Simple Thalloid Liverworts Research Articles

Kahakuloa operculispora, a new Hawaiian simple thalloid liverwort in a new genus and family, Kahakuloaceae (Fossombroniales)

Kahakuloa operculispora, a new simple thalloid liverwort endemic to Hawaiʻi, so far only known from high elevation bogs in western Maui, is described and illustrated. The thallus has prominent reddish-purple rhizoids, uniseriate ventral slime papillae and lacks scales. The plants are dioicous; male plants have antheridia sunken in several rows of dorsal chambers, subtended by scales, while female plants have clustered archegonia enclosed by thick, barrel-shaped involucres that develop serially at the plant apex, before fertilization, and are arranged in a single dorsal row at maturity; perichaetial scales and pseudoperianths (defined as involucres developing after fertilization) are lacking. The capsules are spherical, 2−3 stratose, and dehisce irregularly; the spores are areolate and have a unique operculum-like disk on the proximal face. Molecular and morphological evidence supports placement of the plant in a new genus and family in the order Fossombroniales, suborder Fossombroniineae. Kahakuloa is the first liverwort genus endemic to Hawaiʻi, and Kahakuloaceae is the only known endemic Hawaiian land plant family.

Integrative approaches to a revision of the liverwort in genus Aneura (Aneuraceae, Marchantiophyta) from Thailand.

The genus Aneura Dumort. is a simple thalloid liverwort with cosmopolitan distributions. Species circumscription is problematic in this genus due to a limited number of morphological traits. Two species are currently reported from Thailand, including A. maxima and A. pinguis. At the global scale, A. pinguis is considered a cryptic species, as the species contains several distinct genetic groups without clear morphological differentiation. At the same time, the identity of A. maxima remains unclear. In this work, we examined the level of diversity of Aneura species found in Thailand using both morphological and molecular data. We measured the morphological traits and generated the molecular data (four markers: trnL-F, trnH-psbA, rbcL, and ITS2) from the Thai specimens. The concatenated dataset was then used to reconstruct phylogeny. Species delimitation with GMYC, bPTP, ASAP, and ABGD methods was performed to estimate the number of putative species within the genus. The samples of A. pinguis formed several clades, while A. maxima sequences from Poland were grouped in their clade and nested within another A. pinguis clade. We could not recover a sample of A. maxima from Thailand, even from the reported locality. Two putative species were detected among Thai Aneura samples. However, no morphological trait could distinguish the specimens from the two observed genetic groups. The previously observed paraphyletic nature of A. pinguis globally was also found among Thai samples, including several putative species. However, we could not confirm the identity of A. maxima from Thai specimens. The previous report could result from misidentification and problematic species circumscription within Aneura. The results highlighted the need to include multiple lines of evidence for the future taxonomic investigation of the group.

The organellar genomes of Pellidae (Marchantiophyta): the evidence of cryptic speciation, conflicting phylogenies and extraordinary reduction of mitogenomes in simple thalloid liverwort lineage

Organellar genomes of liverworts are considered as one of the most stable among plants, with rare events of gene loss and structural rearrangements. However, not all lineages of liverworts are equally explored in the field of organellar genomics, and subclass Pellidae is one of the less known. Hybrid assembly, using both short- and long-read technologies enabled the assembly of repeat-rich mitogenomes of Pellia and Apopellia revealing extraordinary reduction of length in the latter which impacts only intergenic spacers. The mitogenomes of Apopellia were revealed to be the smallest among all known liverworts—109 k bp, despite retaining all introns. The study also showed the loss of one tRNA gene in Apopellia mitogenome, although it had no impact on the codon usage pattern of mitochondrial protein coding genes. Moreover, it was revealed that Apopellia and Pellia differ in codon usage by plastome CDSs, despite identical tRNA gene content. Molecular identification of species is especially important where traditional taxonomic methods fail, especially within Pellidae where cryptic speciation is well recognized. The simple morphology of these species and a tendency towards environmental plasticity make them complicated in identification. Application of super-barcodes, based on complete mitochondrial or plastid genomes sequences enable identification of all cryptic lineages within Apopellia and Pellia genera, however in some particular cases, mitogenomes were more efficient in species delimitation than plastomes.

