118 urn:lsid:arphahub.com:pub:71cc5dc6-a767-5334-951f-ef6ae8936459 Plant Ecology and Evolution plecevo 2032-3913 2032-3921 Meise Botanic Garden and Royal Botanical Society of Belgium 10.5091/plecevo.170279 170279 Research Article Bryata Genetics Morphology & Anatomy Systematics World An infrageneric classification of the genus Lejeunea (Marchantiophyta: Lejeuneaceae) using molecular phylogeny and morphology Lee Gaik Ee gaik.ee@umt.edu.my https://orcid.org/0000-0001-5161-6196 1 Conceptualization Writing - original draft Data curation Formal analysis Funding acquisition Investigation Methodology Project administration Gradstein S. Robbert 2 Conceptualization Writing - original draft Formal analysis Investigation Validation He Xiaolan https://orcid.org/0000-0002-7754-2233 3 Writing - review and editing Formal analysis Investigation Bechteler Julia https://orcid.org/0000-0002-5115-657X 4 5 Writing - review and editing Data curation Investigation Methodology Software Schäfer-Verwimp Alfons https://orcid.org/0000-0002-2720-6055 6 Writing - review and editing Data curation Methodology Resources Pócs Tamás 7 Writing - review and editing Data curation Methodology Resources Institute of Tropical Biodiversity and Sustainable Development, Universiti Malaysia Terengganu, Terengganu, Malaysia Senckenberg Institute for Plant Form and Function (SIP) Jena Germany https://ror.org/002pfnf57 Meise Botanic Garden, Meise, Belgium Meise Botanic Garden Meise Belgium https://ror.org/01h1jbk91 Botany Unit, Finnish Museum of Natural History, University of Helsinki, Helsinki, Finland Universiti Malaysia Terengganu Terengganu Malaysia https://ror.org/02474f074 Senckenberg Institute for Plant Form and Function (SIP), Jena, Germany Finnish Museum of Natural History, University of Helsinki Helsinki Finland https://ror.org/040af2s02 Institute of Biodiversity, Ecology and Evolution, Friedrich Schiller University Jena, Jena, Germany Friedrich Schiller University Jena Jena Germany https://ror.org/05qpz1x62 Mittlere Letten 11, Herdwangen-Schönach, Germany Unaffiliated Herdwangen-Schönach Germany Botany Department, Eszterházy Károly Catholic University, Eger, Hungary Eszterházy Károly University Eger Hungary

Corresponding author: Gaik Ee Lee (gaik.ee@umt.edu.my)

Academic editor: Brecht Verstraete

 2026 04 03 2026 159 1 123 141 4A3F894A-F5FB-5830-A637-C09234281FDE 0 28 08 2025 12 11 2025 Gaik Ee Lee, S. Robbert Gradstein, Xiaolan He, Julia Bechteler, Alfons Schäfer-Verwimp, Tamás Pócs This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Background and aims – The genus Lejeunea, with about 375 accepted species, is one of the most species-rich and intricate genera of liverworts. Here, we present the first integrative, worldwide infrageneric classification of Lejeunea based on morphology and molecular-phylogenetic analyses.

Material and methods – Maximum likelihood analysis and Bayesian inference of sequences from two chloroplast regions (trnL-trnF, rbcL) and the nuclear ITS region of about 35% of the species, combined with morphological evidence.

Key results and conclusions – The phylogenetic analyses revealed numerous robust clades within two major lineages, corresponding to subgenera Lejeunea and Crossotolejeunea. Integrating molecular phylogenetic evidence and morphological data, we describe 15 sections: four in subg. Lejeunea (sect. Glaucescentes, sect. Lamacerinae, sect. Lejeunea, sect. Macrolejeunea) and 11 in subg. Crossotolejeunea (sect. Apolejeunea, sect. Crossotolejeunea, sect. Echinocolea, sect. Flavae, sect. Heterolejeunea, sect. Inflatolejeunea, sect. Minutilobae, sect. Nanolejeunea, sect. Papillolejeunea, sect. Sordidae, sect. Xenantholejeunea). Four sections have a neotropical distribution, three are pantropical, two are pantropical and extend into temperate regions, two are Afro-American, two are Asian, one is Asian-Australasian, and one has a tropical amphi-Pacific range.

 classification Lejeunea subgenus Crossotolejeunea Lejeunea subgenus Lejeunea liverworts molecular phylogeny morphology taxonomy Introduction

The genus Lejeunea Lib. (Marchantiophyta), with about 375 currently accepted species (Brinda and Atwood 2024, with updates and with removal of doubtful species), is the most species-rich genus of the family Lejeuneaceae, together with Cololejeunea (Spruce) Steph. Taxonomically, Lejeunea is one of the most intricate genera of the bryophytes as indicated by the large number (22) of generic synonyms (Brinda and Atwood 2024), far higher than in any other bryophyte genus. This high synonymy reflects the large complexity of the family Lejeuneaceae – the largest family of the Marchantiophyta with well over a thousand species – and the difficulty to arrange the numerous species recognized in this family into well-defined genera (Schuster 1963; Gradstein 1979; Gradstein et al. 2003).

The genus Lejeunea is generally recognized by the small, pale green plants with thin stems with a hyalodermis and two cells wide ventral merophytes, lobules with a proximal hyaline papilla, thin-walled leaf cells with small, granular or homogeneous oil bodies, absence of ocelli, bifid underleaves (rarely undivided), and lejeuneoid innovations (Gradstein et al. 2001; Lee and Gradstein 2021; Fig. 1). Phylogenetic evidence suggests that Lejeunea originated in the Neotropics, where it diverged from its sister genus Microlejeunea (Spruce) Steph. during the early Eocene, followed by multiple migrations into Asia, Australasia, Africa, and Europe (Heinrichs et al. 2013; Lee et al. 2020). The genus shows extensive morphological homoplasy and molecular data are therefore essential for elucidating its phylogenetic history and for establishing robust taxonomic hypotheses (Heinrichs et al. 2013; Ye et al. 2013).

10.5091/plecevo.170279.figure1 9D7E2364-F626-520B-A946-488CD85BED4D

Habit of Lejeunea. A. Lejeunea mandonii. B. Lejeunea cavifolia. C. Lejeunea lumbricoides. D. Lejeunea discreta. E. Lejeunea tuberculosa. F. Lejeunea albescens. Photos by Des Callaghan (A), Hermann Schachner (B), and Gaik Ee Lee (C, D, E, F).

https://binary.pensoft.net/fig/1545154

The present paper deals with the infrageneric classification of Lejeunea. Several attempts have been made to divide the genus into subgenera and sections. The first major infrageneric classification was proposed by Spruce (1884), who divided Lejeunea into 39 subgenera based on the shape of the underleaves (divided or undivided), branching pattern, presence or absence of subfloral innovations, ocelli, perianth shape and ornamentation, etc. (Gradstein 1979). Spruce’s circumscription of Lejeunea was very broad and encompassed almost the entire family Lejeuneaceae. Many of Spruce’s subgenera were soon after recognized as well-defined genera and the species described in Lejeunea by Spruce have now been transferred to over 60 genera (Schiffner 1893; Gradstein 1979; Söderström et al. 2015). Following the redefinition of Lejeunea, Schuster (1963) was the first to attempt a worldwide infrageneric classification of the genus, recognizing six subgenera, subg. Chaetolejeunea R.M.Schust., subg. Inflatolejeunea (S.W.Arnell) R.M.Schust., subg. Lejeunea, subg. Microlejeunea Spruce, subg. Otigoniolejeunea (Spruce) Schiffn., and subg. Pleurolejeunea R.M.Schust. & Kachroo. None of these are currently accepted, however; Microlejeunea and Otigoniolejeunea (Spruce) Schiffn. have been shown to be distinct genera (Dong et al. 2013; Ye et al. 2013) and the remaining subgenera are considered synonyms of Lejeunea.

Subsequent attempts to subdivide the genus Lejeunea based on morphology have been of limited scope, focusing only on the species of the New World. In his North American Flora, Schuster (1980) placed the local species of Lejeunea in five subgenera, subg. Apolejeunea R.M.Schust., subg. Lejeunea, subg. Crossotolejeunea Spruce, subg. Microlejeunea, and subg. Nanolejeunea R.M.Schust. The subgenus Lejeunea was further subdivided into nine sections. All of these are still accepted with exception of subg. Microlejeunea. Reiner-Drehwald (1999) and Gradstein et al. (2001) classified the species of tropical America in 12 resp. 7 subgenera, most of which are still accepted today.

