Comparative Analysis of Mandibular Shape Variation in Domestic Geese and Ducks Using Linear and Geometric Morphometrics

Abstract

In this study, a comparative assessment of species- and sex-related differentiation was conducted using two morphometric approaches based on mandibles of domestic geese (Anser anser domesticus) and domestic ducks (Anas platyrhynchos domesticus). A relatively traditional approach based on linear measurements was applied alongside a more recent method employing three-dimensional scanning and landmark-based geometric morphometric techniques. The effectiveness of both methods in discriminating morphological differences associated with species and sex was evaluated. For this purpose, a total of 80 mandibles were analysed, comprising 40 domestic geese (20 females and 20 males) and 40 domestic ducks (20 females and 20 males). In species discrimination based on linear measurements, the LS measurement was found to be statistically significant (p < 0.001). Furthermore, discriminant function analysis correctly classified domestic geese at 72.5% and domestic ducks at 87.5%. In the geometric morphometric analyses, PC1 accounted for 50% of the total shape variation, while PC2 explained 16.9%, and a clear separation between species groups was observed. In the assessment of morphological differences between sex groups, all linear measurements were significantly different between sexes in domestic geese (p < 0.001). Regarding shape variation, species groups showed a relatively homogeneous distribution within each group. Overall, this study aims to demonstrate the combined applicability of linear and geometric morphometric methods and to identify mandibular morphological differences across species and sexes, thereby contributing to research on avian morphology.