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Leiothylax quangensis GHO1667. Vegetative and reproductive structures. a Crosssection of flower bud inside spathella (Fc). Fp pedicel, P free placenta in unilocular ovary, anthers not present at this level. Scale bar 300 lm. b Dehiscence area (asterisk) of nearly mature unilocular capsule with ovule (crosssection ). Inner epidermis (E) cells as transversal fibres, hypodermal (H) cells as longitudinal fibres. Scale bar 100 lm. c Young globular ovary (longitudinal section), hanging upside down inside spathella (Fc). Note placenta (P). Other abbreviations as above. Scale bar 200 lm. d Cross-section of stem (X) with leaf (L) and adjacent flower bud in spathella (Fc, cut longitudinally). Note single stamen (A) above and strongly inclined ovary (G) below. Scale bar 200 lm. e, f Two consecutive cross-sections of stem (X) at and below leaf insertion, respectively. Note insertion of short vegetative shoot (SVS) in non-axillary position on the right flank and slightly below insertion of leaf (L). Scale bar 500 lm. g Same stem as above. Cross-section below leaf insertion. Note broadened shape with discrete strands of rudimentary vascular tissue (arrowheads). Scale bar 500 lm
Source publication
The Podostemaceae are highly enigmatic plants which are restricted to submerged river-rock habitats. The availability of new
material of nine taxa from continental Africa prompted this new study. Five species belonging to the genera Dicraeanthus, Leiothylax, Letestuella, Macropodiella, and Stonesia and another four species of the large genera Inver...
Citations
... In addition, both L. linearifolia and L. pusilla belong to the same subclade within the Ledermanniella-Dyad group (see molecular data and illustrations in Moline et al. 2007: fig. 6A-G;Thiv et al. 2009;Koi et al. 2012). While in L. pusilla, most leaves bear stipules, some are also lacking such features, sometimes on single shoots. ...
Background and aims – Podostemaceae is a family of strictly aquatic plants found in rapids and waterfalls. Despite a recent treatment in the Flore du Gabon, the family remained poorly known, with no major studies including Gabonese collections, and almost no targeted inventories since 1966. We present the first large-scale inventory of this family in Gabon, targeting Podostemaceae throughout the country, providing new additions to the flora of Gabon and many new records of poorly known species.
Material and methods – Fieldwork was conducted in Gabon between 2017 and 2021. The collected specimens were primarily preserved in ethanol with associated silica gel-preserved material and photographs. Material available at BR, BRLU, LBV, MO, P, WAG, and Z/ZT was examined. For each species, information on distribution and ecology is presented, as well as a distribution map in Gabon.
Key results – The 500 newly collected specimens represent 91.4% of all known collections of Podostemaceae from Gabon. Three taxa are newly recorded for the country, including one genus (Inversodicraea tenax, Ledermanniella schlechteri, and Saxicolella nana). New distribution records are also presented for 13 little-known species. Four taxa are excluded from the Gabonese flora (the genus Dicraeanthus, Inversodicraea ledermannii, Ledermanniella sanagaensis, and Macropodiella garrettii). To date, 20 species belonging to five different genera are known to occur in Gabon. A new combination is proposed for Ledermanniella nicolasii, and Inversodicraea tanzaniensis is now considered as a synonym of Inversodicraea tenax.
... The current taxonomic framework for African Podostemaceae was set in place by the revisions and Flora accounts of Cusset (Cusset 1973(Cusset , 1974(Cusset , 1978(Cusset , 1983(Cusset , 1984(Cusset , 1987(Cusset , 1997. Only recently has accumulating molecular phylogenetic data begun to influence the classification (Moline et al. 2007;Thiv et al. 2009;Schenk et al. 2015). Cusset's work has been compiled and updated by Rutishauser et al. (2004) who recognise c. 85 species in 16 genera. ...
... While species of several other genera of African Podostemaceae have been investigated in detail for their morphology and anatomy in such studies as Moline et al. (2007) and Thiv et al. (2009), this has not been the case for any of the species of the genus Saxicolella Engl. as delimited here (the Ghanaian species previously referred to as Saxicolella have been transferred to Pohliella, see Cheek 2020). ...