Recent applications of molecular analysis in Lejeuneaceae have revealed considerable incongruence between morphology-based classifications and molecular phylogeny (see Gradstein 2013 for a review). Examples are the genera Aphanolejeunea A.Evans, Aureolejeunea R.M.Schust., Chondriolejeunea (Benedix) G.Kis & Pócs, Cystolejeunea A.Evans, Dendrolejeunea Spruce, Evansiolejeunea Vanden Berghen, Leucolejeunea A.Evans, Metzgeriopsis K.I.Goebel, Myriocolea Spruce, Omphalanthus Lindenb. & Nees, Pluvianthus R.M.Schust. & Schäf.-Verw., and Trocholejeunea Schiffn., all of which do not merit generic status and were sunk in the synonymy of other genera based on molecular evidence (Gradstein et al. 2006; Wilson et al. 2007; Sukkharak et al. 2011; Heinrichs et al. 2012; Dong et al. 2013; Schäfer-Verwimp et al. 2014; Ye et al. 2015; Wang et al. 2016). Some of them, such as Metzgeriopsis and Myriocolea, are morphologically highly specialized taxa and were placed in separate subfamilies in the past or were even excluded from Lejeuneaceae. In other instances, infrageneric taxa were shown to be distinct genera, such as Cumulolejeunea R.L.Zhu & L.Shu from Australia, Dibrachiella (Spruce) X.Q.Shi, R.L.Zhu & Gradst. from tropical America and Africa, Gradsteinianthus R.L.Zhu & Jian Wang bis from East Asia, Soella R.L.Zhu, L.Shu, Qiong He & Y.M.Wei from Japan, and Yanoella R.L.Zhu, L.Shu, C.J.Bastos & Vilas Bôas-Bastos from Brazil. With regard to Lejeunea, molecular phylogenetic evidence has shown that Oryzolejeunea R.M.Schust., Sphaerolejeunea Herzog, and Taxilejeunea (Spruce) Schiffn. are nested in Lejeunea and are synonyms. In contrast, Microlejeunea and Otigoniolejeunea are distinct genera and not part of Lejeunea (see above). The molecular data have also corroborated morphological concepts, such as, for example, the transfers to Lejeunea of Amblyolejeunea Jovet-Ast, Amphilejeunea R.M.Schust., Cryptogynolejeunea R.M.Schust., Dicladolejeunea R.M.Schust., Echinocolea R.M.Schust., Macrolejeunea Schiffn., and Neopotamolejeunea M.E.Reiner, all of which originally were proposed based on morphological evidence (Grolle 1988; Reiner-Drehwald and Goda 2000; Ilkiu-Borges 2005; Reiner-Drehwald 2005a, 2005b; Gradstein and Reiner-Drehwald 2007).

A first worldwide molecular analysis of the genus Lejeunea based on three loci and a sampling of about 23% of the species showed that Lejeunea is monophyletic and splits into two major lineages, subg. Lejeunea and subg. Crossotolejeunea (Heinrichs et al. 2013). Morphological diagnoses of these two subgenera were not provided, however, and a further infrageneric subdivision of the genus was not attempted.

In the present study, the dataset of Heinrichs et al. (2013) is expanded to further elucidate the relationships within Lejeunea from a molecular and morphological perspective. We present the most comprehensive phylogeny of the genus to date, using accessions of about 35% of total species diversity in Lejeunea and broadly spanning its morphological variation, and we discuss the implications for infrageneric classification of Lejeunea.

 Material and methods Taxon sampling

We sampled 131 species of Lejeunea, including sequences of 85 species from Heinrichs et al. (2013), 41 species from Lee et al. (2019, 2020, 2022), and five newly sequenced species from this study (L. balazsii (Pócs) R.M.Schust., L. candida (Pócs) R.M.Schust., L. furcicornuta (Grolle) G.E.Lee & Pócs, L. rhodesiae (Sim) R.M.Schust., L. sharpii (R.M.Schust.) R.M.Schust.). The ingroup included members of almost all the infrageneric groups of Lejeunea recognized over the last 100 years, and all the major ones. Two species of Lepidolejeunea R.M.Schust., two of Harpalejeunea (Spruce) Schiffn., and two of Microlejeunea were sampled as outgroups, following Heinrichs et al. (2013). In the DNA analysis, one accession per species was analysed in this study. Voucher information and GenBank accession numbers are listed in Supplementary material 1. All voucher specimens were carefully examined morphologically, and original identifications were verified and corrected if necessary.

 DNA extraction, amplification, and sequencing

Total genomic DNA was isolated using the Invisorb Spin Plant Mini Kit (Stratec Molecular GmbH, Berlin, Germany) prior to amplification. The rbcL, trnLF, and ITS regions were amplified with the PCR protocol of Bechteler et al. (2016). Further preparations of the PCR products followed Lee et al. (2016). The rbcL, trnLF, and ITS regions were chosen because they have been shown to effectively resolve phylogenetic relationships at different taxonomic levels in Lejeunea (e.g. Lee et al. 2016, 2020) and other members of Lejeuneaceae. Bidirectional sequences were generated by an ABI 3730 48 capillary sequencing machine using the BigDye Terminator v.3.1 Cycle Sequencing Kit (Applied Biosystems, Foster City, CA, USA). Sequencing primers were the same as those used for the PCR.

 Phylogenetic analyses

Newly generated sequences were assembled and edited with PhyDE v.0.9971 (http://www.phyde.de/). The new sequences were integrated into the Lejeunea alignment of Lee et al. (2020) using BioEdit v.5.0.9 (Hall 1999). Missing sequence stretches were coded as unknown, and ambiguous hotspot positions were excluded. The reverse complement of one inverted repeat in the trnLF region was aligned with the other sequences prior to molecular phylogenetic analyses (Borsch and Quandt 2009).

Maximum likelihood (ML) analysis was conducted with RAxML-HPC v.8.2.8 (Stamatakis 2014). jModelTest 2 (Darriba et al. 2012) was employed to determine the appropriate DNA substitution model, rate of invariable sites, and gamma rate heterogeneity according to the Akaike information criterion (AIC; Akaike 1973) for the chloroplast data and the nuclear data. The analyses resulted in the GTR+G+I model for the chloroplast data and a TIM1+G+I model for the nuclear data. Since RAxML does not allow the implementation of the TIM1 model and to accommodate the suggestions in Stamatakis (2016), the GTR+G model was used for all three partitions. Trees were generated by selecting ten independent runs and the multiparametric bootstrap option autoMRE (Pattengale et al. 2010), resulting in 300 bootstrap replicates. ML bootstrap values (BS) from the RAxML-HPC output were visualised using FigTree v.1.4.3 (https://tree.bio.ed.ac.uk/software/figtree/), which allows displaying node labels, branch lengths, and other tree features. Compatibility of the chloroplast and nuclear regions was explored by comparison of the trees obtained from independent ML analysis of each region. The trees were compared by eye to identify conflicting nodes with bootstrap values higher than 70% (Mason-Gamer and Kellogg 1996). As no evidence of incongruence was detected, the datasets were combined, and an ML analysis was conducted with two plastid (rbcL, trnLF) partitions and a nuclear (ITS) partition.

Bayesian inference (BI) was conducted with the program MrBayes v.3.2.6 (Ronquist et al. 2012). The same dataset, nuclear substitution models, and partitions were used as in the ML analysis. Two simultaneous metropolis-coupled Markov chain Monte Carlo (MCMC), including three heated chains and one cold chain, were run for two million generations and sampled every 200 generations (resulting in 10,000 sampled trees and parameters). The runs were checked for convergence using the potential reduction factor values (PSRF; values close to 1.00) and the effective sample size values (EES; values above 200) in TRACER v.1.7 (Rambaut et al. 2018) and an average standard deviation (SD) of split frequency below 0.01 indicated a sufficiently long run. The first 25% of trees from each run (2,500 out of 10,000) were discarded as burn-in, and the remaining 7,500 trees per run (15,000 trees in total) were combined and summarised by TreeAnnotator v.1.8.3 (Drummond et al. 2012) using median node heights. The resulting maximum clade credibility (MCC) tree was visualised using FigTree v.1.4.3, and values were regarded as significant when the posterior probability (PP) was ≥ 0.95 (Larget and Simon 1999).

