Differential Performance of Sympatric Pomoxis Species Is Explained by Habitat-Linked Morphology

Black Crappie Pomoxis nigromaculatus and White Crappie Pomoxis annularis have contrasting patterns of performance along a gradient of turbidity for reasons that have yet to be elucidated. We examined how distinct, habitat-linked morphologies of these congeners make Black Crappie more specialized for structurally complex vegetation and White Crappie more specialized for open-water habitats and tested how these interspecific differences during early life influence their vulnerability to predation within open-water and vegetated habitats. Juvenile Black Crappie had deeper bodies with a short, deep caudal peduncle, and juvenile White Crappie had more fusiform bodies with an elongated caudal peduncle. These morphological differences had important consequences for predator evasiveness in each habitat, where Black Crappie were more successful at evading capture in vegetation and White Crappie were more successful at evading capture in open water. Because turbid lakes rarely support vegetation and clear lakes are heavily vegetated, our results suggest that differential success observed between these congeners may be better explained by adaptations to structural habitat complexity rather than tolerance to turbidity. Our study supports that habitat-linked morphological variation is critically important for predator evasiveness and can structure populations across species distributions.