High phylogeographical complexity within Mediterranean islands: Insights from the Corsican fire salamander

Aim: Mediterranean islands have been the subject of intense phylogeographical investigation. While most studies have focused on the processes of colonization and dispersal between landmasses, the phylogeographical structures within islands have received less attention. Here, we investigate the Pleistocene evolutionary history of the fire salamander Salamandra corsica. Our main aim is to shed more light on the importance of intra-island micro-evolutionary processes in structuring the patterns of biodiversity on Mediterranean islands. Location: Corsica Island. Methods: We sampled 165 individuals across the entire range of S. corsica, and we sequenced two mitochondrial (cytb and cox1) and one nuclear (ßfib) gene fragments. We used Bayesian phylogeographical and historical demographic analyses based on DNA sequence data, together with species distribution modelling (SDM) under the present and past bioclimatic envelopes. Results: Bayesian phylogeographical analyses indicated that S. corsica (re)colonized its northern range during the Last Interglacial period from an ancestral area located in central-southern Corsica. According to these analyses and the SDM, S. corsica was already established throughout the island during the last glacial phase, although likely with a fragmented distribution. Historical demographic analyses suggested a post-glacial demographic expansion, probably associated with the climate-driven spatial and temporal dynamics of forested habitats. Main conclusions: Despite its restricted and insular distribution, S. corsica showed past demographic and range dynamics that are comparable to those of wide-ranging species on the continent. These dynamics are not consistent with temporal, spatial, and demographic patterns previously seen for other Corsican endemics. Such patterns of complex Pleistocene evolutionary histories and extensive phylogeographical discordance are also emerging from other insular systems. We conclude that island endemics should not be considered, a priori, as single populations and conservation units, and that the use of co-occurrence patterns of island populations as inferential tools in historical biogeography should also be carefully reconsidered.