Chiroxiphia pareola DNA shows diversification in Amazon and recent connection with Atlantic Forest

Disjunct species between the Amazonian and Atlantic forests are good models to test hypotheses of rivers asbiogeographic barriers and Pleistocene forest refuges, which are used to explain diversification in Neotropical rainforests. We use molecular analyses, ancestral area reconstruction, and potential paleodistribution analyses of Chiroxiphia pareola, a bird species with a disjunct distribution between the Amazonian and Atlantic forests, to test the above hypotheses and examine the potential processes of diversification and geographical expansion of its populations. Six genes, two mitochondrial and four nuclear, were analyzed. Our results supported the recognition of four evolutionarily independent lineages of the polytypic species C. pareola that we suggest be divided into the following full species: C. regina, C. napensis, C. pareola, and one new species. All splits were estimated to have occurred in the Pliocene-Pleistocene and were supported by the historical river dynamics in the Amazon. Moreover, the molecular divergence between the Amazonian and Atlantic forest populations of the new species is very low when compared to divergences between the lineages separated by Amazonian rivers. Our results also suggest a connection between the Amazonian and Atlantic forests during the Middle Pleistocene near the mountain slopes and river drainages in the interior of northeastern Brazil. A grater probability of dispersal from Amazon to Atlantic Forest was recorded. Although our results support the stability of Pleistocene forest refuges in the Northeastern Atlantic Forest, they are not consistent with the role of rivers as a diversification mechanism in this region, during the Pleistocene.