Meeting Abstract
Anatomy is the product of both evolutionary history and environmental pressures. The family Cyprinidae (order Cypriniformes) is a hugely diverse group of fishes, 300 of which are endemic to North America. The oral jaw of minnows is edentulous and the entirety of mechanical prey processing occurs via the pharyngeal jaws. Individuals from this clade feed on myriad prey and occupy nearly all freshwater habitats, making them a phenomenal model system for studying the interplay between diet and evolutionary history in shaping anatomy. Here, we used micro-computed tomographic (CT) imaging of 243 species of North American minnows to evaluate how anatomical specialization, evolutionary history, and dietary ecology have shaped morphology in this clade. We utilized phylogenetic data established for this clade, linear landmark-based metrics, and geometric morphometric shape analyses to capture anatomical variation and compare morphological diversity. We see trophic convergence among genera, and considerable variation in morphology of several traits: 1) muscle attachment area (a proxy for muscle force); 2) relative size of the ligament spanning left and right hemi-mandibles (a proxy for strength and range of motion and skeletal flexibility); and 3) jaw elongation (a proxy for gape). These functionally important metrics of bone (hemi-mandibles) and ligament were negatively correlated yet they evolve independently. Moreover, there is extensive overlap in morphospace, suggesting that convergence is widespread among minnow dietary guilds. Our results show a recent burst in diversification with most variation occurring at the extant tips of the phylogenetic tree for both functional and geometric morphometric traits.
