14147 (B destroyed, BM, COI n.v., K, L
n.v., LISC n.v.); Huíla/Cuando Cubango, Rio Cubango, Aug. 1937, G. Boss
in Herb. Trans. Mus. 36671 (BM, PRE n.v.); ibid., In den Fällen bei Vila Ponte
[Kuvango], 1380–1450 m, 19 June 1962, Hess 52/2039 (BM, G n.v., UPS
n.v., ZT n.v.); Cuando Cubango, Prov. Bié, Falle des Rio Cuchi (Kutsi) im
Malova-Gebirge c. 100 km Östlich Vila da Ponte, 1500 m, 25 June 1952,
Hess 52/2071 (BM); Huila/Cuando Cubango, Falle des Rio Cutata, 40 km
Östlich Vila da Ponte, 1470 m, 20 June 1952, Hess 52/2052 (BM).
Further specimens for this taxon are cited in Cusset (1983).
Notes — Unique in Inversodicraea due to the apex of the fruit
having six wings, one from each of the non-commissural longitudinal ribs; also it has the highest altitudinal range of all species
of the genus. Otherwise, I. warmingiana is closely similar to
I. fluitans of Angola, both having oblong-ovate scale-leaves with
139
M. Cheek et al.: A synoptic revision of Inversodicraea
5–7-toothed margins, and long flexible floating stems (30–40
cm, but up to 80 cm long in I. fluitans) that lack scale-leaves
except for the short, flowering side-branches. In this architecture
they are similar to I. paulsitae and I. annithomae, but unlike
these species, the main stems are branched. Inversodicraea
fluitans has an androecium that exceeds the ovary, while that
of I. warmingiana is minute.
Cusset (1983: 382) reports that specimens from the Cuanza
River in Malanje District, Angola, differ in several characters
from the remaining specimens of the species. We have not been
able to review all the specimens concerned so suspend judgement as to whether these represent a separate taxon or not.
Obermeyer (1970) mistakenly attributes this species to Botswana
Inversodicraea warmingiana is recorded from 14 specimens
deriving from three river catchments in Angola (the Cubango
and its tributaries the Cutato and Cuchi, the Cunene, and the
Kwanza (Cuanza)) and appears to be the most frequently
recorded species of the genus in Angola.
Gilg was based in B, but the specimens there were destroyed
(Obermeyer 1970: 208), so a lectotype should be chosen from
specimens at another herbarium, ideally a specimen seen by
Gilg.
13. Inversodicraea fluitans H.Hess
Inversodicraea fluitans H.Hess (1953) 364. — Ledermanniella fluitans
(H.Hess) C.Cusset (1974) 273; (1983) 382. — Type: Hess 50/83 (isolectotypes BM 2 sheets, BR n.v., G n.v.; lectotype ZT), Angola, Malanje, ‘…den
Fällen von Bragança (Rio Lucala), im Norden von Angola, am 28.7.1950
gesammelt. Die Pflanze werd nur am obern Band der Fälle im ressenden
Wasser flutend beobachtet. Sie hat sich dort an Graniten festgesetzt.
Höhe zirka 1200 m. Auf Falsen am oberen Ronde der Fälle’, alt. 1200 m,
fl., fr., July 1950.
Etymology. Presumably referring to the stems which flow in the current
of water.
Distribution — Angola.
Habitat & Ecology — Waterfalls in open, mainly woodland
habitat sometimes with Hydrostachys polymorpha (type locality); 50–1200 m altitude.
Conservation — Inversodicraea fluitans is not listed on www.
iucnredlist.org. It is known from one location on the Lucala River
(tributary of the Kwanza), the Chutes de Bragança (now the
Kalandula Falls), and at two locations on the Kwanza (Cuanza)
River, at Cassoque-Cabrita, and at Cambambe-Dondo. Using
the IUCN-preferred 1 km 2 cells for riverine species results in
an area of occupancy of 3 km 2. Existing threats on the Kwanza
are immense. At 2014 the 520-MW Capanda, 700-MW Cambambe 2, 2 067-MW Lauca, and the 260-MW Cambambe were
already in place or under construction. Studies for CaculoCabaca, Zenzo 1, Zenzo 2, Tumulo do Cacador and Luime
new hydroelectric power projects were conducted in 2014
according to Estevao. The Lauca project is under construction
by the Brazilian company Odebrecht. The five new projects are
to be constructed by Coba (https://constructionreviewonline.
com/2014/10/angola-carry-five-hydroelectric-projects/ downloaded 16 Feb. 2017). Therefore at least two, and possibly all
three known sites for this species are probably threatened. We
here assess the species using IUCN (2012) as Endangered,
EN B2 ab(iii).
Additional specimens. anGoLa, Malanje, Duque de Bragança, Luando Muba,
Lucata, 1000 m, 29 Aug. 1922, Gossweiler 8855 (BM); ibid., Rianondo, 1 Sept.
1922, Gossweiler 8856 (BM); ibid., Loando Muba, 1000 m, 29 Aug. 1922,
Gossweiler 8857 (BM); ibid., Quedes de Duque de Bragança [Quedas de
Kalandula], E16°01' S9°04', 23 Mar. 1973, 1140 m, Bamps, Martins, M. Silva
4259 (P00179286 image); Cuanza Norte/Bengo, Cambambe-Dondo, Catarata Cuanza, 55 m, fl., Gossweiler 9247 (BM); bridge on R. Cuanza [Kwanza],
Cassoque-Cabrita, fr., 25 June 1937, Exell & Mendonca 3086 (BM, COI n.v.).
Notes — Although Cusset (1983) stated that the holotypes
of Hess’s 1953 names are at ZT, specimen locations are not
given in the protologue, so lectotypification is needed. The ZT
duplicate is therefore formally selected as lectotype since Hess
is believed to have been based there.
Similar to the more frequently recorded I. warmingiana (see
there for diagnostic characters), I. fluitans is only known from
three locations, all in Angola, at one of which I. warmingiana has
also been recorded (bridge on R. Cuanza, Cassoque-Cabrita,
Exell & Mendonca 3085, 3086, COI n.v.).
While the type has 80 cm long, flowing stems and almost digitate
lobes at the apex of the oblong scale-leaves, the remaining
specimens are shrubby, with pectinate lobes. The long laciniate,
narrow, acute lobes are similar in some respects to those of
I. cristata. However, in the 5 –7-toothed scale-leaves this
species is closest to sympatric I. warmingiana, which is distinguished primarily by the 6-winged apex of the fruit.
14. Inversodicraea tenax (C.H.Wright) Engl. ex R.E.Fr.
Inversodicraea tenax (C.H.Wright) Engl. ex R.E.Fr. (1914) 56, t. 11; Engl.
(1915) 274; (1926) 462; (1930) 58. — Dicraea tenax C.H.Wright (1909)
125. — Ledermanniella tenax (C.H.Wright) C.Cusset (1974) 275; (1983)
384; (1997) 4, t. 1B; Beentje (2005) 4. — Type: Kolbe 3141 (holotype K;
isotype BOL n.v), Victoria Falls, Livingstone Isl., Zambezi River, ‘Grows in
the very swirl of the rapids. Plant a bronze colour and a horny consistency,
affording foothold to crabs’, fl., mid July 1906.
Etymology. From the Greek tenax meaning, tenacious, clinging, since
this species clings to rocks in rapids (as in fact do all species of the genus).
Distribution — Angola, Botswana, DRC, Namibia, Tanzania,
Zambia, Zimbabwe.
Habitat & Ecology — Forming colonies densely covering
rocks in swiftly flowing water at, or just below, water level, flowering above water level (Cusset 1997); 350 –1200 m altitude.
Conservation — Inversodicraea tenax is not listed on www.
iucnredlist.org since it is so widespread and frequent, being
known from 11 locations (our analysis of specimens cited by
Cusset (1983)), it falls short of the threshold of 10 locations
required to trigger threatened status for non-fragmented species
under Criterion B, which is most frequently used for assessing
plant species. Therefore we here assess it as Near Threatened
(NT). Area of occupancy is estimated as 11 km 2 using IUCNpreferred 1 km 2 cells. Hydroelectric projects pose threats to
this species: 254 such projects occur in Zimbabwe alone.
Additional specimens. anGoLa, Moxico, waterfalls near Luso [Luena],
Thompson 50 (J n.v.). – botSwana, Chobe River, 2 miles N of Kazane, 13
July 1947, PoleEvans 4214 (K, PRE n.v). – DRC, Dilolo, River Luan, rocks
in fast water, 20 July 1932, R.G.N. Young 184 (BM); ibid., 185 (BM); Vallée
de la Eofai, au Nord de Lukafu, sur roches ... a sec ou peu immergeuse
pendant les derniers mois de le saison seche, 17 July 1948, A. Schmitz 1833
(BM). – namibia, Caprivi Strip, Zambezi River, Mambova rapids, West 3702
(SRGH n.v.). – tanzania, Stromgebeit des Oberen Ruhudje. Landschaft Lupembe, nordlich des Flusses, Aug. 1931, Schlieben 1131A (BM, K). – zambia,
Mwinilunga, Kabompo River where it crosses Mwinilunga-Solwezi Rd, mile
69, 17 Sept. 1952, F. White 3282 (BM); ibid., 23 Oct. 1969, Drummond &
G. Williamson 9262 (P00179370 image). – zambia / zimbabwe border, Victoria
Falls, Zambezi River, wet rocks in running water, Worsdell sin, July 1909
(BM); ibid., Cataract Island, July–Aug. 1919, BurttDavy 17827 (BM); ibid.,
July 1926, E.L. Stephens s.n. (BM); ibid., June 1937, Obermeijer 36515 (BM);
ibid., 1 Aug. 1941, Greenway 6255 (BM, K); ibid., just above falls on basalt
rocks, abundant, flowering just above the water, 17 Aug. 1947, Brenan 7729
(BM, K); ibid., Livingstone Island, 21 Nov. 1949, without moss-like growth,
Wild 3129 (BM); ibid., 3000', Eastern Cataract, 6 July 1953, Schelpe 3928
(BM).
Notes — With I. ledermannii the most widespread and frequent Inversodicraea species.
It occurs in every country south of DRC and north of S. Africa
except Malawi and Mozambique. The only other species of the
140
genus recognised in South-Central Africa is I. torrei (Mozambique, a single location). The projections from the dorsal leaflet
surfaces of I. tenax distinguish it from most other species and
otherwise only occur in I. xanderi, I. harrisii, and I. congolana.
The type species of the genus, first collected on the Zambesi
River at the Victoria Falls on the border of Zambia and Zimbabwe (Kolbe 3149, the type location is mistakenly given as
‘Tanzanie’ by Cusset 1983: 384). We have counted 27 collections made at the type locality from those cited for the species
by Cusset (1983). This exceeds all other species of the genus
for number of records at one site. By error, these same 27
specimens are all attributed to Tanzania by Cusset (1983).
Blumea – Volume 62 / 2, 2017
Habitat & Ecology — ‘In fast running shallow water on otherwise bare rockfaces’ (Bos 3592); in evergreen forest zone; 5–10
m altitude.
Conservation — Inversodicraea bosii was listed on www.
iucnredlist.org in 2007 as EN B2 ab(iii), i.e., Endangered
(Ghogue 2010b). Two locations are cited there, the first at Lobé,
threatened by tourist trampling, and the second at Campo (no
threats listed), with an area of occupancy of 2 km 2. The same
assessment was made by Cheek (in Onana & Cheek 2011)
additionally citing hydroelectric development as a threat at the
Campo (Ntem) location.
