Integration of postnatal craniofacial development and the effects of diet consistency in rodents.

Phenotypic covariances between traits, shaped by developmental processes and functional integration, play a critical role in the response to natural selection. The influences of environmental factors (e.g. food availability and consistency) on these covariances might be particularly prevalent when functional and anatomical complexes develop. In this study, we investigate the ontogenetic development and plasticity of the craniofacial complex, focusing on the integration between skull and mandible in three rodent species: house mouse, golden hamster and Mongolian gerbil. By raising these species from birth then, post-weaning and until 63 days old, on hard and soft diets, we assess how diet-induced biomechanical stress influences coordinated changes in craniofacial shape. Using geometric morphometrics, we identify conserved ontogenetic integration patterns in craniofacial development, with species-specific differences in timing and spatial dynamics of shape changes. We demonstrate that post-weaning dietary variation modulates the coordination between skull and mandible development. Our results emphasize the role of mechanical stress in shaping craniofacial morphology, suggesting that plastic mechanisms can serve as an adaptative and evolutionary lever to respond to food availability while preserving a functional craniofacial complex. Moreover, these mechanisms may play a role in integrating complex signals of divergence between evolutionary pools in the craniofacial complex.