Southern Scandinavian lowland populations of Rhytidium rugosum (Hedw.) Kindb. (Bryophyta, Rhytidiaceae) differ significantly from those in the mountains

Abstract

Haplotype diversity patterns based on internal transcribed spacer (ITS) and gpd (glyceraldehyde 3-phosphate dehydrogenase) in Scandinavian Rhytidium rugosum were compared between four populations from the mountain range and two in the southern lowlands. The mountain populations differ from the southern lowland ones in haplotype composition and the lowland ones differ from each other, suggesting different histories. A coalescent-based analysis (LAMARC) indicated immigration into the population now found in the mountains from that represented in the lowlands. Because several factors argue against such a dispersal scenario within the relatively short postglacial period, it is proposed that these migration patterns are older than the postglacial period. It is suggested that the mountain range populations immigrated from a source population either in the north-east or within Scandinavia, whereas the lowland populations are likely to represent remains of the glacial population of lowland Europe. The highest haplotype diversity in Scandinavia was found in the Gudbrandsdalen area in southern Norway. This is probably explained by the fact that this is the only region in Europe where R. rugosum regularly reproduces sexually. The lowest diversity was found on the Great Alvar on the island of Öland off the Baltic coast of southern Sweden, and is most likely a result of gradual loss of haplotypes over time.