Thalloid Liverworts (Marchantiopsida) of Sri Lanka

A comprehensive taxonomic treatment of the thalloid liverworts of Sri Lanka is presented based on specimens collected from throughout the country covering all possible geographical localities. Eight families, nine genera, and seventeen species of complex thalloid liverworts and four families, six genera and seven species of simple thalloid liverworts are described from Sri Lanka. Taxonomic keys, descriptions, along with notes on ecology and distribution, and taxonomic illustrations are provided for all the taxa recognized. Plagiochasma appendiculatum Lehm. & Lindenb., Riccia crispatula Mitt., and Fossombronia cristula Austin, are reported as new to Sri Lanka.

Comparative Analysis of Apopellia endiviifolia Plastomes Reveals a Strikingly High Level of Differentiation between Its Terrestrial and Water Form

The simple thalloid liverwort Apopellia endiviifolia is a widespread Holarctic species belonging to the family Pelliaceae. European populations of this species comprise two distinct evolutionary lineages named “species A”, known also as water form, and typical, mainly terrestrial forms named “species B”. Newly sequenced, assembled and annotated chloroplast genomes of six European specimens belonging to the two cryptic lineages occupying different microhabitats, revealed the structure typical for liverworts and previously sequenced reference. The plastomes of A. endiviifolia are 120,537–120,947 bp long with a structure typical for most plants, including a pair of IR regions (each of 9,092–9,207 bp) separated by LSC (82,506–82,609 bp) and SSC (19,854–19,924 bp) regions and consist of 121 unique genes, including 81 protein-coding genes, 6 genes of unknown function (ycf genes), 4 ribosomal RNAs and 30 transfer RNAs. Comparative analysis of typical, terrestrial and water forms revealed 4971 molecular diagnostic characters (MDCs), which exceeds numbers found in many well recognized liverworts taxa. Moreover, beside the presence of evolutionary hotspots like ycf1 and ycf2 genes and several intergenic spacer like ndhB-psbM, rps4-ndhJ and ndhC-atpE, the molecular identification of Apopellia cryptic species was possible by almost 98% of 500 bp long frames simulating mini barcodes. The different ecological niches can be driven by different pressures of positive selection, which was detected in nine genes including ccsA, ndhD, ndhF, petA, psbB, psbC, rpoB, ycf1 and ycf2. Despite clearly genetic differences and ecological preferences, the current observation of morphological differentiation does not no allow to separate terrestrial and water forms into taxonomic species.

Advances in understanding of mycorrhizal-like associations in bryophytes

Mutually beneficial associations between plants and soil fungi, mycorrhizas, are one of the most important terrestrial symbioses. These partnerships are thought to have propelled plant terrestrialisation some 500 million years ago and today they play major roles in ecosystem functioning. It has long been known that bryophytes harbour, in their living tissues, fungal symbionts, recently identified as belonging to the three mycorrhizal fungal lineages Glomeromycotina, Ascomycota and Basidiomycota. Latest advances in understanding of fungal associations in bryophytes have been largely driven by the discovery, nearly a decade ago, that early divergent liverwort clades, including the most basal Haplomitriopsida, and some hornworts, engage with a wider repertoire of fungal symbionts than previously thought, including endogonaceous members of the ancient sub-phylum Mucoromycotina. Subsequent global molecular and cytological studies have revealed that Mucoromycotina symbionts, alongside Glomeromycotina, are widespread in both complex and simple thalloid liverworts and throughout hornworts, with physiological studies confirming that, in liverworts at least, these associations are mycorrhizal-like, and highlighting important functional differences between Mucoromycotina and Glomeromycotina symbioses. Whether a more prominent role of Mucoromycotina symbionts in plant nitrogen nutrition, as identified in liverworts, extends to other plant lineages, including the flowering plants, is a major topic for future research.
 The latest finding that ascomycete symbionts of leafy liverworts are not restricted to one fungus, Rhizoscyphus ericae, but include species in the genus Meliniomyces, as shown here in Mylia anomala, together with the recent demonstration that R. ericae forms nutritional mutualisms with the rhizoids of Cephalozia bicuspidata, fill other major gaps in our growing knowledge of fungal associations across land plants.

