The carnivoran adaptive landscape reveals functional trade-offs among the skull, appendicular, and axial skeleton

Abstract

Analyses of form-function relationships are widely used to understand links between morphology, ecology, and species fitness across macroevolutionary scales. However, few have investigated functional trade-offs and covariance among functional traits within and between the skull, limbs, and vertebral column simultaneously. In this study, we investigated the adaptive landscape of skeletal form and function in carnivorans to test how functional trade-offs between these skeletal regions contribute to ecological adaptations and the topology of the landscape. We found that functional traits derived from carnivoran skeletal regions exhibit trade-offs and covariation across their performance surfaces, particularly in the appendicular and axial skeletons. These functional trade-offs and covariation corresponded as specializations to different adaptive landscapes when optimized by locomotor mode, diet, or family. Lastly, we found that the topologies of the optimized adaptive landscapes and underlying performance surfaces are largely characterized as smooth, gradual gradients between regions of low and high adaptive zones rather than as rugged, multipeak landscapes. Our results suggest that carnivorans may already occupy a broad adaptive zone as part of a larger mammalian adaptive landscape that masks the form and function relationships of skeletal traits.