Phylogeography of a Patagonian lizard and frog: Congruent signature of southern glacial refuges

Abstract

Pleistocene glaciations produced significant increases in continental ice cover in polar and mid-latitude temperate areas, sea-level declines and shifts and reshuffling of biomes, all of which promote either isolation, coalescence or fragmentation in the distribution of land biota. If populations of several taxa have been co-distributed for a prolonged time, and if the periods between perturbation or vicariance processes have been more or less stable, it is expected that divergence patterns of closely related and ecologically similar species will be congruent because of their similar biological and demographic characteristics. Based on this premise, we analysed the phylogeographic structure (cytochrome b) of Liolaemus pictus and Batrachyla leptopus, two widely co-distributed lizard and frog species, respectively, in the Chiloe Archipelago of southern Chile, to decipher their genetic structure in response to a common climatic and environmental history. Haplotype network analysis and Bayesian inference suggest an evolutionary pattern of genetic diversity for the two species that is consistent with the Quaternary glacial history of southern Chile, and suggests a complex phylogeographic history in the Liolaemus and Batrachyla species. High-divergence levels among haplotypes in some island populations of the archipelago also suggest genetic connectivity between putative refuges from Chiloe Island and the mainland along the exposed continental shelf during sea level minima associated with the most recent Quaternary glaciations. Our results are consistent with our hypothesis that two species have responded to parallel historical events in which the historical process during the last glacial maximum(approximately 41 degrees S) has been sufficient to influence their phylogeographic structure.