Molecular systematics and biogeographic insights of the Calomys callosus complex (Rodentia, Cricetidae)

Abstract

The genus Calomys includes several species that have very similar external morphologies, which often leads to confusing field identification and has resulted in conflictive taxonomic histories. One of its clades involves large-sized body forms, known as the Calomys callosus complex. In a previous study, a biogeographic hypothesis was proposed to explain a south-to-north colonisation of South America by species of this complex. However, other studies which not included all members of the complex' members and that used different molecular markers, did not support that biogeographic hypothesis. Here we explore the relationships among C. callosus sensu stricto (s.s.), C. fecundus, C. callidus, C. venustus, C. tocantinsi and Calomys sp. using two mitochondrial genes (Cyt-b and Control Region) and two nuclear genes (Rhp3 and i7FGB) data. We also applied several gene trees and species delimitation methods to elucidate the taxonomy, distribution and evolutionary relationships among the analysed species. By including sequences of individuals from Argentina, Brazil, Bolivia and Paraguay, we reconstructed the possible ancestral biogeographic origin of the complex. Two main clades were recovered: the western showed the relationships (C. venustus [C. fecundus–Calomys sp.]), while the eastern (C. callidus [C. callosus s.s.–C. tocantinsi]). These results support the original biogeographic hypothesis and suggest the following scenario: in the west, from the Espinal ecoregion, first the Tucumane–Bolivian Yungas and later, the Beni savanna would have been colonised. In the east, from the Espinal, first the Chaco and later the Cerrado ecoregions may have been occupied.