Sectional Classification of the North American Plagiochila (Hepaticae, Plagiochilaceae)

Abstract

The sectional subdivision of the North American Plagiochila is largely based on Schusters' comprehensive treatments of the genus. Here we summarize the results of recent morphological, molecular, and chemical work and present an updated section and species list. Internal Transcribed Spacer sequences of nuclear ribosomal DNA are used to clarify the sectional position of the Western Holarctic endemic Plagiochila austinii (member of the Asian sect. Trabeculatae) and to confirm the recently proposed synonymy of Plagiochila sciophila and P. euryphyllon. North American Plagiochila are subdivided into the sects. Arrectae, Cucullatae, Peculiares, Plagiochila, Rutilantes, Trabeculatae, and Vagae.

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The Bryologist 107(4), pp. 489 496
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2004 by the American Bryological and Lichenological Society, Inc.
Sectional Classification of the North American Plagiochila
(Hepaticae, Plagiochilaceae)
J
OCHEN
H
EINRICHS
,M
ELANIE
L
INDNER
,
AND
H
ENK
G
ROTH
Department of Systematic Botany, Albrecht von Haller Institute of Plant Sciences, Georg August University,Untere
Karspu¨le 2, D-37073 Go¨ttingen, Germany; e-mail: jheinri@gwdg.de
Abstract. The sectional subdivision of the North American Plagiochila is largely based on
Schusters’ comprehensive treatments of the genus. Here we summarize the results of recent mor-
phological, molecular, and chemical work and present an updated section and species list. Internal
Transcribed Spacer sequences of nuclear ribosomal DNA are used to clarify the sectional position
of the Western Holarctic endemic Plagiochila austinii (member of the Asian sect. Trabeculatae)
and to confirm the recently proposed synonymy of Plagiochila sciophila and P. euryphyllon. North
American Plagiochila are subdivided into the sects. Arrectae,Cucullatae,Peculiares,Plagiochila,
Rutilantes,Trabeculatae, and Vagae.
Keywords. Holarctic, internal transcribed spacer, nuclear ribosomal DNA, phylogeny, Plagi-
ochila.
Plagiochila with about 400–450 species world-
wide (So & Grolle 2000) forms the most speciose
and hence, taxonomically ‘‘perhaps the most diffi-
cult’’ (Schuster 1980) genus of liverworts. Species
of Plagiochila are notorious for variation in ga-
metophytic characters, especially leaf shape and
dentation. As a consequence of the complex mor-
phology, several thousand taxa have been described
(Inoue 1989) and until now only regional treat-
ments are available (e.g., Heinrichs 2002; Inoue
1984; Jones 1962; So 2001). However, the real spe-
cies ranges are often not recognized until taxa from
various floristic kingdoms are taken into account.
The limitation of taxonomic studies to portions of
the world range also affects current sectional sub-
divisions of Plagiochila.
Taxonomy and sectional subdivision of North
American Plagiochila are largely based on the sub-
stantial morphological treatments of Schuster
(1959a,b, 1960, 1980). In recent years several stud-
ies incorporating molecular, morphological and
chemical data have led to extensive rearrangements
of previous sectional concepts (e.g., Groth et al.
2002, 2003, 2004; Heinrichs 2002).
Here we summarize the results regarding the
North American Plagiochila flora. We use nrITS
sequence data to clarify the taxonomic position of
Plagiochila austinii A. Evans and to test the syn-
onymy of P. euryphyllon Carl and P. sciophila Lin-
denb. (So & Grolle 1999). Plagiochila austinii was
placed in P. sect. Choachinae Carl (
5
P. sect. Ar-
rectae Carl, Heinrichs 2002) by Schuster (1980) but
is morphologically closer to P. aerea Taylor of P.
sect. Fuscoluteae Carl and P. trabeculata Steph. of
P. sect. Trabeculatae Inoue. Plagiochila euryphyl-
lon resembles both the Asian P. sciophila and the
Neotropical P. subplana Lindenb. (P. sect. Cucul-
latae Schiffn.).
M
ATERIALS AND
M
ETHODS
DNA extraction, PCR amplification, and sequencing.
Upper parts of a few shoots of herbarium specimens were
isolated (Table 1). DNA was extracted with Invisorb Spin
Plant Mini Kit (Invitek, Berlin, Germany). PCR-amplifi-
cation followed the protocol of Heinrichs et al. (2004b).