Species of the genus Saxicolella Engl. (Podostemaceae) are African rheophytes, restricted to rapids and waterfalls as are all members of the family. Previously, Saxicolella sensu lato was shown to be polyphyletic with two separate clades. The name Pohliella Engl. was recently resurrected for one clade that is sister to the American genera Ceratolacis (Tul.) Wedd., Podostemum Michx. and all Old World Podostemoideae. Pohliella has distichous phyllotaxy, bilocular ovaries, filiform roots with paired holdfasts, and rootcaps. The second clade, Saxicolella sensu stricto , including the type of the generic name, has spiral phyllotaxy, unilocular ovaries, ribbon-like or crustose roots that lack both holdfasts and rootcaps. Saxicolella sensu stricto , sampled from the type species, S. nana Engl. of Cameroon, is embedded within and near the base of the major clade of African podostemoids and is sister to all other African genera apart from Inversodicraea R.E.Fr. and Monandriella Engl. Recently reduced to three species in Cameroon and SE Nigeria by the resurrection of Pohliella, Saxicolella sensu stricto is expanded to eight species in this monograph by description of five new taxa. Saxicolella futa Cheek and S. deniseae Cheek are newly described from Guinea, S. ijim Cheek from Cameroon, the informally named S. sp. A from Gabon, and S. angola Cheek from Angola. The known geographic range of the genus is thus expanded c. 2,500 km westwards to Guinea from eastern Nigeria and c.1,500 km southeastwards from near Yaoundé to Cuanza do Sul, Angola. The greatest concentration of species occurs in the Cross-Sanaga interval of western Cameroon and eastern Nigeria, with three species. Cameroon (3 species) followed by Nigeria and Guinea (2 species each) are the countries with highest species diversity. A classification is proposed grouping the species into three subgenera ( Saxicolella, Butumia (G.Taylor) Cheek comb. et stat. nov. and Kinkonia Cheek subgen. nov.) based on root morphology and shoot position and morphology. The discovery, morphology, circumscription, distribution and ecology of Saxicolella is reviewed, an identification key to the species is presented, together with descriptions, synonymy and links to illustrations. All of the species are provisionally assessed as either Endangered or Critically Endangered using the IUCN 2012 Red List Criteria. The major threats, above all, are hydro-electric projects. Saxicolella deniseae may already be globally extinct, and two of the four known locations of S. angola appear lost, S. sp. A of Gabon is threatened at at least one of its three locations, while S. futa is threatened at all three locations. Contamination of watercourses by increased turbidity from silt-load due to anthropic changes and by eutrophication from pollution are also threats for the majority of the species.
... The current taxonomic framework for African Podostemaceae was set in place by the revisions and Flora accounts of Cusset (Cusset 1973(Cusset , 1974(Cusset , 1978(Cusset , 1983(Cusset , 1984(Cusset , 1987(Cusset and 1997. Only recently has accumulating molecular phylogenetic data begun to influence the classification (Moline et al. 2007, Thiv et al. 2009, Schenk et al. 2015 Cusset's work has been compiled and updated by Rutishauser et al. (2004) who recognise c. 85 species in 16 genera. ...
Saxicolella Engl., an African genus of the waterfall specialist plant family Podostemaceae, was shown to be polyphyletic as currently delimited. One clade, sampled from species in Ghana, is sister to American Ceratolacis (Tul.) Wedd., Podostemum Michx. and all Old World Podostemoideae (podostemoids). The second clade, sampled from Cameroonian material, was embedded within the major clade of African podostemoids. In this paper the generic nomenclature applied to Saxicolella sensu lato (Saxicolella, Pohliella Engl., Aulea Lebrun & Stork nom. inval.), is reviewed and the morphological support for the two clades and their correct generic names is determined. Pohliella is shown to be the correct name for the first clade (based on Pohliella laciniata Engl., Cameroon) and a synoptic treatment of its three published species is given, one of which is extinct, and two are threatened. However, a fourth, unpublished species exists. The new combinations Pohliella submersa (J.B.Hall) Cheek and Pohliella amicorum (J.B. Hall) Cheek are made for the two published Ghanaian species. The recently described New World genus Cipoia C.T. Philbrick, Novelo & Irgang is revealed as being morphologically identical to Pohliella, but in view of the geographical disjunction, confirmation from molecular evidence is awaited before its two species are also transferred to Pohliella. The correct name for the second clade, embedded in African podostemoids, is Saxicolella (sensu stricto), now with two known species, Saxicolella nana Engl. (type of Saxicolella, Cameroon) and Saxicolella flabellata (G.Taylor) C. Cusset (Nigeria).
... has been resurrected to accommodate those species previously included in Ledermanniella subg. Phyllosoma C.Cusset (Thiv et al. 2009, Schenk et al. 2015, Cheek & Haba 2016a. This paper builds on the recent synoptic account of the genus which recognised 30 species (Cheek et al. 2017a). ...
