Genetic history, structure and gene flow among populations of Belgica antarctica, the only free-living insect in the western Antarctic Peninsula

Changes in climate and environment can impact the sustainability of populations and biodiversity. Under-standing population genetic diversity in the past and present can help us better predict species' responses to future environmental change. Antarctica has experienced drastic environmental change which threatens its biodiversity. In this study, we characterized the phylogeography and population genetic structure of Belgica antarctica, a wingless midge that is endemic to the western Antarctic Peninsula. This insect has adaptive features to withstand extremes in temperature, salinity, humidity, anoxia and pH. Belgica antarctica is widespread on widely dispersed islands of ice-free habitat, but questions remain regarding its genetic history, diversity and gene flow. We created nuclear-based, single nucleotide polymorphism (SNP) markers and genotyped 229 individuals from 11 populations to examine historical and current population genetic patterns. Our results support recent divergence among populations on different islands within the last 1 Mya. Furthermore, despite a lack of wings, B. antarctica exhibited frequent migration among islands, perhaps via ocean currents or phoresy with Antarctic vertebrates (e.g. seabirds). The close link between the evolutionary history of B. antarctica and the region's environment and ecology emphasize the importance of understanding its population dynamics to predict its persistence under environmental change.