Inversodicraea tenax as currently defined is morphologically
variable with discordant elements, effectively comprising a
species complex that would reward further analysis.
In fact (see notes above), we now know that I. bosii is known
from a single location, the Lobé Falls, at which we assess its
area of occupancy (and so its extent of occurrence) as 1 km2
using the IUCN-preferred cells of that size. Here it is threatened
by trampling from the many tourists that visit what in Cameroon
is a major tourist attraction (Cheek in Onana & Cheek 2011,
Ghogue 2011). Therefore the species is here reassessed as
Critically Endangered, CR B2 ab(iii).
15. Inversodicraea abbayesii G.Taylor
Additional specimen. Cameroon, S. Region, S. Kribi, Chûtes de la Lobé,
fl., 8 Jan. 1969, Bos 3597 (WAG spirit specimen n.v.).
Curiously, the species had not previously to this paper been
reported from DRC, neither by Cusset (1983, 1997) nor by
Hauman (1948).
Inversodicraea abbayesii G.Taylor (1953) 67; (1954) 126. — Ledermanniella
abbayesii (G.Taylor) C.Cusset (1974) 273; (1983) 385. — Type: H. des
Abbayes 898 /1948 (holotype BM; isotypes U n.v., ZT n.v.), Guinea, Pita,
Chûtes Kinkon, 880 m, fl., 22 Feb. 1948.
Etymology. Named for the collector of the type specimen, Prof. H. des
Abbayes, of the University of Rennes, Brittany, France, collector of the type
specimen.
Distribution — Guinea, endemic.
Habitat & Ecology — “Tres abondant dans la rivière au
dessus des Chûtes, attaché aux rochers dans le courant. Seul
le sommet fleuri émerge de l’eau” (H. des Abbayes 898/1948);
waterfall, 880 m altitude.
Conservation — Known from two collections at one location,
Chûtes de Kinkon in the Fouta Djalon of Guinea. Inversodicraea
abbayesii was listed on www.iucnredlist.org as Data Deficient
in 2008 (Diop 2010a) citing the National Monograph of Guinea
as evidence that the species, known only from a single location,
Chûtes de Kinkon, is not threatened. However, in recent years
a Chinese hydroelectric dam has been constructed near the
falls. The resultant changes to the natural alternation of water
levels may explain why this species has not been recollected
since, despite being so close to the major town of Pita. Here
the species is assessed as Critically Endangered since there
is a single location, with area of occupancy estimated at 1 km 2
and with the threats ascribed above: CR B2 ab(iii).
Additional specimens. Guinea, type specimen; ibid., fl., fr., Dec. 1948,
Bourdu s.n. (P00179245 image).
Note — In habit similar to I. adamesii but with well-developed
commissural ribs, and with scale-leaves much more acute,
longer and more slender. The scale-leaves have similarities
to the minute I. pygmaea of Grandes Chûtes, Kindia, but the
habit, and fruit ribs greatly differ.
16. Inversodicraea bosii (C.Cusset) Rutish. & Thiv
Inversodicraea bosii (C.Cusset) Rutish. & Thiv (Thiv et al. (2009) 72). —
Ledermanniella bosii C.Cusset (1983) 385, f. 9; (1987) 78. — Type: Bos
3592 (holotype WAG n.v; isotypes K, P00179266 image, YA), Cameroon,
S. Region, S. Kribi, Chûtes de la Lobé, fl., 8 Jan. 1969.
Etymology. Named for the collector of the type specimen, Dr Bos, of the
Herbarium Vadense, University of Wageningen (now transferred to Leiden).
He was a noted botanical collector in S. Region Cameroon, and specialist in
Dracaena.
Distribution — Cameroon, Chûtes de la Lobé.
Note — The paratype of I. bosii, Letouzey 15333 (Chûtes
du Ntem près de sa deviation sur le Bongola) is I. ntemensis
(see under that species). Inversodicraea bosii is therefore only
known from the type locality at Chûtes de la Lobé. The isotype
at K is I. ledermannii suggesting that this number is a mixed
collection. The large, entire, ovate scale-leaves described and
depicted in the protologue are distinctive. Initially Cusset (in litt.
1975) had determined the type material at YA as Lederman
niella (Inversodicraea) kamerunensis. Elad 1482 and 1484 may
be hybrids between I. bosii and I. ledermannii (see discussion
under I. eladii).
17. Inversodicraea kamerunensis (Engl.) Engl.
Inversodicraea kamerunensis (Engl.) Engl. (1915) 274, f. 180N–R; (1926)
463; (1930) 58, f. 47A–D. — Dicraea kamerunensis Engl. (1909) 380,
f. 2A–D. — Ledermanniella kamerunensis (Engl.) C.Cusset (1974) 274;
(1983) 387; (1987) 76. — Type: Ledermann 440a (holotype B destroyed;
lectotype BM selected here), Cameroon, S. Region, ‘Schnellen des CampoFlusses, bei Dipika’ (falls of the Campo River near Dipika), fr., Aug. 1908.
Etymology. Named for Cameroon (Kamerun is the German spelling) to
which country it remains endemic.
Distribution — Cameroon. Only the type gathering is known.
Habitat & Ecology — Waterfalls at low altitude.
Conservation — Apparently not seen for over 100 years, this
species is vulnerable to proposed hydroelectric projects on the
Campo (Ntem) River, its only known location. Inversodicraea ka
merunensis (as Ledermanniella ) was assessed as Vulnerable
in 2007 (Ghogue 2010e) but in view of imminent construction
of the hydroelectric dams upstream of the only known location
of this species (see under I. ntemensis) we feel that the threat
to the species has risen. Multiple surveys for Podostemaceae
along the length of the Campo (Ntem) River in the last 10 years
have not succeeded in rediscovering this species suggesting
that the 20 km 2 area of occupancy estimated in Ghogue (2010e)
may be an overestimate, and that 1 km 2 is the more realistic
estimate and in keeping with IUCN guidance. Accordingly the
species is here assessed as Critically Endangered, CR B2
ab(iii). In Cheek (in Onana & Cheek 2011) the same assessment was given. It is potentially Extinct.
Notes — According to a note on the type cover at BM: ‘Holotype destroyed in Berlin’. On the sheet itself is written in pencil
‘Portion returned to B. June 1984. J. Laundon’. The specimen
packet is marked ‘Dicraea kamerunensis Engl. (portion of type)’.
Therefore, with the destruction of the holotype at B in 1943,
141
M. Cheek et al.: A synoptic revision of Inversodicraea
the BM material is here selected as lectotype being the largest
remaining portion of the only original specimen mentioned and
illustrated in the protologue of the basionym (Engler 1909).
Ledermann 440 is the type of Ledermanniella linearifolia Engl.,
and also the type of Ledermanniella Engl. The specimen details
are identical with those of Ledermann 440a. The numbering suggests that since they are numbered together the two
specimens were growing together, and that the suffix ‘a’ was
added later to separate them – a standard convention in this
circumstance.
Cusset based her description and illustration (1983) of the species purely on the protologue and its illustration which is misleading in some respects. She was unaware of the BM material
it seems, having failed to find the type at B (Cusset 1983). No
leaf stipules were seen on the lectotype by us although Cusset
states that they are present (Cusset 1983).
The illustration in the protologue is misleading, showing scaleleaves which are linear-oblong, whereas the type specimen has
scale-leaves about as long as wide. The scale-leaves broaden
slightly from base to apex. The apex is semicircular, and either
entire, or minutely and irregularly laciniate.
The affinities of I. kamerunensis appear to be with I. thollonii
(see notes there) and I. adamesii.
18. Inversodicraea torrei (C.Cusset) Cheek
Inversodicraea torrei (C.Cusset) Cheek in Cheek & Haba (2016a) 2. — Leder
manniella torrei C.Cusset (1983) 386, t. 10; (1997) 3. — Type: Torre 5515
(holotype LISC n.v.), Mozambique, summit of Serra Gurué near Mt Namuli,
fl., 9 Apr. 1943.
Etymology. Named for Antonia Rocha da Torre (1904–?), collector of the
type specimen, noted botanist in Mozambique.
Distribution — Mozambique, known only from Serra Gurué
near summit of Mt Namuli.
Habitat & Ecology — No accurate data are available, but
rapids above Gurué occur at c. 750 m altitude (observed on
Google Earth).
Conservation — This species is a point endemic on the little
available evidence. Rapids along a small river, the Licungo, in
a steep-sided valley seen above Gurué town (Google Earth
imagery dated 26 Nov. 2015, viewed 22 Feb. 2017) are a possible location for this species. An area of occupancy of 1 km 2
can be estimated using the standard IUCN cell size for riverine
plants. The river, as habitat for submerged aquatic plants, appears to be at risk from silt from surface run-off, since the east
side of the valley had been cleared for agriculture, with bare soil
extending to within 20 m of the watercourse. The western side
of the valley was a tea plantation monoculture. Intensive tea
plantations were established in the colonial period, and have
recently been rehabilitated. Anthropic degradation is extensive
and increasing at Mt Namuli. Botanical surveys of Mt Namuli in
the early twenty-first century failed to refind any Podostemaceae
(Timberlake et al. 2009). It is to be hoped that this was because
the species was overlooked and not that it is extinct. Given the
apparent threat to, and single location of I. torrei we assess it
here as CR B2 ab(iii), Critically Endangered. The species has
not been listed on www.iucnredlist.org.
Additional specimen. mozambique, summit of Serra Gurué near the peak
of Mt Namuli, fr., 20 Sept. 1944, Mendonça 2166 (LISC n.v).
Notes — Distinctive for its thinly scattered (covering < 40 % of
stem), long slender scale-leaves (length : breadth ratio c. 10 : 1)
which bear two lateral lobes of the same shape as the main
leaflet, and which are held at an angle of c. 45° from it.
Cusset (1997: 3) cites an additional record for this species:
‘Botswana N: junction of Linyanti and Zambezi Rivers, fl. vii.
1930, E.M. Young s.n. (BM)’. However, this specimen is discordant from that described in the protologue having, e.g., mainly
unlobed scale-leaves and a spathellae with a short rostrum.
This specimen may represent an undescribed species, but the
spathellae are unopened and flowers invisible. Inversodicraea
torrei is known only from a single location, whence last recorded
in 1944, about 70 years ago.
19. Inversodicraea thollonii (Baill.) Cheek
Inversodicraea thollonii (Baill.) Cheek in Cheek & Haba (2016a) 2. — Leder
manniella thollonii (Baill.) C.Cusset (1983) 388; (1984) f. 13. — Podo
stemum thollonii Baill. (1890) 877. — Type: Thollon 825 (holotype P
P00179381 image; isotype BM, P00179380 image), Gabon, Ogooué,
Rapides de Lopé, fl., fr., 1887.
Etymology. Named for François-Romain Thollon (1855–1896), an early
French botanist in Gabon and Congo and collector of the type specimen
Distribution — Gabon, Ogooué River.
Habitat & Ecology — Rapids in the Ogooué River; c. 200 m
altitude.
