Quaternary climate changes as speciation drivers in the Amazon Floodplains

The role of climate change as a major speciation driver in the Amazon has long been discussed. Phylogeographic studies have failed to recover synchronous demographic responses across taxa, although recent studies support an interaction between rivers and climate in promoting speciation. Most of those studies, however, are biased towards upland forest organisms, while other habitats are still poorly explored and could have been affected differently by the same historical processes. In contrast, this study uses a comparative phylogenomic approach on floodplain forest birds to test alternative diversification hypotheses, exploring the effects of historical environmental changes and current connectivity between individuals. Our findings support a similar demographic history among species complexes, indicating that the central portion of the Amazon river basin is a suture zone for taxa isolated across the main Amazonian sub-basins. Our results also suggest that changes in the fluvial landscape induced by climate variation during the mid and late Pleistocene drove population isolation leading to diversification with subsequent secondary contact.