Cladistic biogeography of the Neotropical region: identifying the main events in the diversification of the terrestrial biota.

A cladistic biogeographical analysis was undertaken to identify the main events in the biotic diversification of the terrestrial Neotropical biota. For the 36 animal and plant taxa analysed, a component × area matrix was constructed, associating geographical data only with informative nodes, and it was analysed under implied weights using the software TNT. The general area cladogram obtained shows that the Neotropical region constitutes a monophyletic unit, with a first split separating the Antilles and a second one dividing the continental areas into a north-western and a south-eastern component. Within the north-western component the areas split following the sequence northern Amazonia, south-western Amazonia, north-western South America, and Mesoamerica. Within the south-eastern component the areas split following the sequence south-eastern Amazonia, Chaco, and Parana. The three main components are treated as subregions: Antillean, Amazonian (northern Amazonian, south-western Amazonian, Mesoamerican, and north-western South American dominions), and Chacoan (south-eastern Amazonian, Chacoan, and Parana dominions). Dispersal and vicariant events postulated to explain these pattens might have occurred during the Cretaceous, when the Caribbean plate collided with the Americas, a combination of eustatic sea-level changes and tectonic deformations of the continental platform exposed large parts of South America to episodes of marine transgressions, and the Andean uplift reconfigured the Amazonian area. Tertiary and Quaternary events are assumed to have later induced the diversification within these large biogeographical units.