Systematic Botany (2007), 32(1): pp. 16–25
# Copyright 2007 by the American Society of Plant Taxonomists
Molecular Phylogenetic Relationships and Morphological Evolution in the
Heterosporous Fern Genus Marsilea
NATHALIE S. NAGALINGUM,1,3 HARALD SCHNEIDER,2 and KATHLEEN M. PRYER1
1
2
Department of Biology, Duke University, Durham, North Carolina 27708, USA
Albrecht-von-Haller Institut für Pflanzenwissenschaften, Abteilung Systematische Botanik,
Georg-August-Universität, Untere Karspüle 2, 37073 Göttingen, Germany
3
Author for correspondence (n.nagalingum@duke.edu)
Communicating Editor: Sara B. Hoot
ABSTRACT. Using six plastid regions, we present a phylogeny for 26 species of the heterosporous fern genus
Marsilea. Two well-supported groups within Marsilea are identified. Group I includes two subgroups, and is
relatively species-poor. Species assignable to this group have glabrous leaves (although land leaves may have a few
hairs), sporocarps lacking both a raphe and teeth, and share a preference for submerged conditions (i.e., they are
intolerant of desiccation). Group II is relatively diverse, and its members have leaves that are pubescent, sporocarps
that bear a raphe and from zero to two teeth, and the plants are often emergent at the edges of lakes and ponds.
Within Group II, five subgroups receive robust support: three are predominantly African, one is New World, and
one Old World. Phylogenetic assessment of morphological evolution suggests that the presence of an inferior
sporocarp tooth and the place of sporocarp maturation are homoplastic characters, and are therefore of unreliable
taxonomic use at an infrageneric level. In contrast, the presence of a raphe and superior sporocarp tooth are reliable
synapomorphies for classification within Marsilea.
KEYWORDS:
spacer.
ancestral state reconstruction, Marsilea, Marsileaceae, phylogeny, Salviniales, trnG-trnR intergenic
tralia (Jones 1998), India (Gupta and Bhardwaja
1956, 1957, 1958; Gupta 1962), and the New World
(Johnson 1986; Pérez-Garcı́a et al. 1999).
In addition to describing more than 50 species,
Braun (1871) established 13 species groups, each
circumscribed by vegetative and reproductive
morphological similarity. An alternative infrageneric classification of Marsilea was later proposed
by Gupta (1962), based entirely on similarities in
sporocarp arrangement. More recently, Johnson
(1986) established three new sections within
Marsilea using characters such as sporocarp teeth,
sporocarp attachment to the stalk, leaf venation,
and the position of roots along the rhizome.
Including relatively fewer taxa, Johnson (1986)
evaluated Braun’s (1871) species groups: the taxon
list for one group was emended, four groups were
merged into two, and the modified groups were
formally renamed as three sections (Nodorhizae,
Marsilea, and Clemys).
Marsilea has a cosmopolitan distribution, but is
sparsely distributed in cool-temperate regions and
oceanic islands (Launert 1968; Kubitzki 1990).
Species diversity is greatest in Africa. It grows in
seasonally wet habitats where the plants are
emergent or submerged (except for the floating
leaflets), and usually in shallow water at the edges
of ponds, lakes or rivers (Launert 1968, 2003;
Johnson 1986; Kornas 1988). With its fast-growing
rhizomes, Marsilea is highly suited to colonizing
amphibious habitats (Johnson 1986). Marsilea
leaves are distinct from all other ferns, comprising
a petiole terminated by four leaflets (two pairs of
The taxonomy of several aquatic plant groups
has long confounded systematists due to the
paucity and plasticity of morphological characters
available for taxonomic use. Molecular data,
however, have provided a clearer picture of the
phylogenetic history for these aquatic groups such
as Isoëtes (Hoot and Taylor 2001; Rydin and
Wikström 2002), Lemnaceae (Les et al. 1997,
2002), and Nymphaeaceae (Les et al. 1999). Understanding relationships within the heterosporous fern genus Marsilea L. has also been highly
problematic due to rampant morphological plasticity (Gupta 1962; Launert 1968; Johnson 1986) and
phylogenetic relationships within the genus are
generally unknown. A genus-level phylogeny for
the semi-aquatic fern family Marsileaceae indicates
that Marsilea is monophyletic and sister to a clade
comprising Regnellidium Lindm. and Pilularia L.
(Pryer 1999). Of the Marsileaceae, Marsilea is the
most species-rich (,45 spp.), whereas Pilularia
comprises five species and Regnellidium is monotypic (Tryon and Tryon 1982; Johnson 1986;
Kubitzki 1990).
The last comprehensive systematic treatments of
Marsilea are more than 125 years old, in which
Braun (1871, 1873) described 53 species. Subsequent contributions on the genus include worldwide synopses of taxa (Baker 1887; Reed 1954) and
an updated taxonomy and compilation of Braun’s
papers (Sadebeck 1902). More recent treatments of
Marsilea are primarily regional in focus, examining
species from Africa (Launert 1968, 1970, 1971,
1983–1984, 2003; Burrows 1990; Cook 2004), Aus16
2007]
17
NAGALINGUM ET AL.: PHYLOGENY OF MARSILEA
TABLE 1. Summary of DNA sequence data (in bp) and tree statistics for each molecular region sequenced and for the
combined analysis of Marsilea taxa only. Note that missing data values for the individual molecular regions were calculated for
missing nucleotides only, but for the combined analysis, this value incorporates entire regions that were absent for some taxa.
atpB
Alignment length
Included characters
Parsimony variable characters
Parsimony informative characters
Consistency index
Retention index
Tree length (# steps)
No. of trees (MP)
% missing data
-lnL
rbcL
rps4
trnLF
trnGR
rps4-trnS
spacer
Combined
analysis
1221
1309
603
950
934
460
5477
1152
1233
589
942
908
444
5238
48
69
34
74
69
73
367
35
58
21
44
45
58
260
0.960
0.816
1
0.920
0.862
0.900
0.876
0.978
0.902
1
0.932
0.919
0.947
0.924
50
87
35
87
87
90
445
2
56
1
1
59
164
25
0.206
0.003
0.111
0.354
0.267
0.711
8.798
2524.30107 2867.73274 1409.73953 1887.17784 1824.27460 1148.94575 10418.27972
pinnae) in a cruciform arrangement. Leaflets are
typically cuneate to flabellate, and glabrous to
pubescent (Gupta 1962; Launert 1968; Johnson
1986). The leaf morphology of Marsilea varies
according to environmental conditions; in submerged plants, the leaflet margins are entire to
crenulate, whereas in emergent plants, the leaflets
are crenate to lobed (Launert 1968; Johnson 1986;
Kornas 1988). Other leaf characters, such as
indument, stomatal distribution, and leaflet shape,
are generally unreliable for taxonomy due to their
extensive morphological variation within species
(Launert 1968).
