Meeting Abstract
142.2 Monday, Jan. 7 Correlated evolution of jaw muscles and trophic niche in cypriniform fishes STAAB, KL*; BETANCUR-R., R; HERNANDEZ, LP; George Washington Univ; George Washington Univ; George Washington Univ kstaab@gwu.edu
Cypriniform fishes occupy a wide range of trophic niches that include insectivory, planktivory, and benthic feeding. However, no quantitative study has investigated the evolutionary history of feeding in this important group. All cypriniform species (e.g. goldfish, zebrafish, loaches) are characterized by having a protrusible jaw dependent on contractions of the A1 division of the adductor mandibula muscle. Our previous work suggested that the architecture of the adductor mandibula likely allows 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. A time-calibrated molecular phylogeny was constructed using six nuclear genes and 23 fossil calibration points. Mouth position and diet data were used to characterize extant species as benthic, mid-water, and surface feeders and to test for correlations between trophic niche and architecture of A1. We present morphological data for representatives from each major clade in the order. We test hypotheses regarding both the correlated evolution of jaw morphology and trophic niche as well as subsequent diversification among the clade. We also confirm the recently proposed hypothesis that the most recent common ancestor to cypriniforms was a benthic fish. A divided A1 is highly correlated with an inferior mouth position, suggesting that this particular arrangement of A1 is important for benthic feeding. Our results strongly suggest that the most recent common ancestor to the order had an inferior mouth like many of the extant species inhabiting the benthos. Thus, the success of the world’s most speciose clade of freshwater fishes may be due in part to an initial radiation from a benthic species.
