Historical Biogeography of the Leptodactylus fuscus Group (Anura, Leptodactylidae): Identification of Ancestral Areas and Events that Modeled their Distribution.

The objective of the present study was to reconstruct the biogeographic history of the monophyletic group Leptodactylus fuscus. We carried out two complementary historical biogeographic approaches: one estimates the ancestral areas with the statistical dispersion and vicariance method (S-DIVA). The other detects disjoint distributions among sister groups, which provides information about barriers that separate populations through a spatial analysis of vicariance (VIP method). For that, we used a database of species presence records and a topology of a phylogenetic cladogram, both obtained from updated published data that incorporates the current phylogenetic, taxonomic and distributional arrangements for the group. For the analysis of ancestral areas, the following areas of the L. fuscus group distribution were used: the Carribean, Chacoan, Parana, Amazonian and North American in Pacific subregions. The optimal reconstruction obtained with S-DIVA showed five vicariance events, two extinctions and 50 dispersals. The spatial analysis of vicariance revealed 19 disjointed sibling nodes and two distributions on nodes removed in the consensus tree. The results suggest that the ancestor of the Leptodactylus fuscus group occupied large areas within the Amazon and Chacoan subregions. Due to several dispersal events, the ancestor distribution range may have expanded to the Caribbean subregion. This expansion could have occurred during wetter periods, when forests were more extensive, which would have allowed the invasion of open habitats within humid forest systems. It is important to note that ecological factors and marine transgressions that occurred during the Miocene could have had a great influence on the current distribution of the group.