The reproductive structures of Marsilea, the
sporocarps, are borne on stalks (also termed
‘‘peduncles,’’ ‘‘stipes,’’ or ‘‘pedicels’’). Marsilea
sporocarps comprise a sclerified wall surrounding
bisporangiate sori (Nagalingum et al. 2006). The
sori enclose two spore types: megaspores that
produce female gametophytes, and microspores
that produce male gametophytes. Sporocarps of
Marsilea are highly resistant to desiccation, and can
‘‘germinate’’ (i.e., the sporocarp wall ruptures, and
the spores are subsequently released) even after
100 years of dormancy (Gupta 1962; Bhardwaja
1980; Johnson 1985); ‘‘germination’’ occurs when
the sporocarp is hydrated. In contrast with the
paucity and plasticity of leaf characters, the
sporocarp provides numerous characters that have
been used for species delimitation, such as number
of sporocarps attached to a petiole, attachment
point of the sporocarp and stalk, number of sori
per sporocarp, and number of mega- and microsporangia per sorus (Tryon and Tryon 1982;
Johnson 1986; Kubitzki 1990). Sporocarp characters
have been considered taxonomically useful because they are generally consistent across varying
environmental conditions; however, the over-reliance on sporocarp characters for plant identifica-
tion is quickly realized when sterile specimens are
encountered.
Here we analyze DNA sequence data from six
plastid regions to present a phylogenetic hypothesis of species relationships within Marsilea, and
we use this phylogeny to investigate the evolution
of taxonomically important morphological characters.
MATERIALS AND METHODS
Taxonomic Sampling. We sampled Marsilea plant material from herbarium specimens (including plants ‘‘germinated’’ from sporocarps that were obtained from accessioned
vouchers), botanical gardens, and field collections (Appendix 1). Representatives were taken from most of the geographic range of Marsilea, with a focus on the highly diverse
African taxa (Appendix 1). Our ingroup consisted of 33 taxa,
representing 26 Marsilea species and incorporating multiple
geographically distant individuals for seven of these (Appendix 1). Three outgroup taxa (Regnellidium diphyllum,
Pilularia americana, and P. globulifera) were selected, based
on an earlier study that established that Regnellidium and
Pilularia are sister to Marsilea (Pryer 1999).
DNA Isolation, Amplification, and Sequencing. General
laboratory protocols were as described in Pryer et al. (2004).
For each taxon, five plastid regions were amplified separately. Some primers used for amplification and sequencing were
published by Taberlet et al. (1991; TRNLC, TRNLD, TRNLE
and TRNFF for trnL-trnF), Hasebe et al. (1994; AF for rbcL),
Nadot et al. (1994; RPS5F for rps4), Wolf (1997; ATPB672F,
ATPB1419F and ATPB1592R for atpB), Pryer et al. (2001;
RBCL1379R for rbcL; 2004; ATPB910R and ATPE384R for
atpB; RBCL645F for rbcL), Smith and Cranfill (2002; TRNSR
for rps4), and Korall et al. (2006; ESRBCL1F, RBCL663R and
RBCL1361R for rbcL; RPS4IF and RPS4IR for rps4). New
primers (developed by E. Schuettpelz) were used to amplify
atpB (ATPB172F: AATGTTACTTGTGAAGTWCAACAAT
and ATPE45R: ATTCCAAACWATTCGATTWGGAG) and
trnG-trnR (TRNG1F: GCGGGTATAGTTTAGTGGTAA,
TRNG43F1: TGATGCGGGTTCGATTCCCG, TRNG63R:
GCGGGAATCGAACCCGCATCA, and TRNR22R: CTATCCATTAGACGATGGACG).
The plastid regions encompass three protein-coding genes:
atpB, rbcL, and rps4, and three non-coding regions: trnL-trnF
(trnLF), trnG-trnR (trnGR), and the rps4-trnS spacer (the latter
18
[Volume 32
SYSTEMATIC BOTANY
region was amplified along with rps4). See Table 1 for the
alignment length and other tree statistics. The data sets were
near complete for most of the plastid regions: sequences for
atpB, rps4, and the rps4-trnS spacer were obtained for 32 out
of the 33 ingroup taxa; rbcL and trnGR were recovered for 31
taxa, and trnLF for 24 taxa (Appendix 1). For the combined
analysis of six plastid regions and 33 Marsilea taxa, 8.798% of
the data matrix cells were scored as missing (Table 1).
Sequence Alignment and Data Sets. Sequence fragments
were assembled and edited using Sequencher 4.2.2 (Gene
Codes Corporation, Michigan, USA). The consensus sequences were aligned manually using MacClade 4.06
(Maddison and Maddison 2003). In the alignments, portions
of the 59 and 39 regions with large amounts of missing data
were excluded. Alignments of the coding sequences did not
require insertions or deletions. However, indels were present
in the alignments of the non-coding regions, and ambiguously aligned regions were excluded from the data sets.
These regions were identified using a sliding gap method
described by Lutzoni et al. (2000; step 1 in that paper).
The alignment of Marsilea to Pilularia and Regnellidium for
the non-coding regions resulted in the delimitation of 30
ambiguously aligned regions. To reduce the ambiguity, and
thereby increase the amount of data included in the study,
two subsequent analyses were conducted. The first was an
analysis of Marsilea plus outgroups, Pilularia and Regnellidium, for the three coding regions (atpB, rbcL, and rps4). This
analysis identified a small clade (Group I) within Marsilea
that consistently and with robust support, was sister to all
other Marsilea (Group II). A second analysis was used to
assess species relationships within Marsilea (Group II). For
this analysis of Marsilea Group II taxa, Group I was used as
the outgroup (with outgroups Pilularia and Regnellidium
omitted), and both the coding (atpB, rbcL, and rps4) and noncoding (trnLF, trnGR, and rps4-trnS spacer) sequence data
were used. When the non-coding sequences in this latter
combined data set were aligned, only seven ambiguous
regions were identified and excluded, rather than the 30
regions that had been identified initially. Unambiguous
indels and missing sequences were treated as missing data;
indels were not scored. Data sets and phylogenetic trees are
deposited in TreeBASE (study number S1642).