 Morphological investigation

For each species, we scored the presence/absence of gametophytic characters that had been used in Lejeunea taxonomy (e.g. Schuster 1980; Reiner-Drehwald 1999; Gradstein et al. 2001), including sexuality, ventral merophyte width, number and size of epidermal and medullary cells, number of lobule teeth, length of the first lobule tooth, cuticle smooth or papillose, trigone size, presence of intermediate wall thickenings, underleaves undivided or bifid, presence of male bracteoles, innovations sterile or fertile (or absent), ornamentation of perianth keels, presence of perianth keels, type of asexual reproduction, and oil bodies granular or homogeneous (Fig. 2). Characters were scored based on the examination of voucher specimens (multiple specimens per species) and the literature. Sporophyte characters were not considered as they are still very incompletely known in the species of Lejeunea. Character states were plotted on the molecular phylogenetic tree in order to visualise their phylogenetic relevance. Selected morphological characters were illustrated with scanning electron microscopy (SEM) (Fig. 3) and oil body photographs (Fig. 4). SEM images were obtained from dried herbarium specimens, and suitable structures were selected under a compound microscope, fixed in 4% glutaraldehyde, dehydrated through an ethanol series, critical-point dried, sputter-coated with gold, and examined with a Leo 1450 VPSEM scanning electron microscope.

10.5091/plecevo.170279.figure2 9E7F86DA-99C6-5801-95E1-8E29D811EA71

Morphological character states of the investigated Lejeunea species as mapped onto the maximum likelihood topology.

https://binary.pensoft.net/fig/1545155 10.5091/plecevo.170279.figure3 C727F257-1D2D-501A-8577-229DFDA6AE35

Morphological character states of Lejeunea species. A. Underleaves bifid (L. microloba). B. Underleaves undivided (L. mimula). C, H. Male bracteoles limited to the base of the male shoot (L. umbilicata). D. Cuticle smooth (L. lumbricoides). E. Cuticle punctate-papillose (L. mimula). F. Lobule with a single tooth (L patersonii). G. Asexual reproduction by strap-shaped gemmae (L. cocoes). I. Perianth without keels (L. umbilicata). J. Perianth with mammillose keels (L. kinabalensis). K. Perianth with 2-winged keels (L. dipterota). L. Perianth with 2-winged keels (L. lumbricoides).

https://binary.pensoft.net/fig/1545156 10.5091/plecevo.170279.figure4 09F630F2-37F6-54FE-938B-9C03279A3768

Oil bodies of Lejeunea species. A. Granular (L. discreta). B. Homogeneous (L. dimorpha).

https://binary.pensoft.net/fig/1545157 Results

The combined alignment based on sequences of 131 Lejeunea species and six outgroup species had a total length of 2360 base pairs. The three partitions consisted of the rbcL (895 bp), trnLF (441 bp), and ITS (1024 bp) regions. The topologies of the ML and BI trees were largely congruent, with only minor discrepancies at weakly supported nodes that did not influence the overall conclusions.

The phylogenetic analyses revealed that Lejeunea is a well-supported clade with a bootstrap value (BS) of 89% and a posterior probability (PP) of 1.00. The genus split into two main lineages, earlier detected by Heinrichs et al. (2013) based on a more limited dataset, a Lejeunea clade (BS 100, PP 1.00) and a Crossotolejeunea clade (BS 75, PP 0.99). The two lineages were well resolved at branch ends and included a large number of robust clades with a bootstrap support of (90–)97–100% and Bayesian posterior probabilities of 0.99–1.00 (Fig. 5). The backbone of the tree, however, was partially unresolved.

10.5091/plecevo.170279.figure5 2F709753-EC08-5308-A239-1A9250EF08C0

Infrageneric classification of Lejeunea based on the maximum likelihood tree. Sections recognized in this study are highlighted in different colours. Clade numbers are shown in bold face.

https://binary.pensoft.net/fig/1545158

The scored morphological characters were highly homoplasious, although many of the clades had unique combinations of character states. The distribution of character states along the phylogenetic tree is shown in Fig. 6. The Lejeunea clade included mostly autoicous species with bracteoles restricted to the base of the male spike, whereas the Crossotolejeunea clade was predominantly made up of dioicous species with bracteoles restricted to the base of the male spike or present throughout. Other character states that served to characterize clades included the number and size of epidermal and medullary cells, number of lobule teeth and length of the first tooth, roughness of the cuticle (smooth or finely papillose), oil bodies granular or homogeneous, presence and fertility of innovations, presence and ornamentation of perianth keels, and type of asexual reproduction. Ventral merophyte width, trigone size, and presence of intermediate wall thickenings were little informative at the clade level.

10.5091/plecevo.170279.figure6 933CB784-42B0-5696-835A-AE6A621759C9

Maximum likelihood (ML) phylogeny of Lejeunea based on three markers from nuclear and plastid DNA. ML bootstrap probabilities ≥ 70 and Bayesian posterior probability ≥ 0.95 are indicated on the branches. Morphological character states (Fig. 2) are mapped onto the tree. Clade numbers are shown in bold face.

https://binary.pensoft.net/fig/1545159 Discussion

The present study, based on sequences of about 35% of total species diversity of Lejeunea and broadly spanning the morphological variation in the genus, presents the most comprehensive phylogeny of the large genus Lejeunea to date. The results of the phylogenetic analyses confirm the monophyly of the genus and its subdivision into two broad subgenera, subg. Lejeunea (= Lejeunea clade) and subg. Crossotolejeunea (= Crossotolejeunea clade) (Heinrichs et al. 2013). Each subgenus contains several robust clades, with bootstrap values ranging from (90–)97 to 100% and maximum Bayesian posterior probability (PP 0.99–1.00) (Fig. 5), which are described here as sections: four in subg. Lejeunea (sect. Glaucescentes, sect. Lamacerinae, sect. Lejeunea, sect. Macrolejeunea) and 11 in subg. Crossotolejeunea (sect. Apolejeunea, sect. Crossotolejeunea, sect. Echinocolea, sect. Flavae, sect. Heterolejeunea, sect. Inflatolejeunea, sect. Minutilobae, sect. Nanolejeunea, sect. Sordidae, sect. Papillolejeunea, sect. Xenantholejeunea). All of them contain the type species of a previously recognized infrageneric group with exception of the sect. Sordidae, which is described here as new, and can be characterized by a combination of morphological features. A monospecific lineage within subg. Lejeunea containing L. hibernica Bischl., H.A.Mill. & Bonner ex Grolle, and a few minor lineages within subg. Crossotolejeunea, including three species from Africa (L. hepaticola (Steph.) Steph., L. obtusata Gottsche, L. rhodesiae (Sim) R.M.Schust.) and five from Asia (L. konosensis Mizut., L. patersonii (Steph.) Steph., L. reinerae Ilk.-Borg., L. stenodentata M.A.M.Renner & Pócs, L. stevensiana (Steph.) Mizut.), are mostly not well supported and are left unclassified. Their phylogenetic position needs further study.

The proposed sectional classification incorporates almost all the infrageneric groups recognised in Lejeunea in the last 100 years, and all the major ones. Our molecular analyses largely confirm several traditionally recognised groups (e.g. sect. Flavae, sect. Glaucescentes, and sect. Lamacerinae) but also reveal novel relationships. For example, some previously unrecognised groupings, e.g. sect. Papillolejeunea, sect. Sordidae, and sect. Xenantholejeunea, are strongly supported as monophyletic.

The sections also show distinctive geographical patterns: four sections have a neotropical distribution (Crossotolejeunea, Echinocolea, Macrolejeunea, Nanolejeunea), three are pantropical (Flavae, Glaucescentes, Minutilobae), two are pantropical and extend into temperate regions (Lamacerinae, Lejeunea), two are Afro-American (Heterolejeunea, Inflatolejeunea), two are Asian (Apolejeunea, Xenantholejeunea), one is Asian-Australasian (Papillolejeunea), and one is tropical amphi-Pacific (Sordidae). This geographical pattern supports earlier hypotheses regarding the biogeographic history of the genus Lejeunea (Lee et al. 2020) and highlights the evolutionary diversification within the genus.

Although the investigated morphological characters were considerably homoplasious across the genus, the sections are usually distinguishable by a unique combination of character states as shown in the below classification. The importance of sexuality in the infrageneric classification of the genus, shown earlier by Heinrichs et al. (2013), could be confirmed. In addition, male bracteoles and oil bodies proved to be phylogenetically highly informative.

Several not-sequenced species and infrageneric groups are added to the classification based on morphological grounds. Their taxonomic position should be verified by molecular analysis. Two subgenera (subg. Hygrolejeunea Spruce, subg. Prionocolea R.M.Schust.) and four sections (sect. Protolejeunea R.M.Schust., sect. Cladogynae R.M.Schust., sect. Floridanae R.M.Schust., sect. Microstipulata R.M.Schust.) that have not yet been sequenced are not taken into account in the classification. All of them are very minor groups with one or two accepted species only.

Further work on the infrageneric classification of Lejeunea may focus on further expanding the sampling of the species and the infrageneric taxa that have not yet been sequenced. Study of neglected and little-known morphological characters, such as the morphology of the female involucre (bract size relative to vegetative leaves, bract symmetry, the fusion of bracts and bracteoles) and the anatomy of the sporophyte generation, might also help to further unravel the phylogenetic relationships within the large and complex genus Lejeunea.