Chloroplast relocation movement in the liverwort Apopellia endiviifolia.

Changes in the subcellular localisation of chloroplasts help optimise photosynthetic activity under different environmental conditions. In many plants, this movement is mediated by the blue‐light photoreceptor phototropin. A model organism with simple phototropin signalling that allows clear observation of chloroplasts would facilitate the study of chloroplast relocation movement. Here, we examined this process in the simple thalloid liverwort Apopellia endiviifolia. Transverse sections of the thallus tissue showed uniformly developed chloroplasts and no air chambers; these characteristics enable clear observation of chloroplasts and analysis of their movements under a fluorescence stereomicroscope. At 22°C, the chloroplasts moved to the anticlinal walls of cells next to the neighbouring cells in the dark (dark‐positioning response), whereas they moved towards weak light (accumulation response) and away from strong light (avoidance response). When the temperature was reduced to 5°C, the chloroplasts moved away from weak light (cold‐avoidance response). Hence, both light‐ and temperature‐dependent chloroplast relocation movements occur in A. endiviifolia. Notably, the accumulation, avoidance and cold‐avoidance responses were induced under blue‐light but not under red‐light. These results suggest that phototropin is responsible for chloroplast relocation movement in A. endiviifolia and that the characteristics are similar to those in the model liverwort Marchantia polymorpha. RNA sequencing and Southern blot analysis identified a single copy of the PHOTOTROPIN gene in A. endiviifolia, indicating that a simple phototropin signalling pathway functions in A. endiviifolia. We conclude that A. endiviifolia has great potential as a model system for elucidating the mechanisms of chloroplast relocation movement.

Chemical Fingerprinting of Cryptic Species and Genetic Lineages of Aneura pinguis (L.) Dumort. (Marchantiophyta, Metzgeriidae).

Aneura pinguis (L.) Dumort. is a representative of the simple thalloid liverworts, one of the three main types of liverwort gametophytes. According to classical taxonomy, A. pinguis represents one morphologically variable species; however, genetic data reveal that this species is a complex consisting of 10 cryptic species (named by letters from A to J), of which four are further subdivided into two or three evolutionary lineages. The objective of this work was to develop an efficient method for the characterisation of plant material using marker compounds. The volatile chemical constituents of cryptic species within the liverwort A. pinguis were analysed by GC-MS. The compounds were isolated from plant material using the HS-SPME technique. Of the 66 compounds examined, 40 were identified. Of these 40 compounds, nine were selected for use as marker compounds of individual cryptic species of A. pinguis. A guide was then developed that clarified how these markers could be used for the rapid identification of the genetic lineages of A. pinguis. Multivariate statistical analyses (principal component and cluster analysis) revealed that the chemical compounds in A. pinguis made it possible to distinguish individual cryptic species (including genetic lineages), with the exception of cryptic species G and H. The classification of samples based on the volatile compounds by cluster analysis reflected phylogenetic relationships between cryptic species and genetic lineages of A. pinguis revealed based on molecular data.