Conservation — We here assess I. thollonii as Critically
Endangered since the natural fluctuations of water flow in the
Ogooué River, wherein occur its two sites (one location since
facing the same threat), are being affected by the opening in
2013 of the Grand Poubara dam built by China’s Sinohydro
http://www.gauff.net/en/news/articles/article/beginn-desaufstaus-im-wasserkraftwerk-grand-poubara.html. Among
other hydroelectric projects under construction in the area one
is also on the major tributary Ogooué River upstream of our
species at the Chutes de l’Impératrice (https://www.afdb.org/
fileadmin/uploads/afdb/Documents/Environmental-and-SocialAssessments/CDI%20R%C3%A9sum%C3%A9%20PGES%20
coder%20french%2025-05-12.pdf). The two sites and single
location for this species equate to an area of occupancy of
2 km 2 using the standard IUCN cell size for riverine plants. This
gives an assessment of CR B2 ab(iii). Currently the species is
not listed on www.iucnredlist.org.
Additional specimen. Gabon, Booué, lit de L’Ogooué, fr., 29 July 1966,
N. Hallé & A. Le Thomas 202b (P00179379 image).
Notes — Inversodicraea thollonii is still only known from rapids in the Ogooué River of Gabon at two sites which are so
close together (a maximum of 36 km apart, on the same river)
that it can be argued that they should be treated as one location
since they both face the same threat. The most recent record
is over 40 years old. This species is linked with I. kamerunen
sis and I. adamesii by the slender, loosely branched stems,
sparsely covered with irregularly 1– 3-lobed membranous
scale-leaves. These species are also unusual in the elongate
spathellum c. 4–7 times as long as broad, and by the androphore exceeding the ovary. Within this group it is distinguished
by the soft, entire, nail-like scale-leaves on the middle of the
stem, and, but more elongate and curved, at the stem apex.
20. Inversodicraea adamesii G.Taylor
Inversodicraea adamesii G.Taylor (1953) 69, f. 9; (1954) 127. — Lederman
niella adamesii (G.Taylor) C.Cusset (1974) 273; (1983) 388. — Type:
Adames 177 (holotype K), Sierra Leone, Large Scarcies River, Kambia
Bridge, fl., fr., 5 Dec. 1948.
Etymology. Named for Peter Adames (1914–), formerly of the FAO and
British Colonial Service, botanist and collector of the type specimen.
Distribution — Sierra Leone, Guinea.
Habitat & Ecology — Moss-like herb on rocks in Scarcies
and Seli Rivers seemingly with I. mortonii (Harris 10 and 12).
Conservation — Inversodicraea adamesii is listed as Data
Deficient by IUCN based on an assessment made in 2008 (Diop
2010b). That assessment mistakenly includes Guinea-Bissau
142
as part of the distribution of the species. At that time the current
wave of hydroelectric projects were evidently not anticipated
and/or unknown, since they were not mentioned among the
threats. The species is known from four locations on as many
rivers, on two of which, the Kolenté and Seli, multiple industrial
projects, mainly hydroelectric, have been and are being, put in
place that are disrupting the natural rhythm of water levels and
in the case of the Seli, the water quality (iron and gold mining
projects). Using the 1 km 2 cell size favoured by IUCN for riverine
species allows an area of occupancy of 4 km 2. Therefore we
assess the species as EN B2 ab(iii), that is, Endangered.
Additional specimens. Guinea, dans le lit de la Kolenté River, st., 30 Dec.
1938, J. Chillou 1039 (P00179246 image). – Sierra Leone, Kambia, Magbema, Large Scarcies River, fl., 29 Dec. 1951, H.D. Jordan 754 (K); Rapids
200 m upstream of road bridge across river Seli (Rokel) N8°59' W11°48',
Magburaka-Makeni Rd, fr., 17 Nov. 1981, Harris 10 (P00179247 image);
Rapids 4.2 km downstream of Mano on the Taia river, N8°01' W12°07', fl.,
fr., 21 Nov. 1981, Harris 15 (P00179248 image).
Notes — In his protologue Taylor (1953) cites Espiritos San
tos 2760 (K) from Guinea-Bissau, as paratype. Cusset (1983)
states that this specimen is certainly not this species because
there are eight equal capsule ridges not six. This view is supported here. Cusset concludes that a precise identification of
that specimen is not possible because the state of the specimen
is too advanced.
Blumea – Volume 62 / 2, 2017
extinct by the construction and existence of the dam and its
modification of seasonal water level changes of the river. The
species is not listed on www.iucnredlist.org.
Additional specimens. Cameroon, S. Region, Canon du Ntem, 30 km SW
de Nyabessan, fl., 1 Dec. 1982, Nkongmeneck 420 (YA); Ntem Waterfalls
near Bongola, 40 km ESE of Campo, 10 Dec. 1979, R. Letouzey 15333
(P00179267 image, YA 3 sheets); Campo Ma’an area, Memve’ele Waterfalls
N2°24' E10°21'48", fl., fr., 17 Jan. 2002, Tchouto 3373 (K, KRI n.v., SCA n.v.,
WAG, YA).
Note — Inversodicraea ntemensis, together with I. tchoutoi,
also at Memve’ele, are alone in the genus for consistently having 3 (not 2) equal styles. Inversodicraea ntemensis is also
unusual for the extremely sparse and inconspicuous scaleleaves which cover less than 5 % of the distal stems and which
are reduced to short, narrowly triangular to ligulate structures
that appear to be vestigial. The figure in the protologue depicts
the scale-leaves occurring in whorls of three. The flowers are
single, inserted in stem pseudo-dichotomies. Most of the biomass of the plants is comprised of the stout, branching stems
and the numerous dichotomous leaves. This appears to be a
perennial species. The species appears restricted to falls in the
Ntem River above Campo, near Bongola, at Memve’ele.
22. Inversodicraea achoundongii J.J.Schenk, Herschlag &
D.W.Thomas
No additional specimens of this species have been seen in at
least 30 years, despite targeted collecting of Podostemaceae
in 2009 –2016 in Sierra Leone by Xander van der Burgt and
colleagues including Aiah Lebbie and Josef Momoh, mainly in
the Seli River.
Inversodicraea achoundongii J.J.Schenk, Herschlag & D.W.Thomas (in
Schenk et al. (2015) 542). — Type: D.W. Thomas 9642 & G. Achoundong
(holotype MO n.v.; isotypes GAS n.v., K, NO n.v., YA, Z n.v.), Cameroon,
South Region, forest and banks of Ntem River, W of Nyabessan, herb on
rocks, stem flattened, creeping, N02°24' E10°22', 1 Dec. 1992.
Inversodicraea adamesii has close morphological affinities with
I. kamerunensis and I. thollonii of Cameroon and Gabon. It is
distinct inter alia in the absence of commissural ribs.
Etymology. Named for Dr Gaston Achoundong, former head of the IRADNational Herbarium of Cameroon (YA), Secretary-General of AETFAT and
noted specialist in Rinorea and co-collector of the type specimen.
21. Inversodicraea ntemensis (Y.Kita, Koi, Rutish & M.Kato)
J.J.Schenk, Herschlag & D.W.Thomas
Inversodicraea ntemensis (Y.Kita, Koi, Rutish & M.Kato) J.J.Schenk, Herschlag & D.W.Thomas (in Schenk et al. (2015) 542). — Ledermanniella
ntemensis Y.Kita, Koi, Rutish & M.Kato (in Kita et al. (2008) 224). — Type:
R. Imaichi, Y. Kita & JP. Ghogue CMR65 (TNS), Cameroon, S. Region,
rapids of Ntem River, 2 hr by motorboat from Campo beach, N2°14' E9°52',
fl., fr., date unrecorded.
Ledermanniella bosii C.Cusset (1983) 385, p.p., quoad Letouzey 15333.
Etymology. Named for the Ntem River (also known as the Campo), the
only known location for the species.
Distribution — Cameroon, S. Region, Ntem River, falls near
Bongola at Memve’ele.
Habitat & Ecology — ‘On submerged or exposed rocks in
waterfalls, only at Ntem waterfall … grows with Ledermanniella
bifurcata (Engl.) C.Cusset’ (Kita et al. 2008) and “sur rochers
trés exposé aux embruns” (Letouzey 15333); c. 395 m altitude.
Conservation — Inversodicraea ntemensis is known only
from the falls both at, and downstream of Memve’ele (a major
hydroelectric project under construction, due for completion
in 2017). Two additional hydroelectric streams are planned
subsequently along the Ntem River (http://china.aiddata.org/
projects/289 downloaded 15 Feb. 2017), one of which is conjectured to be at Bongola itself. Sinohydro are constructing and
China Exim Bank financing, the project. The area of occupation
(AOO) is estimated as 1 km 2. The extent of occurrence (EOO)
will slightly exceed the AOO. Given the single location and
threat from the hydro project referred to, and EOO/AOO, we
here assess this species using the IUCN (2012) standard as CR
B1+ B2 ab(i,ii,iv) as Critically Endangered following broadly the
assessment of CR B2 ab(iii) given by Cheek in Onana & Cheek
(2011: 250). It is possible that this species will be rendered
Distribution — Cameroon, Memve’ele Falls, Ntem River;
c. 395 m altitude.
Habitat & Ecology — Along the Ntem River, where the river
breaks into multiple channels and goes over an escarpment
in multiple waterfalls at Memv’ele, flowering as the water level
recedes in the dry season.
Conservation — Known only from the type locality at the
Memve’ele Falls on the Ntem River, site of the Memve’ele
Hydropower project. Financed by China Exim Bank, and
constructed by Sinohydro for the Ministry of Power and Water
Resources Cameroon, this is designed to have a 200 MW capacity from a reservoir of 19 million m3 resulting from an earthfill
dam 20 m high built across the top of the falls, diverting water
from the falls through a turbine house (https://www.esi-africa.
com/cameroon-and-sinohydro-partner-for-the-memve-elehydropower-station-project/ accessed 15 Feb. 2017). This
project is expected to have highly negative effects on the
survival of I. achoundongii since the dam will ‘direct the flow
of the river away from the multiple waterfalls … This dam will
disrupt the hydrology of the site by destroying many waterfalls
and flooding or filling the rocky reach of the river above the
falls”. (Schenk et al. 2015 in describing I. achoundongii). These
authors continued “our new species fits the IUCN criteria for
Critically Endangered and could soon become extinct because
of the dam construction and operation”.
Schenk et al. (2015) also cite an earlier conservation assessment of another Podostemaceae species at the same site:
“In the IUCN (2012) Endangered listing for Inversodicraea
annithomae [the Cameroon material is now I. tchoutoi ] known
only from the type locality in Gabon and from the Chutes de
Memve’ele, Jean-Paul Ghogue wrote: The major threat to
this species in Cameroon is the dam construction planned
in the only site locality of this species, the Ntem Waterfalls at
Memve’ele near Nyabizon, 60 km east of Campo”.
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Since I. achoundongii is only known from a single location, with
an estimated AOO of 1 km 2 and with threats as cited above,
using IUCN (2012), we here assess its conservation status as
CR B1+2ab(iii), that is Critically Endangered, confirming the
assessment of Schenk et al. (2015). The species is not listed
on www.iucnredlist.org.
Note — Inversodicraea achoundongii is notable in the genus
for its: 1) small stature: plants are usually < 1 cm tall and can
flower at only 5 mm tall (Schenk et al. 2015: f. 1); and 2) the
primarily deltoid (equilaterally triangular) scale-leaves which
are not imbricate, but only thinly scattered on the stems.
