Relationships in Scorpidium (Calliergonaceae, Bryophyta), especially between S. cossonii and S. scorpioides

Within the genus Scorpidium , the two species S. cossonii (Schimp.) Hedenäs and S. revolvens (Sw.ex Anonymo) Rubers are similar to each other in habit and superficial morphological traits, whereas S. scorpioides (Hedw.) Limpr. appears to be very different. Because finer morphological characteristics seem to tell another story, the taxonomic treatment of these species has been debated. A molecular analysis of exemplar specimens based on ITS, atpB-rbcL, rpl16 , and trnL-trnF sequences reveals that S. cossonii and S. scorpioides differ from each other by 10 base substitutions/indels and from S. revolvens by 46. When relationships based on ITS, rpl16, or both markers together are analysed for numerous specimens, those of S. scorpioides appear with some S. cossonii specimens in a basal grade ( rpl16 ) or in a clade nested within S. cossonii (ITS or both markers together). The molecular data suggest that superficial morphological data are misleading as regards to relationships within Scorpidium . There is no evidence for the recognition of the genus Limprichtia for S. cossonii and S. revolvens , or for merging these species into one. ITS data suggest recombination in S. scorpioides and rpl16 indicate exchange of chloroplast genetic material among populations of S. cossonii .