Phylogenetic Analyses. Maximum parsimony (MP) and
maximum likelihood (ML) analyses were conducted using
PAUP* 4.0b10 (Swofford 2002). For the individual and
combined data sets, the MP analyses used the heuristic
search option with tree bisection and reconnection (TBR)
branch swapping. All of the MP searches used 1,000 randomaddition-sequence (RAS) replicates, and the MP bootstrap
analyses (MPBS) employed 1,000 bootstrap replicates, each
with two RAS replicates.
The hierarchical likelihood ratio test, as implemented in
Modeltest 3.6 (Posada and Crandall 1998), was used to
estimate the nucleotide substitution model and parameters
employed in the ML search. For the ML analyses, TBR branch
swapping was used. For the individual and combined data
sets, the ML search was executed using 1,000 and 100
replicates, respectively, and all bootstrap analyses (MLBS)
comprised 100 bootstrap replicates, each with two RAS
replicates. For MP and ML, a strict consensus of the trees was
calculated.
The Bayesian Inference (BI) searches were conducted using
MrBayes 3.0b (Huelsenbeck and Ronquist 2001). For each of
the six individual data sets, the entire DNA region was
treated as a single partition with only one nucleotide
substitution model, using the same model as found for the
ML analyses. In the combined analyses, each DNA region
was treated as a single partition and assigned the model
identical to that used in the individual analyses, resulting in
six partitions. The BI searches for the combined data set were
repeated three times in order to confirm that searches
converged upon the same topology. In all BI searches, flat
priors and four chains were used. Chains were run for 10
million generations, and trees were sampled every 1,000th
generation. The likelihood values of the sampled trees were
plotted to determine the point where the likelihoods
approached stationarity; all trees prior to this point (1,000
trees; 1,000,000 generations) were discarded as the burnin phase. A majority-rule consensus of the remaining
trees was calculated to obtain a topology and posterior
probabilities (PP). Groups with support values less than 70%
MPBS/MLBS and less than 0.95 PP were regarded as lacking
support.
Conflict among the resultant phylogenies was assessed
according to a 70% bootstrap criterion for both MP and ML,
and a 0.95 posterior probability measure for BI (MasonGamer and Kellogg 1996; Wilcox et al. 2002). Comparison of
the phylogenies from each of the six individual data set
analyses revealed no incongruence supported across methods (e.g., MP vs. BI) or across data sets (e.g., rbcL vs. trnLF).
Hence, the data from the six partitions were combined into
a single data set.
Character State Reconstruction. We investigated morphological character evolution by plotting taxonomically
important characters onto the best estimate of phylogeny
(Fig. 1) obtained from the analysis of Marsilea taxa alone
(three coding and three non-coding regions). In this topology,
branches receiving low support (MPBS/MLBS: ,70%, PP:
,0.95) were collapsed, and taxa with more than one
geographic representative (e.g., M. nubica from Botswana
and Nigeria) were reduced to a single taxon if they were
sister to one another. The non-Marsilea outgroups were
added to the topology based on their position in a preliminary
analysis; inclusion of these outgroups allowed the reconstruction of the ancestral character states for Marsilea.
Characters were reconstructed using parsimony in MacClade
version 4.06 (Maddison and Maddison 2003). Character state
reconstructions at polytomies were resolved using the hard
option. Herbarium specimens and species descriptions
(Launert 1968, 1970, 1983–1984, 2003; Johnson 1986; Burrows
1990; Jones 1998) provided the necessary information to make
character state assignments. Variation within species was
coded as polymorphic.
RESULTS
Phylogeny of Marsilea. Almost all DNA sequences (165 out of 166) were newly generated for
this study, and are deposited in GenBank (Appendix 1). For our first analysis, incorporating Marsilea
plus the outgroups Pilularia and Regnellidium for
the three coding regions, all three search methods
recovered two strongly supported (MPBS/MLBS:
100%, PP: 1.0) sister groups (tree not shown). These
are designated Group I and Group II. Based on
these results, Group I, consisting of three taxa (M.
crotophora, M. polycarpa, and M. mutica), was used
as the outgroup for the analysis of Group II.
Six DNA regions for 33 Marsilea taxa (Groups I
and II) were analyzed in combination (Table 1).
When the data set was analyzed with MP, 25 trees
of 445 steps were recovered. The ML search
yielded two trees with equal likelihood scores
(Table 1) and identical topologies, except for the
2007]
NAGALINGUM ET AL.: PHYLOGENY OF MARSILEA
19
FIG. 1. Phylogenetic relationships of Marsilea using six plastid regions. Phylogram with average branch lengths obtained
from a ML search using atpB, rbcL, rps4, rps4-trnS, trnLF, and trnGR. Locality information follows taxon names when
geographic multiples of the same taxon were sampled. A single node within the ‘‘marsilea’’ subgroup, marked with # symbol,
indicates a congruence between BI and ML topologies, but a conflict with the MP tree. Measures of support are given at the
nodes: MP bootstrap/ML bootstrap/BI posterior probability. MPBS and MLBS values ,70% and PP ,0.95 are either not
reported or indicated as ‘—’; MPBS and MLBS values5100% and PP51.00 are each represented by an asterisk (*). Thickened
lines indicate high support (MPBS and MLBS $70%, and PP$0.95) from all measures. Informal names are designated for
subgroups within Groups I and II. Abbreviations: mu5mutica, clem5clemys, nub5nubica.
resolution of M. aegyptiaca as sister to M. ephippiocarpa, which was poorly-supported (,50% MLBS)
in tree #2, but unresolved in tree #1 (tree #1
shown in Fig. 1). The BI consensus tree was largely
identical (except for the weakly supported
branches) to the strict consensus topologies obtained by MP and ML. Although in the BI and ML
topologies compared to the MP tree, the relative
positions of M. minuta Africa and M. fadeniana are
interchanged, neither of these resolutions receives
strong support (Fig. 1; # symbol). The three search
methods all recovered two subgroups in Group I,
and five subgroups within Group II (Fig. 1); all
subgroups were strongly supported (MPBS/MLBS:
.90%, PP: 1.0). In the BI topology, relationships
among the subgroups of Group II are unresolved;
in the ML phylogram (Fig. 1), and the MP and ML
strict consensus trees, these relationships are more
20
SYSTEMATIC BOTANY
resolved, but are poorly supported (MPBS/MLBS:
,70%, PP: ,0.95).
