Meeting Abstract
Among vertebrates, snakes are the largest, most diverse limbless radiation, making them a model for studies of convergent evolution in limbless locomotor modes. Of the several types of snake locomotion, sidewinding represents an ideal gait for answering questions of the relationship between morphology, behavior, and the environment, given the strong association with specific substrate types (e.g. sand and mudflats). Additionally, sidewinding has appeared multiple times over the course of snake evolution, providing an opportunity to examine convergence in morphology and function. We examined several species of sidewinding vipers (e.g. Crotalus cerastes, Bitis peringueyi, Cerastes cerastes, C. vipera, Pseudocerastes persicus, Eristocophis macmahoni, Echis carinatus, and E. coloratus) plus their close relatives to see if distantly-related sidewinding species converge in their morphology. Using museum specimens, we measured snout-vent length (SVL); width and circumference at 25%, 50%, and 75% of SVL; tail length; head length and width; and number of pre-caudal vertebrae. From these measurements, we calculated an elongation ratio by dividing the total length of the animal by the largest of the three width measurements and relative tail length by dividing tail length by SVL. Then, we used a phylogenetic generalized least squares linear regression for multiple traits to determine whether sidewinding predicted any aspects of morphology. We also used a phylomorphospace approach to determine whether sidewinding species generally occupy different regions of morphospace than non-sidewinding species. Preliminary results show that sidewinding species have more vertebrae per unit body length than non-sidewinding species, but that sidewinding may not correlate with a particular body shape.
