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We present a complete generic‐level phylogeny of the complex thalloid liverworts, a lineage that includes the model system Marchantia polymorpha. The complex thalloids are remarkable for their slow rate of molecular evolution and for being the only extant plant lineage to differentiate gas exchange tissues in the gametophyte generation. We estimated the divergence times and analyzed the evolutionary trends of morphological traits, including air chambers, rhizoids and specialized reproductive structures. A multilocus dataset was analyzed using maximum likelihood and Bayesian approaches. Relative rates were estimated using local clocks. Our phylogeny cements the early branching in complex thalloids. Marchantia is supported in one of the earliest divergent lineages. The rate of evolution in organellar loci is slower than for other liverwort lineages, except for two annual lineages. Most genera diverged in the Cretaceous. Marchantia polymorpha diversified in the Late Miocene, giving a minimum age estimate for the evolution of its sex chromosomes. The complex thalloid ancestor, excluding Blasiales, is reconstructed as a plant with a carpocephalum, with filament‐less air chambers opening via compound pores, and without pegged rhizoids. Our comprehensive study of the group provides a temporal framework for the analysis of the evolution of critical traits essential for plants during land colonization.

Two new hepaticolous ascomycetes from the Kelabit Highlands (Sarawak, Borneo) are described and illustrated. Both of them infect thallose liverworts growing in damp and shaded localities. Octosporopsis erinacea parasitizing Dumortiera hirsuta (Marchantiopsida) has tiny, light yellow, rimless, setose apothecia, usually 8-spored asci and ellipsoid ascospores. Hyphae with appressoria develop superficially on, and intracellularly within, the host thallus. Dumortiera was recorded as a host for any bryophilous fungus for the first time. Octospora kelabitiana parasitizes species of the genus Riccardia (Jungermanniopsida). It is characterised by very small, light orange, setose apothecia, 8-spored asci, ellipsoid, biguttulate spores and very thick hyphae with conspicuous warts and ridges. Generic placement of both species was inferred based on DNA analysis of two nuclear loci (EF1α, LSU rDNA).

As the earliest divergent land plants, bryophytes (mosses, hornworts, and liverworts) provide insight into the evolution of the unique plant process of sporogenesis by which meiosis results in heavy walled spores. New immunohistochemical data on microtubules and γ-tubulin in four genera of complex thalloid liverworts combined with previously published data on another four genera demonstrate grades in the evolution of spindle organization in meiosis. We have discovered that all recognized forms of microtubule organizing centers (MTOCs) in plant cells (plastid MTOCs, spheroid cytoplasmic MTOCs, polar organizers, and nuclear envelope MTOCs) occur in organization of the meiotic spindle of complex thalloid liverworts. In addition, all aspects of pre-meiotic preparation for quadripartitioning of the sporocyte into a tetrad of spores occur, with the exception of pre-meiotic wall precursors found in certain simple thalloids. The preparation includes morphogenetic plastid migration, cortical bands of microtubules that mark future cytokinetic planes in pre-meiosis, quadrilobing of the cytoplasm during meiotic prophase, and quadripolar microtubule systems that are transformed into functionally bipolar metaphase I spindles. Quadripolar spindle origin is typical of bryophyte sporogenesis even though the MTOCs involved may differ. However, in certain crown taxa of complex thalloids the spindle develops with no traces of quadripolarity and placement of intersporal walls is determined after meiosis, as is typical of higher plants.

This monograph presents results of research on genetic diversity of 8 leafy liverwort species differing in reproductive mode. The frst 4 species in Poland are regarded as sterile and reproduce only vegetatively: Bazzania trilobata, Trichoc-olea tomentella, Lophozia hatcheri, and Mylia anomala. The next 4 are fertile, including the monoecious Lepidozia reptans and Calypogeia integristipula as well as the dioecious Mylia taylorii and Tritomaria quinquedentata. For each species, 9-10 populations were sampled. In total, 4744 gametophytes from 73 populations were examined by isozyme analysis. The level of their genetic diversity (total, HT, and within populations, HS) was high, higher than in thallose liverworts, but comparable to the genetic diversity of mosses or even some species of vascular plants. Thus the traditional opinion that the entire group of liverworts has a much lower level of genetic diversity than mosses is erroneous, as it holds true only for thallose liverworts (Metzgeriidae and Marchantiopsida). My results indicate that the effect of reproductive mode on genetic diversity in leafy liverworts is lower than in vascular plants. Sterile and fertile species of liverworts exhibited similar levels of genetic diversity. Moreover, both groups included species that had both high and low levels of HT and HS. In fertile species, monoecious and dioecious species also did not differ signifcantly in genetic diversity, but dioecious liverworts had slightly higher total diversity (HT) than monoecious species. In most of the studied leafy liverworts, the share of genetic diversity within populations in the total genetic diversity of species is greater than between populations. The percentage share of variation among populations (ΦPT) in the total genetic variation was correlated with the total genetic diversity of the species (HT). In species with high HT, differences between populations tended to be rather small. By contrast, in species with lower HT, the percentage share of differentiation among populations in the total diversity of species was much higher. My results confrm theory, based on studies by Kimura, that the main causes of genetic diversity of bryophytes are neutral somatic mutations developing in various vegetative parts of plants. The separation of branches or other plant sections with somatic mutations, followed by the growth of new shoots, can increase the level of genetic diversity. The high level of genetic diversity in sterile liverworts indicates that vegetative reproduction has a greater infuence on the level of genetic diversity than recombination. My results suggest also that mutation rates are similar in closely related species, but species with a wider ecological range exhibit higher genetic diversity because the variability of habitats can infuence the rate and type of somatic mutations. Accordingly, species inhabiting more diverse environments may be more genetically diverse. Patches of the studied species generally consisted of several genotypes (MLGs). Two types of distribution of genotypes in patches were noticed. Patches of species with low total diversity (HT), were often dominated by 1-2 genotypes, which constituted the major part of a patch. In patches of species with higher HT, there was no tendency to form patches with predomination of a single genotype. Different genotypes constituted similar proportions of a patch. In all the studied leafy liverwort species there was a high degree of repeatability of the same genotypes (MLGs) in plants from various patches within the same population or in various populations. Probably the main cause of this is the independent repeatability of the same mutations in different specimens.

