Gene flow and genetic divergence among mainland and insular populations across the south-western range of the Eurasian treecreeper (Certhia familiaris, Aves)

Abstract

The Eurasian treecreeper (Certhia familiaris) comprises two mitochondrial lineages that diverged during the mid-Pleistocene. One palaeoendemic lineage has an allopatric range currently restricted to the island of Corsica and the Caucasus region, whereas the second one has a very large Eurasian range. Here, we used microsatellites (N = 6) and mitochondrial DNA (COI) to assess the genetic structure of insular and mainland populations from Corsica, mainland France and Central Italy (N = 258) and the level of mitochondrial and nuclear gene flow among these populations. Concordant with the mitochondrial DNA signal, the results for microsatellites clearly demonstrate that the Corsican population (Certhia familiaris corsa) is strongly divergent from nearby mainland populations (Certhia familiaris macrodactyla). Microsatellite data also support significant divergence and low gene flow between the Central Italian and mainland French populations. Our results suggest low nuclear gene flow from the mainland into Corsica and no mitochondrial gene flow. Sporadic gene flow from the nearby mainland might explain the presence of continental nuclear alleles in the genome of 5% of sampled insular birds. Our study confirms the existence of an endemic Corsican treecreeper lineage with important conservation value. Our results also imply that Eurasian treecreepers from Central Italy constitute a distinct management unit.