 Taxonomic treatment <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Lejeunea">Lejeunea</tp:taxon-name-part></tp:taxon-name></italic> Lib. (<xref ref-type="bibr" rid="B40">Libert 1820</xref>: 372) Plantae Lejeuneales Lejeuneaceae 508B518A-F9EB-5BCC-8900-70341C3A6465 Lejeunea subg. Lejeunea Lejeunea subg. Eulejeunea Spruce (Spruce 1884: 260), nom. inval. (ICN Art. 21.3, Turland et al. 2025) ? Amblyolejeunea Jovet-Ast (Jovet-Ast 1949: 49) – Type species: A. fulfordiae Jovet-Ast (= L. fulfordiae (Jovet-Ast) R.L.Zhu). ? Lejeunea subg. Pleurolejeunea R.M.Schust. & Kachroo (Schuster 1963: 123) – Type species: L. patagonica Steph. Type species

Lejeunea cavifolia (Ehrh.) Lindb.

 Description

Plants mostly monoicous (in more than 80% of the analysed species). Oil bodies granular or homogeneous. Gynoecial bracts usually broadly fused with the bracteole on both sides. Asexual reproduction by specialized devices usually absent.

 Distribution

Pantropical, with some species extending into temperate regions.

 Species

Forty-eight species were found to belong to this subgenus.

 Notes

The typical characters of subg. Lejeunea are the predominantly monoicous sexuality, the usually broadly connate female bracts and bracteole, and the scarcity of specialized devices for asexual reproduction. Based on the molecular phylogenetic, morphological, and nomenclatural evidence, subg. Lejeunea is subdivided into four sections: sect. Glaucescentes, sect. Lamacerinae, sect. Lejeunea, and sect. Macrolejeunea.

Amblyolejeunea, a monospecific neotropical genus characterized by undivided underleaves and eplicate perianths without beak, and L. subg. Pleurolejeunea, a group of species characterized by gynoecia on abbreviated branches without innovations and with long 5-keeled perianths, are tentatively placed in synonymy of subg. Lejeunea because of the broadly connate female involucre in the two groups, autoicy, and the absence of specialized devices for asexual reproduction. A molecular phylogenetic analysis of the two groups and a study of the oil bodies should be carried out to verify their taxonomic relationship. Interestingly, one of the members of subg. Pleurolejeunea, L. syoshii Inoue, has homogeneous oil bodies (Inoue 1977), suggesting an affinity to sect. Lejeunea.

 Plantae Lejeuneales Lejeuneaceae 9870B232-1D71-5852-82E7-D315CED58F0A Lejeunea sect. Macrolejeunea (Spruce) Gradst. & G.E.Lee stat. nov. Lejeunea subg. Macrolejeunea Spruce (Spruce 1884: 224) Type species

Lejeunea pallescens Mitt. (lectotype, designated by Evans 1906).

 Description

Plants dioicous. Stem epidermis cells large, ca 3.5–6 times larger than medullary cells and strongly bulging outwards, medullary cells in 10–50 rows. Oil bodies granular. Gynoecial innovations absent. Perianths eplicate. Asexual reproduction by specialized devices absent.

 Distribution

Neotropical.

 Species

Lejeunea osculatiana De Not., L. pallescens Mitt.

 Further species (not sequenced)

Lejeunea sessiliflora (Steph.) Grolle.

 Notes

The typical characters of sect. Macrolejeunea are the absence of innovations and the usually eplicate perianth. Lejeunea sessiliflora, a rare Caribbean species known from Cuba and Haiti, is placed in sect. Macrolejeunea following Grolle (1988). The species fits this section in stem anatomy, dioicy, a highly connate female involucre, and absence of innovations and asexual reproduction.

 References

Grolle (1988), Reiner-Drehwald and Schäfer-Verwimp (2008).

 Plantae Lejeuneales Lejeuneaceae 3A2364E9-3D5A-5980-B5DB-CA079A0AC2CC Lejeunea sect. Glaucescentes R.M.Schust. (Schuster 1980: 1001) Lejeunea subg. Taxilejeunea Spruce (Spruce 1884: 212) – Type species: L. pterigonia (Lehm. & Lindenb.) Mont. (lectotype, designated by Jones 1967). Sphaerolejeunea Herzog (Herzog 1938: 88) – Type species: S. umbilicata Herzog. ? Lejeunea subg. Neopotamolejeunea (M.E.Reiner) Gradst. & M.E.Reiner (Gradstein and Reiner-Drehwald 2007: 487) – Type species: L. juruana Gradst. & M.E.Reiner. Type species

Lejeunea glaucescens Gottsche.

 Description

Plants mostly autoicous (occasionally dioicous). Stem epidermis as in sect. Macrolejeunea. Oil bodies granular (homogeneous in L. aquatica and L. topoensis). Gynoecial innovations present and usually repeatedly fertile, with 2–10 gynoecia in a row. Perianths eplicate or shortly plicate, keels smooth or toothed. Asexual reproduction by specialized devices absent.

 Distribution

Pantropical.

 Species

Lejeunea aquatica Horik., L. conformis Nees & Mont., L. debilis (Lehm. & Lindenb.) Nees & Mont., L. drehwaldii Heinrichs & Schäf.-Verw., L. eifrigii Mizut., L. flaccida Lindenb. & Gottsche (= L. obtusangula Spruce), L. furcicornuta (Grolle) G.E.Lee & Pócs, L. glaucescens Gottsche, L. pterigonia (Lehm. & Lindenb.) Mont., L. serpillifolioides (Raddi) Gradst. (= L. isocalycina (Nees) Prantl), L. sulphurea (Lehm. & Lindenb.) Spruce, L. terricola Spruce, L. topoensis Gradst. & M.E.Reiner, Lejeunea sp. 1. (= “L. sikorae (Steph.) Steph.”, Figs 5, 6).

 Notes

This section contains many former members of the genus Taxilejeunea, a group of species with elaborate stems made up of highly enlarged epidermis cells and rather numerous medullary cell rows, and with repeatedly fertile innovations resulting in gynoecia and perianths arranged in rows of 2–10 gynoecia. Underleaves vary considerably in size, and some species have very large and strongly auriculate underleaves. The position of L. drehwaldii in sect. Glaucescentes is somewhat unexpected as it differs from other members of this section in having leaves bordered by hyaline cells and sterile or no innovations. The aberrant morphology of the species, which was previously placed in a separate genus, Sphaerolejeunea, is reflected by its position on a long, although unsupported branch.

The position of L. aquatica and L. topoensis in the Glaucescentes clade is unexpected as these species have homogeneous oil bodies characteristic of sect. Lejeunea. Moreover, L. aquatica is very similar to L. japonica, a member of sect. Lejeunea, differing from the latter only in smaller lobules, slightly thick-walled stem cells, and the semi-aquatic habitat (Mizutani 1961). The latter characters, seen also in L. topoensis, are usually interpreted as adaptations to the riverine habitat (e.g. Gradstein and Reiner-Drehwald 2007). Further study including the type of the rheophilous subgenus Neopotamolejeunea to which L. topoensis has been assigned, are needed to clarify the taxonomic position of these two riverine Lejeunea species.

 References

Reiner-Drehwald and Drehwald (2002), Gradstein and Reiner-Drehwald (2007), Bastos and Gradstein (2020), Gradstein (2021).

 Plantae Lejeuneales Lejeuneaceae 875EADD5-A1C9-5917-824F-08A769B5CE5B Lejeunea sect. Lamacerinae R.M.Schust. (Schuster 1980: 967) Dactylolejeunea R.M.Schust. (Schuster 1970: 341) – Type species: D. acanthifolia R.M.Schust. (= L. paucidentata (Steph.) Grolle). Type species

Lejeunea lamacerina (Steph.) Schiffn.

 Description

Plants autoicous, delicate, usually less than 1 mm wide. Stem epidermis cells ca 2 times or less larger than medullary cells, not strongly bulging outwards, medullary cells in 4–20 rows. Cuticle smooth, rarely punctate-papillose. Oil bodies finely to coarsely granular, 3–10 per cell, relatively large. Gynoecial innovations sterile (rarely fertile). Perianths usually 5-keeled, keels frequently 2-winged and crenate (by mammillose cells) to toothed, dentate-ciliate. Asexual reproduction by specialized devices usually absent (by ribbon-like gemmae in L. pulchriflora).

 Distribution

Tropical America, Europe, and eastern North America; one species, L. pulchriflora, in the Paleotropics.

