Phylogenetic relationships among species of the Neotropical genus Graomys (Rodentia, Cricetidae): contrasting patterns of skull morphometric variation and genetic divergence

JUAN JOSÉ MARTÍNEZ; CRISTINA NOEMÍ GARDENAL

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 118 p. 648 - 667

0024-4066

Subtle external traits differentiation characterizes the rodents of the Neotropical genus Graomys, whereas marked differences in karyotype number were reported among some species. We evaluate here the possible evolutionary forces involved in the evolution of the genus by assessing the degree of intra- and interspecific genetic and morphological variation. The phylogenetic analysis demonstrates the existence of at least three species with high levels of genetic distance (10%), diverged between 1-1.5 million years ago. Neither G. griseoflavus nor G. chacoensis presents marked phylogeographic structure. Regarding morphological characters, these species show shape differences in the skull, which could be attributable to differences in the ecoregions they inhabit, being more marked in G. griseoflavus than in G. chacoensis. The skull shape of G. chacoensis could have evolved under genetic drift, whereas evidence here presented indicates that this character could be under selective pressures in G. griseoflavus. Reconstruction of the ancestral area suggests that G. griseoflavus originated in the central Monte desert and G. chacoensis in the Chaco ecoregion surrounding the austral extreme of the Yungas rainforest; later both species would have undergone demographic and geographic expansions nearly simultaneously, starting around 150,000 - 175,000 years ago. The complex evolutionary history of the genus could, at least in part, be explained by the decoupling of morphological, karyological and molecular characters.