UCB Moorea Class: Biology and Geomorphology of Tropical Islands

Studies on island biogeography in the Pacific have shown a biodiversity gradient that decreases from west to east, a pattern followed by numerous land and marine organisms. Based on this gradient, it has been hypothesized that Scleractinian coral biodiversity should follow the same gradient and be considerably lower in Mo‟orea, French Polynesia, than in the Great Barrier Reef (GBR). Rapid ecological assessments on six barrier reef sites surrounding Mo‟orea, as well as transects following the line intercept method at one site, provided data on Scleractinian coral species richness and composition. A phylogenetic study of character evolution was also performed to examine the evolutionary history of four characters related to coral reproduction and dispersal. Results revealed site-to-site heterogeneity between the six Mo‟orea sites and a mean site species richness of 30 species. Alpha diversity of the Mo‟orea barrier reefs and the GBR were not found to be statistically different, but total diversity was found to be considerably higher in the GBR than in Mo‟orea, suggesting that beta diversity is what accounts for most of the difference in species richness. Phylogenetic character analysis revealed that the broadcast spawning character was highly conserved throughout evolutionary history, and that patterns in the other three characters, brooding, fragmentation, and rafting ability were not quite as clear. Increased knowledge on coral diversity patterns and dispersal can help focus conservation efforts to preserve maximum biodiversity and protect coral reefs from adverse human impact.