23. Inversodicraea pepehabai Cheek
Inversodicraea pepehabai Cheek in Cheek & Haba (2016a) 3. — Type: Pepe
M. Haba 292 (holotype HNG; isotypes K, P), Guinea-Conakry, GuineéForestère, Seredu, Mt Ziama, N8°21'25.8" W9°18'30.7", fl., fr., 8 Feb. 2010.
Etymology. Named for the collector of the only known specimen, Pepe
Haba of N’zerekore, one of the most expert field botanists in Guinea, cofounder of the environmental NGO Guinée-Biodiversité.
Distribution — Republic of Guinea (Guinea-Conakry).
Habitat & Ecology — Rapids in submontane evergreen forest; c. 600 m a.s.l. altitude.
Conservation — Inversodicraea pepehabai was assessed
in Cheek & Haba (2016a) as Endangered under Criterion D,
since less than 250 individuals are estimated to have been
observed at the single location known (EN D1). The AOO is
assessed as 1 km 2. Currently there are no obvious threats to
this species. But there is a risk that former activities within the
Ziama Foret Classe are resumed. These activities are tea and
quinine plantations, and timber extraction. Where any of these
to happen then increased surface run-off can be expected.
This would raise levels of nutrients and silt in the watercourse
in which I. pepehabai is found. In turn this would increase
algal growth that would compete with, and (due to increased
silt levels), reduce establishment of new plants of the species.
It is to be hoped that additional records of this species will be
found at further sites, lowering its conservation assessment.
Additional specimens. Guinea-Conakry, Guineé-Forestère, Seredu, Mt
Ziama, N8°21'25.8" W9°18'30.7", fl., fr., 8 Feb. 2010, Pepe Haba 292 (holotype HNG; isotypes K, P).
Notes — Inversodicraea pepehabai is unusual among African Podostemaceae being found in the rapids of a submontane
forest area. Other species with this ecology are Saxicolella
amicorum J.B.Hall (Hall 1971; pers. obs. Cheek 1995), Leder
manniella letouzeyi C.Cusset (Cusset 1987, Cheek et al.
2004), L. onanae Cheek (Cheek 2003, Cheek et al. 2004), and
L. pollardiana Cheek & Ameka (Cheek & Ameka 2008). Most
other species of the genus occur in rapids of lowland forest or
woodland habits.
The affinities of I. pepehabai are probably with other West African species of the genus which have slender, usually lobed,
scale-leaves. At first sight I. pepehabai appears very similar to
the relatively common and widespread I. ledermannii, but the
scale-leaves in that species are consistently, deeply and equally
3-lobed, and cover most of the stem, being ± appressed, not
patent. The scale-leaves of I. pygmaea (L. taylori) are also
similar, but are also consistently 3-lobed resembling I. leder
mannii excepting that the central lobe is always longer than
the laterals, and again, the stems are short (1–2 cm long) and
completely covered in scale-leaves. In I. mortonii the scaleleaves are needle-like, and completely lacking lobes. Most
similar to I. adamesii, in the irregularly lobed (lobes 1, 2, or
absent) scale-leaves which cover < 50 % of the stem. Distinct
in the scale-leaves being patent (not ± appressed), the flowers
with 1 stamen (not 2), the fruits 8-ribbed (not 6).
Inversodicraea pepehabai is one of several plant species unique
to the Ziama Massif inside the Ziama Man & Biosphere reserve.
It is likely to be proposed in the future as an ‘Important Plant
Area’ for Guinea (see Darbyshire, continuously updated). Several other new species have recently been discovered at this
location in Ziama including Gymnosiphon samoritourei Cheek
(Cheek & Van der Burgt 2010) and Allophylus samoritourei
Cheek (Cheek & Haba 2016b).
24. Inversodicraea feika Cheek, sp. nov. — Fig. 2, 3
Differs from all other species of Inversodicraea which have scale-leaves
dense on the spathellae-bearing spur shoots and sparse or absent on the
main shoot, in that the ovary and fruit are strongly laterally flattened and not
cylindrical. Most similar to Inversodicraea adamesii, e.g., in fruit having only 6
longitudinal ribs, but differing in that c. 90 % of the scale-leaves are entire (not
90 % 3-lobed). Unique in the genus is that the styles are narrowly triangular
in side view (Fig. 2f), resembling those of Dicraeanthus, not subulate, filiform
or botuliform. — Type: Feika 146 (holotype K; isotypes BR, EA, FBC n.v.,
G, K, LISC, MA, MO, P, PRE, S, SL, US, WAG, Z), Sierra Leone, Western
Area, Port Loko District, Port Loko, N8°45'29.0" W12°47'10.0", near bridge
across Port Loko river in Port Loko town, 10 m alt., fl., fr., 17 Dec. 2010.
Etymology. Named in honour of Mr. Abdulai Feika of the National Herbarium of Sierra Leone (SL) at Njala University. He is the collector of the
only two known specimens of the species.
Perennial herb, long stems streaming in the water, 15–80 cm
long, terete, 1.5–2(–3) mm diam along most of their length, internodes 1.5–3 cm long in the proximal 1/2–3/4, decreasing to
0.7–1.5 cm long in the distal portions, sometimes with 1–3 principal branches. Root horizontal, terete, stolon-like, 0.6–1 mm
diam, extending at least 5 cm long or more, internodes 2.5–7
mm long, nodes bearing opposite leaves which subtend fertile,
leaflet-clad spur shoots (Fig. 2c–d) which can develop into erect
highly branched candelabra-like stems c. 5 cm tall (Fig. 2a (upper portion) and Fig. 2b) and/or long sparingly branched stems.
Lateral stems 0.8–7 cm long, usually regularly spaced along
the principal stems, arising 1–4 mm below (and later than) the
long ribbon-like leaves, scale-leaves and flowers at the nodes.
Leaves ribbon-like, (0.7–)3–5(–7) cm long, 0.6–1.5 mm wide,
1–4-dichotomously branched, strongly dorsiventrally flattened
(ribbon-like), apices acute. Scaleleaves more or less confined
to the short spur shoots, 13–23 scale-leaves per shoot, spirally
inserted; acicular, ascending, 0.2 – 0.3(– 0.4) by 0.15 by 0.1
mm, apex acute to obtuse, entire, or rarely (1–2 in 10) with a
lateral lobe c. 0.05 mm long. Spathellum cylindrical, substipitate
3.5–4(–4.2) by (1–)1.2–1.3(–1.4) mm apex rounded-obtuse,
dehiscing irregularly at apex. Pedicel 7–8.5 mm long, 0.5 mm
diam at base, narrowing towards the apex. Tepals 2, opposite
stamen, narrowly oblanceolate, (0.9 –)1.3 –1.5 by 0.1 mm,
minutely papillate. Androecium of 2 stamens, nearly as long
or slightly longer than the ovary; united filaments 1–1.3 mm
long (3 mm in fruit), free filaments 1.3–1.5 mm long (2 mm
in fruit); anthers 4-celled, oblong, 0.9–1 by 0.5 mm. Pollen in
dyads, 70–75 by 37–42 µm, the two grains each subspheroidal.
Gynoecium with gynophore 1–1.1 mm long (2.5 mm in fruit).
Ovary unilocular, oblong-elliptic in side view, 1.3–1.8(–2.2) by
0.6–0.8 by 0.4–0.5 mm. Styles erect, narrowly triangular, 1.2
mm long, 0.2 mm wide at base. Fruit oblong-elliptic, strongly
laterally flattened, 2.5 by 0.9 by 0.6 mm, with 6 longitudinal
ribs, ribs pronounced, each projecting 1.0–1.5 mm; sutures
not pronounced, dehiscing by a single suture. Seeds oblongellipsoid 0.2 –0.25 by 0.1–0.12 mm.
Distribution — Sierra Leone, Port Loko.
Habitat & Ecology — On rocks in rapids of river, with I. leder
mannii, in the evergreen forest zone; 10 m altitude.
Conservation — Known only from one location within Port
Loko town limits, at two sites on the river locally known as the
Gbankasoka. The AOO is estimated as 1 km 2. Threats observed
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c
b
h
a
g
f
e
d
Fig. 2 Inversodicraea feika Cheek. a. Habit in dry season; a1. branched, erect flowering plant, leaves fallen; a2. subcylindrical root developing from old stem;
b1. detail of a1; b2. detail of spur shoot with scale-leaves; c. stolon-like root upper surface, showing opposite, distichous short leaves and endogenous branching; d. stolon-like root, lower surface, with two undifferentiated endogenous root branches (detail from a2); e. spur shoot with spathellum just after dehiscence;
f. spur shoot, with flower at anthesis; g. fruit; h. fruit in transverse section, three seeds in lateral view above (all from Feika 78B, K). — Scale bars: a = 1 cm;
b–d = 5 mm; e–g = 2 mm; h, b (small inset) = 0.5 mm. — Drawn by Andrew Brown.
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M. Cheek et al.: A synoptic revision of Inversodicraea
b
a
c
Fig. 3 Inversodicraea feika Cheek. a. Habit, end wet season, long stem with branches, dichotomous leaves attached; b. detail of spur shoot with scale-leaves,
spathellae and one dichotomous leaf; c. flattened, ribbon-like, dichotomous leaf (transverse section at lower right) (all from Feika 146, K). — Scale bars: a = 10
cm; b = 1 cm; c = 2 cm. — Drawn by Andrew Brown.
are pollution of the habitat from clothes washing (Ben Pollard
pers. comm. to M. Cheek 2010) and bridge construction for iron
ore transport (Lebbie pers. comm.). Further, a micro-hydroelectric project is planned for the site. Therefore, I. feika is here
assessed as Critically Endangered, CR B2 ab(iii). Port Loko
in the most populous district in Sierra Leone after Freetown's
Western Areas District.
Additional specimens. Sierra Leone, Western Area, Port Loko District, Port
Loko, N8°45'29.0" W12°47'10.0", near bridge across Port Loko river in Port
Loko town, 10 m alt., fl., fr., 17 Dec. 2010, Feika 146 (holotype K; isotypes
BR, EA, FBC n.v., G, K, LISC, MA, MO, P, PRE, S, SL, US, WAG, Z); ibid.,
fl., fr., Mar. 2010, Feika 78B (K, SL n.v.).
Notes — Inversodicraea feika is one of the most completely
known species of the genus thanks to the two collections of
Feika made by Mr. Feika and his associate collectors Ben Pollard, Sue Frisby, and Xander van der Burgt.
It has been collected in the reproductive state in mid dry season (March, Feika 78B), when it produced spathellae from the
stolons and short (5 cm tall) candelabra-like stems, and in December at the end of the wet season when long streaming stems
and leaves were present as well as spathellae (Feika 146).
Material of this taxon first came to light in March 2010 (Feika
78) as a result of a baseline botanical study for the transport
corridor for the Tonkolili iron ore mine, at that time operated by
African Minerals Limited (AML) but now owned by Shandong
Iron & Steel. Feika 78 was found to be a mixed collection of
I. ledermannii (formerly Ledermanniella ledermannii) segregated as Feika 78A, with a second undescribed species (segregated as Feika 78B) which was recognised as new to science
and drawn up for publication (Fig. 2). Since the 6 ribbed ovary
and fruit (resulting from inverted flowers) was strongly laterally
compressed, the generic attribution of Macropodiella Engl. was
initially made, following the prevailing classification of Cusset
(e.g., Cusset 1987). However, in the interim increasingly better
sampled molecular studies (Moline et al. 2007, Thiv et al. 2009,
Schenk et al. 2015) have thrown doubt on some of the generic
limits of Cusset’s classification (1978, 1983, 1984, 1987). So far
as Macropodiella and Ledermanniella are concerned, morphological data also give cause to doubt the generic delimitation
(Cheek & Ameka 2016). It is now clear that Feika 78B, due to
the flattened, sometimes lobed, scale-like scale-leaves that
it presents, is unambiguously best placed in the newly resurrected genus Inversodicraea (Cheek & Haba 2016a). Since the
completion of Fig. 2, extensive additional material (17 sheets)
was collected from the same site in December 2010 (Feika 146)
which shows additional character of the taxon and which has
been selected as type of the species and illustrated as Fig. 3.
