Geographic variation in quantitative cranial characters of Kerodon rupestris (Wied, 1820) (Rodentia, Caviidae)

Abstract

Geographic variation in cranial characters in nine recent population samples and one sub-fossil sample was investigated throughout the range of distribution of the histricomorph rodent Kerodon rupestris (Wied, 1820), endemic of the semi-arid region in Brazil. Univariate and multivariate analyses based on 22 measurements taken from 319 specimens show that overall size variation follows a north-south clinal pattern of increasing size. The northern population from Itapajé (CE) showed the smaller cranial size when compared to the southern population from Botumirim (MG). The Itapajé and the Botumirim populations were completely discriminated in the multivariate space. The other populations occupied an intermediate position in relation to the northern and southern samples. A sample of Kerodon acrobata, included in a second analysis, occupied a completely distinct multivariate space in relation to K. rupestris samples. revealing the morphological distinction between the two species of the genus. A clinal pattern of variation has not been considered in the delimitation of subspecies. Nevertheless, different levels of variation are occurring among the populations of K. rupestris.The pattern observed in K. rupestris suggests a structure of variation that may be related to the isolation among rock outcrops inhabited by the species throughout its distributional range. Additional studies addressing the geographical limits of genetic variation will be necessary to show the precise level of differentiation among these populations.