Morphology of the limb, shell, and head explain the variation in performance and ecology across 14 turtle taxa (12 species)

Because morphology directly influences an organism's ability to utilize its habitat and dietary resources, it also influences fitness. Comparing the relationship between morphology, performance, and ecology is fundamental to understand how organisms evolve to occupy a wide range of habitats and diets. In turtles, studies have documented important relationships between morphology, performance, and ecology, but none were field based or considered limb, shell, and head morphology simultaneously. We compare morphology, performance, and ecology of 14 turtle taxa (12 species) in Mexico that range in their affinity to water and in their diet. We took linear measurements of limb, shell, and head variables, measured maximum swimming speed, maximum bite force, how often turtles were encountered on land, and used stable isotopes to assess trophic position. We use these data to test three hypotheses. The first, that morphology, performance, and ecology covary. The second, that limb and shell variables, like hand length, correlate to swim speed and the percent time spent on land. The third, was that that head variables, like head width, correlate to bite force and stable isotopes. We find support for these hypotheses and provide the first evidence that morphology influences performance and ecology in turtles in the field.