25. Inversodicraea ebo Cheek, sp. nov. — Fig. 4
Differs from I. cristata Engl. in having wings extending from the distal parts
the non-commissural ribs of the ovary (vs wings absent), in having the
base of the stem with either scattered, non-pectinate scales or (next to the
substrate) naked, with a corky epidermis (in I. cristata the stem is covered
in pectinate scales to the base), and in the leaflet lobes being nearly parallelsided with an abruptly rounded apex (not narrowly triangular with an acute
apex). — Type: van der Burgt 1716 (holotype YA; isotype K), Cameroon,
Littoral Region, Yabassi, Ebo proposed National Park, near Locndeng, Ebo
River, fl., 7 Dec. 2013.
Etymology. Named for the Ebo River and Ebo proposed National Park
to which this species is unique according to the evidence available.
Rheophytic, probably perennial herb. Basal thalloid portion
thick, orbicular, 1.5 –1.6 cm diam, margin shallowly lobed,
upper surface entirely lacking leaves but with a single tree or
shrub-like stem arising from the centre (Fig. 4a). Stem erect, robust, 0.6–0.8 cm diam at base, unbranched for (0.6–)1–2 cm,
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b
c
h
a
k
l
i
j
g
f
e
d
Fig. 4 Inversodicraea ebo Cheek. a. Habit, whole plant in flower and fruit, showing disc-like thalloid portion anchored to rock; b. details of non-flowering
plant, showing (below) base of stem (inset detail of corky epidermal cells) and non-pectinate scale-leaves on branches; (above) terminal origin of leaves (inset
transverse section of leaf base); c. detail of dichotomously branched leaves; d. portion of lower stem showing scale-leaves lacking pectinate margins; e. stem
from midpoint of plant showing pectinate scale-leaves covering c. 50 % of surface; f. stem apex with spathellae buds and scale-leaves covering 80–100 %
of surface; g. three scale-leaves showing variation (dotted basal line indicates insertion on stem); h. flower emerging from spathellum, before anthesis;
i. flower detail at anthesis, note the distally united wings of the ovary ribs; j. whole flower at anthesis, including spathellum; k. fertilised ovary, transverse section,
slightly laterally flattened; l. seed, side view (all from Xander van der Burgt 1716, K). — Scale bars: a = 5 cm; b = 1 cm; c–f = 2 mm; g–j = 1 mm; k–l = 500
µm. — Drawn by Andrew Brown.
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M. Cheek et al.: A synoptic revision of Inversodicraea
then dividing into 2 – 3 subequal branches, those branches
themselves dividing every 1–2 cm along their length, and the
resultant branches further, until c. 50 stem apices are present;
stem apices 1.5–2 mm diam, 80–100 % clothed in pectinate
scale-leaves (Fig. 4f); stems equidistant between apex and
base becoming wider, 1.8–2.2 mm diam, 40–50 % covered
by scale-leaves; stems 1– 3 cm above the base 2.2 – 3 mm
diam, the scale-leaves lacking their pectinate margin; stem
bases, at junction with thalloid area, lacking scale-leaves,
surface with grey-brown corky isodiametric cells 0.003 mm
diam (Fig. 4b, inset detail). Scaleleaves appressed, flattened,
orbicular-oblong in outline (0.75–)0.85–1.2(–1.3) by (0.4–)0.5–
1.2 mm, the proximal, entire part crescent-shaped, its distal
margin extending into 8–14 subequal, subparallel, linear divisions 0.3 – 0.5 by 0.05(– 0.1) mm, apices acute, the shorter
divisions marginal, leaflet attachment curved, 0.3–0.75 mm
long. (Fig. 4g). Leaves arising terminally on stems, stems
then dividing into two, so that the leaves appear to arise in the
axils of dichotomous stem forks (Fig. 4b); proximal 1/2–2/3
(1.7–2.1 cm) of leaf entire, ribbon-like in transverse section
c. 1.5 by 0.5 mm; distal 1/2–1/3 branching dichotomously up
to 5–7 times, with 27–70 terminal filiform segments c. 1.5–2 by
0.05 mm, stipules absent (Fig. 4c). Spathellae single or in pairs
at stem apex (Fig. 4f); buds cylindric-ellipsoid c. 2 by 1 mm,
mucro 0.25 mm long, apex truncate-rounded, base sessile,
concealed by scale-leaves; opening by an irregular tear into
two parts, pedicel c. 3.5 mm long at anthesis. Tepals filiform,
0.5–1.1 mm long inserted opposite to the androecium 0.1–0.3
mm below the insertion of the gynophore. Androecium slightly
longer than the ovary (2.2–2.5 mm long), stamens two, free
filaments 0.8–0.9 mm long, anthers 0.65–0.7 by 0.3–0.4 mm.
Pollen in monads, prolate, 54–69 by 38 µm. Ovary ellipsoidoblong, slightly laterally flattened, the median and submedian
nerves of each valve extended distally into rounded-triangular,
fin-like wings, 0.15–0.2 by 0.2–0.35 mm; united to each other
distally; gynophore 0.15 – 0.3 mm long; stigmas irregularly
swollen, subcylindrical, tapering gradually to apex, 0.9 by 0.15
mm. Capsule hexagonal in transverse section, 0.8 by 0.6 mm
(Fig. 4k) with 6 major and 2 minor (commissural) longitudinal,
convex ribs (Fig. 4k). Seeds ellipsoid 0.3 by 0.15 mm.
Distribution — Cameroon endemic, known only from the Ebo
River near Locndeng in Littoral Region.
Habitat & Ecology — Rheophyte on rocks in rapids of river.
Conservation — Known only from the type location in the
Ebo proposed National Park to which this species is unique
according to the evidence available. Threats include forest
clearance for oil palm plantations, logging, and open cast iron
ore mining, any of which would result in increased surface runoff and increased turbidity of the water which forms the habitat
for this species. The AOO is estimated as 1 km 2. Accordingly,
I. ebo is here assessed as Critically Endangered, CR B2 ab(iii).
Notes — Inversodicrea ebo appears to have a close affinity
to both I. cristata and I. tchoutoi. All three species resemble
miniature, highly branched, bonsai trees. All three have the
broad, convex apex of the leaflet divided often into ten or more
subequal regular divisions. While in the last species these divisions are equilaterally triangular, those in the two former are
long and slender. However, I. cristata and I. ebo are separated
by the characters given in the diagnosis. The distally winged
ovary ribs of I. ebo are unusual in the genus, otherwise occurring only in I. warmingiana, I. eladii, and I. congolana.
The robust construction of I. ebo suggests that it is a long-lived,
perennial species. It is conjectured that the scale-leaves near
the base of the stem lack pectinate margins due to age, and
that the corky base of the stem is an adaptation to guard against
desiccation in the drier season when the plants are exposed
above waterlevel.
26. Inversodicraea xanderi Cheek, sp. nov. — Fig. 5
With Inversodicraea harrisii C.Cusset, I. congolana Hauman and I. tenax
(C.H.Wright) Engl., unusual in the genus in having projections from the
abaxial surface of the leaflet (not flat, as in all other species). Most similar
to I. tenax in having multiple projections, but differing from all three species in having 5 or more marginal teeth, not tridentate, and in the strongly
dimorphic scale-leaves, those on the stem distant from the spathellae having
(6–)7–9 teeth and lacking abaxial projections (not tridentate with abaxial
projections). — Type: van der Burgt 1940 (holotype K; isotypes P, YA n.v.,
Z), Cameroon, South Region, Campo, Campo-Ma’an National Park, North
of the road Campo to Ma’an, N2°20'57.1" E10°13'21.8", old fr., alt. 230 m,
4 Mar. 2016.
Etymology. Named for Xander van der Burgt (1958–) Dutch botanist,
formerly of the Herbarium Vadense, Wageningen, now of the Royal Botanic
Garden, Kew, specialist in field surveys in tropical Africa, and especially in
the LeguminosaeCaesalpinoideae. Collector of the only known specimen
of Inversodicraea xanderi.
Erect annual herb, 1.5–3 cm tall including fruits (Fig. 5b). Root
horizontal, dorsiventrally flattened (ribbon-like), adhering to
substrate, 1.5–2 mm wide, lateral branches arising at 50–60°
from the main axis, at intervals of 6–8 mm; internodes 1–5
mm long (Fig. 5a). Stems erect, terete, leaflet-clad, 0.1–1.6
cm long, 0.4–0.6 mm diam, 0.7–0.8 mm wide including scaleleaves. Leaves not seen, probably caducous, dichotomously
branched. Scaleleaves completely covering the stems, appressed, dimorphic: a) normal scale-leaves (Fig. 5e) 1–1.6 by
0.7 mm, distal part hemi-orbicular, digitately (6–)7–9-toothed,
teeth marginal, subequal, narrowly conical, length : breadth
c. 2–3 : 1, length 0.1–0.2 mm; b) distal scale-leaves (Fig. 5d),
subtending spathellae, 1–1.1 by 0.7 mm, free, distal part oblong
to triangular, marginal teeth 5–6, each (0.1–)0.2–0.3 mm long,
abaxial surface with (4–)5–7(–10) conical projections, each
0.05–0.3 mm long. Spathellae single, terminal or subterminal.
Pedicel 12–14 mm long in fruit. Gynophore with distal 0.9–1.1
mm decorticating, leaving only the 6 vascular strands (Fig
5c2). Tepals, androecium and ovary unrecorded. Fruit narrowly
cylindric-ellipsoid, c. 2.5 by 0.4–0.5 mm, with 6 longitudinal ribs,
ribs conspicuous, subequal (Fig. 5c2); sutures not pronounced
(commissural ribs absent), dehiscing by two sutures, valves not
caducous. Seeds unrecorded.
Distribution — Cameroon, South Region, Campo.
Habitat & Ecology — On rocks in stream 0–50 cm above
water level near Campo town in primary evergreen forest; 230 m
altitude.
Conservation — Known only from one location on the river
near Campo inside the Campo-Ma’an National Park currently
one of the most protected areas in Cameroon. The AOO is
estimated as 1 km 2. It is here assessed as NT in view of the
small AOO, since no threats are currently known. Should threats
be evidenced, this species should be reassessed as Critically
Endangered.
Additional specimens. Cameroon, South Region, Campo, Campo-Ma’an
National Park, North of the road Campo to Ma’an, N2°20'57.1" E10°13'21.8",
old fr., alt. 230 m, 4 Mar. 2016, van der Burgt 1940 (holotype K; isotypes P,
YA n.v., Z).