Group I comprises a monotypic ‘‘mutica’’ subgroup (M. mutica), and a highly supported ‘‘clemys’’
subgroup, the latter incorporating M. crotophora and
M. polycarpa (MPBS/MLBS: 100%, PP: 1.0). Group II
consitutes five clades that we designate as ‘‘macrocarpa,’’ ‘‘nubica,’’ ‘‘capensis,’’ ‘‘marsilea,’’ and
‘‘nodorhizae,’’ all with strong support (MPBS/
MLBS: .90%, PP: 1.0; Fig. 1). The ‘‘macrocarpa’’
subgroup consists of a polytomy of five taxa plus
one robustly supported (93% MPBS, 91% MLBS, 1.0
PP) clade with three taxa (M. schelpiana, M. vera and
M. villifolia). The ‘‘nubica’’ subgroup includes two
disjunct representatives of M. nubica. In the ‘‘capensis’’ subgroup, M. capensis and M. gibba form
a well-supported clade (99% MPBS, 100% MLBS, 1.0
PP) that is sister to M. distorta. In the ‘‘marsilea’’
subgroup, the separation of M. quadrifolia from all
other taxa is moderately supported in MP and ML
(71% MPBS, 72% MLBS), but lacks support in BI
(,0.95 PP). The remaining taxa in this subgroup
form two robustly supported (MPBS/MLBS: $98%,
PP: 1.0) clades: 1) M. angustifolia and M. drummondii,
and 2) six taxa belonging to the M. minuta-M.
crenata-M. fadeniana complex. In the ‘‘nodorhizae’’
subgroup, M. mollis is poorly supported as the
earliest-diverging lineage (MPBS/MLBS: ,50%, PP:
,0.95); all of the remaining taxa, except M.
ancylopoda, comprise two clades (MPBS/MLBS:
$79%, PP: $0.99): 1) M. oligospora-M. vestita-M.
villosa, and 2) M. macropoda-M. nashii (with two
geographically distant collections of the latter),
which is poorly supported as sister to M. ancylopoda
(MPBS/MLBS: ,50%, PP: ,0.95).
Character Evolution. Evolution of the superior
and inferior sporocarp teeth, raphe, and place of
sporocarp maturation were plotted on the topology
resulting from the combined data (Fig. 2). For
Marsilea, the pleisiomorphic states are the absence
of the two sporocarp teeth and raphe, and the
maturation of the sporocarp above ground. The
superior tooth and raphe are synapomorphies of
Group II (Fig. 2a, c). The inferior tooth is homoplastic and occurs only in some members of Group
II (Fig. 2b). Below ground sporocarp development
evolved at least three times and most species of
Marsilea produce their sporocarps above ground
(Fig. 2d).
DISCUSSION
Based on the analysis of DNA sequence data, the
phylogeny of Marsilea has a basal dichotomy with
two robustly supported (MPBS/MLBS: 100%, PP:
1.0) groups, Groups I and II (Fig. 1). This agrees
with previous morphological work by Schneider
[Volume 32
and Pryer (2001), and their designations, Groups I
and II, are followed here.
Group I. This robustly-supported group is
species-poor compared to Group II. In our study,
Group I comprises three species—M. mutica, M.
polycarpa, and M. crotophora (Fig. 1). Species of
Group I have megaspores with an obovoidal outer
gelatinous perine, a bell-shaped inner perine, and
a solid acrolamella that is slightly raised from the
spore body (Schneider and Pryer 2001). They also
possess glabrous leaves (land leaves may have
a few hairs), sporocarps that lack both a raphe (an
elongated region of attachment along the sporocarp body and stalk) and sporocarp teeth, and are
intolerant of desiccation. The two members of
subgroup ‘‘clemys’’ (M. polycarpa and M. crotophora) were included in sect. Clemys by Johnson
(1986), and a similar grouping, based on sporocarp
arrangement, has been consistently recognized by
earlier workers (polycarpa group: Braun 1871;
Gupta 1962). Taxa assigned to this section have
globose sporocarps arranged in a row along the
petiole, and possess a transverse sporocarp vein,
which is the result of anastomoses among the
lateral veins (Johnson 1986, 1988). In contrast, the
sister species M. mutica (‘‘mutica’’ subgroup) has
elliptical sporocarps that lack a transverse vein, are
borne at the base of the petiole, and are either
solitary or in clusters of 2–4 on branched pedicels.
Although this species shares features of sect.
Clemys (e.g., habitat preference, megaspore morphology and the absence of a raphe and sporocarp
teeth), M. mutica also has characters found in
Group II taxa (e.g., sporocarp shape, venation, and
arrangement). Based on megaspore morphology
and the occurrence of sporocarps along the petiole,
additional, unsampled species that are possible
members of the ‘‘clemys’’ subgroup are M.
berhautii Tardieu, M. deflexa A. Br., and M. scalaripes
D. M. Johnson (Johnson 1988; Schneider and Pryer
2001).
Group II. In our study, this group comprises
five robustly supported subgroups, but relationships among them are not well-supported (Fig. 1).
As indicated by Schneider and Pryer (2001),
members of Group II have megaspores with
a distally folded and proximally lobed outer
gelatinous perine, a bell-shaped inner perine, and
a solid acrolamella that is not raised relative to the
spore body. The sporocarps of taxa in Group II
typically possess a raphe and bear from zero to
two teeth. The occurrence of teeth is not a consistent character among, and sometimes within
species, but the presence of a tooth is a definitive
indicator of affinity to Group II. Taxa in this group
can also be identified by having hirsute leaves,
2007]
NAGALINGUM ET AL.: PHYLOGENY OF MARSILEA
21
FIG. 2. Ancestral state reconstructions for selected sporocarp characters. a. Superior tooth. b. Inferior tooth. c. Raphe. d.
Place of maturation. In the diagrams, the arrows point to the character of interest. The names above each of the trees indicate
groups (above) and subgroups (below). Abbreviations: Gp5group, cl5clemys, m5mutica, cap5capensis, n5nubica.
and are often emergent at the edges of lakes and
ponds.
The five newly identified subgroups of Group II
are here named after informal groups (Braun 1871;
Launert 1968) and formally described sections
(Johnson 1986) and, except in the case of ‘‘nodorhizae,’’ these subgroups do not circumscribe the
same groups as earlier works. With further taxon
sampling, relationships may be more resolved
(especially among the African subgroups and
22
SYSTEMATIC BOTANY
species), and subgroups could then be recognized
formally as sections. For each subgroup (Fig. 1), we
define morphological synapomorphies and identify biogeographical features below.
THE AFRICAN SUBGROUPS: ‘‘MACROCARPA,’’ ‘‘NUBICA,’’ AND ‘‘CAPENSIS.’’ According to our sampling, there are three subgroups that consist solely
of taxa either endemic to Africa, or occurring in
Africa plus Asia (Fig. 1; M. aegyptiaca also occurs in
India, and M. capensis in the Middle East).
