Taxonomic validity of species groups in the genus Akodon (Rodentia, Cricetidae)

Abstract

In an effort to evaluate the four Akodon species groups, phylogenetic relationships among individuals of the genus Akodon, selected from throughout South America, were examined using cytochrome b and a concatenated data set consisting of data from cytochrome b, exon 6 of the dentin matrix protein 1 and the nuclear intron thyrotropin. Both the cytochrome b data set and the combined data set were analysed under maximum parsimony, maximum likelihood and Bayesian criteria. Like previous studies, a monophyletic Akodon clade was recovered. Monophyly of the boliviensis and cursor groups was supported, and the two form a strongly supported sister relationship. Akodon azarae is basal to and forms a monophyletic group with the boliviensis + cursor clade, resolving the placement of A. azarae but leaving it unassignable to a current Akodon species group. The aerosus and varius groups are paraphyletic as four members of the varius group (A. glaucinus, A. simulator, A. tartareus and A. varius) fall within the aerosus group. Akodon lindberghi is formally placed in the cursor group. Akodon caenosus is recognized as a species distinct of A. lutescens, A. orientalis is recognized as a species distinct of A. orophilus, and A. aerosus, A. baliolus and A. surdus are recognized as three separate species. Based upon chronophylogenetic analysis, the initial divergence within Akodon likely began during the late Pliocene and ancestors of the four extant species groups (aerosus, boliviensis, cursor and dolores) appeared around the Pleistocene–Pliocene boundary or shortly thereafter.