Meeting Abstract

S8-1.1  Jan. 6  Functional and ecological correlates of ecologically-based dimorphisms in squamate reptiles VINCENT, S.E.*; HERREL, A; Stony Brook University svincent@ethol.zool.kyoto-u.ac.jp

Sexual dimorphism in phenotypic traits associated with resource use is a widespread phenomenon throughout the animal kingdom. Ecological dimorphisms can be generated initially by sexual selection on body or head size, but are typically maintained by natural selection acting to reduce intrasexual resource competition. The trophic apparatus of ophidian squamates (snakes) has attracted a significant amount of research in this regard because head size is not known to be under sexual selection, enabling researchers to make straightforward hypotheses regarding the evolution of ecological dimorphisms. However, significantly less attention has been paid to the evolution of ecological dimorphisms in lizards. This lack of research is likely due to the fact that the feeding apparatus of lizards can be under both sexual and natural selection simultaneously, making it difficult to distinguish between natural and sexual selection pressures. In order to tease apart the respective influences of natural and sexual selection on the feeding apparatus of squamates, we take a functional morphological approach here to formulate two straightforward hypotheses for snakes and lizards, respectively: 1) For gape-limited predators such as snakes we predict that natural selection will act to generate differences in maximum gape, which will translate into ecological differences in maximum ingestible prey size between the sexes. 2) For lizards which mechanically reduce their prey, we predict that the sexes will differ in maximum bite force, which will be correlated with differences in maximum consumed prey size and hardness. Finally, we predict that functional differences in the feeding apparatus of both lizards and snakes will result in differences in sex-based prey selection in the wild.