... 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 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 the mitochondrial marker matR in sampling 10 genera and 27 species of African Podostemaceae). ...
... Podostemaceae has been only c. 30 % complete at species level (Schenk et al. 2015). Thiv et al. (2009) andSchenk 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. ...
Two new species of Inversodicraea, I. koukoutamba and I. tassing , both from the Republic of Guinea, are described as new to science, increasing the number of species known in this African genus to 32, making it the most species-diverse among African Podostemaceae . Both species are remarkable, among other features, for their styles. Inversodicraea koukoutamba is only the third species of the genus with 3, not 2 styles, and is unique in the genus, and in the family, in having each style bifurcate. Inversodicraea tassing has styles equal or exceeding the length of the ovary, being nearly twice as long as those of the species which previously was noted for the longest styles in the genus. Both new species are single-site endemics, the first is assessed here as Critically Endangered according to the IUCN 2012 standard, due to the incipient construction of the World Bank backed Koukoutamba hydroelectric dam which threatens several other plant species assessed as Critically Endangered or Endangered. The second species, I. tassing, is assessed as Near Threatened, since there are currently no threats known at present to the single known site.
... ex R.E.Fr. lacks a septum and has a free central placenta (Thiv et al., 2009). However, the gynoecium has two free stigmatic tips and the early opening is not circular. ...
Carpels and ovules have been differently interpreted over the past two centuries. In this review, some of these interpretations are highlighted, with particular emphasis on the current situation. Ovules are part of and are enclosed in carpels in all living angiosperms. Living angiosperms are monophyletic, and the evolutionary association between ovules and the leaf-like part, the carpel wall, had taken place at or before the time the clade of extant angiosperms was established. From what we know at present, there are no â € cauline' ovules in extant angiosperms. Developmentally, carpel walls and ovules are not always synchronous across all extant angiosperms. In early development ovules may be relatively precocious or relatively late compared with carpel walls. They are late in early-diverging angiosperms (ANITA grade, magnoliids, some early-diverging eudicots) but precocious in some more derived groups (e.g. some Caryophyllales and Primulaceae). Carpel primordia have a certain depth in the floral apex, and the entire activated area of a carpel primordium may be several cell layers thick. Thus, the carpel is â € embedded' or â € rooted' within the remaining floral apex. The parts of a carpel develop at different times in carpel ontogeny and probably evolved at different times on the line leading to the angiosperms, which needs to be considered in interpretations. Carpel development depends on a complex genetic network, which increased stepwise over evolutionary time and contains hundreds of genes revealed in molecular developmental biology. The evolutionary history of such networks in carpel walls and ovules is unlikely to be easily disentangled, as most of these genes are not transcription factors.
... 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 recognised in Africa. This was revealed by 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. ...
... In recent years the accumulated molecular phylogenetic data (Thiv et al. 2009;Schenck et al. 2015) has shown that Ledermanniella subg. Phyllosma C. Cusset (1984) merits elevation to genus level as the resurrected genus Inversodicraea Engl. ...
... better indicator of evolutionary relationships of species than floral characters hitherto exclusively used in defining the genera of African Podostemaceae (Cusset 1973(Cusset , 1974(Cusset , 1978(Cusset , 1983(Cusset , 1984(Cusset , 1987. Genera such as Macropodiella may be artificial as currently defined (Cheek & Ameka 2016) as is Ledermanniella (Thiv. et al. 2009). ...
Ledermanniella yiben Cheek is described from the Seli (Rokel) river bed at a single rapid to be flooded by the proposed Yiben hydroelectric dam and reservoir in Sierra Leone. It is assessed as Critically Endangered using the IUCN categories and criteria. The species appears to be unique among African Podostemaceae in bearing dimorphic shoots having either cupuliform or short ribbon-like leaves.
... 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 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). ...
... 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. ...
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 Macropodiella.
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.
... The scale-like leaves outnumber the compound leaves considerably. Only the compound leaves show helical or distichous phyllotaxis whereas the additional feuillettes are scattered irregularly (see [34] and literature cited therein). Other examples of angiosperms with two waves of leaf initiation along the same shoot axis are found in Gunnera tinctoria and allies (Gunneraceae within eudicots), and Hydrothrix gardneri (Pontederiaceae within monocots) [13]. ...
