Cranial integration and modularity in chamois: The effects of subspecies and sex

Abstract

Covariance structure patterning of the phenotype can provide important insights into the evolution of forms. In this paper, we characterize the sex-specific phenotypic structure of cranial morphology in the four subspecies of chamois Rupicapra rupicapra (balcanica, carpatica, tatrica and rupicapra). We investigate variation in 18 craniometric characters of 360 adults chamois. Compared to the other subspecies, tatrica showed a highly integrated cranium. The cranium of carpatica and balcanica evolved in a more modular fashion, with most conspicuous nasal and oral modules. Females showed stronger correlations among cranial traits than males, suggesting higher potential for adaptations to new environmental conditions in the latter, matching sex-specific behavioral features. Subspecies rupicapra and tatrica showed contrasting levels of overall integration, followed by low levels of modularity, with sexual differences only in rupicapra. Our results suggest that, patterns and magnitudes of correlations among skeletal elements of the skull can evolve within a species through habitat and sexual selection.