COOPER, W. James; Univ. of Chicago & Field Museum: The Evolution of Feeding Biomechanics in Damselfishes

The damselfishes (Perciformes; Pomacentridae) comprise one of the dominant groups of fishes on all coral reefs and are a major component of the trophic ecology within these systems. This study examined the evolution of damselfish feeding mechanisms by combining morphological, biomechanical and phylogenetic analyses of all damselfish genera. Digital images of dissected specimens were used to generate coordinate data for the location of morphological landmarks important for feeding. Thin plate spline, principal components, and procrustes superimposition techniques were then used to determine relative differences in the location of these landmarks among pomacentrid species and to describe the distribution of their skulls in shape space. These same coordinates were also used to make functional predictions of damselfish trophic capabilities (e.g. maximum jaw protrusion, mechanical advantage employed during biting). Both the morphological and functional data were then plotted on a pomacentrid phylogeny generated by Bayesian analyses of DNA sequences from 3 nuclear genes (RAG1, RAG2 and Bmp-4) and 3 mitochondrial genes (12S, 16S and ND3) extracted from over 100 species in all 29 damselfish genera. This comprehensive approach has yielded detailed information about the diversification of feeding mechanisms within the Pomacentridae. The more stalwart skulls of the primarily benthic feeding, basal damselfishes have repeatedly given rise to gracile forms and there is also a general trend away from the habitation of rocky reefs towards coral reefs. Such transitions are associated with increased planktivory, a trophic habit that has evolved multiple times from different morphological starting points within this lineage.