Morphology and microstructure of Pellites hamiensis nov. sp., a Middle Jurassic liverwort from northwestern China and its evolutionary significance

Pelliales is a basal lineage of the simple thalloid liverworts. Here, we describe a simple thalloid liverwort from the Middle Jurassic Xishanyao Formation of the Turpan–Hami Basin, Xinjiang Uygur Autonomous Region in northwestern China. The thalloid fossil liverwort is described as a new species: Pellites hamiensis (Pelliaceae, Pelliales). Pellites hamiensis nov. sp. resembles the extant species of Pelliaceae in having ribbon-like segments, conspicuous costae that appear as ridges on the ventral surface, rectangular cells with thickened walls adjacent to the margin, and elongated cells in the middle part of the thallus. The occurrence of P. hamiensis nov. sp. extends the fossil records of Pellites back to the Aalenian-Bajocian or Bajocian (ca. 170 Ma) and suggests that the divergence time of the Pelliaceae is no later than the Middle Jurassic.

The identification of differentially expressed genes in male and female gametophytes of simple thalloid liverwort Pellia endiviifolia sp. B using an RNA-seq approach

Main conclusionThis study shows differences in gene expression between male and female gametophytes of the simple thalloid liverwort with a distinction between the vegetative and reproductive phases of growth.Pellia endiviifolia is a simple thalloid liverwort that, together with hornworts and mosses, represents the oldest living land plants. The limited taxon sampling for genomic and functional studies hampers our understanding of processes governing evolution of these plants. RNA sequencing represents an attractive way to elucidate the molecular mechanisms of non-model species development. In the present study, RNA-seq was used to profile the differences in gene expression between P. endiviifolia male and female gametophytes, with a distinction between the vegetative and reproductive phases of growth. By comparison of the gene expression profiles from individuals producing sex organs with the remaining thalli types, we have determined a set of genes whose expression might be important for the development of P. endiviifolia reproductive organs. The selected differentially expressed genes (DEGs) were categorized into five main pathways: metabolism, genetic information processing, environmental information processing, cellular processes, and organismal systems. A comparison of the obtained data with the Marchantia polymorpha transcriptome resulted in the identification of genes exhibiting a similar expression pattern during the reproductive phase of growth between members of the two distinct liverwort classes. The common expression profile of 87 selected genes suggests a common mechanism governing sex organ development in both liverwort species. The obtained RNA-seq results were confirmed by RT-qPCR for the DEGs with the highest differences in expression level. Five Pellia-female-specific and two Pellia-male-specific DEGs showed enriched expression in archegonia and antheridia, respectively. The identified genes are promising candidates for functional studies of their involvement in liverwort sexual reproduction.

Fossombronia isaloensis Cargill & D.A.Callaghan, a new liverwort from sandstone massifs in southern Madagascar

ABSTRACT Introduction. Although Madagascar is known for its unique fauna and vascular flora, the country’s bryophyte flora in contrast is understudied and under collected. Arising from a bryophyte collecting expedition undertaken in May–June 2016, this paper describes a new species of simple thalloid liverwort, Fossombronia isaloensis, from Madagascar. Methods. Morphological traits across specimens were reviewed and compared with related species. DNA sequence data from rbcL, rps4 and trnL-trnF was obtained from 7 accessions of Fossombronia from Madagascar and 18 other named species of the genus and used to produce a plastid-based phylogeny. Results. DNA sequence data show that Fossombronia isaloensis is not closely related to any other Fossombronia taxon sampled for this study. A description and diagnosis is provided and a type specimen designated for the new species. Conclusions. The bryophyte flora of Madagascar urgently deserves further inventory and taxonomic investigation.

Hepaticites(Marchantiophyta) in the Lower Permian Arroyo Totoral Formation (La Rioja Province, Argentina)

In this contribution we present the first record of a liverwort from the Arroyo Totoral Formation in the Paganzo Basin. The sample is preserved as a compression, founded in a greenish-gray shale with parallel lamination, associated with gymnosperms. The delicate thallus differentiated into wings and midrib with elongate cells but lacking evidence of air-pores like those developed in complex thalloid liverworts, suggests that the fossil is a simple thalloid liverwort. The lack of reproductive traits restricted the assignation to Hepaticites sp. This record supports the interpretation of local humid conditions and improves the Gondwanan Paleozoic record of Bryophytes.

