Regional species diversity is ultimately explained by speciation, extinction, and dispersal. Here we estimate dispersal and speciation rates in Neotropical rainforest biomes to propose an explanation for the distribution and diversity of extant butterfly species. We focus on the butterfly tribe Brassolini (Owl butterflies and allies): a Neotropical group that comprises 17 genera and 108 species, most of them endemic to rainforest biomes. We infer a total-evidence species tree of Brassolini using the multispecies coalescent framework. By applying biogeographical stochastic mapping, we infer ancestral ranges and estimate rates of butterfly dispersal and cladogenesis at the scale of millions of years. We suggest that speciation in Mesoamerica and the northwestern flank of the Andes has only increased within the past 2 million years. In contrast, speciation in the Brazilian Atlantic Forest has been constant throughout the past 10 million years. The disparate species diversification dynamics may be explained by the geological and environmental history of each bioregion: the Central American Arc was likely intermittently inundated by water for most of the Miocene (15 to 3 Ma), thus, reduced landmass area until the Plio-Pleistocene may have hindered species diversification; the Atlantic Forest, in turn, likely went through episodes of expansion and contraction and has probably been biologically connected with the Amazonian forest since at least the early Miocene until the Pliocene, about 5 Ma. Importantly, a longer time for speciation in the Atlantic Forest than in Mesoamerica plus NW Andes is ruled out because the dispersal rates into both regions increased simultaneously in the middle-Miocene. Our results reveal a mosaic of bioregion-specific evolutionary histories within the Neotropics, where species have diversified rapidly (cradles: e.g., Mesoamerica), have accumulated gradually (museums: e.g., Atlantic Forest), or have alternately diversified and accumulated (e.g., Amazonia).