Members of these subgroups occur in extremely
dry habitats that are subject to occasional, but
short, wet periods. Preliminary molecular divergence dating of Marsilea (Nagalingum et al. 2005)
suggests the diversification of the African subgroups occurred during a period of increasing
aridification in a similar timeframe to the Cape
flora radiation (Linder and Hardy 2004). A monophyletic origin of these three African subgroups is
ambiguous—‘‘macrocarpa’’ and ‘‘nubica’’ are sister, but this relationship is poorly supported
(MPBS/MLBS: ,70%, PP: ,0.95), and the position
of ‘‘capensis’’ is unresolved (Fig. 1).
Species in the ‘‘macrocarpa’’ subgroup can
typically be recognized by the concave or straight
dorsal margin of the sporocarp (compared to
convex in other taxa). The close relationship of
some of the taxa in the ‘‘macrocarpa’’ subgroup
(M. macrocarpa, M. farinosa, M. schelpiana, M. vera,
and M. villifolia) was suggested previously by
Launert (1968). Within ‘‘macrocarpa’’ is a smaller
well-supported group comprising M. schelpiana, M.
vera, and M. villifolia—all are endemic to southern
Africa (Kornas 1988; Burrows 1990). In contrast,
most of the other taxa in ‘‘macrocarpa’’ (with the
exception of M. ephippiocarpa) are generally widespread throughout Africa (Launert 1968; Kornas
1988; Burrows 1990). The two samples of M. nubica
comprise the monospecific ‘‘nubica’’ subgroup that
is also widespread across Africa (Kornas 1988). A
close relationship of members of the ‘‘capensis’’
subgroup (Fig. 1; M. capensis, M. gibba, and M.
distorta) has never been proposed. Earlier workers
considered M. capensis a member of the largely
African ‘‘macrocarpa complex’’ and M. gibba as
separate from all other African marsileas (Braun
1871; Launert 1968). However, our results indicate
that M. capensis occurs in a subgroup separate from
M. macrocarpa, and that M. gibba is in fact closely
related to it (Fig. 1).
THE WIDESPREAD-OLD WORLD SUBGROUP: ‘‘MARSILEA.’’ The most geographically diverse subgroup
in our study is ‘‘marsilea’’ (Fig. 1). It comprises
three distinct biogeographic clades: 1) two Australian taxa (M. angustifolia and M. drummondii),
2) members from Africa and Asia (M. crenata, M.
[Volume 32
minuta, and M. fadeniana), and 3) a single taxon, M.
quadrifolia, from Europe to temperate Asia (but
introduced in North America). Within the AfricanAsian clade, M. crenata is nested within M. minuta
(Fig. 1). The morphological distinction between
these two species is unclear. Braun (1871) suggested a close relationship between them, but still
regarded the two as separate species. Holttum
(1966) and Launert (1968) also recognized the
similarity between M. crenata and M. minuta, but
distinguished M. crenata by the absence of either
a distinct border or rim at the sporocarp margin,
raised ridges (‘‘ribs’’) on the sporocarp lateral walls
(Holttum 1966), and by the number and size of the
sporocarps (Launert 1968). Traditionally, material
is assigned to one of the two species based on
geographic origin. Specimens from Australia, the
Malay Peninsula, eastern parts of Indochina, Thailand, Japan, and Taiwan are designated as M.
crenata, whereas plants from India, western parts of
Indochina, subtropical Asia, and Africa are assigned to M. minuta. Our phylogenetic analyses do
not provide strong evidence for separating these
two taxa, suggesting that they should be considered a single species (M. minuta has priority);
however, a thorough morphological investigation
is required to confirm that M. crenata and M.
minuta are conspecific.
THE NEW WORLD SUBGROUP: ‘‘NODORHIZAE.’’
The ‘‘nodorhizae’’ subgroup comprises species
restricted to the New World (North and South
America, the Caribbean islands, and Hawaii). This
subgroup includes all of the taxa that were treated
as sect. Nodorhizae by Johnson (1986) and is
distinguished from other members of the genus
by having roots only at the nodes, sporocarps that
are large (2.5–9 mm long) with high numbers of
sori (10–23) and lacking transverse veins. The
‘‘nodorhizae’’ subgroup is tropical to subtropical,
except for M. oligospora and M. vestita. These two
temperate species from North America partially
overlap in range and are morphologically similar;
however, Johnson (1986) found sufficient and
consistent morphological differences to recognize
the two species as distinct. The Hawaiian species
M. villosa is strongly to moderately supported as
sister to M. oligospora and M. vestita (Fig. 1) and,
therefore, appears to have a North American
origin. Members of the species pair M. macropodaM. nashii (Fig. 1) occur in adjacent regions: M.
nashii on islands in the northern Caribbean (Cuba,
Bahama, and Barbuda Islands), and M. macropoda
on the Gulf coast of North America (where it is
native to Texas and the northeastern states of
Mexico, but introduced into Alabama and Louisiana; Johnson 1986).
2007]
NAGALINGUM ET AL.: PHYLOGENY OF MARSILEA
Morphological Character Evolution in Marsilea.
Our Marsilea molecular phylogeny provides an
independent hypothesis for investigating taxonomically important morphological characters, such as
sporocarp teeth, raphe, and place of maturation.
Sporocarps are borne on stalks, and in some
species, a portion of the stalk fuses with the
sporocarp body, forming a structure called the
raphe (Fig. 2c). In some cases, the distal portion of
the stalk does not fuse with the sporocarp, instead
it projects above the sporocarp body. This projection is regarded as the inferior tooth and is
dependent on the presence of a raphe (Fig. 2b).
Whereas the inferior tooth occurs at the tip of the
stalk, the superior tooth occurs directly at the apex
of the sporocarp body (Fig. 2a). The inferior and
superior teeth are clearly not homologous, deriving
from different components of the sporocarp, and
sometimes co-occurring. The teeth exhibit a high
degree of variability within and among species,
from completely absent to a shallow hump to
a conspicuous projection. Gupta (1962) regarded
the teeth as too inconsistent for systematic use,
whereas Braun (1871) considered them to be
taxonomically important. Johnson (1986) noted
that the inferior tooth was quite variable, and
could be present or absent within a species;
however, he regarded the superior tooth as a more
consistent character for species-level identification.
Our ancestral state reconstructions for the
superior and inferior teeth indicate that the
plesiomorphic condition for Marsilea is the absence
of sporocarp teeth (Fig. 2a, b). Our reconstructions
suggest that the superior tooth evolved once in the
ancestor to Group II, and was lost in M. distorta
(Fig. 2a). Based on our taxon sampling, the
superior tooth is polymorphic in some species in
the ‘‘nodorhizae’’ and ‘‘marsilea’’ subgroups
(Fig. 2a). The inferior tooth is reconstructed as
having evolved within Group II, but it is unclear
whether it arose in the ancestor to the group or
occurred independently among several subgroups
(Fig. 2b).
