Geographic variation in quantitative skull traits and systematic of southern populations of the leaf-eared mice of the Phyllotis xanthopygus complex (Cricetidae, Phyllotini) in southern South America

Abstract

The leaf-eared mice of the genus Phyllotis (Cricetidae, Phyllotini) encompasses at least 20 species of medium-sized Neo- tropical rodents mostly distributed throughout the Andean region. Its limits and contents were reviewed by several au- thors, based both on morphological and molecular data. However, no integrative approaches were conducted based on large samples of individuals with a wide geographical coverage. The purposes of this paper are: (i) to evaluate species limits; and (ii) to test the congruence between molecular and quantitative morphological evidences within the Phyllotis xanthopygus complex in southern South America. Our results questioned the specific status of P. bonariensis, a geograph- ically isolated form that was either considered as a valid species or as a synonym of P. xanthopygus. Quantitative morpho- logical (size and shape of the skull) and molecular data linked P. bonariensis with populations from central Argentina traditionally referred as P. xanthopygus vaccarum. Individuals belonging to populations from southern Argentina and Chile (P. x. xanthopygus) were remarkably homogeneous in their skull morphology, showing a subtle to non-existent dif- ferentiation from those of north-central and west-central Argentina referred to P. x. vaccarum. We found some incongru- ence between groups inferred from morphological (this work) and mitochondrial DNA results of previous studies. This is the case of the north-central and west-central populations, where morphological traits do not show the strong differentia- tion detected by molecular characters. Our results highlight the need for integrative taxonomic studies, not only to delim- itate taxonomic units but also for a better and more comprehensive understanding of population variability and differentiation.