Dispersal-Vicariance analyses in the tribe Sinningieae (Gesneriaceae): a clue to understanding biogeographical history of the Brazilian Atlantic Forest

The historical biogeography of the tribe Sinningieae (Gesneriaceae) was analyzed based on distribution data and a molecular species-level phylogeny of 76 species. This plant group is distributed from Mexico to northern Argentina, but by far the highest diversity occurs within the Brazilian Atlantic forest. The dispersal-vicariance analysis method and a cladistic approach were used to infer ancestral areas as well as patterns of dispersal and vicariance. Results indicate that the Sinningieae probably arose in the coastal rain forest or in the neighboring tropical area delimited by the Sao Francisco river in Brazil. The majority of the dispersal-vicariance episodes were reconstructed between the Brazilian Atlantic rain forests and their neighboring inland areas (i.e., Parana and Sao Francisco regions). In contrast, few dispersal-vicariance events were reconstructed between the tropical and subtropical areas of the Atlantic rain forest and between the Parana and Sao Francisco regions. These results, together with ancestral areas inferred at the root of the main lineages, indicate an early north-south disjunction in Sinningicae. Occurrence of Sinningieae species in other areas, such as the Andes, the cerrado, Amazonia, northern South America, and Central America, are mainly explained by independent range expansions of single species from either the Parana or the Sao Francisco regions. According to the dispersal-vicariance optimization, 20% of the speciation events are subsequent to inter-area dispersal and range expansion, 23% are associated with inter-area vicariance, and 57% occurred at a lower geographical scale within a single biogeographic area. These results pinpoint the need for a phylogenetic framework to correctly understand area relationships and the relative contribution of dispersal and vicariance events in present-day distribution patterns.