Patterns of genetic diversity in the red squirrel (Sciurus vulgaris L.): Footprints of biogeographic history and artificial introductions

摘要

British S. vulgaris are classified as a separate subspecies, S. v. leucourus, to mainland Europe. While S. vulgaris is not under threat across most of its Eurasian range, in Britain, Ireland and Italy populations are declining, mainly due to the introduction of the American grey squirrel (S. carolinensis). In this study, we conducted an extensive survey of mitochondrial DNA variation in British S. vulgaris populations and a preliminary survey of continental European populations. Our main aims were to determine the extent to which any populations of S. vulgaris in Britain are partially or wholly the product of artificial translocation of red squirrels from continental Europe, and whether continental population variation will provide information on post-glacial reafforestation patterns in Europe. We found that the majority of extant populations of British S. vulgaris are of continental ancestry, many with a very recent (last 40 years) Scandinavian ancestry. The Scandinavian haplotype has rapidly become the most dominant in northeastern Britain, despite not appearing in northern English populations until 1966. This suggests that these squirrels may have an adaptive advantage in the non-native spruce dominated conifer plantations of northern England. Our preliminary examination of continental populations demonstrated that they are sufficiently differentiated to allow a phylogeographic study of this species.