The current state of molecular studies in liverworts, including original data, was considered. The traditional concepts of the liverwort phylogeny and systematics have greatly changed as a result of recent molecular researches. The phylogenetic inferences from studies of different DNA loci of different species sampling are mainly congruent. The phylogeny and systematics of the suborder Jungermaniineae, one of the largest and taxonomically difficult groups, is discussed on the basis of nucleotide sequence analyses of internal transcribed spacers 1 and 2 (ITS1-2) of nuclear rDNA and chloroplast trnL-F in a representative species sampling.

Complete sequences for the 18S-rRNA gene of 22 bryophytes (12 completely new) were determined and used to construct phylogenetic trees. The evaluation of sequence data according to the maximum parsimony principle (PAUP 3.1.1) and the neighbor-joining method (MEGA) results in similar phylogenetic trees in which the Bryopsida appear as a sister group to the Jungermanniopsida, and both together as a sister group to the Marchantiopsida. Among the Marchantiopsida, the Sphaerocarpales diverge early as a separate clade. The Metzgeriales and Jungermanniales are monophyletic. They belong to one clade and cannot be separated by either method of evaluation.

Molecular phylogenies of the complex-thalloid liverworts (Marchantiales) were reconstructed using independent nuclear and plastid data sets to explore relative age, relationships, and character evolution in this ancient group. The sample includes 10 carpocephalate taxa and 24 acarpocephalate taxa (emphasizing Riccia) within Marchantiales sensu stricto. In addition, Monoclea, Sphaerocarpos, Riella, three Metzgeriales (Fossombronia, Pellia, and Blasia), the hornwort Anthoceros, four mosses, and outgroup Coleochaete are also sampled. Two nucleotide sequence alignments were used 1) partial nuclear-encoded Large Subunit rDNA (LSU rDNA) for all 48 taxa and 2) the plastid-encoded trnL-F region for the marchantioids and outgroup Blasia. Alignment-ambiguous regions of each alignment were culled. A combined matrix consisting of concatenated nuclear and plastid culled alignments was assembled for marchantioids and Blasia. The two alignments were utilized in four analyses: 1) nuclear LSU rDNA for all taxa, 2) nuclear LSU rDNA for marchantioids + Blasia, 3) plastid trnL-F region for marchantioids plus Blasia, and 4) combined nuclear and plastid data for marchantioids plus Blasia. Selected pairwise comparisons reveal significant rate heterogeneity in the nuclear LSU rDNA data; metzgerioid liverworts, hornworts and primitive mosses evolve significantly slower than other taxa relative to the outgroup Coleochaete. The LSU rDNA genes of some marchantioid taxa and sampled bryalean mosses are apparently evolving relatively fast. Rate heterogeneity is also documented within Marchantiales. Lunularia positions as the most basal of sampled Marchantiopsida; Sphaerocarpales, Marchantia, and Corsinia represent early diverging lines. A monophyletic Aytoniaceae, Cleveaceae, and Riccia are indicated. Topologies imply that extant acarpocephalate taxa are derived from carpocephalate forms. Monoclea positions well within Marchantiales sensu stricto. A well-supported long branch (Decay Index = 19) unites all sampled Marchantiopsida and isolates this clade from other liverworts and bryophytes. This long branch may suggest extensive extinction of proto- and eomarchantioid forms that led to modern taxa. A recurring theme in the topologies presented here is the unresolved marchantioid polytomy that follows well-supported basal nodes. A similar polytomy results from either independent data set and may correspond to a rapid radiation of marchantioid forms (e.g., Aytoniaceae, Cleveaceae, Targionia, Monoclea, and riccioids) coincident with extreme conditions and ecological reorganizations of the Permo-Triassic. The origin of Marchantiopsida probably occurred long before; amidst, perhaps, a series of long-extinct Blasia-like ancestors that colonized and innovated on any of various xeric surfaces (either cool or warm) that were available throughout embryophyte history in the Paleozoic.