Glacial history and colonization of Europe by the blue tit Parus caeruleus

Mitochondrial control region sequences from European populations of the blue tit Parus caeruleus were used to reveal the Pleistocene history and the post-glacial recolonization of Europe by the species. The southern subspecies, P. c. ogliastrae was found to represent a stable population with isolation-by-distance structure harboring a lot of genetic variation, and the northern subspecies P. c. caeruleus a recently bottlenecked and expanded population. We suggest that after the last Ice Ages, the subspecies have colonized Europe from two different southern refuges following previously proposed general recolonization routes from the Balkans to northern and Central Europe, and from the Iberian Peninsula north- and eastwards. The two subspecies form a wide secondary contact zone extending from southern Spain to southern France.