Sequencing was carried out on an ABI 3100 capillary se-
quencer using the BigDye
TM
Terminator Cycle Sequencing
v2.0 kit (PE Biosystems).
Taxon sampling and phylogenetic analyses. The P.
austinii and P. euryphyllon/sciophila sequences were
compared with GenBank sequences using the BLASTN
program and integrated into a large alignment of Plagi-
ochilaceae ITS sequences. In all cases sequences of Pla-
giochila ‘‘clade B’’ sensu Groth & Heinrichs (2003) were
identified as most similar to the new sequences (data not
shown). Based on these results, representatives of Plagi-
ochila sects. Cucullatae Schiffn., Fruticosae Inoue, Pe-
culiares Schiffn., Plagiochila,Poeltiae Inoue, Trabecu-
latae, and Vagae Lindenb. were sampled. The matrix was
completed with Plagiochila aerea and P. fuscolutea Tay-
lor (P. sect. Fuscoluteae Carl) as well as P. retrorsa Gott-
sche and P. stricta Lindenb. (P. sect. Arrectae). Pedino-
phyllum interruptum (Nees) Kaal. and Plagiochilion may-
ebarae S.Hatt. were chosen as outgroups
Thirty-three ITS1–5.8S-ITS2 sequences from Groth et
al. (2003, 2004), Groth and Heinrichs (2003), Heinrichs
(2002), Heinrichs et al. (2002a), Renker et al. (2002), Ry-
croft et al. (2002), and the three new sequences were
aligned manually in BioEdit version 5.0.9 (Hall 1999),
resulting in an alignment including 778 putatively ho-
mologous sites (alignment available from JH).
Phylogenetic trees were inferred using maximum like-
lihood (ML) and maximum parsimony (MP) criteria as
implemented in PAUP* version 4.0b10 (Swofford 2003).

490 [VOL. 107THE BRYOLOGIST
T
ABLE
1. Geographic origins, voucher numbers, and GenBank/EMBL accession numbers of the investigated taxa. Accession numbers of new sequences are in bold.
Taxon Origin Voucher Accession number
Pedinophyllum interruptum (Nees) Kaal.
P. aerea Taylor
P. asplenioides (L.) Dumort.
P. austinii A. Evans
P. austinii
United Kingdom
Costa Rica
Germany
U.S.A., North Carolina
U.S.A., Kentucky
Rycroft 020907 (
GOET
)
Heinrichs et al. 4321 (
GOET
)
Heinrichs & Groth 4339 (
GOET
)
Davison & Hicks 2961 (
DUKE
)
Risk 10849 (
DUKE
)
AY438234
AJ422028
AJ414629
AJ748129
AJ748130
P. bantamensis (Reinw., Blume & Nees) Mont.
P. britannica Paton
P. carringtonii (Balf.) Grolle ssp. lobuchensis Grolle
P. deflexirama Taylor
P. disticha (Lehm. & Lindenb.) Lindenb.
Japan
United Kingdom
Bhutan
Costa Rica
Ecuador
Yamaguchi 16890 (
HIRO
)
Rycroft 00015 (
GOET
)
Long 28857 (
GOET
)
Heinrichs et al. 11 (
GOET
)
Holz EC-01-436 (
GOET
)
AY275160
AY275162
AJ414631
AY550135
AJ422014
P. flexuosa Mitt.
P. frondescens (Nees) Lindenb.
P. fruticosa Mitt.
P. magna Inoue
P. orbicularis (Hatt.) Hatt.
Japan
Indonesia
India
Japan
Japan
Kurita 147 (
HIRO
)
Scha¨fer-Verwimp 20704 (
GOET
)
Long 23002 (
GOET
)
Kurita 258 (
HIRO
)
Kurita 32 (
HIRO
)
AY550138
AY438237
AY438235
AY275167
AY275168
P. ovalifolia Mitt.
P. peculiaris Schiffn.
P. poeltii Inoue & Grolle
P. porelloides (Nees) Lindenb.
P. pulcherrima Horik.
Japan
Bhutan
India
Germany
Japan
Ohnishi 5723 (
HIRO
)
Long 28832 (
GOET
)
Long 22802 (
GOET
)
Heinrichs & Groth 4340 (
GOET
)
Ohnishi 5771 (
HIRO
)
AY275169
AY550141
AY550142
AJ414633
AY438239
P. raddiana Lindenb.
P. retrorsa Gottsche
P. sandei Sande Lac.
P. sciophila Lindenb.
P. sciophila (‘‘euryphyllon’’)
Ecuador
Costa Rica
Indonesia
Japan
U.S.A.