Additions and corrections for liverworts and hornworts of Singapore

Since the first record of liverworts and hornworts in Singapore was reported in 1845, the liverwort and hornwort flora of Singapore remain poorly known. Based on the examination on herbarium specimens kept in FH, GOET, SING, and SINU, as well as additional field collections, we found 12 liverworts new to Singapore. The occurrence of Caudalejeunea cristiloba and Jackiella javanica in Singapore is confirmed. Records of Lejeunea parva are erroneous because the voucher specimens from Singapore are assignable to Lejeunea cocoes. A total of 120 liverwort and hornwort species in 45 genera have thus far been recorded in Singapore, including 100 leafy liverworts, 12 simple thalloid liverworts, 5 complex thalloid liverworts, and 3 hornworts. The illustrations of Cheilolejeunea malaccensis, Drepanolejeunea vesiculosa, Jackiella javanica, J. singapurensis, and Lejeunea cocoes are provided.

New insights into the phylogeny and relationships within the worldwide genus Riccardia (Aneuraceae, Marchantiophytina)

With 280 accepted species, the genus Riccardia S.F.Gray (Aneuraceae) is one of the most speciose genera of simple thalloid liverworts. The current classification of this genus is based on morphological and limited-sampling molecular studies. Very few molecular data are available and a comprehensive view of evolutionary relationships within the genus is still lacking. A phylogeny focusing on relationships within the large genus Riccardia has not been conducted. Here we propose the first worldwide molecular phylogeny of the genus Riccardia, based on Bayesian inference and parsimony ratchet analyses of sequences from three plastid regions (psbA-trnH, rps4, trnL-F). The results support the monophyly of Riccardia and a new monospecific genus, Afroriccardia Reeb & Gradst. gen. nov., is described based on molecular and morphological evidence. The results indicate that several currently recognized infrageneric divisions and a few species are not monophyletic, suggesting that further analyses are needed to arrive at a proper understanding of the phylogeny of the genus. Although evidence for an Andean clade was found, most of the species appear scattered in different clades without clear geographical segregation. Broader sampling and further analyses are necessary in order to improve our understanding of the phylogeny of this poorly known liverwort genus.

Effectiveness of ISSR markers for determination of the Aneura pinguis cryptic species and Aneura maxima

Aneura pinguis and Aneura maxima belong to the simple thalloid liverworts. Previous isozyme studies revealed that A. pinguis is a complex of cryptic species difficult to distinguished based on morphology. In the present study four cryptic species of the A. pinguis complex and A. maxima were examined by means of ISSR method to assess genetic variation and to develop species-specific markers. Eight ISSR primers used generated 460 bands, of which 453 were polymorphic. The highest values of resolving power 28.4 and marker index 18.1 were noted for primer 835 (AG)8-YC, while polymorphism information content for primer 842 (GA)7-AYG. The total gene diversity (HT) based on polymorphic loci was 0.284 for A. pinguis and 0.06 for A. maxima. ISSR markers supported existence of cryptic species in A. pinguis and showed genetic isolation between them. Species-specific bands were found for all studied cryptic species of A. pinguis and A. maxima, thus ISSRs can be used for their identification. A. maxima clearly differ from all the A. pinguis cryptic species in each amplified ISSR primer. The AMOVA conducted for the A. pinguis complex showed that most of genetic variation (ΦPT 0.586) was present among species.

