Molecular variation and phylogeography within European Isothecium alopecuroides and Pseudisothecium myosuroides (Bryophyta, Lembophyllaceae)

Earlier studies on Isothecium s.l. suggested potential interchange of genetic material between species that are nowadays known to belong to separate genera. In this study, we analyse the variation in three molecular markers (nuclear gpd; mitochondrial nad5; and plastid trnG) in a wide selection of Isothecium alopecuroides and Pseudisothecium myosuroides specimens to infer whether this potential exchange of genetic material is frequent. In addition, we explore the phylogeographic structure of these two species in Europe. Our results seem to show repeated genetic interchange for the nuclear and mitochondrial markers in both species, suggesting intergeneric hybridization, although horizontal gene transfer and/or incomplete lineage sorting could also explain the detected incongruences. The genetic lineages found indicate a complex biogeographical history for I. alopecuroides, including both post-glacial immigration from different glacial refugia and developing haplotypes potentially adapted to cold climates. As for P. myosuroides, genetic variants could either indicate a post-glacial immigration history or adaptation to oceanic conditions. Further studies including a larger set of more variable molecular markers could help to reach final conclusions on the results here presented.