A revision of the genus Tomentypnum (Amblystegiaceae) in northern Eurasia

A combined molecular phylogenetic and morphological analysis revealed four species in the genus Tomentypnum. In addition to the commonly accepted widespread T. nitens and North American T. falcifolium, a strong genetic isolation is shown for two taxa. Tomentypnum involutum is elevated from variety to species status; it is widely distributed in permafrost areas in Siberia, the islands of the Arctic Ocean, high mountains in Scandinavia, and is known from the Rocky Mountains of Canada and from Greenland. Tomentypnum vittii is described as a new species for eastern Asia and Siberia, in China and Russia previously referred to T. falcifolium. Descriptions, illustrations, a key for identification, and a map for the Eurasian distributions are provided. Tomentypnum nitens is represented by four groups of haplotypes, which lack morphological distinction, and are therefore referred to one species. However, the distributions of the haplotype groups are revealing; some are more confined to mires rich in relic species composition, whereas others are more widely distributed and partly seem to occur in recently recolonized sites. Different distribution patterns in densely sampled Sweden suggest different glacial and postglacial histories.