Sister species, different histories: comparative phylogeography of two bird species associated with Amazonian open vegetation

Although the expansion of open vegetation within Amazonia was the basis for the Forest Refugia hypothesis, studies of Amazonian biota diversification have focussed mostly on forest taxa. Here we compare the phylogeographic patterns and population history of two sister species associated with Amazonian open-vegetation patches, Elaenia cristata and Elaenia ruficeps (Aves: Tyrannidae). We sampled individuals across Amazonia for both species, and in the central Brazilian savannas (Cerrado) for E. cristata. We sequenced one mitochondrial (ND2) and two nuclear (BFib7 and ACO) markers. We tested for population structure, estimated migration rates and elucidated the historical demography of each species. The Amazon River is the strongest barrier for E. ruficeps and the Branco River is a secondary barrier. For the more broadly distributed E. cristata, there was no discernible population structure. Both species attained their current genetic diversity recently and E. cristata has undergone demographic expansion since the Last Glacial Maximum, The results suggest distinct effects of recent landscape change on population history for the two species. E. ruficeps, which only occurs in Amazonian white sand habitats, has been more isolated in open-vegetation patches than E. cristata, which occupies Amazonian savannas, and extends into the Central Brazilian Cerrado.