Macroevolutionary ecomorphology of the Carnivora skull: adaptations and constraints in the extant species

The mammalian order Carnivora is characterized by a broad taxonomic and ecological diversity. By using a large sample of extant species, we tested the impact of ecological factors on carnivoran skull (cranium and mandible) morphology, taking advantage of a combined geometric morphometrics and comparative method approach. We implemented several evolutionary models to account for different tempo and mode of evolution in size and shape data. These models validated the association between skull morphology and diet at the interspecific scale. The functional distinction between pinniped (aquatic) and fissiped (mostly terrestrial) taxa was found valid only in mandible shape and cranial size. High levels of morphological disparity and evolutionary rates were identified in specialized dietary groups, and positive association between rates and disparity was found for skull size. Cranium and mandible showed consistent patterns of covariation that reflect constrained functional processes, which stabilize the ecomorphological evolution of Carnivora. Aquatic adaptations allowed carnivorans to invade and persist within novel regions of the mandibular morphospace. This ecological shift did not increase morphological disparity but occurred at a faster rate than in terrestrial species. Those species exhibit a stronger level of cranio-mandibular covariation due to constraints imposed by more demanding masticatory adaptations.

Automated summary

This study used a large sample of extant species and a combined geometric morphometrics and comparative method approach to investigate the impact of ecological factors on carnivore skull morphology. The results showed that skull morphology is associated with diet at the interspecific scale, but the functional distinction between aquatic and terrestrial species is only valid in mandible shape and cranial size. Specialized dietary groups exhibit high levels of morphological disparity and evolutionary rates, with a positive association between rates and skull size disparity. The cranium and mandible show consistent patterns of covariation, reflecting constrained functional processes. Aquatic adaptations allowed carnivorans to invade novel regions of the mandibular morphospace at a faster rate than terrestrial species.