Need for split: integrative taxonomy reveals unnoticed diversity in the subaquatic species of Pseudohygrohypnum (Pylaisiaceae, Bryophyta)

Abstract

We present an integrative molecular and morphological study of subaquatic representatives of the genus Pseudohygrohypnum (Pylaisiaceae, Bryophyta), supplemented by distribution modelling of the revealed phylogenetic lineages. Phylogenetic analyses of nuclear and plastid datasets combined with the assemble species by automatic partitioning (ASAP) algorithm revealed eight distinct species within the traditionally circumscribed P. eugyrium and P. subeugyrium. These species are therefore yet another example of seemingly widely distributed taxa that harbour molecularly well-differentiated lineages with narrower distribution ranges. Studied accessions that were previously assigned to P. eugyrium form three clearly allopatric lineages, associated with temperate regions of Europe, eastern North America and eastern Asia. Remarkably, accessions falling under the current morphological concept of P. subeugyrium were shown to be even more diverse, containing five phylogenetic lineages. Three of these lineages occur under harsh Asian continental climates from cool-temperate to Arctic regions, while the remaining two, referred to P. subeugyrium s.str. and P. purpurascens, have more oceanic North Atlantic and East Asian distributions. Niche identity and similarity tests suggested no similarity in the distributions of the phylogenetically related lineages but revealed the identity of two East Asian species and the similarity of two pairs of unrelated species. A morphological survey confirmed the distinctness of all eight phylogenetic lineages, requiring the description of five new species. Pseudohygrohypnum appalachianum and P. orientale are described for North American and East Asian plants of P. eugyrium s.l., while P. sibiricum, P. subarcticum and P. neglectum are described for the three continental, predominantly Asian lineages of P. subeugyrium s.l. Our results highlight the importance of nontropical Asia as a center of bryophyte diversity. Phylogenic dating suggests that the diversification of subaquatic Pseudohygrohypnum lineages appeared in late Miocene, while mesophilous species of the genus split before Miocene cooling, in climatic conditions close to those where the ancestor of Pseudohygrohypnum appeared. We speculate that radiation of the P. subeugyrium complex in temperate Asia might have been driven by progressive cooling, aridification, and increases in seasonality, temperature and humidity gradients. Our results parallel those of several integrative taxonomic studies of North Asian mosses, which have resulted in a number of newly revealed species. These include various endemics from continental areas of Asia suggesting that the so-called Rapoport’s rule of low diversity and wide distribution range in subpolar regions might not be applicable to bryophytes. Rather, the strong climatic oscillations in these regions may have served as a driving force of speciation and niche divergence.

Sphagnum Warnstorfii complex in Northern Asia

“…These species also were described from Beringian region which is considered as a glacial refugium for Alaskan and Eastern Russian species (Shaw et al, 2008;Kyrkjeeide et al, 2016). In our opinion, current distributions of these species, predominantly associated with cryolithozone, suggest that this area was the speciation arena during cryoxeric epochs of late Cenosoic as was shown for the genus Pseudohygrohypnum by Fedosov et al (2022). Recent discovery of S. lydiae, limited to Arctic areas of Beringian Asia underlines importance of this area as a center of Sphagnum diversity origin.…”

New Taxonomic Arrangement of Dicranella s.l. and Aongstroemia s.l. (Dicranidae, Bryophyta)

“…Newly generated trnK–psbA data were added for at least one representative of each major lineage left. Laboratory protocols for isolation of DNA, amplification and sequencing followed the protocols described in [ 8 , 10 , 56 , 57 ]. Genbank accession numbers of the included specimens and vouchers of specimens studied de novo are compiled in Appendix A .…”

New records of rare and otherwise interesting mosses from The Ussurijsky State Reserve (Primorsky Territory, Russia)

“…However, from the vicinity of Peyshula field station of Ussurijsky reserve another species of the genus, M. rotundifolia Cardot was reported (Lazarenko, 1941b), and later based on this record also by Bardunov & Cherdantseva (1982) Shkurko (MW, MHA). This species was recently described based on specimens from Primorsky Territory, Shikotan Island and Japan (Fedosov et al, 2022b). In Primorsky Territory localities of the species are mostly concentrated north-eastwards of Ussurijsky Reserve, in humid middle elevations of Sikote-Alin mountains (Olkhovaya Mt., Benevskie waterfalls, Pidan Mt., waterfalls near Milogradovka, etc.…”

“…), although recent revision of collections in IRK confirmed its occurrence also in Kedrovaya Pad' State Reserve, from where it was reported as Hygrohypnum eugyrium by Bardunov & Cherdantseva (1982). A specimen from Mironov Klyuch (Ussurijsky Reserve) kept in LE under the latter name, also represents P. orientale (Fedosov et al, 2022b), but Bardunov & Cherdantseva (1982 OQ085093) is identical to the GenBank sequence LT576470, originated from the specimen from Japan (Hedenäs, 2017). This species (as Oncophorus crispifolius Mitt.)…”