Assessing the Impact of Adaptation and Species Range Shift during Glacial Cycles on Mitochondrial DNA Introgression

The neutral theory of molecular evolution provides an invaluable frame to infer demographic history from genetic variation patterns, and to serve as a null model to quantify the contribution of natural selection to the evolution of organisms in changing environments.

The accumulation of genetic polymorphism data and the refinement of analytical methods allow unprecedented ability to take apart effects of demographic history (and thus genetic drift) and natural selection. Mitochondrial DNA (mtDNA) has been the most studied part of the animal genome, often with the assumption that patterns of sequence variability were determined by neutral processes only. This view is however severely challenged by inferences of adaptation directly linked to mtDNA variation, of functional coevolution of the nuclear and mitochondrial genomes, and of lack of correlation between population sizes and mtDNA variation. This strongly suggests that mtDNA evolution is mostly driven by episodes of selection. Because of the physiological role of the few genes carried by the small mitogenome, mtDNA is an excellent model to assess the importance of adaptation in evolution. The objective of the present project is to test i) the relative influences of demography and adaptation in reticulated mtDNA evolution and ii) nuclear-mtDNA co-evolution using hares ( Lepus spp.) as biological model.