Variabilidade craniana de três espécies do gênero Thrichomys (Rodentia, Echimyidae), através de técnicas de Morfometria geométrica

Abstract

The genus Thrichomys Trouessart, 1880 (Histricognathi: Echimyidae), shows a wide variation in dietary, locomotor and behavioral habits. This genus has a complex systematic history. Although morphological and molecular studies on the genus are available, it is still difficult to identify and classify these individuals who have a high karyotypic diversification. Such peculiarities make them interesting to test the relationship between these characteristics and skull variation. In order to differentiate the species Thrichomys apereoides, Thrichomys laurentius and Thrichomys pachyurus we used geometric morphometrics on skull landmarks. Pictures were taken dorsal, ventral and lateral sides of 204 skulls, in which homologous reference points were established. From the coordinates of these points, it was possible to eliminate the effect of size of the species and to 1) test the differences among species and between animals born and raised in the lab and field animals as well as between sexes and the interaction between these factors 2) quantify shape differences among species 3) to describe differences obtained among the groups tested. The results revealed statistically significant differences in shape among species, between sexes and between laboratory and field animals. Size was not significantly different between any of the factors analyzed. Major shape differences were located in the parietal and parieto-frontal region, in the zygomatic arches e in the incisive region. Differences in skull shape between laboratory and field animals involve the posterior portion of the zygomatic arches. The individual fo Caetité, BA, are morphologically different from other T. laurentius populations indicating a possible dissociation between morphological and karyotypical evolution.