Holz EC-01-45 (
GOET
)
Heinrichs et al. 4154 (
GOET
)
Gradstein 9970 (
GOET
)
Ohnishi 5400 (
HIRO
)
Smith & Davison s.n. (
GOET
)
AJ422020
AJ422021
AJ414634
AY275171
AJ748128
P. semidecurrens (Lehm. & Lindenb.) Lindenb.
P. stricta Lindenb.
P. subplana Lindenb.
P. subplana
P. trabeculata Steph.
Nepal
Costa Rica
French Guiana
Peru
Japan
Long 21348 (
GOET
)
Heinrichs et al. 4401 (
GOET
)
Holz FG-00-32 (GEOT)
Drehwald 4422 (
GOET
)
Kurita 257 (
HIRO
)
AY275173
AJ416646
AY275174
AJ422023
AY550146
Plagiochilion mayebarae S. Hatt. Japan Ohnishi 5588 (
HIRO
) AY438238

2004] 491HEINRICHS ET AL.: PLAGIOCHILA IN NORTH AMERICA
ML analyses: To decide on the nucleotide substitution
model with the smallest number of parameters that best
fits the data, the program Modeltest 3.06 (Posada & Cran-
dall 1998) was used. Based on the results of the tests, the
model selected by the hierarchical LRT was the TrN mod-
el (Tamura & Nei 1993) with gamma shape parameter(G)
for among site variation calculated from the data set (TrN
1
G). A ML analysis (with the TrN
1
G model) was
implemented as heuristic search with 10 random-addition
sequence replicates. The confidence of branching was as-
sessed using 100 bootstrap resamplings in ML-analysis
(Felsenstein 1985).
MP analyses were performed with the following options
implemented: heuristic search mode with 1,000 random-
addition-sequence replicates (holding 10 trees per repli-
cate), tree bisection-reconnection branch swapping (TBR),
MULTrees option on, and collapse zero-length branches
off. All characters were treated as equally weighted and
unordered. Gaps were coded as unknown characters.
Clade support was estimated from 1,000 bootstrap repli-
cates using heuristic searches with TBR branch swapping.
R
ESULTS AND
D
ISCUSSION
Affinities of Plagiochila austinii and P. euryphyl-
lon according to phylogenetic analyses of the ITS
dataset. Of the 778 investigated characters, 216
were parsimony informative, 124 autapomorphic
and 438 constant. The MP search recovered 50
equally most parsimonious trees (not shown) with
a length of 699 steps, a consistency index (CI) of
0.62, a CI excluding uninformative characters of
0.53, a retention index (RI) of 0.70, and a rescaled
consistency index (RC) of 0.43. The strict consen-
sus of these trees (Fig. 1) is largely congruent to
the ML tree (Fig. 1). The well (MP) to moderately
(ML) supported Plagiochila ‘‘clade B’’ sensu Groth
and Heinrichs (2003) is placed sister to a weakly
supported clade with the robust P. sects. Arrectae
and Fuscoluteae. Accessions of P. austinii from
Kentucky and North Carolina form a well support-
ed monophyletic lineage and are placed sister to a
robust clade with P. flexuosa and P. trabeculata.
The sister relationship of P. austinii and P. flexu-
osa/trabeculata achieves a bootstrap support of 76
in the MP analyses and of 73 in the ML analyses,
leading to a placement of P. austinii in P. sect.
Trabeculatae Inoue. Plagiochila sect. Trabeculatae
is placed sister to P. sect. Fruticosae in a robust
sister relationship. Placement of P. austinii in P.
sect. Arrectae or P. sect. Fuscoluteae is not sup-
ported in the molecular analyses.
Plagiochila euryphyllon (specimen from Tennes-
see) is placed sister to P. sciophila from Japan with
a bootstrap support of 100% both in ML and MP.
This topology as well as the low genetic distance
between both sequences (Fig. 2) supports the spe-
cies concept of So and Grolle (1999) and So (2001)
with a synonymy of P. sciophila and P. euryphyl-
lon.Plagiochila sciophila is nested in the robust P.
sect. Cucullatae clade and is placed sister to a sub-
clade with P. sandei Sande Lac. and P. bantamensis
(Reinw. et al.) Mont. in a well (ML) to moderately
(MP) supported sister relationship. The P. banta-
mensis/sandei/sciophila subclade is sister to a not
(MP) to moderately (ML) supported subclade with
P. integerrima Steph. and P. subplana.
The above results in combination with earlier in-
vestigations allow to propose the following new
sectional subdivision of North American Plagi-
ochila with updated species names:
P
LAGIOCHILA
sect. A
RRECTAE
Carl
Plagiochila retrorsa Gottsche [
5
P. sharpii H.Blomq.,
syn. fide Rycroft et al. (2001)]
This is a section with its center of diversity in
mountainous tropical America (e.g,. Heinrichs et al.