 Species

Lejeunea bermudiana (A.Evans) R.M.Schust., L. corynantha Spruce, L. cristulata (Steph.) M.E.Reiner & Goda, L. grossitexta (Steph.) M.E.Reiner & Goda, L. intricata Prantl, L. laeta (Lehm. & Lindenb.) Lehm. & Lindenb., L. lamacerina (Steph.) Schiffn., L. paucidentata (Steph.) Grolle, L. pulchriflora (Pearson) G.E.Lee, Bechteler, Pócs, Schäf.-Verw. & Heinrichs, L. sporadica Besch. & Spruce, L. urbanii (Steph.) Steph.

 Further species (not sequenced)

Lejeunea patens Lindb.

 Notes

Typical of sect. Lamacerinae are the delicate, autoicous plants with crenate to dentate-ciliate, 2-winged perianth keels, a usually smooth cuticle (finely punctate-papillose only in L. intricata and L. pulchriflora), granular oil bodies, and sterile innovations. Lejeunea corynantha deviates by its eplicate perianth but otherwise fits the section well morphologically. The European L. patens is placed in this section based on its granular oil bodies and its close similarity to L. lamacerina.

Section Lamacerinae is morphologically very similar to sect. Microlobae (subg. Crossotolejeunea), but the perianths in the latter section are not 2-winged.

 References

Schuster (1980), Paton (1999), Reiner-Drehwald and Goda (2000), Reiner-Drehwald and Schäfer-Verwimp (2008), Lee et al. (2016), Bastos and Gradstein (2020).

 Plantae Lejeuneales Lejeuneaceae E52A8765-1197-5B8E-BF4F-BFD400C5307C Lejeunea sect. Lejeunea Lejeunea sect. Cladiophorae R.M.Schust. (Schuster 1980: 995) – Type species: L. cladiophora (R.M.Schust.) R.M.Schust. (= L. cancellata Nees & Mont.). ? Lejeunea subg. Pleurolejeunea R.M.Schust. (Schuster 1963: 123) – Type species: L. patagonica (Steph.) Steph. Amphilejeunea R.M.Schust. (Schuster 1978: 431) – Type species: A. viridissima R.M.Schust. (= L. catinulifera Spruce). Ciliolejeunea S.W.Arnell (Arnell 1953: 176) – Type species: C. capensis S.W.Arnell (= L. villaumei (Steph.) Grolle). Cladolejeunea Zwickel (Zwickel 1933: 112) – Type species: Ceratolejeunea aberrans Steph. (= L. gradsteiniana Pócs). Cryptogynolejeunea R.M.Schust. (Schuster 1994: 215) – Type species: C. reflexistipula (Lehm. & Lindenb.) R.M.Schust. (= L. reflexistipula (Lehm. & Lindenb.) Lehm. & Lindenb.). Oryzolejeunea (R.M.Schust.) R.M.Schust. (Schuster 1992: 249) – Type species: O. antillana (R.M.Schust.) R.M.Schust. (= L. herminieri (Steph.) R.L.Zhu). Lejeunea sect. Cavifoliae R.M.Schust. (Schuster 1957: 142), nom. inval. – Type species: same as for genus Lejeunea. Type species

Lejeunea cavifolia (Ehrh.) Lindb.

 Description

Plants mostly autoicous (occasionally dioicous), glossy green, slightly altered by drying. Stem epidermis cells ca 2–4 times larger than medullary cells, not strongly bulging outwards; medullary cells in 4–16 rows (exceptionally, in L. reflexistipula, epidermis cells strongly bulging outwards, ca 6 times larger than inner cells, and medullary cell rows more numerous, 19–40). Cuticle smooth or punctate-papillose, oil bodies homogeneous, ca 10–30 per cell. Underleaves bifid or undivided. Gynoecial innovations sterile or fertile, with up to two gynoecia in a row. Perianths equally 5-keeled, keels usually long, extending to the lower half of the perianth, often winged or with appendices (horns, teeth, tuberculae). Asexual reproduction by specialized devices usually absent (by caducous branches in L. cancellata).

 Distribution

Pantropical and extending into temperate regions of the Northern and Southern Hemisphere.

 Species

Lejeunea alata Gottsche, L. amaniensis E.W.Jones, L. cancellata, L. caripensis Lindenb. & Gottsche (= L. cerina auct. non (Lehm. & Lindenb.) Lehm. & Lindenb.), L. catinulifera, L. cavifolia, L. drummondii Taylor, L. eckloniana Lindenb., L. geisslerae Pócs, L. helmsiana (Steph.) Steph., L. herminieri, L. holtii Spruce, L. japonica Mitt., L. obscura Mitt., L. oracola M.A.M.Renner, L. perichymidia M.A.M.Renner (= L. epiphylla Colenso), L. puiggariana Steph., L. reflexistipula, L. sharpii (R.M.Schust.) R.M.Schust., L. subsessilis Spruce (= L. monimiae (Steph.) Steph.), Lejeunea sp. 2. (= “L. caracensis Lindenb.”, Figs 5, 6).

 Further species (not sequenced)

Lejeunea cyathearum E.W.Jones, L. gradsteiniana Pócs, L. villaumei (Steph.) Grolle.

 Notes

The typical character of sect. Lejeunea, separating it from most other sections of Lejeunea, are the small, homogeneous, Massula-type oil bodies, ca 10–30 per cell. In other sections, oil bodies are usually granular, being built of very small to large granules, and less than 10 per cell. Further characters of sect. Lejeunea are the thin stems with only 4–12 medullary cell rows (exceptionally more cell rows in L. reflexistipula) and the occasional occurrence of two lobule teeth, with the first tooth being more than one cell long, and undivided underleaves (L. catinulifera, L. herminieri, L. reflexistipula). Lejeunea herminieri, type species of Oryzolejeunea, was not sequenced in this study and is placed in this section based on Ye et al. (2013) who sequenced it and found that the species was sister to L. catinulifera. Both have homogeneous oil bodies.

Lejeunea holtii has long been considered a synonym of L. eckloniana (Söderström et al. 2002). However, the position of L. holtii on a long branch within the L. eckloniana species group and its distinctive morphology (Hodgetts et al. 2024), suggests that it may be a distinct taxon. The species is accepted here pending further work on its taxonomic status. Lejeunea cyathearum, L. gradsteiniana, and L. villaumei from Africa were not sequenced and are placed in sect. Lejeunea based on their homogeneous oil bodies and close similarity to L. eckloniana (Jones 1974).

 References

Jones (1974), Schuster (1980), Wigginton (2004), Reiner-Drehwald (2005a), Pócs (2010), Ye et al. (2013), Lee (2013), Renner et al. (2010, 2021), Gradstein (2021).

 Plantae Lejeuneales Lejeuneaceae F81C9904-AEC5-5BC8-BE09-EFB96F7F5540 Lejeunea subg. Crossotolejeunea Spruce (Spruce 1884: 161) Crossotolejeunea (Spruce) Schiffn. (Schiffner 1893: 127) Type species

Lejeunea boryana Mont. (lectotype, designated by Vanden Berghen 1945).

 Description

Plants mostly dioicous (in about 70% of the analysed species). Oil bodies granular (very rarely homogeneous). Male bracteoles restricted to the base of the male spike or occurring throughout. Female bracts and bracteole free or shortly connate on one side (broadly fused on both sides in sect. Echinocolea). Asexual reproduction by specialized devices rather common, including caducous leaves (or leaf lobes), caducous branches, and strap-shaped gemmae. In addition, vegetative reproduction by shoot fragmentation occurs in several sections.

 Distribution

Pantropical, with some species extending into temperate regions.

 Species

Eighty three species were found to belong to this subgenus.

 Notes

The typical characters of subg. Crossotolejeunea are the predominance of dioicy, granular oil bodies, female involucre free or only shortly fused at the base, and the common presence of specialized devices for asexual reproduction. The commonness of asexual reproduction in the subgenus may be explained by the predominantly dioicous sexual system, causing an impediment to sexual reproduction (Devos et al. 2011; Kraichak 2012).

Based on the results of the analyses, subg. Crossotolejeunea is subdivided into 11 sections: sect. Apolejeunea, sect. Crossotolejeunea, sect. Echinocolea, sect. Flavae, sect. Heterolejeunea, sect. Inflatolejeunea, sect. Minutilobae, sect. Nanolejeunea, sect. Papillolejeunea, sect. Sordidae, and sect. Xenantholejeunea.

 Plantae Lejeuneales Lejeuneaceae FFE8D98C-7DFF-55ED-BEAF-4F1E3B59141A Lejeunea sect. Echinocolea (R.M.Schust.) Gradst. (Gradstein 2018: 7) Echinocolea R.M.Schust. (Schuster 1963: 125) Type species

Lejeunea asperrima Spruce.

