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.
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A working checklist of accepted taxa worldwide is vital in achieving the goal of developing an online flora of all known plants by 2020 as part of the Global Strategy for Plant Conservation. We here ...present the first-ever worldwide checklist for liverworts (Marchantiophyta) and hornworts (Anthocerotophyta) that includes 7486 species in 398 genera representing 92 families from the two phyla. The checklist has far reaching implications and applications, including providing a valuable tool for taxonomists and systematists, analyzing phytogeographic and diversity patterns, aiding in the assessment of floristic and taxonomic knowledge, and identifying geographical gaps in our understanding of the global liverwort and hornwort flora. The checklist is derived from a working data set centralizing nomenclature, taxonomy and geography on a global scale. Prior to this effort a lack of centralization has been a major impediment for the study and analysis of species richness, conservation and systematic research at both regional and global scales. The success of this checklist, initiated in 2008, has been underpinned by its community approach involving taxonomic specialists working towards a consensus on taxonomy, nomenclature and distribution.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Ferns are well known for their shade-dwelling habits. Their ability to thrive under low-light conditions has been linked to the evolution of a novel chimeric photoreceptor—neochrome—that fuses ...red-sensing phytochrome and blue-sensing phototropin modules into a single gene, thereby optimizing phototropic responses. Despite being implicated in facilitating the diversification of modern ferns, the origin of neochrome has remained a mystery. We present evidence for neochrome in hornworts (a bryophyte lineage) and demonstrate that ferns acquired neochrome from hornworts via horizontal gene transfer (HGT). Fern neochromes are nested within hornwort neochromes in our large-scale phylogenetic reconstructions of phototropin and phytochrome gene families. Divergence date estimates further support the HGT hypothesis, with fern and hornwort neochromes diverging 179 Mya, long after the split between the two plant lineages (at least 400 Mya). By analyzing the draft genome of the hornwort Anthoceros punctatus , we also discovered a previously unidentified phototropin gene that likely represents the ancestral lineage of the neochrome phototropin module. Thus, a neochrome originating in hornworts was transferred horizontally to ferns, where it may have played a significant role in the diversification of modern ferns.
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The vast abundance of terpene natural products in nature is due to enzymes known as terpene synthases (TPSs) that convert acyclic prenyl diphosphate precursors into a multitude of cyclic and acyclic ...carbon skeletons. Yet the evolution of TPSs is not well understood at higher levels of classification. Microbial TPSs from bacteria and fungi are only distantly related to typical plant TPSs, whereas genes similar to microbial TPS genes have been recently identified in the lycophyte Selaginella moellendorffii. The goal of this study was to investigate the distribution, evolution, and biochemical functions of microbial terpene synthase-like (MTPSL) genes in other plants. By analyzing the transcriptomes of 1,103 plant species ranging from green algae to flowering plants, putative MTPSL genes were identified predominantly from nonseed plants, including liverworts, mosses, hornworts, lycophytes, and monilophytes. Directed searching for MTPSL genes in the sequenced genomes of a wide range of seed plants confirmed their general absence in this group. Among themselves, MTPSL proteins from nonseed plants form four major groups, with two of these more closely related to bacterial TPSs and the other two to fungal TPSs. Two of the four groups contain a canonical aspartate-rich “DDxxD” motif. The third group has a “DDxxxD” motif, and the fourth group has only the first two “DD” conserved in this motif. Upon heterologous expression, representative members from each of the four groups displayed diverse catalytic functions as monoterpene and sesquiterpene synthases, suggesting these are important for terpene formation in nonseed plants.
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Unraveling the macroevolutionary history of bryophytes, which arose soon after the origin of land plants but exhibit substantially lower species richness than the more recently derived angiosperms, ...has been challenged by the scarce fossil record. Here we demonstrate that overall estimates of net species diversification are approximately half those reported in ferns and ∼30% those described for angiosperms. Nevertheless, statistical rate analyses on time-calibrated large-scale phylogenies reveal that mosses and liverworts underwent bursts of diversification since the mid-Mesozoic. The diversification rates further increase in specific lineages towards the Cenozoic to reach, in the most recently derived lineages, values that are comparable to those reported in angiosperms. This suggests that low diversification rates do not fully account for current patterns of bryophyte species richness, and we hypothesize that, as in gymnosperms, the low extant bryophyte species richness also results from massive extinctions.
