Phylogeographical patterns in the northwestern European moss <i>Scorpidium revolvens</i> (Sw. ex Anonymo) Rubers (Scorpidiaceae, Bryophyta)

The phylogeography of <i>Scorpidium revolvens</i> (Sw. ex Anonymo) Rubers in northwestern Europe, primarily Scandinavia, was explored. Possibly because of human activity and atmospheric pollution, the species is sparser in the south than in the north, therefore its genetic diversity may be lowest in the south. Relationships within <i>Scorpidium revolvens</i> were evaluated in a network context, based on nuclear ITS and plastid <i>rpl</i>16 data. The regional diversity and haplotype composition of <i>Sc. revolvens</i>, <i>Sc. cossonii</i> (Schimp.) Hedenäs and <i>Sarmentypnum exannulatum</i> (Schimp.) Hedenäs were compared. When the sister species <i>Scorpidium cossonii</i> was used as an outgroup to determine polarity, the basalmost <i>Sc. revolvens</i> haplotype was found to be arctic, and the closest haplotypes to this were found in northern or montane specimens. From a basal grade, three lineages evolved, with differential north and south distribution. The haplotype diversity of <i>Sc. revolvens</i> was lowest in the south, and the haplotype composition of <i>Sc. revolvens</i>, <i>Sc. cossonii</i> and <i>Sarmentypnum exannulatum</i> in the south differed from that in other regions. A northern origin for <i>Scorpidium revolvens</i> in Scandinavia is suggested, in common with <i>Sc. cossonii</i>. Wider geographical sampling might confirm a northern origin for <i>Scorpidium</i>. Geographical distributions of the three <i>Sc. revolvens</i> lineages suggest partly separate colonisation routes. Compared with the north, <i>Sc. revolvens</i> in the sparsely populated south has lower haplotype diversity and different haplotype composition. The two other species investigated also had different haplotype composition, and further investigations might determine whether this represents a general pattern in Scandinavia.