Morphometric analysis of dung beetle (Gymnopleurus mopsus: Scarabaeidae: Coleoptera) populations from two different biomes in Mongolia

Studying the phenotypic variation of organisms along environmental gradients can provide insight into the influences of specific environmental factors. Mongolia, which is distributed across three different biomes, is an ideal location for studying the mechanisms that underlie such phenotypic variation over a large range of climate. The present study examined the variation in shape and size of the body in a ball-rolling dung beetle, Gymnopleurus mopsus (Pallas), in Mongolia and investigated the effects of climate on the species' morphology. A total of 290 individuals were collected from seven sites and were analysed using multivariate and regression approaches, as well as geometric morphometrics. Body shape and size varied across the study sites and between the different biomes. Populations from the desert-steppe region had thinner bodies and longer heads than those from the steppe region, possibly to facilitate burrowing. Variation in the species' body size followed a pattern that was the converse of Bergmann's rule and, thus, might increase heat capacity and enhance thermoregulation ability in the desert-steppe region. Accordingly, the results of the present study provide novel insight into the influence of climate on the variation of dung beetle phenotypes.