Notes — Decortication of the outer surface of the developing
fruit exposes the longitudinal ribs of Inversodicraea according
to Thiv et al. (2009). In I. xanderi this same process appears to
extend from the base of the fruit to the gynophore, leaving the
first connected to the pedicel only by the six vascular strands
that comprise the fruit ribs (Fig. 5c2). The annual nature of
I. xanderi is confirmed by the type material, all of which appears
to have been dead before it was collected.
The abaxial leaflet projections are conjectured to aid the protection of the developing spathellae from predation by grazing
animals.
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Inversodicraea xanderi is known from a post-mature, fruiting
collection. In the shape and toothing of the majority of its scaleleaves it is similar to I. cristata, which also occurs in Cameroon.
It is likely that the two have an affinity. The points of separation
between the two species are detailed in Table 1. The abaxial
projections of the spathellae-subtending scale-leaves of I. xan
deri are rarely encountered in Africa, being seen in only three
other species, all of which differ from I. xanderi in numerous
points (see above, under ‘diagnosis’). Flowering material of
this taxon is desirable.
Table 1 Characters separating Inversodicraea cristata and Inversodicraea
xanderi (data for I. cristata from Cusset (1983)).
I. cristata
I. xanderi
Root width
1 mm
1.5 – 2 mm
Fruiting pedicel length
9 –10 mm
12 –14 mm
Distal portion of gynophore decorticated
No
Yes
Scale-leaves dimorphic
No
Yes
No. marginal teeth (normal scale-leaves)
5 –7(–10)
(6 –)7– 9
Scale-leaves with abaxial projections
No
Yes
Fruit dimensions (mm)
1.8 – 2 by 0.8 –1
2.5 by 0.4 – 0.5
c2
d
a
b
c1
e
Fig. 5 Inversodicraea xanderi Cheek. a. Root viewed from above, showing erect leaflet covered stems and pedicel bases; b. erect, sparingly branched stem
with fruits; c1. detail of fruiting stems, with c2 detail of dehisced fruits; d. detail of spathellae-subtending scale-leaves; e. detail of normal scale-leaves (all from
Xander van der Burgt 1940, K). — Scale bars: a–b = 1 cm; c1–c2 = 2 mm; d–e = 1 mm. — Drawn by Andrew Brown.
27. Inversodicraea cussetiana (Cheek & Ameka) Cheek,
comb. nov.
Basionym. Macropodiella cussetiana Cheek & Ameka (2016) 2. — Type:
J. de Koning 5232 (holotype K; isotypes UCJ n.v. WAG), Côte d’Ivoire, Sassandra River, near Louga, N5°03'02.53" E6°12'32.55", fl., fr., 25 Jan. 1975.
Etymology. Named in honour of Colette Cusset of P, to whom all working
on African Podostemaceae owe a great debt for establishing the taxonomic
framework on which all current research is based.
Distribution — Côte d’Ivoire, Sassandra River (type collection only).
Habitat & Ecology — On rocks of rapids in river in evergreen
forest zone; 17 m altitude.
Conservation — Rapids and waterfalls are often favoured
sites for placing hydroelectric projects, which threaten Podo
stemaceae species present at such sites by construction of
dams, turbine houses, canals, and other connected infrastructure on their habitat, by the permanent submergence and loss of
aerated water in areas flooded by the dam, and by the change
to the natural hydrological regime in areas downstream of the
dam.
The only known locality for Macropodiella cussetiana is on the
Sassandra river about 20 km N of the coastal town of Sassandra. Further upriver, about 92 km N of the type locality of
M. cussetiana, is the town of Soubre, and the Naoua Falls where
a new hydroelectric scheme managed by Sinohydro is planned
(http://www.hydroworld.com/articles/2014/01/alstom-winscontract-to-outfit-ivory-coast-s-soubre-hydropower-project.html
downloaded 26 June 2014). This project threatens the only
known global locality for Macropodiella taylorii (J.J.de Wilde &
Guillaumet) C.Cusset whereat multiple specimens have been
made (Cusset 1978). In June 2014 interest was being shown
in developing hydropower sites downriver of Soubre, which
threatens Macropodiella cussetiana (http://www.hydroworld.
com/articles/2014/06/ivory-coast-seeks-hydropower-sitestudies-below-270-mw-soubre-hydro-project.html downloaded
26 June 2014). Since the latest Google Earth imagery for the
area dates from 4 Oct. 2013 (downloaded 12 Jan. 2016) the
exact location and state of development of the project cannot
be viewed remotely through this means.
The only known site for this species lies just inside the ‘Parc
Naturel de Gaoulou’ as demarcated on Google Earth (viewed
M. Cheek et al.: A synoptic revision of Inversodicraea
13 Jan. 2016). This area appears to be less heavily impacted
by development than adjoining areas, although it still contains
villages and palm oil plantations and is far from pristine.
Since there is a single location, with an EOO and AOO estimated (using current IUCN guidance for aquatic plants) of 1 km 2,
and with the clear threat of a hydroelectric scheme being constructed in the vicinity of the only known location, we here assess I. cussetiana as Critically Endangered, CR B1+B2 ab(iii).
This assessment follows that of Cheek & Ameka (2016). Should
the project referred to go ahead, it is possible that this species
will become extinct, given the evidence available at present.
Notes — Inversodicraea cussetiana is transferred here from
Macropodiella since it has been established through molecular
means (e.g., Thiv et al. 2009) that the possession of scaleleaves (indicating Inversodicraea) has primacy over whether
or not the ovary and fruit are laterally flattened (flattened ovaryfruits previously defining Macropodiella, e.g., Cusset 1983).
Inversodicraea cussetiana may have a close affinity with I. feika
of Sierra Leone since that species also has laterally flattened
ovaries. However, this character may have arisen independently
several times (see Cheek & Ameka 2016). Within Macropodiella
we had placed I. cussetiana with M. garrettii and M. macrothyrsa
(G.Taylor) Cusset, however, these last two species appear to
lack the scale-leaves which indicate Inversodicraea so are not
similarly transferred in this paper. However, it is possible that
they may simply have lost scale-leaves entirely. If this can be
shown as probable with molecular phylogenetic methods then
consideration should be giving to transferring these two species
also.
This is the only known species of the genus known for Cote
D’Ivoire apart from a single record of I. ledermannii (Aké Assi
2002).
28. Inversodicraea tchoutoi Cheek, sp. nov. — Fig. 6
Similar to Inversodicraea ebo Cheek in the perennial, subshrubby, erect,
highly branched habit; differing in that the ovaries and fruits lack apical wings,
usually have 3 (not 2) stigmas, the leaflet margins have (5 –)9 –11(–16)
equilaterally triangular teeth, not 8 –14 linear divisions. — Type: Tchouto
Peguy with Elad Maurice, Nnangah Austin 3378 (holotype K; isotypes KRI
n.v., SCA n.v., WAG, YA n.v.), Cameroon, South Province (now Region),
Campo Ma’an Area, Memve’ele waterfalls, N2°24' E10°21'48", alt. 360 m,
fl., fr., 17 Jan. 2002.
Ledermaniella cf. cristata sensu Ghogue (2011: 95).
Etymology. Named for Dr. Peguy Gildas Tchouto, botanist and forester,
formerly of the Mount Cameroon Project, later Professor at Mbalamayo Forestry School, now GTZ Biodiversity Adviser, Programme for the Sustainable
Management of Natural Resources, Mount Cameroon.
Perennial, erect, subshrubby rheophytic herb, 4(–20) cm tall,
repeatedly pseudodichotomously branched in the upper part
forming flat-topped crowns 4.8–9 cm diam, with 40–90 ultimate branches. Root horizontal, narrowly ribbon-like (dorsiventrally flattened), adhering to substrate, 0.6–1.3 mm wide,
lateral branches arising at (45–)70–90° from the main axis,
at intervals of 1.2 – 5 mm. Stems arising at margin of root,
opposite, sparse, developing a circular holdfast base to 4–12
mm diam, stem unbranched, terete, for 2–15 mm, 4–5 mm
diam, surface wrinkled. Scaleleaves closely appressed and
completely covering the upper part of the main axis and the
ultimate stem branches, drying green, completely flat, papery
in texture. Scale-leaves produced when underwater (when
leaves are also present) are denser, with a low length : breadth
ratio. Scale-leaves produced when plants emerged (leaves
absent) are longer and less congested. Emerged scale-leaves
are oblong-spatulate, 1.35 – 2(– 2.5) by (0.4 –)0.5 – 0.8(–1.3)
mm, distal portion obtusely rounded in outline, and wider
than the 0.3–0.5 mm wide proximal c. half which has entire,
149
concave sides, the margin of distal portion with (5–)9–11(–16)
± regular equilaterally triangular subequal teeth, teeth dentate,
0.03–0.08(–0.1) mm long. Scale-leaves of the mid and lower
part of the main axis with 5 % cover, semicircular, lacking welldeveloped lobes or teeth drying black, 0.8 by 0.9 mm, apex
rounded. Leaves 2.2–8.3(–10) cm long, 5 times (or more) dichotomously branched, arising singly at the stem dichotomies;
stipules absent; petiole flattened, at base, 0.5 mm wide, 0.9–3.5
cm long, narrowly ribbon-like, 0.5–0.75 mm wide, repeatedly
dividing, gradually tapering to a point at apices. Spathellae
arising at branch dichotomies, single, obovoid 1.1–1.3 mm long
including the basal stipe c. 0.4 by 0.12 mm, partly concealed
by the scale-leaves, mucro 0.1 mm long; the obovoid central
portion 0.7–0.8 by 0.3–0.4 mm, dehiscing in c. 4 deep, irregular
lobes, margins becoming involute. Flower pink (Tchouto 3378),
erect. Pedicel 14–15 mm. Tepals 2, subulate, erect, 0.9–1 mm
long. Stamens 2, shorter than gynoecium; united portion of
filaments 1.5–1.7 mm long, free portions 1–1.1 mm long, the
branches diverging at c. 90°. Anthers white, 1–1.1 by 0.35–0.4
mm pollen in monads, 0.03–0.038 mm diam. Gynophore 1.6
mm, dilating gradually at apex into the ovary. Ovary unilocular,
fusiform 1.8 – 2.3 by 0.5(– 0.7) mm, apex rounded-truncate.
Stigmas 3, subulate, 0.65 mm long, gradually tapering to the
apex, papillate, united at the base, spreading. Longitudinal ribs
6, equally prominent and spaced, the two commissural ribs
much more weakly developed, with a central line of dehiscence.
Fruit dehiscing into 2 equal, persistent valves, containing c. 40
seeds. Seeds ovoid, 0.25 by 0.07 mm, laterally flattened.
Distribution — Cameroon, South Region, Ntem River, known
only from the Memv’ele Falls.
Habitat & Ecology — Waterfalls in the evergreen forest zone,
with two wet and dry seasons. ‘Accroché en tapis sur rochers recouverts d’eau torrenteuse et cascadant. Abondant’.
(Letouzey 10299); 350 – 450 m altitude. The species grows
mixed with Ledermanniella bifurcata (e.g., Letouzey 15334).
Conservation — Since I. tchoutoi is only known from a single
location, with an estimated AOO of 1 km 2 and with threats as
cited under I. achoundongii and I. ntemensis, we here assess
its conservation status as Critically Endangered, CR B1+2ab(iii).
