Cranial morphological variation in a tropical rodent (Rodentia: Heteromyidae): taxonomic implications

. The tropical genus Heteromys includes 17 species that have undergone several taxonomic changes and have unclear interspecific limits. We compared the intraspecific, interspecific, and geographic variation in ten species of Heteromys using geometric morphometrics, and evaluated whether the genetic differences between the species were reflected in differences in cranial morphology. We digitized three cranial views and one mandibular view of 638 adult specimens, and performed morphometric analyses. Sexual variation and differences in cranial morphology were evaluated with analysis of variance, multivariate analysis of variance, and canonical variate analysis. Cranial differences were observed with deformation grids, and a cluster analysis was performed with Procrustes distances to compare with a phylogenetic tree. The geographic variation analyses were carried out using clusters based on physiographic regions. Only H. desmarestianus and H. irroratus presented sexual variation. Heteromys species showed differences between physiographic regions probably due to variation in abiotic factors, vegetation cover, and precipitation. Each species had a distinctive morphotype, with differences in their rostri, zygomatic arches, cranial vaults, occipitals, and foramina magna, as well as in the angular processes, condylar processes, and diastemas of the mandibles. The species clusters matched with clades previously identified by molecular markers. The specimens of one candidate species ( Heteromys sp.) showed unique morphometric characteristics that separated them from the other species.