Phyllotaxis, i.e., the arrangement of leaves around the stem and leaf-like organs inside flowers is regular in most vascular plants. Thus, developmental models usually explain regular phyllotactic patterns such as Fibonacci spirals and decussate/whorled patterns that obey Hofmeister’s rule: primordia form as far away as possible from previously initiated primordia. However, flowering plants showing at first Fibonacci spirals or whorled phyllotaxes may switch to other patterns that lack an obvious order and thus may be called irregular or even chaotic. Vegetative shoot tips of various Australian wattles ( Acacia spp., Leguminosae in eudicots) and flower buds of ylang-ylang ( Cananga odorata ) and other Annonaceae (basal angiosperms) provide examples of irregular patterning. This pictorial report provides food for thought for scientists interested in phyllotaxis patterns beyond the usual spiral and whorled patterns. Emphasis is given on irregular phyllotaxes that occur in wild-type plants, mainly correlated with geometrical parameters such as leaf and stamen primordia that are very small as compared to the size of their apical meristems. They call for additional explanatory models, combining auxin-driven development with geometrical constraints and biophysical processes.
... This work has been compiled and updated by Rutishauser (2004). 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 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). ...
... 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. Phyllosma C. Cusset forms a well-supported clade of species that are sister to the rest of all other African Podostemaceae sampled, mainly comprising Ledermanniella subg. ...
... Ledermanniella and, embedded within it, seven smaller genera: Macropodiella, Winklerella, Djinga, Dicraeanthus, Leiothylax, Letestuella and Stonesia. Thiv et al. (2009) andSchenk et al. (2015) both advocate resurrecting the generic name Inversodicraea Engl., as the oldest generic name for the species of Ledermanniella subg. Phyllosma and both transfer species formerly included under the last taxon to Inversodicraea. ...
Inversodicraea, shown by previous workers to merit resurrection, is restored here, to include all those species previously included in Ledermanniella subg. Phyllosma. The final seven species remaining in subg. Phyllosma are formally transferred to Inversodicraea as I. mortonii, I. gabonensis, I. boumiensis, I. harrisii, I. paulsitae, I. torrei and I. thollonii. A new species from the submontane forest of Mt Ziama, in Guinea-Conakry is formally described as I. pepehabai. Similar to I. adamesii, it is assessed as Endangered according to the IUCN 2012 standard.
... Oserya Tul. and Wedd. pro parte; Tippery et al., 2011) is close to Marathrum–Vanroyenella (see Ruhfel et al., 2011); (iii) Ledermanniella is polyphyletic, scattered throughout a clade composed of Inversodicraea, Monandriella, Saxicolella, Dicraeanthus, Djinga, Stonesia, Letestuella , Macropodiella, Winklerella, and Leiothylax, corroborating the results of Thiv et al. (2009) and Schenk et al. (2015) regarding the treatment of Ledermanniella; (iv) the placement of Podostemum is not resolved; (v) Torrenticola queenslandica Cook & Rutish), but Zeylanidium is still not monophyletic here (see Ruhfel et al., 2011; Koi et al., 2012). Zeylanidium subulatum (Gardner) C. Cusset is sister to (Farmeria þ Griffithella) þ Polypleurum (BS ¼ 97%), whereas the rest of the genus is sister to Willisia (BS ¼ 76%). ...
Rosidae, a clade of ∼ 90 000 species of angiosperms, exhibits remarkable morphological diversity and extraordinary heterogeneity in habitats and life forms. Resolving phylogenetic relationships within Rosidae has been difficult, in large part due to nested radiations and the enormous size of the clade. Current estimates of phylogeny contain areas of poor resolution and/or support, and there have been few attempts to synthesize the available data into a comprehensive view of Rosidae phylogeny. We aim to improve understanding of the phylogeny of Rosidae with a dense sampling scheme using both newly generated sequences and data from GenBank of the chloroplast rbcL, atpB, and matK genes and the mitochondrial matR gene. We combined sequences from 9300 species, representing 2775 genera, 138 families, and 17 orders into a supermatrix. Although 59.26% of the cells in the supermatrix have no data, our results generally agree with previous estimates of Rosidae phylogeny and provide greater resolution and support in several areas of the topology. Several noteworthy phylogenetic relationships are recovered, including some novel relationships. Two families (Euphorbiaceae and Salvadoraceae) and 467 genera are recovered as non-monophyletic in our sampling, suggesting the need for future systematic studies of these groups. Our study demonstrates the value of a botanically informed bioinformatics approach and dense taxonomic sampling for resolving rosid relationships. The resulting tree provides a starting point for large-scale analyses of the evolutionary patterns within Rosidae.
