The evolution of bite force and head morphology in scincid lizards: diet and habitat use as possible drivers

Abstract

Diet and habitat use impose mechanical constraints that may impact head morphology and bite force. Skinks (Scincidae) comprise the largest family of lizards with ~1700 species currently described. They also show an important morphological and ecological diversity. Using phylogenetically informed analyses, we studied the interrelationships between ecology (diet, habitat use), head morphology and bite force in these lizards. Our results show a strong link between body size, bite force and diet, with herbivorous species being larger and biting harder than species from other dietary groups. Despite a lack of differences in body size and head morphology, omnivorous species bite harder than insectivorous species, in order to process the fibrous plant material that is part of their diet. Overall, lineages that evolved greater bite forces also showed an increase in relative head height allowing for more vertically oriented jaw muscles. Moreover, we find evidence for correlated evolution between bite force and head length: skinks that bite harder tend to have shorter jaws that likely provide a greater mechanical advantage when biting at the tip of the jaw. Surprisingly, habitat use does not appear to be correlated with morphological traits or bite force, but this needs to explored further.