Nucleotide sequence data from three chloroplast genes (rbcL, rps4 and psbA), one nuclear gene (the ribosomal LSU) and one mitochondrial gene (nad5) were assembled for 173 species in 117 genera of ...liverworts, making this the largest molecular phylogeny of the group to date. Analyses of these data provide support for the monophyly of the liverworts, and for previously resolved backbone relationships within the Marchantiophyta. The earliest divergence involves the “simple thalloid” taxa of the Haplomitriaceae and Treubiaceae. A Blasiaceae/complex thalloid clade is resolved as sister to all remaining liverworts. The leafy liverworts do not resolve as monophyletic. The separation of the Aneuraceae/Metzgeriaceae from all other simple thalloids and their placement within the “leafy” clade as sister to the enigmatic leafy genus Pleurozia, as suggested in earlier molecular phylogenies, is also supported by this far larger data set.
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The phylogenetic history of and evolutionary trends within the simple thalloid liverworts (Jungermanniopsida, subclass Metzgeriidae) are reconstructed in a combined analysis of molecular and ...morphological data. The molecular dataset comprises loci from all three genomes, including trnL-F, rps4, rbcL, atpβ and psbA from the chloroplast, SSU rRNA and LSU rRNA from the nucleus, and nad5 from the mitochondrion, and 65 characters are scored in the morphological dataset. An initial analysis of a molecular dataset that included 16 outgroup and 50 ingroup taxa resolved a Haplomitrium/Treubiaceae clade as the earliest diverging lineage of the ingroup. Subsequent analyses of ingroup only datasets, rooted on this clade, resolve Metzgeriidae as paraphyletic, with Blasiaceae sister to Marchantiopsida in all analyses. A combined analysis of morphological and molecular datasets resolves basically the same clades as analyses of the molecular dataset alone, except for the resolution of a weak sister group relationship between Metzgeriineae and the leafy liverworts. Reconstructions of morphological character evolution on the combined analysis topology confirm that there is substantial homoplasy in the morphology dataset, even in characters that have been traditionally considered diagnostic of hierarchial relationships, such as apical cell geometry, calyptral type and capsule wall thickness. Ancestral state reconstructions contradict many prevailing hypotheses of character evolution in hepatics, including the model of the ancestral liverwort prototype as an erect, radially symmetric plant. Instead, a more likely model is a prostrate, bilaterally symmetric plant with the diagnostic features of a simple thalloid liverwort.
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The genus Aitchisoniella with a single species A. himalayensis (Marchantiopsida, Cleveaceae), previously considered endemic to the north-west Himalayas of India, is reported for the first time from ...Sichuan Province, China. The genus is distinctive amongst complex thalloid liverworts in lacking stalked carpocephala but having archegonia and sporophytes borne on the ventral side of a short receptacle arising in a terminal thallus bifurcation. The receptacle tissue is continuous with that of the main thallus, with dorsal air chambers and air pores, and a ventral groove containing pegged rhizoids. Both molecular data and morphological characters, particularly spore ornamentation, suggest that its previous placement in Exormothecaceae is incorrect and it is now transferred to Cleveaceae, wherein it becomes the fifth genus. Revised descriptions of the families Cleveaceae and Corsiniaceae (including Exormothecaceae) are provided.
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The monospecific Phycolepidoziaceae with the single neotropical speciesPhycolepidozia exiguais a highly specialized leafy liverwort without vegetative leaves. The extreme reduction of morphological ...and anatomical characters ofPhycolepidoziahas caused uncertainties as to the systematic position of the genus and family. In 2012, a second species ofPhycolepidoziawas detected in the Western Ghats, South India. The Indian plant differs fromP. exiguain several respects and is described here asP. (subg.Metaphycolepidozia)indicaGradst., J.-P.Frahm & U.Schwarz. Differences include the massive stem ofP. indica, the larger perianth with a crenate, 3-lobed mouth, and the epidermis of the capsule wall made up of non-tiered cells with nodular thickenings on both longitudinal and transverse walls. A phylogenetic analysis using four different chloroplast regions (psbA, psbT, rps4, rbcL) ofP. indicaand putatively related groups shows thatPhycolepidoziais nested within the leafy liverwort family Cephaloziellaceae. Consequently, Phycolepidoziaceae is placed in the synonymy of Cephaloziellaceae. The discovery ofP. indicaadds a further example to the list of amphi-Pacific tropical disjunctions in bryophytes.
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