Spatiotemporal patterns of historical connections between Amazonian and Atlantic forests

Despite the disjunct distribution of the Amazonian and the Atlantic forests, three historical connections between those biomes have been hypothesized: through Northeast Brazil, the Brazilian Cerrado, and the Southeast-Northwest. Temporal variation has been suggested to occur in these connections, with recent connections for the Northeast and older connections for the Southeast-Northwest. We tested for the hypothesis of temporal variation in these connections using Neotropical mammals as a study group. Phylogenetic and spatial data of sister groups from each forest were combined to access the spatiotemporal patterns of these connections. The relationship between distance route and divergence times was tested using linear regression. The results revealed that the previously suggested spatiotemporal pattern was corroborated only for Rodentia but not for Didelphimorphia and Chiroptera, showing both old and recent connections for all routes. In addition, each family revealed specific connections at different times. We refute the previously proposed absence of old connections through the Northeast route. Rather, temporal variation in the Northeast differs among the mammalian groups according to their evolutionary histories. Owing to the biogeographical history of each group, different connections were found at different times. Therefore, connections between these forests cannot be explained by a single spatiotemporal pattern.