2004a,b); several species occur also in atlantic Eu-
rope (e.g,. Groth et al. 2003) and tropical Africa
(Lindner et al. 2004). The only North American
representative, Plagiochia retrorsa, occurs from the
Appalachian Mts. to Central America, and on the
Azores (Rycroft et al. 2001). Arrectae species are
characterized by nearly exclusively intercalary
branching; a cylindric perianth; simple, intercalary
androecia; homogeneous to indistinctly coarse seg-
mented oil bodies; mostly unispiral elaters; and
baculate spores. Several species are provided with
a vitta. The cuticle is smooth or rough. Plagiochila
sect. Arrectae is morphologically close to P. sect.
Peculiares (see there).
P
LAGIOCHILA
sect. C
UCULLATAE
Schiffn.
Plagiochila sciophila Nees ex Lindenb. [
5
P. acantho-
phylla Gottsche, syn. fide Inoue (1984),
5
Plagiochila
euryphyllon Carl, syn. fide So & Grolle (1999)].
The section includes numerous species from
tropical Asia; one species from Africa (P. integer-
rima, Groth et al. 2003), and another from the Neo-
tropics (P. subplana, Heinrichs 2002; Heinrichs et
al. 1999). The polymorphic species, P. sciophila,is
widespread in Asia and scattered in southern parts
of the U.S.A. (e.g., Inoue 1984; So 2001). Cucul-
latae are medium to large-sized species with dom-
inating intercalary branching, segmented oil bodies,
often large underleaves, a pseudocucullum, and a
capsule with a thin-walled epidermal layer (Groth
et al. 2003; Heinrichs 2002; Inoue 1984). Plagi-
ochila sciophila, with small underleaves, is a rather
non-typical representave that lacks a pseudocucul-
lum.
P
LAGIOCHILA
sect. P
ECULIARES
Schiffn. [
5
P. sect.
Zonatae Carl (Groth et al. 2004)]
Plagiochila semidecurrens (Lehm. & Lindenb.) Lindenb.
Representatives of this Asian-Melanesian section

492 [VOL. 107THE BRYOLOGIST
F
IGURE
1. Rooted strict consensus of 50 equally parsimonious trees recovered during 1,000 random taxon addition
heuristic searches of the nrITS1–5.8S-ITS2 DNA data set. Bootstrap support (
.
50%) is indicated at branches.

2004] 493HEINRICHS ET AL.: PLAGIOCHILA IN NORTH AMERICA
F
IGURE
2. Molecular phylogeny of Plagiochila species based on nrITS1–5.8S-ITS2 DNA sequence comparisions
using 778 aligned positions. The single, most-likely tree (
2
ln
5
4798,7890) was found during during 10 random taxon
addition heuristic searches under the model of Tamura and Nei (1993) with estimated gamma shape (G
5
0.53),
calculated as the best model by Modeltest 3.06 (Posada & Crandall 1998). Bootstrap percentage values (
.
50%) at
branches.
are characterized by vermiculate, flexuous leaf cells
(e.g., Grolle & So 1999). In other respects, sect.
Peculiares resembles the Asian-Western North
American P. sect. Zonatae. Based on inferences
from rps4 (cpDNA) and nrITS sequence data (see
also Figs. 1–2), Groth et al. (2004) merged these
two sections. Section Peculiares resembles sect.
Arrectae; however, the Arrectae usually have
homogeneous to indistinctly coarsely segmented oil
bodies and unispiral elaters, whereas Peculiares are

494 [VOL. 107THE BRYOLOGIST
usually provided with botryoidal oil bodies and bi-
spiral elaters.
P
LAGIOCHILA
sect. P
LAGIOCHILA
Plagiochila asplenioides (L.) Dumort.
Plagiochila columbiana A. Evans
Plagiochila porelloides (Nees) Lindenb.
Plagiochila satoi S. Hatt.
