WAINWRIGHT, P.C.; Univ. of California, Davis: Morphological similarity is not limiting in labrid fishes: global diversity patterns on coral reefs

The concept of limiting similarity states that species can only coexist in a community if they maintain some minimum degree of ecological difference. I searched for evidence of limiting similarity in labrid fishes by evaluating morphospace packing of coral reef communities across geographic and habitat diversity gradients. My morphological data base consisted of body size and nine cranial variables that characterize functional properties of the feeding apparatus, all measured on specimens of 156 species of labrid fishes from coral reefs in the Western Indo-Pacific and the Caribbean. From these data I created a global labrid morphospace with a PCA conducted on the correlation matrix of species values. I looked for patterns in regional biotas and in habitat-specific communities of coexisting species. Regional species lists were obtained from published accounts for the Great Barrier Reef (145 spp, 130 sampled), Palau (138 spp, 97 sampled), and the Caribbean (30 spp, 24 sampled) and at each location quantitative visual transects were conducted in classic reef zones at several sites to establish local community lists. Remarkably, the morphological variance of regional assemblages was unaffected by species richness, indicating that as species are added to regional pools they are packed increasingly tightly into morphospace. This pattern held within regions as well, as communities of species found in any given habitat also showed no evidence of a minimum similarity: morphological variance of communities was constant while nearest-neighbor distance decreased with the number of species in the community. These patterns of constant variance suggest that communities of labrids are drawn randomly from the regional species pool with respect to their trophic morphology.