Data from: Ecological and phylogenetic variability in the spinalis muscle of snakes

Understanding the origin and maintenance of functionally important
subordinate traits is a major goal of evolutionary physiologists and
ecomorphologists. Within the confines of a limbless body plan, snakes are
diverse in terms of body size and ecology, but we know little about the
functional traits that underlie this diversity. We used a phylogenetically
diverse group of 131 snake species to examine associations between habitat
use, sidewinding locomotion, and constriction behavior with the number of
body vertebrae spanned by a single segment of the spinalis muscle, with
total numbers of body vertebrae used as a covariate in statistical
analyses. We compared models with combinations of these predictors to
determine which best fit the data among all species and for the advanced
snakes only (N = 114). We used both ordinary least squares models and
phylogenetic models in which the residuals were modeled as evolving by the
Ornstein-Uhlenbeck process. Snakes with greater numbers of vertebrae
tended to have spinalis muscles that spanned more vertebrae. Habitat
effects dominated models for analyses of all species and advanced snakes
only, with the spinalis length spanning more vertebrae in arboreal species
and fewer vertebrae in aquatic and burrowing species. Sidewinding
specialists had shorter muscle lengths than non-specialists. The
relationship between prey constriction and spinalis length was less clear.
Differences among clades were also strong when considering all species,
but not for advanced snakes alone. Overall, these results suggest that
muscle morphology may have played a key role in the adaptive radiation of
snakes.