Fallback Food Seasonality and the Plasticity of Craniomandibular Development

University Of Notre Dame, Notre Dame IN

Investigators

Abstract

Cranial variation in primates is influenced by masticatory stresses, with taxa relying on stiff and/or tough foods often possessing more robust skulls, jaws and jaw muscles. Most primates exhibit seasonal diets, focusing on difficult-to-process "fallback" foods only part of the year rather than continuously. Indeed, the ecomorphological significance of fallback foods is emerging as one of the key outstanding issues in primate biology and evolution. Unfortunately, the extent to which the seasonal vs. annual processing of such resistant foods might affect variation in cranial growth and form is unknown. Exploring the influence of seasonality in food material properties on skull development is vital for paleobiological reconstructions as well as for understanding the ecological bases of adaptive plasticity and phenotypic variation in the primate skull and feeding apparatus. Thus, this research tests the hypothesis that the long-term frequency of elevated loading during post-weaning ontogeny results in higher growth trajectories and larger adult masticatory proportions. Important similarities exist in the morphology, behavior, function, ontogeny and plasticity of the feeding complex between rabbits and primates that will facilitate such comparisons. Rabbit siblings are raised on diets of different properties, with one group having a control/normal diet, one eating an "annual" fracture-resistant diet, and one subjected to "seasonal" increases in dietary toughness and stiffness to model fluctuations in the reliance on fallback foods. Three postnatal stages are being examined, with cranial variation evaluated via 3D imaging of internal and external anatomy. In bridging the gap between lab- and field-based studies of plasticity and evolution, this research offers a novel and timely assessment of the role of dietary seasonality on cranial ontogeny. A broader impact will be to provide interdisciplinary training for postdoctoral, graduate and undergraduate trainees, especially under-represented groups and the local K-12 community. The benefit to society includes collecting data on load-induced responses necessary for understanding how to mimic the growth activity of musculo-skeletal tissues, and for identifying masticatory parameters to be examined in field specimens.