Phylogenetic inference in Leucodon Schwagr. subg. Leucodon (Leucodontaceae, Bryophyta) in the North Atlantic region

Systematic and biogeographic relationships of mainly European and North American taxa of the moss genus Leucodon subg. Leucodon are inferred by phylogenetic reconstructions and haplotype analyses, based on sequence data from three plastid regions and nrITS. The two Macaronesian endemic species L. canariensis and L. treleasei are clearly separated from each other and from L. sciuroides, which is widespread in Eurasia including Macaronesia. A well-supported sister-group relationship with the American species L. curvirostris and L. julaceus indicates a New World ancestor of L. treleasei, which is probably a neoendemic species that colonized the Macaronesian islands after (recent) dispersal. The position of L. canariensis sister to the clade of L. treleasei and the American species is less well-supported, leaving its evolutionary history ambiguous. The Eastern North American L. andrewsianus is neither molecularly nor morphologically unambiguously distinguishable from L. sciuroides. Synonymisation of L. andrewsianus with L. sciuroides solves the long-debated question whether the latter species occurs in North America, and results in a Holarctic instead of Palaearctic distribution pattern of L. sciuroides. The A fromontane L. dracaenae cannot be clearly separated from L. sciuroides as well, whereas the Eastern Mediterranean to Central Asian L. immersus differs from L. sciuroides by few substitutions and indels as well as morphologically by the short seta and immersed capsule. Further analyses are necessary before taxonomic conclusions should be inferred for L. dracaenae and L. immersus. Intraspecific diversity in L. sciuroides does not support recognition of the mainly Mediterranean var. Morensis. Instead, a basic separation of Mediterranean (plus Macaronesian) versus non-Mediterranean haplotypes is indicated. The higher haplotype diversity in the Mediterranean (and Macaronesia) in contrast to the other parts of Europe is in accordance with genetic depletion in formerly glaciated areas.