Craniofacial morphometric analysis as a differentiation tool in mystax group of Saguinus Hoffmannsegg, 1807 (Cebidae, Callitrichinae): a preliminary test

Resumo

This study provides a quantitative assessment of the craniofacial variation among currently recognized species and subspecies in the Saguinus mystax species group and tests the reliability of the proposed method in detecting differences among taxa. Thirty measurements were taken of 66 tamarin specimens representing Saguinus imperator, S. inustus, S. labiatus and S. mystax. We used the nonparametric MANOVA to test for differentiation
among species and among subspecies (S. i. imperator and S. i. subgrisescens; S. m. mystax e S. m. pileatus). Interspecific analyses showed significant variation among all species, except for S. inustus (which we attribute to the small sample size). We also detected significant differentiation between S. mystax mystax and S. m. pileatus, whereas no significant morphometric difference was found between S. imperator subspecies. In order to explore the variation of each individual measurement, we plotted diagrams comparing the mean variation among species. Measurements presenting some degree of differentiation among species were selected for subsequent analysis of variance. Univariate analyses detected significant differences among species only for three measurements. Our results suggest that the cranial morphometric variation has limited information to discriminate among the taxa in the S. mystax group. However, we cannot disregard the lack of statistical power due to small sampling in some taxa, absence of some subspecies in the analyses, or even lack of informativeness of the chosen measurements. Morphometric analyses were useful to detect some degree of differentiation among species, but it was also
insufficient to demonstrate complete differentiation in Saguinus. Therefore, the use of morphometric analyses should not be considered as a definitive method for taxa differentiation and delimitation in Saguinus.