 Description

Plants very delicate, less than 1 mm wide. Stems with only 3–7 rows of medullary cells. Leaf lobes with a very narrow base (abruptly dilated beyond the keel), dorsal leaf surface and margins with projecting, often spinose mammillae with thickened outer walls. Cuticle smooth. Oil bodies finely granular, few (1–4) per cell, often brownish. Gynoecia with one sterile or fertile innovation, bracts and bracteole broadly connate. Perianths inflated, 5-keeled, keels crenate to ciliate-laciniate. Asexual reproduction by caducous leaves, cladia, and strap-shaped gemmae.

 Distribution

Neotropical.

 Species

Lejeunea asperrima, L. subspathulata Spruce.

 Further species (not sequenced)

Lejeunea asprella Spruce, L. meridensis Ilk.-Borg.

 Notes

Lejeunea sect. Echinocolea is a robust lineage, being sister to sect. Crossotolejeunea and sharing ciliate-laciniate perianths and finely granular oil bodies with the latter section. The section differs from sect. Crossotolejeunea in the much smaller plants with leaf lobes narrowed at the base and ornamented on the dorsal surface and margins, a smooth cuticle, and an abundance of modes of vegetative reproduction. Unexpectedly, L. reinerae from eastern Malesia, the only paleotropical species of Lejeunea with a roughened dorsal leaf surface and having been placed in Echinocolea in the past, was not resolved in sect. Echinocolea despite its close similarity to L. asperrima (Ilkiu-Borges 2005). Instead, the species was found in subg. Crossotolejeunea in a moderately supported sister relationship to L. patersonii from Malesia. The latter species approaches L. reinerae in having strongly crenulate leaf margins, but the dorsal leaf surface of L. patersonii is smooth, the leaf base is not highly narrow, and the outer walls of the projecting leaf margin cells are not thickened. The position of L. reinerae in the sect. Crossotolejeunea clade indicates that the peculiar leaf shape and ornamented leaf surface of sect. Echinocolea are homoplasious characters.

 Reference

Ilkiu-Borges (2005).

 Plantae Lejeuneales Lejeuneaceae 6F64BC19-0A2F-52FA-8110-7B9E441446D8 Lejeunea sect. Crossotolejeunea Spruce (Spruce 1884: 161) Crossotolejeunea (Spruce) Schiffn. (Schiffner 1893: 127) Type species

Same as for subg. Crossotolejeunea.

 Description

Plants autoicous, dull green. Stems with 7–20 rows of medullary cells. Leaf lobes with a broad base, dorsal leaf surface smooth, leaf margin entire or crenulate, outer wall of margin cells thin. Cuticle densely and rather coarsely papillose. Oil bodies finely granular, 2–8 per cell, colourless. Male bracteoles restricted to the base of the male spike. Gynoecial innovations are sterile or fertile. Perianths inflated, 4–5-keeled, keels ± 2-winged, crenate to ciliate-laciniate. Asexual reproduction by strap-shaped gemmae.

 Distribution

Neotropical.

 Species

Lejeunea boryana, L. controversa Gottsche, L. pulverulenta (Steph.) M.E.Reiner.

 Notes

The autoicous plants with a densely papillose cuticle and crenate to ciliate-laciniate, ± 2-winged perianth keels are typical characters of this section. In its original circumscription (e.g. Spruce 1884; Stephani 1913), Crossotolejeunea contained almost 40 species, including numerous autoicous ones, but most of them have a smooth cuticle and proved to belong to other sections of Lejeunea, especially sect. Lamacerinae.

 Reference

Reiner-Drehwald and Goda (2000).

 Plantae Lejeuneales Lejeuneaceae ADBF30D8-474A-54EC-AD6B-D8B025459D83 Lejeunea sect. Heterolejeunea (R.M.Schust.) G.E.Lee & Gradst. comb. et stat. nov. Rectolejeunea subg. Heterolejeunea R.M.Schust. (Schuster 1955: 122) Dicladolejeunea R.M.Schust. (Schuster 1962: 68) – Type species: D. anomala R.M.Schust. (= L. rotundifolia Mitt.). Lejeunea subg. Chaetolejeunea (R.M.Schust.) R.M.Schust. (Schuster 1962: 68) – Type species: L. setacea Steph. Stylolejeunea Sim (Sim 1926: 67) – Type species: S. duncaniae Sim (= L. duncaniae (Sim) M.E.Reiner). Type species

Lejeunea phyllobola Nees & Mont.

 Description

Plants dull green, rarely glossy. Vegetative branches Lejeunea-type, occasionally Radula-type. Stem epidermis cells ca 2–3 times larger than medullary cells, rarely strongly inflated; medullary cell rows few, usually 4–7. Leaf cells with small trigones, with or without intermediate cell wall thickenings. Lobules sometimes with a very long tooth. Oil bodies granular, 2–10 per cell, colourless, relatively large, up to 20 µm long and sometimes fill the entire cell lumen. Male bracteoles restricted to the base of the male spike or present throughout. Gynoecial innovations usually fertile. Perianths often compressed, with 5 smooth keels. Asexual reproduction common, by strap-shaped gemmae, caducous leaves and branches.

 Distribution

Afro-American.

 Species

Lejeunea deplanata Nees, L. kuerschneriana Pócs, L. oligoclada Spruce, L. parviloba Ångstr. (= L. tapajosensis Spruce), L. phyllobola Nees & Mont., L. ptosimophylla C.Massal., L. rotundifolia Mitt., L. ruthii (A.Evans) R.M.Schust., L. subplana (Steph.) C.J.Bastos, L. trinitensis Lindenb.

 Further species (not sequenced)

Lejeunea duncaniae, L. evansiana (R.M.Schust.) Schäf.-Verw., L. rionegrensis Spruce, L. setacea, L. spiniloba Lindenb. & Gottsche.

 Notes

Characteristic of sect. Heterolejeunea are the rather dull green, dioicous plants with ± compressed perianths and frequent occurrence of vegetative reproduction. The position of L. rotundifolia in the section is somewhat unexpected, standing out by its large size with stems to 8 cm long and made up of 11–18 rows of epidermal cells and 22–55 rows of medullary cells, with 4–6 cells wide ventral merophytes. Previously, the species was placed in a separate genus, Dicladolejeunea. Interestingly, L. rotundifolia occasionally produces vegetative branches of the Radula-type. The latter character is very rare in Lejeunea and is otherwise seen in L. deplanata and L. phyllobola, both in the same section.

 References

Schuster (1980), Reiner-Drehwald (2005b, 2010a), Bastos and Gradstein (2020).

 Plantae Lejeuneales Lejeuneaceae F1FFDFB2-6984-5CB7-9E0E-B3BFBC740786 Lejeunea sect. Inflatolejeunea (S.W.Arnell) G.E.Lee & Gradst. comb. et stat. nov. Inflatolejeunea S.W.Arnell (Arnell 1953: 173) Type species

Lejeunea capensis Gottsche.

 Description

Plants glossy pale green, delicate, ca 0.5–1 mm wide. Stems with 7 rows of epidermal cells surrounding 5–12 rows of smaller medullary cells. Leaf cells with rather small trigones, with or without intermediate cell wall thickenings. Cuticle punctate-papillose. Oil bodies finely granular, ca 3–10 per cell, colourless. Male bracteoles restricted to the base of the male spike or absent. Gynoecial innovations frequently fertile. Perianths terete, eplicate. Asexual reproduction sometimes occurs by shoot fragmentation (L. globosiflora).

 Distribution

Afro-American.

 Species

Lejeunea capensis, L. cyathophora Mitt., L. globosiflora (Steph.) Steph.

 Further species (not sequenced)

Lejeunea pluridichotoma Schust., nom. inval.

 Notes

The small, glossy, greenish plants with a finely punctate-papillose cuticle, granular oil bodies and inflated, eplicate perianths are characteristic of sect. Inflatolejeunea. Although oil bodies in the section are usually described as being finely granular, Jungermannia-type (Arnell 1963; Schuster 1992; Gradstein and Cuvertino 2015), Reiner-Drehwald and Schäfer-Verwimp (2008) reported subhomogeneous oil bodies in L. capensis. As Jungermannia-type oil bodies may turn homogeneous upon degeneration following drying of the plants (Gradstein et al. 2001), the report of subhomogeneous oil bodies in L. capensis may have been based on degenerated oil bodies.

 References

Arnell (1963), Schuster (1992), Reiner-Drehwald and Schäfer-Verwimp (2008), Gradstein and Cuvertino (2015).

