Meeting Abstract

103.6  Sunday, Jan. 6  Plasticity of a complex, integrated structure: The impact of diet on mandibular form ZELDITCH, M. L.*; SWIDERSKI, D. L.; Univ. of Michigan, Ann Arbor; Univ. of Michigan, Ann Arbor zelditch@umich.edu

Plasticity may play a critical role in the persistence of populations threatened by climate change and even populations that track their thermal habitat are likely to be challenged by extreme or novel biotic environments. Phenotypes responsive to the biotic environment may be under intense selection, and, in the case of complex morphologies such as the mammalian jaw, adaptive evolution may be impeded by the (co)variance structure. If plasticity can produce a large enough change, in a direction specific to the environmental change, plasticity can circumvent both demographic and quantitative-genetic constraints. But large changes may incur other costs, e.g., disrupted developmental homeostasis. As a model system, we use mandibles of deer mouse, Peromyscus maniculatus bairdii, fed pellets, powder or gruel, to examine the impact of dietary consistency on size and shape. We find that plasticity has a moderate impact on size, shifting the mean of the gruel-fed mice by 0.6 standard deviations, but it has a large impact shape, shifting the means by 7.5 Mahalanobis distance units and in significantly different directions depending on diet. Despite those large changes, jaw development is not decanalized, destabilized or distintegrated. The covariance structure does change, however. Our results suggest that plasticity can modify trophic morphologies by more than is feasible by natural selection over by 10-100 generations at the maximal sustainable rate, incurring neither demographic nor developmental costs.