Plagiochila schofieldiana Inoue
Plagiochila sect. Plagiochila is widespread
throughout the Holarctic with a center of diversity
in Asia. Representatives of P. sect. Plagiochila are
characterized by intercalary branching;
6
suborbic-
ular leaves; papillose oil bodies; small leaf teeth;
long cylindrical perianths; an elongate capsule with
thickenings in all layers; bispiral, smooth elaters;
and small, verrucate-vermiculate spores (Groth et
al. 2003).
P
LAGIOCHILA
sect. R
UTILANTES
C
ARL
[
5
P. sect.
Caducilobae Inoue (Groth et al. 2002)].
Plagiochila caduciloba H. Blomq.
Plagiochila exigua (Taylor) Taylor
Plagiochila sect. Rutilantes is known from Af-
rica, Europe, Asia, and the Americas. The two
North American representatives were formerly as-
signed to P. sect. Caducilobae (e.g., Inoue 1975)
or P. sect. Bidentes Carl (e.g., Schuster 1980).
However, the latter is a synonym of P. sect. Arrec-
tae (Groth et al. 2002). The North American rep-
resentatives belong to a well supported subclade
within the Rutilantes that includes tiny species with
easily fragmenting or strongly caducous leaves, and
perianths usually not covered by bracts (e.g., Groth
et al. 2002, 2004). Rutilantes are furthermore char-
acterized by dominating intercalary branching; ho-
mogeneous to indistinctly coarse-segmented oil
bodies; a capsule with wall-thickenings in all lay-
ers; and 1–2 spiral, smooth or rough elaters. Several
species give off a peppermint-like odor (e.g., Groth
et al. 2002).
P
LAGIOCHILA
sect. T
RABECULATAE
Inoue
Plagiochila austinii A. Evans
Plagiochila sullivantii A. Evans
Plagiochila sect. Trabeculatae is a poorly un-
derstood Asian section whose range is here extend-
ed to North America The small to medium sized
members of P. sect. Trabeculatae have
6
oblong
leaves with a trabeculate leaf cell pattern. Morpho-
logically, the Trabeculatae resemble the Neotropi-
cal-European P. sect. Fuscoluteae, but lack the sur-
face wax known from representatives of this section
(e.g., Heinrichs 2002). The sister section, P. sect.
Fruticosae (Figs. 1–2, Groth et al. 2004), differs by
a dendroid habit. Some authors (e.g., Inoue 1984)
merged P. sect. Trabeculatae with the Neotropical
sect. Cobanae Carl. However, we abstain from
combining both names because the characters of
the type species, P. cobana Steph., are still largely
unknown (Groth et al. 2004).
P
LAGIOCHILA
sect. V
AGAE
Lindenb. [
5
P. sects.
Contiguae Carl (Heinrichs et al. 2002b), Cris-
patae Carl, Hypnoides Carl (Heinrichs 2002),
Parallelae Carl, Subtropicae Carl (Groth et al.
2004); P. sect. Yokogurenses Inoue
5
P. sect.
Subtropicae (So 2001)].
Plagiochila aspleniformis R. M. Schust.
Plagiochila diffusa Steph.
Plagiochila floridana A. Evans
Plagiochila invisa (R. M. Schust.) R. M. Schust.
Plagiochila miradorensis Gottsche
Plagiochila montagnei Nees [
5
P. hypnoides Lindenb.
(Heinrichs & Gradstein 2000)]
Plagiochila parvifolia Lindenb. [
5
P. yokogurensis Steph.
(So 2001)].
Plagiochila patula (Sw.) Lindenb. [
5
P. dubia Lindenb.
& Gottsche (Heinrichs et al. 2002a)]
Plagiochila raddiana Lindenb. [
5
P. ludoviciana Sull.
(Heinrichs & Gradstein 2000)]
Plagiochila undata Sull.
Plagiochila virginica A. Evans
The Vagae are perhaps the most speciose section
of Plagiochila. This group is pantropical in distri-
bution (Groth et al. 2004) with one species in Ma-
caronesia (Heinrichs et al. 2002a). Previously P.
sect. Vagae was split into numerous sections (e.g.,
Carl 1931; Schuster 1980) which were based on
differences in density of foliation or leaf shape.
However, this broadly circumscribed section forms
a robust monophyletic lineage in phylogenetic anal-
yses of ITS and of rps4 datasets (e.g., Groth et al.
2004). Morphologically, Vagae are characterized
by the usually dominating terminal branching, fre-
quent presence of propagules and plantlets on the
leaves, a capsule wall with thickenings in all layers,
and the sometimes multi-cellular, baculate spores.