Additional specimens. Cameroon, South Region, Campo Ma’an Area,
Boucle du Ntem, Around Meyas Ntem, N2°20'80" E10°35'16", fr., alt. 480 m,
16 Feb. 2001, Tchouto 3170 (K, KRI n.v., SCA n.v., WAG); ibid., Memve’ele
waterfalls, N2°24' E10°21'48", fr., alt. 360 m, 17 Jan. 2002, Tchouto 3376
(K, KRI n.v., SCA n.v., WAG, YA); ibid., 3377 (K, KRI n.v., SCA n.v., WAG,
YA n.v.); ibid., 3378 (K, KRI n.v., SCA n.v., WAG, YA n.v.); ibid., Chutes du
Ntem ou de Memve’ele prés Nyabessan (60 km E de Campo), st., 8 Apr.
1970, Letouzey 10299 (P00179253 image; P00179252 image); ibid., Chutes
du Ntem prés de sa derivation sur la Bongola, 40 km ESE Campo, fl., 10
Dec. 1979, Letouzey 153399 (P00179268 image; P00179269 image; YA 3
sheets); ibid., fr., 21 Jan. 2016, Sene 1–15 (K, YA); ibid., 21 Jan. 2016, Sene
1–16 (K, YA).
Notes — Using Cusset (1983, 1987), I. tchoutoi would key
out as I. cristata. The species can be separated using the
features in Table 2. Podostemologists working in Cameroon
(Koi et al. 2012, Schenk et al. 2015) appear to have referred
to I. tchoutoi as I. (Ledermanniella) annithomae as discussed
below and under the last species. Inversodicraea annithomae
differs in having unbranched, floating, flexible stems which
have short inflorescence shoots opposed to leaves at nodes,
and constant internode lengths. It appears to be confined to
the Ogouué River of Gabon.
The presence of three stigmas in I. tchoutoi otherwise only
occurs within the genus in I. ntemensis, which, however, appears not to be particularly similar to I. tchoutoi. Horizontal gene
transfer can be postulated, since they occur at the same site
and both appear globally restricted to the Ntem River.
First collected in 1970 when sterile (Letouzey 10299), Cusset
initially determined this specimen as I. cristata Engl. in June
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k
c
d
l
b
i
f
g
j
e
h
a
Fig. 6 Inversodicraea tchoutoi Cheek. a. Branched root, with base of perennial erect stems; b. distal portion of branching stems showing scale-leaves and
leaves; c. detail of distal leaflet from b; d. detail of older leaflet from b; e. distal part of stem with unopened spathellae; f. detail of upper part of leaflet from e
(base concealed by scale-leaves below); g. entire leaflet from e, including base; h. stem apices with flower at anthesis; i. detail of flower excluding pedicel,
note the three styles; j. monad pollen grain; k. ovary, transverse section; l. fruit after dehiscence, inner surface of valves (all from Tchouto 3377, K). — Scale
bars: a–b = 1 cm; c–g, i, k–l = 1 mm; h = 3 mm. — Drawn by Andrew Brown.
M. Cheek et al.: A synoptic revision of Inversodicraea
Table 2 Characters separating Inversodicraea tchoutoi and Inversodicraea
cristata (data for I. cristata from Cusset (1983)).
I. cristata
I. tchoutoi
Leaflet shape (branches)
Broadly elliptic to
obovate
Oblong-spatulate
Leaflet dimensions
1.2 –1.5 by
0.9 –1.2 mm
(1.35 –)1.7– 2(– 2.5) by
(0.4 –)0.65 – 0.8(–1.3) mm
No. of teeth per leaflet
5 –7(–10)
(5 –)9 –11(–16)
Length of leaflet teeth
0.2 – 0.3 mm
0.05 – 0.08(– 0.1) mm
Length of post-anthetic
pedicel
5 –10 mm
14 –15 mm
Fruit shape and width
Ellipsoid, 0.8 –1 mm
Fusiform, 0.5 – 0.7 mm
Stem base scale-leaves
Tridentate
Subentire, rounded
1971, which is logical in view of the habit and the multiple
dissections of the leaflet edge, albeit that these dissections
are shallower and more triangular than those of that species.
Consciousness of this may have led Cusset (1983) to redetermine the specimen as paratype of I. annithomae which can
have similar shallow multiple dissections. Cusset may have
attributed the absence in Letouzey 10299 of the long, flexible
flowing stems of I. annithomae as well as the great differences
in inflorescence arrangement, to the juvenile, sterile state of
Letouzey 10299.
Letouzey 15339 identified by Cusset in 1980, and published
as paratype of Ledermanniella boumiensis (Cusset 1983) is
I. tchoutoi. There is no evidence that I. boumiensis occurs
outside Gabon.
From Letouzey’s (10299) field notes and from the notes of
Tchouto’s copious specimens, it appears that this species grows
in colonies that cover rocks, like a green pile carpet, flowering
mid December to mid January (leaves present), with fruits in
mid February (leaves absent) and becoming sterile by mid April.
29. Inversodicraea eladii Cheek, sp. nov. — Fig. 7
Inversodicraea eladii (Fig. 7) has its closest affinity with two species,
I. bosii (see Table 3 for differences), which occurs at the same locality, and
I. congolana which occurs at the other side of the Congo basin. The first
lacks the distinctive apical 2-winged ovary-fruit of I. eladii, and also differs in
the scale-leaves being mostly (> 90 %) ovate; the proximal half of the stems
being naked of scale-leaves; the leaves being 1-dichotomous. In I. eladii the
scale-leaves are mainly triangular or with 1–2 small lateral triangular lobes
(apart from subulate scale-leaves near the spathellae) and the stems have
a c. 5 % covering of scale-leaves; the leaves are many-times dichotomously
branched. Inversodicraea congolana closely resembles I. eladii in the apically 2-winged ovary and fruits. However, the fruits of I. eladii are 6-ribbed,
not 8-ribbed as in I. congolana. Further, the leaves are only dichotomous
(not 4–5-times dichotomous), the habit only 0.5–1.5 cm tall, not 6–10 cm
tall. — Type: Elad Maurice with Tchouto Peguy 1485A (holotype K; isotypes
KRI, WAG, YA), Cameroon, South Region, Camp Ma’an area, Lobe, Lobe
Waterfalls in Grand Batanga area at the edge of the sea, N2°52'57" E9°53'50",
fl., alt 5 m, 30 Nov. 2001.
Table 3 Characters separating Inversodicraea bosii and Inversodicraea
eladii (data for I. bosii taken from Cusset (1983)).
I. bosii
I. eladii
Leaflet shape
(below spathellae)
Ovate, entire (rarely
with 1– 2 lateral lobes),
0.5 – 0.6 by 0.2 mm
Subulate (near spathellae),
narrowly triangular or slightly
1– 2-lobed, 1–1.25 by
0.28 – 0.4 mm
Leaves
1-dichotomous
4 – 5 × dichotomous
Ovary-fruit
Lacking wings; 8-ribbed
With 2 conspicuous triangular apical wings;
6-ribbed
Main axes
Lacking scale-leaves
Scale-leaves present,
regularly placed, c. 5 – 10 %
cover entire to shallowly trifid
151
Etymology. Named for the late Maurice Elad, tree-spotter and botanical
collector, collector of the type and only known specimen of Inversodicraea
eladii, known to the first author since 1992.
Rheophytic herb, probably annual, root not recorded; stems
erect, free-standing, highly branched, 6–10 cm tall, terete, 1–1.9
mm diam at base, each stem arising from rock with 30–50
ultimate branches. Scaleleaves on main stem and branches
(below the distal 3–6 mm) wrinkled, naked apart from c. 5 %
cover of narrowly to equilaterally triangular (rarely slightly
lobed), partly spreading scale-leaves 0.25 – 0.5 by 0.2 – 0.4
mm. Distal 3 – 6 mm ± completely covered in scale-leaves,
scale-leaves narrowly triangular, 1–1.25 by 0.28 – 0.4 mm,
apex acute, margin entire, at about 10 % of scale-leaves with a
deep lateral division or bifurcation, sometimes with two shallow,
unequal lateral triangular divisions each 0.02–0.15 mm long,
which one greatly smaller than the central lobe, these 2-lobed
scale-leaves most common in the interstitial zone between the
densely covered distil 3–6 mm of the branches, and the 5 %
sparsely covered lower branches and main stems. Leaves
1.6 – 5 cm long, arising laterally, 4 – 5-times dichotomously
branched, rarely a single, scale-leaf-like lobe near bases of
younger leaves, triangular, 0.25–0.1 mm, placed on the petiole margin up to 0.7 mm from the base; petiole 0.9–3.2 cm
long dorsiventrally flattened, 0.4–1.5 mm wide (widest in the
older leaves produced on the main axis); blade ribbon-like
(dorsiventrally flattened), 0.5–0.8 mm wide, tapering gradually
to the acute apices. Spathellae inserted at stem dichotomies,
single, obovoid-cylindric 2.5–3.2 by 1 mm, apex rounded, base
concealed among scale-leaves, cylindric; opening irregularly
into 3–5-deep, integral lobes. Pedicel 8.5–9(–10) mm long.
Tepals 2, linear, 0.75–0.8(–1.1) mm long, inserted at new base
of androecium. Androecium exceeding gynoecium, c. 5 mm
long, anthers 2; united filaments 1–2 mm long, free filaments
diverging by c. 20–45°, 2–3 mm long. Anthers subtriangular,
1–1.25 by 0.3 mm. Pollen in dyads, long axis 0.05 mm long.
Gynophore 0.3 – 0.5 mm long, dilating gradually to base of
ovary. Ovary unilocular, narrowly cylindrical-ellipsoid 2.5–2.7
by 0.6–0.75 mm. Styles 2, erect, narrowly subulate, 0.75–1.1
by 0.05 mm wide at base, sometimes united in the proximal
0.2 mm. Longitudinal ribs 8, subequal in spacing and development, the two submedial ribs on each side united by a triangular
or rounded membranous protrusion, making the ovary apex
2-winged; commissural ribs each with a sutural groove. Fruit
dehiscing by two valves, not caducous. Seeds not recorded.
Distribution — Cameroon, South Region, Lobé river at Lobé
Falls.
Habitat & Ecology — Rheophyte on rocks in waterfall near
the sea, in evergreen forest zone; 5 m altitude.
Conservation — Inversodicraea eladii is known from a single
location, the Lobé Falls, at which we assess its AOO (and so
its EOO) as 1 km 2 using the IUCN-preferred cells of that size.
Here, as is the case for I. bosii, similarly restricted to this location, it is threatened by trampling from the many tourists that
visit what in Cameroon is a major tourist attraction (Cheek in
Onana & Cheek 2011, Ghogue 2011). Therefore the species
is here assessed as Critically Endangered, CR B2 ab(iii).
Notes — Ovary wings are rare in the genus. Otherwise they
are only known in I. ebo, I. congolana, and I. warmingiana, the
last with a triangular wing from the apex of all six longitudinal
ribs. Only in I. eladii and I. ebo of Cameroon do the wings appear to connect more than one rib on each valve of the ovary.
Distal (and also lateral) ovary wings are highly developed in
the genus Winklerella Engl. In fact this appears to be the only
character supporting recognition of that genus, leading us to
question whether this distinction is merited or not.