 Plantae Lejeuneales Lejeuneaceae F93A7312-7B0A-5285-B66E-DA9A17857FF2 Lejeunea sect. Nanolejeunea (R.M.Schust.) G.E.Lee & Gradst. stat. nov. Lejeunea subg. Nanolejeunea R.M.Schust. (Schuster 1980: 1092) Type species

Lejeunea laetevirens Nees & Mont.

 Description

Plants dull green. Stems with 7 rows of epidermal cells surrounding few, 3–8(–10) rows of slightly smaller medullary cells. Cuticle finely to rather coarsely papillose. Oil bodies finely to coarsely granular, ca 3–10 per cell. Male bracteoles present throughout the male spike. Asexual reproduction by caducous branches and fragmenting shoots.

 Distribution

Neotropical.

 Species

Lejeunea laetevirens, L. multidentata M.E.Reiner & Mustelier, L. ramulosa Spruce.

 Notes

The section is primarily characterized by rather dull green, dioicous plants with thin stems made up of rather few rows of medullary cells (less than 10), a papillose cuticle, bracteoles present throughout the male spike, and asexual reproduction via caducous branches or shoot fragmentation. Lejeunea multidentata approaches the sect. Crossotolejeunea by its coarsely papillose cuticle and 2-winged, dentate-ciliate perianths, but the members of the latter section differ in monoicy, restriction of bracteoles to the base of the male spike, and absence of asexual reproduction by caducous branches or shoot fragmentation.

 References

Reiner-Drehwald and Mustelier Martinez (2004), Reiner-Drehwald (2010b).

 Plantae Lejeuneales Lejeuneaceae 416BBD5E-0D5E-5B54-8F50-29DD39B8E035 Lejeunea sect. Apolejeunea (Inoue) R.M.Schust. (Schuster 1980: 941) Lejeunea subg. Apolejeunea Inoue (Inoue 1976: 186) Type species

Lejeunea compacta (Steph.) Steph.

 Description

Plants frequently rather small, less than 1 mm wide. Stems with 8–22 rows of medullary cells. Leaves asymmetrically ovate with widely arched dorsal margin and straight to slightly curved ventral margin, leaf apex narrowly pointed or rounded, usually decurved. Cuticle finely punctate-papillose. Oil bodies finely granular, 2–8 per cell. Lobules large, 1/3–1/2× leaf length, strongly inflated. Androecia usually with an apical innovation; bracteoles present throughout the male spike. Gynoecia on long shoots, with one sterile innovation, bracts shortly fused with the bracteole at the base. Perianths 5-keeled in the upper half, beak very short. Asexual reproduction by specialized devices absent.

 Distribution

East Asia.

 Species

Lejeunea compacta, L. curviloba Steph. (?), L. neelgherriana Gottsche (= L. claviflora (Steph.) S.Hatt.), L. nepalensis Steph., L. parva (S.Hatt.) Mizut., L. soae R.L.Zhu, Y.M.Wei, L.Söderstr., A.Hagborg & von Konrat, L. wightii Lindenb.

 Notes

The outstanding characters of this section are the rather small plants with asymmetric leaf lobes and a pointed (or rounded), decurved leaf apex, the rather large, inflated lobules and the presence of bracteoles throughout the male spike. The common presence of an apical innovation on the male spike is a further characteristic feature seen in some members of this section (Mizutani 1992).

Lejeunea curviloba was resolved in an unsupported sister position to the Apolejeunea clade and is provisionally placed in sect. Apolejeunea because of its close morphological similarity to members of this section (Mizutani 1992).

 References

Mizutani (1961, 1992), Inoue (1976), Schuster (1980).

 Plantae Lejeuneales Lejeuneaceae C51BD9C7-C3AE-5058-A114-10D3820FB765 Lejeunea sect. Flavae R.M.Schust. (Schuster 1980: 941) Nesolejeunea Herzog (Herzog 1947: 327) – Type species: N. intercalaris Herzog (= L. acuta Mitt.). Type species

Lejeunea flava (Sw.) Nees.

 Description

Plants prostrate, glossy yellowish green, autoicous or dioicous. Stems with ca 10–16 rows of medullary cells. Leaves symmetrically ovate, apex usually rounded, rarely acute (L. acuta). Leaf cells with distinct trigones and intermediate thickenings. Cuticle mostly smooth, occasionally roughened by wax crystals. Oil bodies finely granular, 2–10 per cell. Lobules small, ca 1/4× leaf length. Underleaves rather large, 3–6× stem width, frequently imbricate. Male bracteoles restricted to the base of the male spike (exceptionally present throughout: L. brenanii E.W.Jones). Gynoecial innovations usually fertile but not repeatedly, with up to 2 gynoecia in a row. Perianths with 5 ± smooth keels, rarely eplicate (L. ramosissima Steph.). Asexual reproduction by specialized devices absent.

 Distribution

Pantropical; centre of species diversity in tropical Africa (Jones 1968).

 Species

Lejeunea acuta, L. brenanii, L. flava, L. isophylla E.W.Jones, L. lomana E.W.Jones, L. ramosissima Steph., L. tuberculosa Steph.

 Notes

The main characters of sect. Flavae are the rather unspecialized, prostrate, glossy yellowish-green plants with rather large underleaves (3–6× stem width), leaf cells with distinct trigones, finely granular oil bodies, and 5-keeled perianths with ± smooth keels.

 References

Jones (1968), Schuster (1980), Wigginton (2004).

 Plantae Lejeuneales Lejeuneaceae F53FD3F8-3337-50E0-9DB0-2999B5E07CEC Lejeunea sect. Sordidae Gradst. & G.E.Lee sect. nov. Type species

Lejeunea sordida (Nees) Nees.

 Description

Plants dioicous, brown when dry. Stem epidermis cells distinctly larger than medullary cells, bulging outwards, medullary cells in 10–23 rows. Cuticle densely papillose. Lobules small, ovate-orbicular, strongly inflated, angle between keel and ventral leaf margin narrow, ca 90–120°. Underleaves divided or undivided, large, reniform, ca 4–7× stem width. Male bracteoles restricted to the base of the male spike. Gynoecia with sterile or fertile innovations. Perianths shortly 5-keeled in the upper half, keels crenate by mammillose cells. Asexual reproduction by specialized devices absent (regeneration from leaf margins observed in L. sordida).

 Distribution

Tropical amphi-Pacific.

 Species

Lejeunea dipterota (Eifrig) G.E.Lee, L. leratii (Steph.) Mizut., L. mimula Hürl., L. sordida.

 Further species (not sequenced)

Lejeunea anomala Lindenb. & Gottsche.

 Notes

The typical characters of sect. Sordidae are the darkish brown plants (dried condition) with reniform underleaves, small, strongly inflated lobules and a densely papillose cuticle. Undivided underleaves, seen in L. leratii and L. mimula, are within subg. Crossotolejeunea unique to sect. Sordidae and are a further typical character of this section.

Lejeunea anomala, a rare and little-known Neotropical species that was long placed in Ceratolejeunea because of its brown colour, is placed in this section based its close morphological similarity to L. sordida (Gradstein 2021).

 References

Eifrig (1937), Lee (2013).

 Plantae Lejeuneales Lejeuneaceae D983A238-227D-5EEF-B8CB-9C7C85D9B91C Lejeunea sect. Papillolejeunea Gradst. & G.E.Lee stat. nov. Papillolejeunea Pócs (Pócs 1997: 2) Type species

Papillolejeunea balazsii Pócs (= L. balazsii (Pócs) R.M.Schust.).

 Description

Plants dioicous or paroicous, greatly varying in size, stems with few to many medullary cell rows (3–35). Leaf surface smooth or with slime papillae. Lobules frequently large, to 1/2× leaf length, and with two teeth, first tooth sometimes stylus-like prolonged, to three cells long, hyaline papilla entally displaced. Cuticle smooth or punctate-papillose. Oil bodies finely granular (L. colensoana, L. tumida). Male bracteoles restricted to the base of the male spike. Gynoecia: innovations usually repeatedly fertile. Perianths eplicate or 5-keeled, keel smooth or crenate. Asexual reproduction by specialized devices absent.

 Distribution

Southeast Asia-Australasia; centre of species diversity in the mountains of New Guinea.

 Species

Lejeunea balazsii, L. candida Pócs, L. colensoana (Steph.) M.A.M.Renner, L. gradsteinii G.E.Lee, Damanhuri & Latiff, L. stephaniana Mizut., L. tumida Mitt.

 Further species (not sequenced)

Lejeunea falcata (Pócs & J.Eggers) Pócs, L. koponenii (Pócs & J.Eggers) Pócs, L. touwii (Pócs) R.M.Schust.

