The species richness-energy hypothesis in a system where historical factors are thought to prevail: Coral reefs

Much of the variance in species richness of terrestrial organisms has been related to levels of available energy (the species richness-energy hypothesis). In contrast, the global patterns of coral diversity have been hypothesized to depend mainly on disturbance and historical factors. In this study, we test several general diversity hypotheses as they relate to hermatypic corals by examining the relationships between coral generic richness at 130 sites worldwide and descriptors of the environment that would be suggested by the hypotheses. The best environmental predictors of diversity are mean annual ocean temperature and an estimate of regional coral biomass, which suggests that available energy limits regional generic richness. In contrast, we found little evidence supporting other ecological hypotheses, including the hypotheses that disturbance or environmental stability is an important control of diversity. We also investigated historical hypotheses proposed to explain coral distributions. We found a relationship between coral richness and up-current island density that is consistent with vicariance models of speciation and theories of coral dispersal. Using multiple regression, 71% of the variation in coral generic richness could be statistically explained using a combination of variables representing both ecological and historical factors. Similar patterns exist for both coral species and reef fishes.