Research Article |
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Corresponding author: Gaik Ee Lee ( gaik.ee@umt.edu.my ) Academic editor: Brecht Verstraete
© 2026 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.
Citation:
Lee GE, Gradstein SR, He X, Bechteler J, Schäfer-Verwimp A, Pócs T (2026) An infrageneric classification of the genus Lejeunea (Marchantiophyta: Lejeuneaceae) using molecular phylogeny and morphology. Plant Ecology and Evolution 159(1): 123-141. https://doi.org/10.5091/plecevo.170279
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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
The genus Lejeunea Lib. (Marchantiophyta), with about 375 currently accepted species (
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 (
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
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,
Recent applications of molecular analysis in Lejeuneaceae have revealed considerable incongruence between morphology-based classifications and molecular phylogeny (see
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 (
In the present study, the dataset of
We sampled 131 species of Lejeunea, including sequences of 85 species from
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
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
Maximum likelihood (ML) analysis was conducted with RAxML-HPC v.8.2.8 (
Bayesian inference (BI) was conducted with the program MrBayes v.3.2.6 (
For each species, we scored the presence/absence of gametophytic characters that had been used in Lejeunea taxonomy (e.g.
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).
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
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.
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.
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) (
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 (
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
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.
Lejeunea subg. Eulejeunea Spruce (
? Amblyolejeunea Jovet-Ast (
? Lejeunea subg. Pleurolejeunea R.M.Schust. & Kachroo (
Lejeunea cavifolia (Ehrh.) Lindb.
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.
Pantropical, with some species extending into temperate regions.
Forty-eight species were found to belong to this subgenus.
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 (
Lejeunea subg. Macrolejeunea Spruce (
Lejeunea pallescens Mitt. (lectotype, designated by
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.
Neotropical.
Lejeunea osculatiana De Not., L. pallescens Mitt.
Lejeunea sessiliflora (Steph.) Grolle.
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
Lejeunea subg. Taxilejeunea Spruce (
Sphaerolejeunea Herzog (
? Lejeunea subg. Neopotamolejeunea (M.E.Reiner) Gradst. & M.E.Reiner (
Lejeunea glaucescens Gottsche.
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.
Pantropical.
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
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 (
Dactylolejeunea R.M.Schust. (
Lejeunea lamacerina (Steph.) Schiffn.
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).
Tropical America, Europe, and eastern North America; one species, L. pulchriflora, in the Paleotropics.
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.
Lejeunea patens Lindb.
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.
Lejeunea sect. Cladiophorae R.M.Schust. (
? Lejeunea subg. Pleurolejeunea R.M.Schust. (
Amphilejeunea R.M.Schust. (
Ciliolejeunea S.W.Arnell (
Cladolejeunea Zwickel (
Cryptogynolejeunea R.M.Schust. (
Oryzolejeunea (R.M.Schust.) R.M.Schust. (
Lejeunea sect. Cavifoliae R.M.Schust. (
Lejeunea cavifolia (Ehrh.) Lindb.
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).
Pantropical and extending into temperate regions of the Northern and Southern Hemisphere.
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
Lejeunea cyathearum E.W.Jones, L. gradsteiniana Pócs, L. villaumei (Steph.) Grolle.
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
Lejeunea holtii has long been considered a synonym of L. eckloniana (
Crossotolejeunea (Spruce) Schiffn. (
Lejeunea boryana Mont. (lectotype, designated by
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.
Pantropical, with some species extending into temperate regions.
Eighty three species were found to belong to this subgenus.
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 (
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.
Echinocolea R.M.Schust. (
Lejeunea asperrima Spruce.
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.
Neotropical.
Lejeunea asperrima, L. subspathulata Spruce.
Lejeunea asprella Spruce, L. meridensis Ilk.-Borg.
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 (
Crossotolejeunea (Spruce) Schiffn. (
Same as for subg. Crossotolejeunea.
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.
Neotropical.
Lejeunea boryana, L. controversa Gottsche, L. pulverulenta (Steph.) M.E.Reiner.
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.
Rectolejeunea subg. Heterolejeunea R.M.Schust. (
Dicladolejeunea R.M.Schust. (
Lejeunea subg. Chaetolejeunea (R.M.Schust.) R.M.Schust. (
Stylolejeunea Sim (
Lejeunea phyllobola Nees & Mont.
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.
Afro-American.
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.
Lejeunea duncaniae, L. evansiana (R.M.Schust.) Schäf.-Verw., L. rionegrensis Spruce, L. setacea, L. spiniloba Lindenb. & Gottsche.
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.
Inflatolejeunea S.W.Arnell (
Lejeunea capensis Gottsche.
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).
Afro-American.
Lejeunea capensis, L. cyathophora Mitt., L. globosiflora (Steph.) Steph.
Lejeunea pluridichotoma Schust., nom. inval.
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 (
Lejeunea subg. Nanolejeunea R.M.Schust. (
Lejeunea laetevirens Nees & Mont.
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.
Neotropical.
Lejeunea laetevirens, L. multidentata M.E.Reiner & Mustelier, L. ramulosa Spruce.
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.
Lejeunea subg. Apolejeunea Inoue (
Lejeunea compacta (Steph.) Steph.
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.
East Asia.
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.
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 (
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 (
Nesolejeunea Herzog (
Lejeunea flava (Sw.) Nees.
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.
Pantropical; centre of species diversity in tropical Africa (
Lejeunea acuta, L. brenanii, L. flava, L. isophylla E.W.Jones, L. lomana E.W.Jones, L. ramosissima Steph., L. tuberculosa Steph.
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.
Lejeunea sordida (Nees) Nees.
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).
Tropical amphi-Pacific.
Lejeunea dipterota (Eifrig) G.E.Lee, L. leratii (Steph.) Mizut., L. mimula Hürl., L. sordida.
Lejeunea anomala Lindenb. & Gottsche.
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 (
Papillolejeunea Pócs (
Papillolejeunea balazsii Pócs (= L. balazsii (Pócs) R.M.Schust.).
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.
Southeast Asia-Australasia; centre of species diversity in the mountains of New Guinea.
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.
Lejeunea falcata (Pócs & J.Eggers) Pócs, L. koponenii (Pócs & J.Eggers) Pócs, L. touwii (Pócs) R.M.Schust.
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.
Taxilejeunea subg. Xenantholejeunea R.M.Schust. (
Lejeunea umbilicata (Nees) Nees.
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).
Indo-Pacific.
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.
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.
Byssolejeunea Herzog (
Cardiolejeunea R.M.Schust. & Kachroo (
Stenolejeunea R.M.Schust. (
Lejeunea minutiloba A.Evans.
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).
Pantropical.
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.
Lejeunea morobensis (Grolle) M.A.M.Renner & Pócs.
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 (
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 (
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.
Taxa used in the present study, with information about the origin of the studied material, vouchers, and GenBank accession numbers.