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h
d
e
g
b
i
a
c
f
Fig. 7 Inversodicraea eladii Cheek. a. Habit, showing stem basal branching, note origin of leaves from pseudo-dichotomies; b. detail from a (point marked *)
pseudo-dichotomous node; c. detail of scale-leaves from base and central parts of stems shown in a; d. stem apex with leaves and flowers; e. scale-leaves
from d, note the subulate scale-leaves subtending the spathellum at left; f. flower; g. gynoecium and tepals; h. ovary apex with stigmas; i. transverse section
of ovary (all from Elad et al. 1485, K). — Scale bars: a = 1 cm; b, d = 5 mm; c, e, g–i = 1 mm; f = 2 mm. — Drawn by Andrew Brown.
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M. Cheek et al.: A synoptic revision of Inversodicraea
Near the base of three young leaves, a single lobe, similar to a
scale-leaf, was noted. Initially, these were taken to be stipular
lobes, but since each leaf has only one such lobe and not a
pair, and since they are not present on most leaves, this has
been ruled out.
Hybridisation — The type collection Elad 1485A was mixed
(Kew sheet) with an equal amount of sterile I. ledermannii (Elad
1485) which superficially looked very similar, but which was
identified by its scale-leaves being broadest in the distal half,
and equally, and deeply acutely trilobed. That I. eladii was in
flower while the I. ledermannii had not yet developed spathellae suggests that the first flowers in advance of the second,
which suggests reproductive separation of the two species.
Nevertheless, specimens from this same locality (Elad 1482,
1484) appear to be intermediate between these two species in
leaflet shape, the scale-leaves being long and slender, as in I.
eladii, but with c. 50 % divided at the apex into three subequal,
but not spreading, lobes. These plants may represent hybrids
between the two species.
30. Inversodicraea liberia Cheek, sp. nov. — Fig. 8
Differs from Inversodicraea pepehabai in the scale-leaves being arranged
in c. 3 ranks (not 5), the basal half of the scale-leaves being appressed and
sheathing the stem (not patent, with the leaflet flat), the fruit 1–1.2 mm long
(not 3–4 mm long). — Type: Robert M. Warner 87A (holotype K), Liberia,
on rocks in water, 1942–43.
Etymology. Named (noun in apposition) for the country of Liberia.
Probably annual rheophytic herb, root not recorded, 1.5 cm
tall. Stems erect, 2–4-branched, terete, 0.5 mm diam at base,
main stem 40–50 % covered by scale-leaves arranged in c. 3
ranks, stem apex more densely covered (Fig. 8). Scaleleaves
0.75(–1.5) by (0.25–)0.4–0.6 mm with proximal half appressed
and sheathing the stem, the lateral margins folded towards the
stem; distal portion dilating, the apex broadly rounded, sometimes with a lateral triangular lobe c. 0.1 by 0.1 mm. Leaves
c. 4 mm long, lateral insertion, once dichotomous, petiole 3 mm
long, dorsiventrally flattened, 0.2–0.3 mm wide at base, blade
ribbon-like, c. 0.1 mm wide, 0.6 mm long, apices rounded.
Spathellum in bud, unrecorded, at dehiscence subglobose,
0.75 by 0.6 mm. Pedicel 2.5–3(–3.7) mm long. Tepals and
androecium unrecorded. Gynophore 0.25 mm long. Ovary and
styles unrecorded. Fruit ellipsoid, brown, 1–1.1 by 0.5 – 0.6
mm, apex rounded, base gradually decurrent into gynophore,
decorticating to expose 6 vascular strands; longitudinal ribs
6, equal, the commissural ribs only weakly developed with a
central longitudinal groove (suture); dehiscing into two equal
non-caducous valves, dehiscence extending into gynophore.
Seeds 1.1 by 0.75 mm.
Distribution — Only known from the type specimen in Liberia.
Habitat & Ecology — Unknown, but probably waterfalls in
the lowland rainforest zone.
Conservation — Since the location for I. liberia, and therefore threats, are unknown, we assess the species here as NT,
indicating that since it is known from a single location, probably
with only a few hundred plants, it is vulnerable to loss from
hydroelectric projects and other habitat modification events
such as silt input into rivers from run-off due to logging and/or
from artisanal mining.
Notes — Warner 87 (K) is a mixture of two species, determined by Cusset in 1974 as Macropodiella garrettii (C.H.Wright)
C.Cusset (here designated as Warner 87) and Ledermanniella
cf. gabonensis C.Cusset (here designated as Warner 87A). It
is 87A, L. cf. gabonensis, that is here described as I. liberia.
Inversodicraea gabonensis and I. liberia are two geographically distant yet both share a similar habit, and membranous
g
d
a
c
e
f
b
Fig. 8 Inversodicraea liberia Cheek. a. Habit, fruiting plant; b. detail of stem below spathellum, * indicates young scale-leaves; c. post-anthetic flower showing
remains of 2 anthers and spathellum; d. fruit, dehiscence incipient, note absence of commissural ribs; e. dehiscing fruit with seeds; f. transverse section of
fruit; g. seed (all from R.M. Warner 87A, K). — Scale bars: a = 2 mm; b–g = 1 mm. — Drawn by Andrew Brown.
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Table 4 Characters separating Inversodicraea liberia and Inversodicraea
pepehabai.
I. liberia
I. pepehabai
No. leaflet files per stem
c. 3
c. 5
Leaflet posture
(below stem apex)
Proximal half appressed, Patent or spreading
sheathing stem, distal
from base (never appart spreading
pressed or sheathing
in basal part)
Leaflet apex broadly
rounded?
Apex broadly rounded
in > 50 % of leaves,
rarely acute or obtuse
Apex obtuse or acute,
never rounded
Leaf branching
1 × dichotomous
3 – 4 × dichotomous
Fruit-ovary length
(undehisced)
1–1.2 mm
3 – 4 mm
scale-leaves. However, I. gabonensis has scale-leaves tapering
at the apex and which are appressed to the stem, covering it
completely in the distal half, while in I. liberia the scale-leaves
cover only 40–50 % of the stem and the distal part of the scaleleaves are often spreading, > 50 % having a broadly rounded
apex. Moreover, in I. liberia the fruits are only c. 1 mm long vs
c. 2 mm in I. gabonensis.
Inversodicraea liberia is possibly more closely related to I. pepe
habai of neighbouring Guinea than to I. gabonensis since they
are geographically close. Both species share more or less
spreading or patent scale-leaves, which occurs nowhere else
in those Inversodicraea species with membranous scale-leaves
which lack regular margin ornamentation or lobes. The two species can be distinguished using the characters shown in Table 4.
Although Warner 87 was seen by Cusset in 1974, she did not
refer to it in her revision of Ledermanniella subg. Phyllosoma
(Cusset 1983).
Warner 87 (with 87A), comprising the two species of Podo
stemaceae referred to, appears to be the first and so far only
record of any member of that family from Liberia (apart from
Tristicha trifaria, mentioned in Taylor 1954). Undoubtedly many
more species of Podostemaceae, including those new to science, await discovery in Liberia since neighbouring countries
east and west each have several endemic species of the family.
The absence of any previous published record to Warner 87 is
probably partly due to the incomplete nature of both species that
it contains. Regarding I. liberia, the material is both meagre, and
lacks flowers. The localisation is also poor since only ‘Liberia’
is given as the source. Better and more complete material
which would allow a full description of the species, would be
welcomed. The species was described to encourage interest
in this distinct species and to guard against the possibility that
it might not be found again.
EXCLUDED SPECIES
The following names published as Inversodicraea are excluded
from that genus:
Africa
Inversodicraea aloides Engl. = Ledermanniella aloides (Engl.)
C.Cusset
I. batangensis (Engl.) Engl. = Ledermanniella batangensis
(Engl.) C.Cusset
I. bifurcata Engl. = Ledermanniella bifurcata (Engl.) C.Cusset
I. bowlingii J.B.Hall = Ledermanniella bowlingii (J.B.Hall)
C.Cusset
I. garrettii C.H.Wright = Macropodiella garrettii (C.H.Wright)
C.Cusset
I. keayi G.Taylor = Ledermanniella keayi (G.Taylor) C.Cusset
I. laciniata Engl. = Saxicolella laciniata (Engl.) C.Cusset
I. letestui Pellegr. = Ledermanniella letestui (Pellegr.) C.Cusset
I. macrothyrsa G.Taylor = Macropodiella macrothyrsa
(G.Taylor) C.Cusset
I. minima Engl. = Ledermanniella bifurcata (Engl.) C.Cusset
I. monanthera H.Hess = Sphaerothylax abyssinica (Wedd.)
Warm.
I. musciformis G.Taylor = Ledermanniella musciformis
(G.Taylor) C.Cusset
I. pellucida Engl. = Macropodiella pellucida (Engl.) C.Cusset
I. pusilla (Warm.) Engl. = Ledermanniella pusilla (Warm.)
C.Cusset
I. schlechteri (Engl.) Engl. = Ledermanniella schlechteri (Engl.)
C.Cusset
I. tenuifolia Engl. = Ledermanniella tenuifolia (Engl.) C.Cusset
I. tenuissima Hauman = Ledermanniella schlechteri (Engl.)
C.Cusset
I. thalloidea Engl. = Ledermanniella thalloidea (Engl.) C.Cusset
I. variabilis G.Taylor = Ledermanniella variabilis (G.Taylor)
C.Cusset
I. zenkeri Engl. = Ledermanniella bifurcata (Engl.) C.Cusset
Madagascar
Inversodicraea bemarivensis (Tul.) H.Perrier = Endocaulos
mangorense (H.Perrier) C.Cusset
I. imbricata (Tul.) H.Perrier = Paleodicraeia imbricata (Tul.)
C.Cusset
I. isalensis (H.Perrier) H.Perrier = Thelethylax isalensis
(H.Perrier) C.Cusset
I. manorensis (H.Perrier) H.Perrier = Endocaulos mangorense
(H.Perrier) C.Cusset
I. minutiflora (Tul.) H.Perrier = Thelethylax minutiflora (Tul.)
C.Cusset
I. rubra (H.Perrier) H.Perrier = Sphaerothylax abyssinica
(Wedd.) Warm.
Acknowledgements Fieldwork leading to the discovery of the new species
reported in this paper was supported by Environmental Impact Assessment
studies for the Tonkolili Iron Ore project (I. feika) and the Memv’ele Dam
(I. tchoutoi, in part). The discovery of I. ebo and I. xanderi were due to surveys funded by the Bentham-Moxon Trust of RBG, Kew, while I. eladii and
I. tchoutoi (in part) were found during doctoral studies by Dr Tchouto at the
University of Wageningen, funded by the Dutch government. Inversodicraea
liberia was discovered as a result of herbarium studies.
Professor Basile Camara and Dr Seydou Magassouba, respectively former
and current Director General, Université de Gamal Abdel Nasser-Herbier
National de Guinée, and Dr Jean Michel Onana and Dr Marie Florence Ngo
Ngwe, respectively former and current Head of IRAD-National Herbarium of
Cameroon, are thanked for arranging permits for the fieldwork that enabled
the collection of some of the data presented in this paper, including some
of the new species to science. They are also thanked for their support and
collaboration. Drs Bethan Morgan and Ekwoge of the Ebo Forest project
gave logistic support to the survey that discovered I. ebo. Janis Shillito is
thanked for typing the manuscript. George Gosline assisted with access to
electronic specimen data and made valuable comments on an early version
of this paper. This paper was partly completed under the project Important
Plant Areas in the Republic of Guinea supported by the Darwin Initiative of
the Department of the Environment Food and Rural Affairs (DEFRA), UK
government (project Ref. 23-002). Two anonymous reviewers are thanked
for their constructive comments.
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