Aim Three mechanisms have been proposed to explain the adaptive radiations and species diversifications of Madagascar’s biota: the ecogeographical constraint, the riverine barrier and the micro-endemism models. On the intraspecific level, each model predicts different patterns of gene flow across the island’s physical and ecological features. To evaluate these models, phylogeographical analyses were conducted on a widespread and endemic species of bat, Myotis goudoti (Vespertilionidae).
Methods In order to reconstruct the phylogeographical history of M. goudoti, the mitochondrial D-loop and the cytochrome b gene were sequenced for 195 bats from 41 localities. Phylogenetic reconstructions and a minimum spanning tree were used to infer haplotype relationships. The effect of barriers on gene flow was evaluated using analyses of molecular variance and pairwise population differentiation. Mismatch distribution and coalescence-based estimates were conducted to infer the demographic history of M. goudoti.
Results The sequenced individuals showed 159 distinct D-loop haplotypes, most of them being unique to a single location. Populations were significantly structured (ΦST = 0.170, P < 0.001) across Madagascar, but only a minor part of the overall genetic variance was explained by any of the three models. Shared ancestry of lineages across most physical or ecological barriers was common, whereas the uncovered genetic differences between southern and central-northern populations were unexpected.
Main conclusions Major barriers predicted by the three biogeographical models do not explain the segregation of mitochondrial lineages of M. goudoti across Madagascar. This is not simply attributable to the high dispersal ability of this species, as populations are notably structured. The genetic contrast between southern and central-northern populations, separated by a zone of admixture, suggests that these areas currently support populations that expanded during the Late Pleistocene. This latitudinal differentiation of populations has been observed in less vagile animals, such as geckos and lemurs, suggesting that climate fluctuations of the Pleistocene had an impact across several groups and resulted in northern and southern refugia in Madagascar.