Patterns of mtDNA introgression suggest population replacement in Palaearctic whiskered bat species

Secondary contacts can play a major role in the evolutionary histories of species. Various taxa diverge in allopatry and later on come into secondary contact during range expansions. When they meet, their interactions and the extent of gene flow depend on the level of their ecological differentiation and the strength of their reproductive isolation. In this study, we present the multilocus phylogeography of two cryptic whiskered bat species, Myotis mystacinus and M. davidii, with a particular focus on their putative sympatric zone. Our findings suggest that M. mystacinus and M. davidii evolved in allopatry and came into secondary contact during range expansions. Individuals in the area of secondary contact, in Anatolia and the Balkans, have discordant population assignments based on the mitochondrial and the nuclear datasets. These observed patterns suggest that the local M. mystacinus populations hybridized with expanding M. davidii populations, which resulted in mitochondrial introgression from the former. In the introgression area, M. mystacinus individuals with concordant nuclear and mitochondrial genotypes were identified in relatively few locations, suggesting that the indigenous populations might have been largely replaced by invading M. davidii. Changing environmental conditions coupled with ecological competition is the likely reason for this replacement. Our study presents one possible example of a historical population replacement that was captured in phylogeographic patterns.