Forest corridors between the central Andes and the southern Atlantic Forest enabled dispersal and peripatric diversification without niche divergence in a passerine.

The central Andean rainforests and the Atlantic Forest are separated by the Chaco and the Cerrado domains. Despite this isolation, diverse evidence suggests that these rainforests have been connected in the past. However, little is known about the timing and geographic positions of these connections, as well as their effects on diversification of species. In this study, we used the Black-goggled Tanager (Trichothraupis melanops, Thraupidae) as a model to study whether the Andean and the Atlantic forests have acted as a refugia system, and to evaluate biogeographic hypotheses of diversification and connection between these rainforests. We compared alternative biogeographic scenarios by using Approximate Bayesian Computation (ABC), modeled range shifts across time, and assessed niche divergence between regions. The results indicated that the major phylogeographic gap within T. melanops is located between these rainforests. The ABC analysis supported peripatric diversification, with initial dispersal from the Atlantic Forest to the Andes during the Mid-Pleistocene. Also, the results supported an Andean-Atlantic forests connection through the current Cerrado-Chaco transition, linking the southern Atlantic Forest with the central Andes. Our findings, taken together with other studies, support that the connection between these biomes has been recurrent, and that has occurred mostly through the Cerrado and/or the Cerrado-Chaco transition. The data also support that the connection dynamic has played an important role in the biological diversification, by promoting peripatric divergence in some forest taxa restricted to both biomes.