Infraspecific diversity in a spore-dispersed species with limited distribution range

Infraspecific genetic diversity is generally underestimated in biodiversity assessments. We use haplotype patterns based on the nuclear gpd and plastid rpl16 to examine whether genetic diversity is related to geography, gender, habitat and/or frequency of sexual reproduction in Drepanocladus lycopodioides. This moss is restricted to western Eurasian semi-natural and natural habitats and decreases in frequency in many parts of Europe. Haplotype diversity differs among three regional populations (Öland, Gotland, Stockholm archipelago) in its South Swedish Baltic core distribution area and is positively affected by patch size. The regional populations differ from each other genetically and haplotype variation is unequally partitioned between the genders, most likely a result of immigration history and limited equalizing effects of sexual reproduction. In a Holocene context, the regional populations of Öland and Gotland display evidence of a decrease or bottleneck, and immigration into both regions. We suggest that higher haplotype diversity in Gotland and Öland and lack of migration to the Stockholm archipelago may be an effect of longer colonization history of the former, and niche pre-emption in the natural habitats of the latter. The Baltic population is representative for the genetically relatively homogeneous European population, and D. lycopodioides displays low ITS variation compared with other European mosses. In a conservation context it is relevant that the three regional populations are not interchangeable. It is of concern that three populations within the species’ core distribution are vulnerable. Our results strongly suggest that infraspecific genetic diversity must be considered in the management of the species at the continental level.