Preliminary Attempts to Conserve Bryophytes in Lowland Forests of Sri Lanka: A Case Study at Yagirala Forest Reserve

Bryophytes were the first dwellers of the land plant history and play a vital role in the dynamics of the forest ecosystems such as water flow regulation and nutrient cycling. Considerable efforts on surveying and taxonomic studies of bryoflora in Sri Lanka was done in the early and mid-19th century by foreign scientists and there is a huge gap for several decades till late 1990s and no proper systematic survey of bryoflora in lowland forests in Sri Lanka has been carried out in the recent past. Sri Lanka is a biodiversity hotspot and it has a rich and diverse tropical bryoflora in the lowland and highland natural wet -moist forests. Yagirala forest reserve is a lowland tropical rainforest situated in the low country wet zone. Many floristic researches on angiosperms have been carried out but there is no systematic survey has been carried out to study the cryptogamic plants in the forest. Hence this is the first attempt to study and identify distribution of the bryoflora at Yagirala forest reserve. The bryophyte diversity in three main ecosystems in the forest including the primary forest, secondary forest and the forest associated with the Pinus plantation was studied. Ten (10) different families of mosses (including 12 genera, 16 species), Six (06) families of leafy liverworts (including 12 genera, 14 species) and 03 families of simple thalloid liverworts (including 03 genera, 03 species) were found. All species records were mapped and seemed to be new species records to Sri Lanka. DNA samples were collected for further barcoding studies and voucher specimens were prepared. A comparison of the species diversity in each major habitat type was studied and some anthropogenic and natural threats to the native bryoflora in the forest were studied. Further intensive research work is needed to prepare a complete checklist of bryoflora in the Yagirala Forest reserve and the final output of the project will be developing a user-friendly pocket guide to study the common bryophytes in the forest and this will open a novel avenue to initiate the conservation and IUCN redlisting of lowland bryoflora in Sri Lanka. Keywords: Bryophytes, Preliminary survey, Yagirala Forest Reserve, Conservation

Pallaviciniites oishii(comb. nov.), a thalloid liverwort from the Late Triassic of Japan

Abstract The fossil liverwort Hepaticites oishii from the Momonoki Formation in Western Honshu, Japan is critically reviewed. The type material exhibits the following characteristics: (1) small thalloid plants with well-defined midrib and lamina; (2) regularly dichotomously branching habit; (3) attenuate apical part of thallus with unnotched apex; (4) lack of ventral scales; (5) undulate lamina and margin of thallus without marginal teeth or hair; and (6) presence of rhizoids on midrib. These characters suggest an affinity of H. oishii to members of simple thalloid liverworts, particularly Pallaviciniales (Jungermanniopsida, Marchantiophyta). The species is therefore assigned to the fossil genus Pallaviciniites with a new combination: Pallaviciniites oishii (Huzioka & Takahasi) T. Katag. This liverwort fossil is significant because it constitutes the first fossil record of the order Pallaviciniales from the Late Triassic of Eurasia and is the second-oldest fossil liverwort in East Asia after Riccardiothal...

