Phylogeography and systematic notes on two species of gracile mouse opossums, genus Gracilinanus (Marsupialia: Didelphidae) from Brazil

摘要

Although they were described more than a century ago, Gracilinanus agilis and Gracilinanus microtarsus are still mistaken for each other and their status as valid species has been challenged. Morphological studies are rare and accounts of molecular characters are even scarcer. In this paper, we present the first phylogeographic analysis for these two species based on mitochondrial cytochrome b sequences and provide a morphological analysis and extended diagnosis for both species. We show that G. agilis and G. microtarsus are valid species, geographically bounded and distinguishable by morphological and molecular characters. Gracilinanus agilis is geographicaly widespread and genetically more homogenous, with low levels of divergence between three clades in central, northeastern and eastern Brazil. Gracilinanus microtarsus occurs in southeastern and southern Brazil, being comprised of two clades that show a considerable level of sequence divergence. Although at this time we regard these two clades as geographic units of G. microtarsus, it is possible that more samples will show that there is greater diversity in this group than the current taxonomy recognizes.