Morphometric Differentiation and Distributional Notes of Three Species of Akodon (Muridae, Sigmodontinae, Akodontini) in the Atlantic Coastal Area of Brazil

Abstract

Twenty cranial measurements and three body variables were compared among samples of three species of the genus Akodon previously identified by karyotype, using univariate (ANOVAs) and multivariate (Discriminant analyses) methods. A geographic analysis for A. montensis and A. cursor from localities in the State of Rio de Janeiro and adjacent areas was also performed. Akodon montensis presented smaller values for most cranial measurements, whereas A. aff. cursor showed larger values, with A. cursor showing intermediate cranial size. The discriminant analysis revealed a clear separation of A. aff. cursor from A. cursor, while all other pair of species presented partial overlap. All A. aff. cursor and most A. cursor were correctly classified, but classification of the A. montensis sample was less successful, probably due to the greater size or to the size-related variation in cranial shape of some older specimens. In the studied area, A. montensis was exclusively collected in altitudes higher than 800m above sea level, whereas A. cursor was found from sea level to altitudes above 1000m. ANOVAs showed one significantly different climatic variable, suggesting some segregation between these two species. Correct classification based solely on the discriminant function extracted on the basis of the present samples could not be fully achieved, although our results suggest that larger samples of kariotypically identified specimens will allow more conclusive patterns on the morphometric differentiation of these taxa.