P1.108 Wednesday, Jan. 4 Evolutionary origin and diversification of adductor mandibula structure in cypriniform fishes STAAB, KL*; BETANCUR-R, R; HERNANDEZ, LP; George Washington Univ email@example.com
Cypriniform fishes comprise over 25% of the world’s freshwater fishes and their success is likely due to adaptations associated with feeding. This diverse clade is united by several feeding novelties, including a protrusible jaw. Cypriniform jaw protrusion is used differently by species feeding in diverse trophic niches including insectivory, planktivory, and benthic feeding. Modifications to the pleisiomorphic architecture of the adductor mandibula muscle likely allowed for fine-tuning of jaw protrusion associated with these distinct trophic niches. Here we reconstruct the evolutionary history of adductor mandibula structure and trophic diversity within Cypriniformes. Measurements of mouth angle were combined with available diet data to characterize extant species as benthic, mid-water, and surface feeders and to test for correlations between trophic niche and architecture of the A1 division of the adductor mandibula. We coded characters associated with diet, adductor mandibula structure, and jaw shape in 50 cypriniform and 10 outgroup species, including representatives from each major clade in the order. We test hypotheses regarding both the origin of jaw protrusion and subsequent diversification of jaw morphologies among the clade. Specifically, we hypothesize that benthivory has evolved multiple times and that it is correlated with multiple branches of A1. Using phylogenetic comparative methods, we also test the recently proposed hypothesis that the most recent common ancestor to cypriniforms was a benthic fish. We find that benthic species have independently evolved multiple branches of A1, underscoring this muscle’s importance in protruding the upper jaws toward the benthos.