FESSLER, Jennifer L.; WESTNEAT, Mark W.; Univ. of Illinois at Chicago and the Field Museum; Field Museum: Evolutionary analysis of feeding mechanisms in angelfishes and butterflyfishes

Marine butterflyfishes (Chaetodontidae) and angelfishes (Pomacanthidae) are conspicuously beautiful and abundant animals found on coral reefs worldwide. These two families are thought to be closely related, and have evolved a number of feeding specializations including long jaws, brush-like teeth, and novel jaw protrusion mechanisms. The exact phylogenetic relationship of butterflyfishes and angelfishes remains unresolved, thus hindering phylogenetic analysis of trophic evolution in both groups. To address this, we created a molecular phylogeny based on two genes (mitochondrial 12s and nuclear Tmo 4c4) for 86 species, including representatives of nearly every genus and subgenus in the two families plus five outgroups. Using this phylogenetic hypothesis we analyzed skull morphology and biomechanics in select lineages in order to test hypotheses concerning the evolution of long jaws in butterflyfishes, and the evolution of jaw protrusion and biting in angelfishes. We also propose new computer models of feeding mechanics that enable us to predict the functional performance of fish jaw mechanism from morphological measurements of the multiple levers and linkages in their skulls. The combination of a robust molecular phylogeny with biomechanical models and morphological analyses provides strong insight into the evolutionary history of jaw function in two coral reef fish families.