Meeting Abstract
22.4 Sunday, Jan. 4 Modularity and integration of mandibular size and shape ZELDTICH, M.L.*; SWIDERSKI, D.L.; WOOD, A.R.; Univ. of Michigan, Ann Arbor; Univ. of Michigan, Ann Arbor; Univ. of Michigan, Ann Arbor zelditch@umich.edu
The mammalian mandible is a developmentally modular, functionally integrated system. Whether morphological integration can evolve to match functional integration may depend on the developmental origin of integration, specifically, on the role played by direct epigenetic interactions, which are hypothesized to be conservative and therefore potentially constraining. Using the prairie deer mouse and fox squirrel mandibles as model systems, we examine patterns of integration in size and shape, isolating direct epigenetic interactions by analyzing correlation structure of fluctuating asymmetry (FA). In both species, we find shapes of adjacent parts to be correlated along the proximodistal jaw axis whereas more distant ones generally are not. Species differ in relationships between dental alveoli and muscle-bearing parts of the jaw, with the molar alveolus linked to more parts, and the incisor alveolus to fewer, in deer mice than squirrels. Size is more highly integrated for both symmetric and FA components, even in conditional independence graphs. Dental alveoli are typically as highly integrated with muscle-bearing parts of the jaw as with each other, arguing against the several hypotheses that regard them as separate developmental and/or functional modules. For size, the structure of integration is similar between symmetric and FA components, although the two components differ more in conditional independence relationships. The two species are moderately similar in both components, slightly less so in conditional independence relationships for FA. The structure of integration suggests that the mandible is a single connected unit, a result consistent with its functional integration. The weak similarity in structure of conditional independence relationships for FA argues against direct epigenetic interactions being constraints.