Ancestral state reconstruction for the sporocarp
raphe demonstrates that it is a reliable synapomorphy for Group II (Fig. 2c). Unlike the polymorphic
superior tooth, the raphe is consistently present in
all sampled species of this group.
A highly specialized feature, found in three
species of Marsilea that we sampled, is the burial of
mature sporocarps. This feature may be an
adaptation to ensure survival in arid areas,
particularly during prolonged drought (Launert
1968). Launert (1968) recognized that those African
species that shared the ability to bury their
sporocarps were not ‘‘closely related.’’ Johnson
23
(1986) later identified this feature in a New World
species, and questioned whether it arose through
a shared evolutionary history with the African taxa
or through parallelism. Our ancestral state reconstruction shows that the burial of sporocarps
occurs in three subgroups within Group II, and
demonstrates that this trait evolved independently
at least three times (Fig. 2d).
ACKNOWLEDGMENTS. The authors thank D. Hearn, P.
Korall, J. Metzgar, C. Pickett, E. Schuettpelz, and M. Windham for their comments on an earlier version of the
manuscript; P. Herendeen, S. Hoot, D. Johnson, and an
anonymous reviewer for their valuable suggestions; curators
and staff of BM, DUKE, F, GOET, H, MEL, MELU, UC, and
US herbaria; Duke University Greenhouse staff for assistance
with growing plants; and S. G. Beck, F. Caplow, C. B.
Hellquist, B. Hoshizaki, C. C. Jacono, M. Kato, Bai-Ling Lin,
V. S. Manickam, M. Martin, D. D. Palmer, WuXiao Qin, G.
Steinauer, K. P. Rajesh, L. J. Ramberg, and A. R. Smith for
donating plant material for this study. J. Hunt, J. Kirchman,
and M. Skakuj are acknowledged for their assistance with
DNA sequencing, and E. Schuettpelz for providing new
amplification and sequencing primers. This work was
supported in part by National Science Foundation grant
DEB-0089909 to K. M. P. and H. S, and DEB-0347840 to
K. M. P.
LITERATURE CITED
BAKER, J. G. 1887. Handbook of the fern-allies: a synopsis of the
genera and species of the natural orders: Equisetaceae,
Lycopodiaceae, Selaginellaceae, Rhizocarpeae. London:
George Bell and Sons.
BHARDWAJA, T. N. 1980. Recent advances in our knowledge of
the water fern Marsilea. Aspects of Plant Sciences 3: 39–42.
BRAUN, A. 1871. Hr. Braun theilte neuere Untersuchungen
über die Gattungen Marsilea und Pilularia. Monatsbericht
der Königlichen Akademie der Wissenschaften zu Berlin 1870:
653–753.
———. 1873. Nachtragliche Mittheilungen über die Gattungen Marsilea und Pilularia. Monatsbericht der Königlichen
Akademie der Wissenschaften zu Berlin 1872: 635–679.
BURROWS, J. E. 1990. Southern African ferns and fern allies.
Sandton: Frandsen Publishers.
COOK, C. D. K. 2004. Aquatic and wetland plants of southern
Africa. Sandton: Backhuys Publishers.
GUPTA, K. M. 1962. Marsilea. Botanical Monograph No. 2.
New Delhi: Council of Scientific and Industrial Research.
——— and T. N. BHARDWAJA. 1956. Indian marsileas: their
morphology and systematics. I. Marsilea aegyptiaca
Willd. with remarks on the present systematic position
of Indian species. Journal of the Bombay Natural History
Society 53: 423–446.
——— and ———. 1957. Indian marsileas: their morphology
and systematics. 2. On the examination of some
collections of Marsilea in India. Journal of the Bombay
Natural History Society 54: 550–567.
——— and ———. 1958. Indian marsileas: their morphology
and systematics. 3. On the examination of some further
collections of Marsilea from South India and Rajasthan.
Journal of the Bombay Natural History Society 55: 287–296.
HASEBE, M., T. OMORI, M. NAKAZAWA, T. SANO, M. KATO, and
K. IWATSUKI. 1994. rbcL gene sequences provide evidence
for the evolutionary lineages of leptosporangiate ferns.
24
SYSTEMATIC BOTANY
Proceedings of the National Academy of Sciences, USA 91:
5730–5734.
HOLTTUM, R. E. 1966. Ferns of Malaya. A revised flora of Malaya.
Vol. II. Singapore: Government Printing Office.
HOOT, S. B. and W. C. TAYLOR. 2001. The utility of nuclear
ITS, a LEAFY homolog intron, and chloroplast atpB-rbcL
spacer region data in phylogenetic analyses and species
delimitation in Isoëtes. American Fern Journal 91: 166–177.
HUELSENBECK, J. P. and F. RONQUIST. 2001. MRBAYES:
Bayesian inference of phylogenetic trees. Bioinformatics
17: 754–755.
JOHNSON, D. M. 1985. New records for longevity of Marsilea
sporocarps. American Fern Journal 75: 30–31.
———. 1986. Systematics of the New World species of
Marsilea (Marsileaceae). Systematic Botany Monographs
11: 1–87.
———. 1988. Marsilea scalaripes, a new member of Marsilea
section Clemys from the Asian tropics. American Fern
Journal 78: 68–71.
JONES, D. L. 1998. Marsileaceae. Pp. 166–173 in Flora of
Australia, Vol. 48, Ferns, gymnosperms and allied groups,
eds. A. E. Orchard and P. M. McCarthy. Melbourne:
CSIRO Publishing.
KORALL, P., K. M. PRYER, J. S. METZGAR, H. SCHNEIDER, and D.
CONANT. 2006. Tree ferns: monophyletic groups and
their relationships as revealed by four protein-coding
plastid loci. Molecular Phylogenetics and Evolution 39:
830–845.
KORNAS, J. 1988. Adaptive strategies of Marsilea (Marsileaceae: Pteridophyta) in the Lake Chad Basin of N. E.
Nigeria. Fern Gazette 13: 231–243.
KUBITZKI, K. 1990. Pteridophytes and gymnosperms, Vol. 1.
Pp. 1–404 in The families and genera of vascular plants, eds.
K. U. Kramer and P. S. Green. Berlin: Springer-Verlag.
LAUNERT, E. 1968. A monographic survey of the genus
Marsilea Linnaeus. I. The species of Africa and Madagascar. Senckenbergiana Biologica 49: 273–315.
