Balkan glacial history and modern Drosophila subobscura population genetics

Abstract

Background: The Balkan Peninsula was one of three main refugia for many European species during the last glaciation. During that period, glacial-interglacial climate oscillations probably shaped the habitat characteristics and influenced the population genetic structures of the Balkan species we see today, including Drosophila subobscura. Hypothesis: Some central Balkan gorges were refugia for D. subobscura. We can detect the effects of these refugia by identifying specific patterns of genetic variability using different genetic markers. We expect conspecific populations to be geographically structured and to differ in particular parameters of population genetic structure. Methods: We analyse the genetic structure of six D. subobscura populations that occupy geographically and ecologically different habitats from the central part of the Balkans using inversion polymorphism, microsatellites, and mtDNA markers. Results: The variability generally fits the European population distribution, with specific gene pool structure in some local populations. Populations from gorges are distinctive in particular rare gene arrangements, mtDNA haplotype diversity providing negative Tajima D-values, whereas the analysed microsatellite loci did not show significant departures from neutrality. Conclusions: The degree and pattern of the differences leaves open the question of the refugial existence of D. subobscura in the central Balkans. The inversion polymorphism data show that some endemic arrangements are present with high frequency. But the molecular markers do not fully support the refugial hypothesis. The adaptive divergence we see among the populations indicates that local adaptations at the molecular level can occur despite high gene flow and large effective population sizes. © 2012 Marina Stamenkovic-Radak.