Geographical structure, narrow species ranges, and Cenozoic diversification in a pantropical clade of epiphyllous leafy liverworts

The evolutionary history and classification of epiphyllous cryptogams are still poorly known. Leptolejeunea is a largely epiphyllous pantropical liverwort genus with about 25 species characterized by deeply bilobed underleaves, elliptic to narrowly obovate leaf lobes, the presence of ocelli, and vegetative reproduction by cladia. Sequences of three chloroplast regions (rbcL, trnL-F, psbA) and the nuclear ribosomal ITS region were obtained for 66 accessions of Leptolejeunea and six outgroup species to explore the phylogeny, divergence times, and ancestral areas of this genus. The phylogeny was estimated using maximum-likelihood and Bayesian inference approaches, and divergence times were estimated with a Bayesian relaxed clock method. Leptolejeunea likely originated in Asia or the Neotropics within a time interval from the Early Eocene to the Late Cretaceous (67.9 Ma, 95% highest posterior density [HPD]: 47.9-93.7). Diversification of the crown group initiated in the Eocene or early Oligocene (38.4 Ma, 95% HPD: 27.2-52.6). Most species clades were established in the Miocene. Leptolejeunea epiphylla and L. schiffneri originated in Asia and colonized African islands during the Plio-Pleistocene. Accessions of supposedly pantropical species are placed in different main clades. Several monophyletic morphospecies exhibit considerable sequence variation related to a geographical pattern. The clear geographic structure of the Leptolejeunea crown group points to evolutionary processes including rare long-distance dispersal and subsequent speciation. Leptolejeunea may have benefitted from the large-scale distribution of humid tropical angiosperm forests in the Eocene

Comment on the letter of the Society of Vertebrate Paleontology (SVP) dated April 21, 2020 regarding 'Fossils from conflict zones and reproducibility of fossil‑based scientific data': Myanmar amber

Recently, the Society of Vertebrate Paleontology (SVP) has sent around a letter, dated 21st April, 2020 to more than 300 palaeontological journals, signed by the President, Vice President and a former President of the society (Rayfield et al. 2020). The signatories of this letter request significant changes to the common practices in palaeontology. With our present, multi-authored comment, we aim to argue why these suggestions will not lead to improvement of both practice and ethics of palaeontological research but, conversely, hamper its further development. Although we disagree with most contents of the SVP letter, we appreciate this initiative to discuss scientific practices and the underlying ethics. Here, we consider different aspects of the suggestions by Rayfield et al. (2020) in which we see weaknesses and dangers. It is our intent to compile views from many different fields of palaeontology, as our discipline is (and should remain) pluralistic. This contribution deals with the aspects concerning Myanmar amber. Reference is made to Haug et al. (2020a) for another comment on aspects concerning amateur palaeontologists/citizen scientists/private collectors

Comprehensive phylogenomic time tree of bryophytes reveals deep relationships and uncovers gene incongruences in the last 500 million years of diversification

Premise: Bryophytes form a major component of terrestrial plant biomass, structuring ecological communities in all biomes. Our understanding of the evolutionary history of hornworts, liverworts, and mosses has been significantly reshaped by inferences from molecular data, which have highlighted extensive homoplasy in various traits and repeated bursts of diversification. However, the timing of key events in the phylogeny, patterns, and processes of diversification across bryophytes remain unclear. Methods: Using the GoFlag probe set, we sequenced 405 exons representing 228 nuclear genes for 531 species from 52 of the 54 orders of bryophytes. We inferred the species phylogeny from gene tree analyses using concatenated and coalescence approaches, assessed gene conflict, and estimated the timing of divergences based on 29 fossil calibrations. Results: The phylogeny resolves many relationships across the bryophytes, enabling us to resurrect five liverwort orders and recognize three more and propose 10 new orders of mosses. Most orders originated in the Jurassic and diversified in the Cretaceous or later. The phylogenomic data also highlight topological conflict in parts of the tree, suggesting complex processes of diversification that cannot be adequately captured in a single gene-tree topology. Conclusions: We sampled hundreds of loci across a broad phylogenetic spectrum spanning at least 450 Ma of evolution; these data resolved many of the critical nodes of the diversification of bryophytes. The data also highlight the need to explore the mechanisms underlying the phylogenetic ambiguity at specific nodes. The phylogenomic data provide an expandable framework toward reconstructing a comprehensive phylogeny of this important group of plantsFunding was provided by the NSF collaborative project “Building a Comprehensive Evolutionary History of Flagellate Plants” (DEB #1541506 to J.G. Burleigh, E.C. Davis, S.F. McDaniel, and E.B. Sessa, and #1541545 to M von Konrat). B.G. acknowledges DEB‐1753811. J.C.V.A. acknowledges the Canada Research Chair (950‐232698); the CRNSG‐RGPIN 05967–2016 and the Canadian Foundation for Innovation (projects 36781, 39135). The authors thank the two anonymous reviewers and the Associate Editor for their constructive comments on previous versions of the manuscrip