———. 1970. Marsileaceae. Pp. 59–67 in Flora Zambesiaca—
Pteridophyta: the fern flora of Mozambique, Malawi, Zambia,
Zimbabwe and Botswana, eds. A. W. Exell and E. Launert.
Kew: Royal Botanic Gardens.
———. 1971. A remarkable new African species of Marsilea
Linnaeus. Senckenbergiana Biologica 52: 449–452.
———. 1983–84. A revised key to and new records of African
species of the genus Marsilea. Garcia de Orta, Série de
Botanica 6: 119–140.
———. 2003. Marsileaceae. Pp. 1–16 in Flora of tropical East
Africa, eds. H. J. Beentje and S. A. Ghanzantar. Lisse: AA
Balkema Publishers.
LES, D. H., D. J. CRAWFORD, E. LANDOLT, J. D. GABEL, and R. T.
KIMBALL. 2002. Phylogeny and systematics of Lemnaceae, the duckweed family. Systematic Botany 27:
221–240.
———, E. LANDOLT, and D. J. CRAWFORD. 1997. Systematics of
the Lemnaceae (Duckweeds): inferences from micromolecular and morphological data. Plant Systematics and
Evolution 204: 161–177.
———, E. L. SCHNEIDER, D. J. PADGETT, P. S. SOLTIS, D. E.
SOLTIS, and M. ZANIS. 1999. Phylogeny, classification and
floral evolution of water lilies (Nymphaeales): a synthesis of non-molecular, rbcL, matK and 18S rDNA data.
Systematic Botany 24: 28–46.
LINDER, H. P. and C. R. HARDY. 2004. Evolution of the speciesrich Cape flora. Philosophical Transactions of the Royal
Society of London. Series B, Biological Sciences 359:
1623–1632.
LUTZONI, F., P. WAGNER, V. REEB, and S. ZOLLER. 2000.
Integrating ambiguously aligned regions of DNA
[Volume 32
sequences in phylogenetic analyses without violating
positional homology. Systematic Biology 49: 628–651.
MADDISON, W. P. and D. R. MADDISON. 2003. MacClade.
Analysis of phylogeny and character evolution. Version 4.06.
Sunderland: Sinauer Associates.
MASON-GAMER, R. J. and E. A. KELLOGG. 1996. Testing for
phylogenetic conflict among molecular data sets in the
tribe Triticeae (Gramineae). Systematic Biology 45:
524–545.
NADOT, S., R. BAJON, and B. LEJEUNE. 1994. The chloroplast
gene rps4 as a tool for the study of Poaceae phylogeny.
Plant Systematics and Evolution 191: 27–38.
NAGALINGUM, N. S., K. M. PRYER, H. SCHNEIDER, M. D.
NOWAK, D. HEARN, and R. LUPIA. 2005. Dating the
Marsileaceae: evolutionary and biogeographical implications. International Botanical Congress XVII Vienna,
Austria. Abstracts. 12.7.2.
———, H. SCHNEIDER, and K. M. PRYER. 2006. Comparative
morphology of reproductive structures in heterosporous
water ferns and a reevaluation of the sporocarp.
International Journal of Plant Sciences 167: 805–815.
PÉREZ-GARCı́A, B., R. RIBA, and D. M. JOHNSON. 1999.
Pteridofitas. Familia Marsileaceae. Flora de Mexico 6:
1–16.
POSADA, D. and K. A. CRANDALL. 1998. Modeltest: testing the
model of DNA substitution. Bioinformatics 14: 817–818.
PRYER, K. M. 1999. Phylogeny of marsileaceous ferns and
relationships of the fossil Hydropteris pinnata reconsidered. International Journal of Plant Sciences 160: 931–954.
———, E. SCHUETTPELZ, P. G. WOLF, H. SCHNEIDER, A. R.
SMITH, and R. CRANFILL. 2004. Phylogeny and evolution
of ferns (monilophytes) with a focus on the early
leptosporangiate divergences. American Journal of Botany
91: 1582–1598.
———, A. R. SMITH, J. S. HUNT, and J.-Y. DUBUISSON. 2001.
rbcL data reveal two monophyletic groups of filmy ferns
(Filicopsida: Hymenophyllaceae). American Journal of
Botany 88: 1118–1130.
REED, C. F. 1954. Index Marsileata et Salviniata. Boletim da
Sociedade Broteriana 28: 1–61.
RYDIN, C. and N. WILKSTRÖM. 2002. Phylogeny of Isoëtes
(Lycopsida): resolving basal relationships using rbcL
sequences. Taxon 51: 83–89.
SADEBECK, A. 1902. Hydropteridinae. Pp. 381–421 in Die
natürlichen Pflanzenfamilien, Vol. 1, Pt 4, eds. A. Engler
and K. Prantl. Leipzig: W. Engelmann.
SCHNEIDER, H. and K. M. PRYER. 2001. Structure and function
of spores in the aquatic heterosporous fern family
Marsileaceae. International Journal of Plant Sciences 163:
485–505.
SMITH, A. R. and R. CRANFILL. 2002. Intrafamilial relationships
of the thelypteroid ferns (Thelypteridaceae). American
Fern Journal 92: 131–149.
SWOFFORD, D. L. 2002. PAUP*: phylogenetic analysis using
parsimony (*and other methods). Sunderland: Sinauer
Associates.
TABERLET, P., L. GIELLY, G. PAUTOU, and J. BOUVET. 1991.
Universal primers for amplification of three non-coding
regions of chloroplast DNA. Plant Molecular Biology 17:
1105–1109.
TRYON, R. M. and A. F. TRYON. 1982. Ferns and allied plants:
with special reference to tropical America. New York:
Springer-Verlag.
WILCOX, T. P., D. J. ZWICKL, T. A. HEATH, and D. M. HILLIS.
2002. Phylogenetic relationships of the dwarf boas and
a comparison of Bayesian and bootstrap measures of
phylogenetic support. Molecular Phylogenetics and Evolution 25: 361–371.
WOLF, P. G. 1997. Evaluation of atpB nucleotide sequences for
2007]
NAGALINGUM ET AL.: PHYLOGENY OF MARSILEA
phylogenetic studies of ferns and other pteridophytes.
American Journal of Botany 84: 1429–1440.
APPENDIX 1. Marsilea and outgroup species examined in
this study, listed in the following order: vouchers, database
numbers (refers to unique record numbers in the Fern DNA
database: http://www.pryerlab.net/DNA_database.shtml),
and GenBank accession numbers for each of the six plastid
regions sequenced [i.e., atpB, rbcL, rps4 & rps4-trnS spacer,
trnL-trnF (trnLF), trnG-trnR (trnGR); ‘‘—’’ indicates missing
region).
