Genetic diversity, differentiation and historical origin of the isolated population of rooks Corvus frugilegus in Iberia

Current bird populations in southern temperate latitudes often represent relicts of glacial refugia from which northern populations expanded as the climate became suitable following the last glacial maximum, 18 000 years before present. Alternatively, these southern populations could be the result of the fragmentation of large distributions and other processes not related to glaciations, like recent recolonization from northern populations and human impact in historical times. Here, we investigate the origin of a small, isolated population of rooks Corvus frugilegus in north‐western Iberia. We use genetic data from mitochondrial sequence markers and seven microsatellite loci to assess levels of genetic diversity, structure and gene flow among extant populations in Iberia and its broad distribution across western Europe. Microsatellite markers revealed the existence of two genetic clusters corresponding to Iberia and the remaining European populations, respectively. Haplotype networks based on mtDNA markers revealed a marked star‐like phylogenetic pattern and evidence of a recent population expansion in northern Europe, but not in the Iberian population. Our results suggest that contemporary gene flow between Iberia and western Europe is restricted, and that breeding recruitment over recent generations in the Iberian population is local. The results are consistent with a relatively recent post‐glacial colonization of Europe and western Siberia by rooks surviving the last glacial maximum in an Iberian refugium, and likely from refugia in other southern peninsulas. The unique ecological features and genetic differentiation of the Iberian rooks underscore the importance of ensuring the long‐term conservation of this declining population.