Meeting Abstract

72.5  Tuesday, Jan. 6  Morphological and Mechanical Patterns of Evolution in Triggerfish Fins DORNBURG, A*; SIDLAUSKAS, BL; SORENSON, L; SANTINI, F; ALFARO, ME; Yale University; National Evolutionary Synthesis Center; Virginia Institute of Marine Science; Univ. of California, Los Angeles; Univ. of California, Los Angeles alex.dornburg@yale.edu

Balistiform swimming is an unusual form of locomotion involving undulations of the dorsal and anal fins. Triggerfish have been used to study the fluid dynamics of this locomotion strategy, yet little is known about the evolution of triggerfish fin morphology. In this study we quantify fin shapes using a combined landmark/sliding semilandmark approach and also calculate aspect ratio as a functional property of fin shape for 25 triggerfish species. We test several hypotheses of morphological and mechanical evolution using a balistid phylogeny with divergence times estimated under an uncorrelated rates model in conjunction with several fossil calibrations: (1) Are multiple morphologies producing the same mechanical output and what is the distribution of these morphologies in the morphospace?; and (2) What model of evolution best fits the pattern of shape change observed across the triggerfish tree? Morphological and mechanical disparity through time plots reveal balistids to have separated into disparate regions of the morpho and mechanospace early in their history. Information theory based model selection recovers equal support for either a constrained Ornstein-Uhlenbeck or an evolutionary burst model of fin evolution for the balistids. Our results also indicate a correlation in the evolution of dorsal and anal fin shape, suggesting a potential functional or developmental constraint imposed by the coupling of these fins during locomotion.