Marsupials from the South American “Dry Diagonal”: Diversity, Endemism, and Biogeographic History

Abstract

The so-called “Dry Diagonal” comprises the major areas of Neotropical savannas and seasonally dry forests located below the Equator, mainly represented by the Caatinga, Cerrado, and Chaco domains. Currently, 13 didelphid genera and 36 species occur in these regions. Despite the lower richness compared to moist forests, the “Dry Diagonal” presents a unique marsupial fauna, represented by endemic genera (1) and species (13) that have diversified into these South American open formations. Indeed, these domains are characterized by a mosaic of open and forested habitats, thus resulting in the co-occurrence of taxa well adapted to grasslands, shrublands, savannas, dry, gallery, and humid montane forests. The intertwined nature of the vegetation has led to a complex history of this region and the diversification of its mammals, with endemic didelphids presenting closer affinities to Amazonian and Atlantic Forest taxa while others descend from lineages that evolved exclusively in open areas. This fauna is not only spatially but also temporally heterogeneous in terms of time of diversification – some divergences date back to the Late Miocene while others occurred as recently as the Early Pleistocene.