Fallback Food Seasonality and the Plasticity of Craniomandibular Development

灵长类动物的颅骨变异受到咀嚼压力的影响，依赖坚硬和/或坚韧食物的类群通常拥有更坚固的颅骨、下颌和下颌肌肉。 大多数灵长类动物都表现出季节性饮食，仅在一年中的部分时间而不是持续关注难以加工的“后备”食物。 事实上，后备食物的生态形态学意义正在成为灵长类生物学和进化中关键的突出问题之一。 不幸的是，这种抗性食品的季节性与年度加工可能在多大程度上影响颅骨生长和形状的变化尚不清楚。 探索食物材料特性的季节性对头骨发育的影响对于古生物学重建以及了解灵长类动物头骨和摄食器的适应性可塑性和表型变异的生态基础至关重要。 因此，本研究检验了这样的假设：断奶后个体发育过程中长期增加负荷频率会导致更高的生长轨迹和更大的成年咀嚼比例。 兔子和灵长类动物在形态、行为、功能、个体发育和摄食复合体的可塑性方面存在重要的相似性，这将有助于进行这种比较。 兔子兄弟姐妹在不同特性的饮食下长大，一组吃对照/正常饮食，一组吃“每年”的抗骨折饮食，另一组接受“季节性”饮食韧性和硬度的增加，以模拟对后备食物依赖的波动。 正在检查三个产后阶段，并通过内部和外部解剖结构的 3D 成像评估颅骨变异。 为了弥合实验室和现场可塑性和进化研究之间的差距，这项研究为饮食季节性对颅骨个体发育的作用提供了新颖而及时的评估。 更广泛的影响将是为博士后、研究生和本科生学员，特别是代表性不足的群体和当地 K-12 社区提供跨学科培训。 对社会的好处包括收集负载引起的反应的数据，这些数据对于了解如何模仿肌肉骨骼组织的生长活动以及识别要在现场标本中检查的咀嚼参数是必要的。

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.