Several Neotropical species reach the Southern
United States (P. diffusa,P. montagnei,P. patula,
and P. raddiana). Plagiochila parvifolia, a species
with fragmenting leaves, is widespread in Asia.
D
ISCUSSION
The incorporation of molecular data into the sys-
tematic study of Plagiochila has led to new insights
regarding biogeography and sectional subdivision
of this large genus. Plagiochila (sect. Trabeculatae)
austinii was placed in its own Plagiochila subsec-
tion Austiniae R. M. Schust. (nom. inval. Art. 36.1
ICBN) by Schuster (1959b: 309) and disposed to
P. sect. Choachinae. However, morphological con-
sensus of P. austinii and typical elements of P. sect.

2004] 495HEINRICHS ET AL.: PLAGIOCHILA IN NORTH AMERICA
T
ABLE
2. The North American Plagiochila flora according to Schuster (1980) and current knowledge.
According to Schuster (1980) Current knowledge
Sect. Bidentes
P. caduciloba,P. corniculata Sect. Arrectae
P. retrorsa (P. sharpii)
Sect. Choachinae
P. austinii,P. sullivantii Sect. Cucullatae
P. sciophila (P. acanthophylla,P. eury-
phyllon)
Sect. Ciliatae
P. acanthophylla,P. euryphyllon Sect. Peculiares
P. semideccurens
Sect. Contiguae
P. aspleniformis,P. dubia,P. floridana,P. virginica Sect. Plagiochila
P. asplenioides,P. columbiana,P. porel-
loides,P. satoi,P. schofieldiana
Sect. Crispatae
P. invisa,P. ludoviciana,P. miradorensis,P. undata Sect. Rutilantes
P. caduciloba,P. exigua (P. corniculata)
Sect. Hypnoides
P. hypnoides Sect. Trabeculatae
P. austinii,P. sullivantii
Sect. Parallelae
P. diffusa Sect. Vagae
P. aspleniformis,P. diffusa,P. floridana,
P. invisa,P. miradorensis,P. montag-
nei (
5
P. hypnoides), P. parvifolia (P.
yokogurensis), P. patula (P. dubia), P.
raddiana (P. ludoviciana), P. undata,
P. virginica
Sect. Plagiochila
P. asplenioides,P. columbiana,P. satoi
Sect. Yokogurenses
P. yokogurensis
Sect. Zonatae
P. semidecurrens
P. sharpii
Choachinae sensu Carl [1931 e.g., P. punctata
(Taylor) Taylor, P. choachina Gottsche] is rather
poor. Plagiochila austinii differs from the latter
taxa by the botryoidal oil bodies, the
6
oblong
leaves and the trabeculate leaf cell pattern. Schuster
(1980) recognized these differences when compar-
ing P. sect. Trabeculatae with his invalid subsect.
Austiniae; however, P. sect. Choachinae (
5
P. sect.
Arrectae, see above) and P. sect. Trabeculatae are
clearly separated in molecular topologies and
placed in different main clades of Plagiochila
(Groth et al. 2004; Figs. 1–2) The exclusion of P.
austinii and P. sullivantii from the Neotropical-At-
lantic European-African P. sect. Arrectae and
placement in P. sect. Trabeculatae points at close
relationships of the north American and Asian Pla-
giochila floras. Other examples of this relationship
can be seen in P. sect. Peculiares (P. semidecur-
rens), P. sect. Vagae (P. parvifolia), and P. sect.
Cucullatae. It is now clear that phenotypes of the
polymorphic Asian P. (sect. Cucullatae)sciophila
occur in North America and that the morphologi-
cally similar P. subplana is most likely restricted
to the Neotropics.
Schuster (1980) recognized 10 Plagiochila sec-
tions in North America whereas in the present over-
view seven sections are accepted for the region (Ta-
ble 2). The reduction is caused mainly by our
broader concept of P. sect. Vagae.
The subkingdoms of the Holarctic are dominated
by different Plagiochila elements. Plagiochila sect.
Vagae is the largest natural species group of the
genus in the western Holarctic whereas the eastern
Holarctic is dominated by species of P. sect. Ar-
rectae (e.g., Groth et al. 2003).
A
CKNOWLEDGMENTS
We thank Christine Davis and Jon Shaw for sending the
DNA vouchers of Plagiochila austinii and Bernard Gof-
finet for comments. Financial support of the Deutsche For-
schungsgemeinschaft (DFG 3584/1) is gratefully acknowl-
edged.
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