Systematics of the small non-volant mammals from the open formations of South America: the case of the genus Cryptonanus (Didelphimorphia: Didelphidae)

Abstract

This project is part of my research line which objectives are to solve taxonomic problems, to raise phylogenetic hypothesis, and biogeographic and phylogeographic patterns related to species and populations of small non-volant mammals (marsupials and rodents) inhabitants of the open Neotropical formations. In order to raise consistent biogeographic hypothesis for the Cerrado and Caatinga biomes, poorly explored nowadays, first of all we must define the taxonomic status, delimit the geographic distribution, reconstruct hypothesis of phylogenetic relationships, and estimate the genetic divergence among the studied species and its populations. As the majority of the species that inhabits Cerrado and Caatinga also occurs in the Chaco and southern temperate areas, the study of this group of species will permit to comprehend a very important part of the evolutionary history of South America: the history of the open formations and its fauna. In this project, the marsupial genus Cryptonanus was chosen as the target taxa to answer these questions due to its recent description and the lack of knowledge about its taxonomy, systematics and phylogeography, specially related to the Brazilian species. Cryptonanus contains five species distributed in the open formations of Bolivia, Paraguay, Uruguay, Argentina and Brazil. Based in the examined material during my PhD thesis, I registered the presence of at least three distinct taxa of Cryptonanus, including specimens from São Paulo State that did not fit in the diagnosis of any of the species considered as valid today. The survey of new areas in the Cerrado and Caatinga, and the analysis of a higher number of individuals deposited in scientific collections, including morphologic and molecular data, probably will modify the diagnose and the present taxonomic array of this genus, besides furnishing essential information about the natural history, phylogeny and biogeography of Cryptonanus. (AU)