Demographic history, genetic structure and gene flow in a steppe-associated raptor species

Consistent with our hypothesis, Montagu's harrier has relatively low genetic variation at the mitochondrial DNA. The highest levels of genetic diversity were found in coastal Spain, France and central Asia. These areas, which were open landscapes during the Holocene, may have acted as refugia when most of the European continent was covered by forests. We found significant genetic differentiation between two population groups, at the SW and NE parts of the species' range. Two events of past population growth were detected, and occurred ca. 7500-5500 and ca. 3500-1000 years BP in the SW and NE part of the range respectively. These events were likely associated with vegetation shifts caused by climate and human-induced changes during the Holocene.The relative genetic homogeneity observed across populations of this steppe raptor may be explained by a short isolation time, relatively recent population expansions and a relaxed philopatry. We highlight the importance of considering the consequence of isolation and colonization processes in order to better understand the evolutionary history of steppe species.Contemporary patterns of genetic diversity and population structure reflect not only current patterns of genetic exchange but also past dispersal processes and levels of gene flow among populations during historical climatic events [1,2]. In many species inhabiting temperate zones, climate-vegetation feedbacks during the Pleistocene caused range contractions to lower latitudes followed by range expansions during interglacial periods [2,3], which in turn promoted much of the diversification observed today. However, not all species responded similarly to these past climatic events. Species-specific responses to these changes are the result of a complex interplay between the behavioral, physiological and ecological characteristics of the species, including their biogeographic origin, habitat preferences and dispersal capabilities [4]. Climatic conditions prevailing at dif