Genetic structure in the European endemic seabird, Phalacrocorax aristotelis, was shaped by a complex interaction of historical and contemporary, physical and non-physical drivers

Geographically separated populations tend to be less connected by gene flow, as a result of physical or non-physical barriers preventing dispersal, and this can lead to genetic structure. In this context, highly mobile organisms such as seabirds are interesting because the small effect of physical barriers means non-physical ones may be relatively more important. Here we use microsatellite and mitochondrial data to explore the genetic structure and phylogeography of Atlantic and Mediterranean populations of a European endemic seabird, the European Shag, Phalacrocorax aristotelis, and identify the primary drivers of their diversification. Analyses of mitochondrial markers revealed three phylogenetic lineages grouping the North Atlantic, Spanish/Corsican and Eastern Mediterranean populations, apparently arising from fragmentation during the Pleistocene followed by range expansion. These traces of historical fragmentation were also evident in the genetic structure estimated by microsatelli...