Three-dimensional (3D) photogrammetric-based geometric morphometric analysis of the skull in the social vole (Cricetidae: Microtus)

Geometric morphometric analysis has significantly advanced the study of size and shape variation of the mammalian skull. In this study, we used photogrammetry to build three-dimensional models of Microtus skulls to investigate the shape variation of five species using the geometric morphometric approach. We hypothesized that three-dimensional (3D) skull shape data would accurately discriminate between closely related species. Canonical analysis of variance revealed a similar level of species classification based on both 2D and 3D shape data. These findings indicate the precision and accuracy of the photogrammetric method (3D geometric morphometric) in morphologically similar and taxonomically problematic groups, such as Microtus. In species with similar diploid chromosome numbers (Microtus guentheri-M. hartingi and Microtus anatolicus-M. schidlovskii) and in groups in which linear morphometric analyses (Discriminant function analysis and MANOVA) could not distinguish between species (Microtus dogramacii, Microtus schidlovskii, and M. guentheri), the photogrammetry-based 3D GM analyses showed a high level of correct classification rates, demonstrated differences between groups in the cluster dendrogram, and showed significant differences in the shape of the skulls.