 Notes

The distinctive characters of sect. Papillolejeunea are the strongly inflated and often large lobules (to half the lobe length) with a stout, to 3 cells long tooth and an entally displaced hyaline papilla. In other sections of Lejeunea, the hyaline papilla is positioned on the leaf margin or, occasionally, at the tip of the tooth in species with a prolonged, stylus-like tooth (sect. Heterolejeunea: L. setacea, L. trinitensis). The usually repeatedly fertile innovations, with rows of up to four gynoecia, and the absence of asexual reproduction are further characteristics of this section. The occurrence of slime papillae on the dorsal leaf surface, seen in L. balazsii and L. koponenii, is an autapomorphy of the section.

The centre of diversity of sect. Papillolejeunea are the mountains of New Guinea, where five species occur. Three of them (L. falcata, L. koponenii, L. touwii) have not been sequenced and are included in the section on morphological grounds because of their morphological similarity to the type species.

 References

Pócs (1997), Schuster (1998), Pócs and Eggers (1999), Renner et al. (2010, 2021), Lee (2013).

 Plantae Lejeuneales Lejeuneaceae 2006B262-741B-5269-841B-204D2939146C Lejeunea sect. Xenantholejeunea (R.M.Schust.) G.E.Lee & Gradst. comb. et stat. nov. Taxilejeunea subg. Xenantholejeunea R.M.Schust. (Schuster 1980: 1166) Type species

Lejeunea umbilicata (Nees) Nees.

 Description

Plants relatively large, 1.0–2.0 mm wide. Stem epidermis cells large, ca 3–6 times larger than medullary cells, sometimes strongly bulging outwards, medullary cells in 10–50 rows. Leaf cells with distinct trigones and frequent intermediate thickenings, up to 4 per cell. Lobules frequently with a large disc cell. Male bracteoles restricted to the base of the male spike. Innovations usually repeatedly fertile. Perianths 0–5-keeled, with or without a beak. Asexual reproduction by specialized devices absent (regeneration from leaf margins observed in L. umbilicata).

 Distribution

Indo-Pacific.

 Species

Lejeunea albescens (Steph.) Mizut., L. asperula (Steph.) Mizut., L. fleischeri (Steph.) Mizut., L. kinabalensis Mizut., L. lumbricoides (Nees) Nees, L. microloba Taylor, L. mizutanii Grolle, L. pectinella Mizut., L. umbilicata, L. utriculata (Steph.) Mizut., L. vitiensis G.E.Lee & Pócs.

 Notes

Lejeunea sect. Xenantholejeunea, a former infrageneric group of Taxilejeunea, is characterized by relatively robust, dioicous plants with stems with highly enlarged epidermis cells and numerous medullary cells (up to 50 in rows), distinct trigones and intermediate cell thickenings, usually repeatedly fertile innovations, and absence of asexual reproduction by specialized devices. The section contains a robust, morphologically distinct subclade (BS 100, PP 1.00) consisting of L. lumbricoides, L. mizutanii, L. pectinella, L. utriculata, L. fleischeri, and L. vitiensis. Characteristic of this subclade are the recurved leaf apex, both in moist and dry conditions, the relatively large lobules, and the presence of a large, rectangular disc cell on the apical margin beyond the first tooth. The group is not formally described as it would render sect. Xenantholejeunea paraphyletic. A further subclade consisting of L. albescens, L. asperula, L. microloba, and the type of the section, L. umbilicata, stands out by having a terete, eplicate perianth without a beak. This subclade is not well-supported, however, and is therefore not described.

 References

Eifrig (1937), Lee (2013).

 Plantae Lejeuneales Lejeuneaceae D4586B7D-6503-54D7-A8B6-3687469F4900 Lejeunea sect. Minutilobae R.M.Schust. (Schuster 1980: 1031) Byssolejeunea Herzog (Herzog 1941: 84) – Type species: Lejeunea abnormis Herzog (= L. exilis var. abnormis (Herzog) G.E.Lee). Cardiolejeunea R.M.Schust. & Kachroo (Schuster 1963: 149) – Type species: C. cardiantha R.M.Schust. & Kachroo (= L. papilionacea Prantl). Stenolejeunea R.M.Schust. (Schuster 1963: 144) – Type species: S. thallophora (Eifrig) R.M.Schust. (= L. thallophora (Eifrig) Gradst.). Type species

Lejeunea minutiloba A.Evans.

 Description

Plants delicate, mostly less than 1 mm wide. Stem epidermis cells only slightly larger than medullary cells, rarely bulging outwards, medullary cells few, in 5–12(–15) rows. Cuticle smooth or finely punctate-papillose. Oil bodies usually granular, rarely homogeneous (L. dimorpha, L. minutiloba). Male bracteoles restricted to the base of the male spike. Innovations present, sterile or fertile but not repeatedly fertile. Perianth 5-keeled (eplicate in L. exilis var. exilis), keels smooth to frequently crenate by mammillose cells or toothed, lateral keels sometimes expanded as auricles (L. papilionacea). Asexual reproduction by strap-shaped gemmae in Asian-Australasian members of the section, rarely by cladia (L. dimorpha).

 Distribution

Pantropical.

 Species

Lejeunea adpressa Nees, L. anisophylla Mont., L. apiculata Sande Lac., L. compressiuscula (Steph.) G.E.Lee & Heinrichs, L. dimorpha T.Kodama, L. dipterocarpa E.W.Jones, L. discreta Lindenb., L. exilis (Reinw., Blume & Nees) Grolle, L. heinrichsii G.E.Lee, Bechteler, Pócs & Schäf.-Verw., L. ibadana A.J.Harr. & E.W.Jones, L. malaysiana G.E.Lee & Pócs, L. micholitzii Mizut., L. minutiloba A.Evans, L. papilionacea, L. patriciae Schäf.-Verw., L. subolivacea Mizut., L. tasmanica Gottsche (?), L. thallophora.

 Further species (not sequenced)

Lejeunea morobensis (Grolle) M.A.M.Renner & Pócs.

 Notes

This large section stands out by small plant size, frequency of autoicy (e.g. in a large, robust subclade consisting of L. subolivacea, L. adpressa, L. dipterocarpa, L. papilionacea, L. anisophylla, L. ibadana, L. heinrichsii, L. minutiloba, and L. compressiuscula), thin stems with few medullary cell rows, presence of innovations but absence of repeatedly fertile ones, and the frequency of strap-shaped-gemmae, e.g. in L. exilis, L. malaysiana, and some members of the former genus Stenolejeunea, including L. apiculata, L. morobensis, and L. thallophora. Interestingly, Stenolejeunea schiffneri (Herzog) Pócs (= L. pulchriflora) was found to be a member of sect. Lamacerinae (subg. Lejeunea). The latter section shares numerous characters with sect. Microlobae but differs in 2-winged perianth keels and predominantly neotropical distribution. The morphological similarity of sect. Lamacerinae and sect. Microlobae exemplifies the strong parallel evolution within Lejeunea.

Lejeunea tasmanica has been considered a synonym of L. drummondii (Renner 2013). However, in this study L. drummondii was resolved in the sect. Lejeunea clade highly distant from L. tasmanica. The latter is therefore retained here as a separate species pending further work on the relationship of these two Australian taxa.

Several species complexes, potentially comprising multiple independent entities, are identified within the section, including the paleotropical L. papilionacea and the pantropical L. adpressa, which is morphologically similar to L. anisophylla (Gradstein 2021) but occupies a separate lineage in the phylogenetic tree. In view of the molecular results, L. anisophylla and L. adpressa are retained as separate species (despite the lack of discriminating morphological characters) pending further study.

 References

Wigginton (2004), Reiner-Drehwald (2009), Lee (2013), Lee et al. (2019, 2022).

 Acknowledgements

We express our gratitude to the directors and curators of the herbaria E, EGR, G, GOET, JE, and UKMB for the loan of specimens and the permission to extract DNA. The study of the first author was supported by the Universiti Malaysia Terengganu through the Research Intensified Research Grant Scheme (UMT/RIGS/2023/55437), Alexander von Humboldt Foundation, a SYNTHESYS+ grant (FI-TAF-8303) for visiting the Finnish Museum of Natural History (LUOMUS) in Helsinki, Finland, for studying Lejeunea from Papua New Guinea, and the Academic Staff Mobility Grant 2024 from the Embassy of France to Malaysia for studying Lejeunea in the French overseas territories. We also thank Des Callaghan and Hermann Schachner for photographs and Alain Vanderpoorten for his comments on the manuscript.

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Taxa used in the present study, with information about the origin of the studied material, vouchers, and GenBank accession numbers.

 https://binary.pensoft.net/file/1545160