Functional Morphology of the Mandible in Caviomorph Rodents from Northern South America: A Geometric Morphometric Analysis of Shape Variation and Diet Differentiation

The relationship between mandibular morphology and diet provides key insights into functional adaptation in mammals. Caviomorph rodents, a diverse Neotropical clade, exhibit a wide range of feeding habits, making them an ideal model for ecomorphological studies. This study evaluates whether mandibular shape variation can discriminate among dietary categories and identifies the morphological components associated with these differences. A total of 184 mandibles from 20 species, including several poorly known northern South American taxa (e.g., Dasyprocta guamara, Pattonomys spp., Proechimys spp. and Coendou spp.), were analyzed using geometric morphometrics. Shape variation was examined through Principal Component Analysis (PCA). To avoid overestimation of group segregation, Canonical Variate Analysis (CVA) and Discriminant Function Analysis (DFA) were performed using the first 13 PC scores. Allometry was assessed using permutation procedures. Results revealed significant differences among dietary groups, with correct classification rates reaching 100% for the grass-feeding group and exceeding 97% for the mixed-diet groups. Grass-feeding species displayed elongated and slender mandibles, whereas fruit–leaf and fruit–seed groups exhibited shorter and more robust configurations. Allometry explained a small proportion of shape variation, indicating that morphological differences are primarily driven by functional adaptation. While phylogenetic signal is inherent in the sample, these findings confirm that mandibular shape variation is strongly associated with dietary differentiation reinforcing the mandible as a reliable proxy for dietary ecology and providing a vital regional baseline for understanding the morphological evolution of Neotropical rodents.