Fungal symbioses in bryophytes: New insights in the Twenty First Century

Fungal symbioses are one of the key attributes of land plants. The twenty first century has witnessed the increasing use of molecular data complemented by cytological studies in understanding the nature of bryophyte-fungal associations and unravelling the early evolution of fungal symbioses at the foot of the land plant tree. Isolation and resynthesis experiments have shed considerable light on host ranges and very recently have produced an incisive insight into functional relationships. Fungi with distinctive cytology embracing short-lived intracellular fungal lumps, intercellular hyphae and thick-walled spores in Treubia and Haplomitrium are currently being identified as belonging to a more ancient group of fungi than the glomeromycetes, previously assumed to be the most primitive fungi forming symbioses with land plants. Glomeromycetes, like those in lower tracheophytes, are widespread in complex and simple thalloid liverworts. Limited molecular identification of these as belonging to the derived clade Glomus Group A has led to the suggestion of host swapping from tracheophytes. Ascomycetes, all identified to date as Rhizoscyphus ericae and having an extremely wide host range extending into the Ericales, occur in the rhizoids of a range of leafy liverwort families that are sister to the Schistochilaceae, where the fungus induces rhizoid branching and septation. Dating of the Schistochilaceae suggests that these liverwort rhizoid associations predated ericoid mycorrhizas. A more restricted distribution of basidiomycetes, all identified as members of the genus Sebacina, is interpreted as a secondary acquisition in leafy liverworts following the loss of ascomycetes. Unlike the latter and ectomycorrhizal basidiomycetes in tracheophytes, these are host specific. Whereas there is no evidence of host digestion for either the ascomycetes or basidiomycetes in leafy liverworts, basidiomycetes in the Aneuraceae display regular colonization and digestion cycles. Considerable molecular diversity in the aneuracean fungi, mainly in the genus Tulasnella with occasional sebacinoids, mirrors the same in the host liverworts. Nesting of the only mycoheterotrophic liverwort Cryptothallus within Aneura is congruent with the phylogeny of the endophytes. Glomeromycete fungi have been identified in Phaeoceros and Anthoceros whereas Dendroceros, Megaceros and Nothoceros lack endophytes but the distribution of fungi across hornworts has yet to be explored. In contrast to liverworts and hornworts, there is no evidence of mycorrhiza-like associations in mosses. Claims that the fossil Prototaxites was a fossil fungus-associated liverwort are discounted.

On the morphology, systematics and phylogeny of Noteroclada (Noterocladaceae, Marchantiophyta)

Noteroclada Taylor ex Hook. & Wilson has long been recognized as a unique leafy taxon having affinities to the north temperate, simple thalloid liverwort genus, Pellia Raddi. Although a suite of diagnostic characters clearly separate it from Fossombronia Raddi and other leafy, anacrogynous taxa, considerable confusion regarding its identity exists in historical treatments. There are unresolved questions in regards to the extent and significance of morphological variation within the genus, the number of species that should be recognized, the geographic range that it occupies and its position in liverwort phylogeny. Morphological, experimental and molecular techniques are employed to address these questions. These studies show that there are two forms of perennating tubers, which are geographically partitioned, that plants are always monoicous, that sporophytes are enclosed by a shoot calyptra and Fossombronia-like caulocalyx and that sporeling ontogeny is different from that of Pellia. Molecular analyses show some genetic variation within Noteroclada, but both morphological and molecular data support the recognition of but a single species, N. confluens Taylor ex Hook. & Wilson. It is confirmed that there are no reliable specimens of Noteroclada from Africa, Australasia or the Kerguelen sector and that the genus has two centers of distribution in Latin America, with disjunct populations in the Falkland Islands, South Georgia, Tristan da Cunha and Gough Island. Significant ontogenetic differences between Noteroclada and Pellia support their placement in separate monogeneric families of the Pelliales.

Systematic position of the enigmatic liverwort Mizutania (Mizutaniaceae, Marchantiophyta) inferred from molecular phylogenetic analyses

AbstractPhylogenetic analyses of liverworts using chloroplast rbcL and rps4 sequences were performed with special reference to the enigmatic thalloid liverwort, Mizutania riccardioides. The results showed that Mizutania is nested within leafy liverwort family Calypogeiaceae (subclass Jungermanniidae), thereby refuting the traditional interpretation that Mizutania is a member of the simple thalloid liverworts (subclass Metzgeriidae) related to Aneuraceae. Male plants with three ranked bracts, which are newly discovered in this study, also show a close morphological affinity to those of leafy liverworts. Parallel evolution of the flattened gametophyte seems to have occurred sporadically in the Jungermanniidae in association with adaptation to prostrate growth on the ground or on living leaves. The unistratose thalloid features of Mizutania are interpreted as an extremely reduced or highly specialized form of a creeping leafy liverwort. The rudimentary sexual branches which develop on the margins of the thallus are similar in many characteristics to those of Calypogeiaceae. We reduce the monotypic family Mizutaniaceae to a synonym of Calypogeiaceae.