Comment on the letter of the Society of Vertebrate Paleontology (SVP) dated April 21, 2020 regarding “Fossils from conflict zones and reproducibility of fossil‑based scientific data”: Myanmar amber

Non peer reviewe

Sequence alignments of South Shetland Placopsis mycobionts and photobionts

Since ice-free areas in Antarctica are predicted to increase by up to 25% before the end of this century, lichens such as the genus Placopsis will be important colonizers of these newly available grounds and will still be present in later successional stages of the lichen community. The main symbionts of Placopsis species are examined for 56 specimens collected from the South Shetland Islands, Antarctica using molecular (fungal and algal nrITS, fungal RPB1, algal rbcL sequences) and morphological methods. The specimens were collected from soils with different deglaciation times. Eight uni-algal photobiont cultures were obtained and analysed from two specimens. Placopsis antarctica and P. contortuplicata proved to be monophyletic and are sister species, only the former producing vegetative diaspores (soredia). Both share the same photobiont pool and are lichenized with two closely related species, Stichococcus antarcticus and S. allas. Two haplotypes of S. antarcticus are restricted to areas deglaciated for more than 5000 years and the volcanic Deception Island indicating a shift in the photobionts of Placopsis in the course of the soil and lichen community development. These photobiont haplotypes exhibit different ecological preferences, possibly leading to adaptation of the symbiotic entity to changing environmental conditions

The pioneer lichen Placopsis in maritime Antarctica: Genetic diversity of their mycobionts and green algal symbionts, and their correlation with deglaciation time

Since ice-free areas in Antarctica are predicted to increase by up to 25% before the end of this century, lichens such as the genus Placopsis will be important colonizers of these newly available grounds and will still be present in later successional stages of the lichen community. The main symbionts of Placopsis species are examined for 56 specimens collected from the South Shetland Islands, Antarctica using molecular (fungal and algal nrITS, fungal RPB1, algal rbcL sequences) and morphological methods. The specimens were collected from soils with different deglaciation times. Eight uni-algal photobiont cultures were obtained and analysed from two specimens. Placopsis antarctica and P. contortuplicata proved to be monophyletic and are sister species, only the former producing vegetative diaspores (soredia). Both share the same photobiont pool and are lichenized with two closely related species, Stichococcus antarcticus and S. allas. Two haplotypes of S. antarcticus are restricted to areas deglaciated for more than 5000 years and the volcanic Deception Island indicating a shift in the photobionts of Placopsis in the course of the soil and lichen community development. These photobiont haplotypes exhibit different ecological preferences, possibly leading to adaptation of the symbiotic entity to changing environmental conditions

Different from tracheophytes, liverworts commonly have mixed 35S and 5S arrays

Abstract Background and Aims Unlike other nuclear genes in eukaryotes, rDNA genes (5S and 35S loci) are present in numerous copies per cell and, when stained, can therefore provide basic information about genome organization. In tracheophytes (vascular plants), they are usually located on separate chromosomes, the so-called S-type organization. An analysis of 1791 species of land plants suggested that S-type arrays might be ancestral in land plants, while linked (L-type) organization may be derived. However, no outgroup and only a handful of ferns and bryophytes were included. Methods We analysed genome sizes and the distribution of telomere, 5S and 35S rDNA FISH signals in up to 12 monoicous or dioicous species of liverworts from throughout a phylogeny that includes 287 of the 386 currently recognized genera. We also used the phylogeny to plot chromosome numbers and the occurrence of visibly distinct sex chromosomes. Key Results Chromosome numbers are newly reported for the monoicous Lejeunea cavifolia and for females of the dioicous Scapania aequiloba. We detected sex-related differences in the number of rDNA signals in the dioicous Plagiochila asplenioides and Frullania dilatata. In the latter, the presence of two UU chromosomes in females and additional 5S-35S rDNA loci result in a haploid genome 0.2082 pg larger than the male genome; sex-specific genome differences in the other dioicous species were small. Four species have S-type rDNA, while five species have mixed L-S rDNA organization, and transitions may have occurred multiple times, as suggested by rDNA loci not being conserved among closely related species of Pellia. All species shared an Arabidopsis-like telomere motif, and its detection allowed verification of the chromosome number of Radula complanata and chromosome rearrangements in Aneura pinguis and P. asplenioides, the latter also showing sex-specific interstitial telomere repeats. Conclusions The S and L rDNA arrangements appear to have evolved repeatedly within liverworts, even in the same species. Evidence for differential accumulation of rDNA between the sexes so far is limited. </jats:sec

Transfer of the Eocene<i>Jungermannia berendtii</i>Grolle to<i>Solenostoma</i>

The Baltic amber fossil Jungermannia berendtii is transferred to Solenostoma based on the presence of numerous long rhizoids, distinct trigones, and subquadrate-rotund to elongate-elliptical leaves