Meeting Abstract
Independent lineages often evolve similar morphologies in response to similar functional demands; however, there are diverse clades where such convergence is underappreciated due to perceived phenotypic homogeneity. Many fishes, including leuciscids (Cypriniformes), are equipped with a secondary set of jaws (gill arch elements in the pharynx) that have become the primary site for prey processing. The shape of these pharyngeal jaws presumably relates to their function in feeding (i.e., robust teeth for crushing hard prey), and in minnows there are significant correlations between diet and anatomy. Using comparative macroevolutionary methods with a published phylogeny, we tested how pharyngeal phenotypes are shaped by evolutionary integration, phylogenetic signal, and diet. We used geometric morphometric methods to explore overall shape diversity, and measured functionally-relevant traits relating to feeding performance from micro-computed tomography scans of 165 species. Our geometric morphometric dataset provides us with a measure of shape change independent of functional connotations, whereas our linear morphometrics measure function directly. Our results suggest widespread anatomical and dietary convergence: clades largely overlap in morphospace and similar patterns of shape change correlate with shifts to similar diets. However, the overall shape of the pharyngeal jaws and their functional diversity do not always evolve in parallel through time; rather, changes in jaw shape and function can evolve independently. These instances of form-function decoupling are concomitant with periods of widespread climate change in North America and ecomorphological shifts in feeding zone (benthic to pelagic).