Ingroup. Marsilea aegyptiaca Willd., Namibia: Smith 3623
(BM), 2206, DQ643257, DQ643291, DQ536323, DQ643359,
DQ643325; M. ancylopoda A. Br., Puerto Rico: Pryer et al. 963
(F), 979, —, DQ643292, DQ536324, DQ643360, DQ643326; M.
angustifolia R. Br., Australia: Hoshizaki 1250, cultivated in
garden of A. R. Smith, CA (UC), 733, DQ643258, DQ643293,
DQ536325, DQ643361, DQ643327; M. botryocarpa Ballard,
Kenya: Faden s.n., cultivated in California State University,
CA (UC), 462, DQ643259, DQ643294, DQ536326, DQ643362,
DQ643328; M. capensis A. Br., Botswana: Ramberg s.n.
(DUKE), 2466, DQ643260, DQ643295, DQ536327, DQ643363,
DQ643329; M. crenata Presl, Indonesia: Kato J-38 (DUKE),
2129, DQ643261, DQ643296, DQ536328, DQ643364,
DQ643330; M. crenata, Thailand: Kato s.n. (DUKE), 2131,
DQ643262, DQ643297, DQ536329, DQ643365, DQ643331; M.
crotophora D. M. Johnson, Bolivia: Ritter et al. 4561 (H), 2509,
DQ643263, DQ643298, DQ536330, —, DQ643332; M. distorta
A. Br., Nigeria: Kornas 6271 (BM), 2177, DQ643264, —,
DQ536331, —, —; M. drummondii A. Br., Australia: Hoshizaki
577, cultivated in garden of A. R. Smith, CA (UC), 463,
AF313551, DQ643299, DQ536332, DQ643366, DQ643333; M.
ephippiocarpa Alston, Zimbabwe: Chase 2255, cultivated in
University of California Botanic Garden, CA (UC), 2840,
DQ643265, DQ643300, —, —, DQ643334; M. fadeniana
Launert, Kenya: Evans & Maikweki 55, cultivated in Chelsea
Physic Garden, London (US), 989, DQ643266, DQ643301,
DQ536333, DQ643367, DQ643335; M. farinosa Launert, Kenya:
Faden 70/902, ‘germinated’ from sporocarp (US), 990,
DQ643267, DQ643302, DQ536334, DQ643368, DQ643336; M.
gibba A. Br., Kenya: Faden & Ng’weno 87/33, ‘germinated’ from
sporocarp (US), 991, DQ643268, DQ643303, DQ536335,
DQ643369, DQ643337; M. macrocarpa Presl, South Africa:
Hoshizaki 236, cultivated in garden of A. R. Smith, CA (F, UC),
976, DQ643269, DQ643304, DQ536336, DQ643370, DQ643338;
M. macropoda Engelm. ex A. Br., USA: Texas, Hoshizaki 1458
25
(DUKE), 2360, DQ643270, DQ643305, DQ536337, DQ643371,
DQ643339; M. minuta L., Burma: Shimozono s.n. (DUKE), 2118,
DQ643271, DQ643306, DQ536338, DQ643372, DQ643340; M.
minuta, India: Rajesh 87983 (DUKE), 2122, DQ643272,
DQ643307, DQ536339, —, DQ643341; M. minuta, Africa:
Hoshizaki 237, cultivated in Duke University Greenhouse,
NC (DUKE), 2359, DQ643273, DQ643308, DQ536340,
DQ643373, DQ643342; M. mollis Robinson & Fernald, Mexico:
Johnson s.n., cultivated in Matthaei Botanical Gardens,
University of Michigan, MI (F), 2512, DQ643274, —,
DQ536341, —, —; M. mutica Mett., New Caledonia: Hoshizaki
840, cultivated in Duke University Greenhouse, NC (DUKE),
465, DQ643275, DQ643309, DQ536342, DQ643374, DQ643343;
M. nashii Underw., Turks and Caicos Islands: Grand Turk
Island, Correll 46631 (F), 981, DQ643276, DQ643310,
DQ536343, DQ643375, DQ643344; M. nashii, West Indies:
Correll s.n. (DUKE), 2361, DQ643277, DQ643311, DQ536344,
DQ643376, DQ643345; M. nubica A. Br. var. gymnocarpa (A.
Br.) Launert, Botswana: Smith 1988 (BM), 2198, DQ643278,
DQ643312, DQ536345, —, DQ643346; M. nubica var. gymnocarpa, Nigeria: Kornas 6379 (BM), 2202, DQ643279, DQ643313,
DQ536346, —, DQ643347; M. oligospora Goodding, USA:
Nevada, Tiehm 13199 (UC), 2034, DQ643280, DQ643314,
DQ536347, DQ643377, DQ643348; M. polycarpa Hook. &
Grev., Puerto Rico: Pryer 960 (DUKE, F), 978, DQ643281,
DQ643315, DQ536348, DQ643378, DQ643349; M. quadrifolia
L., Japan: Honshu, Anno s.n., cultivated in University of
Tokyo Botanical Gardens, Tokyo (DUKE), 2132, DQ643282,
DQ643316, DQ536349, DQ643379, DQ643350; M. schelpiana
Launert, South Africa: Hoshizaki 742, cultivated in garden of
A. R. Smith, CA (DUKE), 2358, DQ643283, DQ643317,
DQ536350, DQ643380, DQ643351; M. vera Launert, Botswana:
Burrows 3716 (BM), 2193, DQ643284, DQ643318, DQ536351,
—, DQ643352; M. vestita Hook. & Grev., USA: California,
Howell 47460 (US), 982, DQ643285, DQ643319, DQ536352,
DQ643381, DQ643353; M. villifolia Bremek. & Oberm. ex
Alston & Schelpe, Botswana: Hansen 3232 (BM), 2036,
DQ643286, DQ643320, DQ536353, —, DQ643354; M. villosa
Kaulf., USA: Hawaii, Degener 9049 (US), 983, DQ643287,
DQ643321, DQ536354, DQ643382, DQ64335.
Outgroup. Pilularia americana A. Br., USA: Georgia, Pryer
978 (DUKE), 2060, DQ643288, DQ643322, DQ536355,
DQ643383, DQ643356; P. globulifera L., Germany: Düsseldorf,
Schneider s.n., cultivated in Göttingen Botanic Garden,
Göttingen (GOET), 2161, DQ643289, DQ643323, DQ536356,
DQ643384, DQ643357; Regnellidium diphyllum Lindm., Brazil:
Smith s.n. (UC), 474, DQ643290, DQ643324, DQ536357,
DQ643385, DQ643358