BIODIVERSITY AND THE HISTORY OF REEFS

Abstract

Current biodiversity estimates suggest that modern coral reefs house between 4 and 5% of all described species, although increasingly sophisticated molecular techniques may reveal the actual diversity to be far higher. The origins and maintenance of this considerable taxonomic biodiversity remain, however, poorly known, particularly as the relative importance of controls that maintain the structure of reef communities differ according to the scale of consideration. The diversity of local coral reef communities is strongly correlated with water depth and differences between habitats. Ecological structure is considered to be ordered mainly by interspecific interactions and differential responses to disturbance, whereas determinants of diversity at regional geographical scales include variation in rates of dispersal and recruitment from the available metapopulation. On evolutionary timescales, historical events such as unique radiations of key taxa and mass extinctions appear to be the main controls on biodiversity change. All these processes operate simultaneously, and must be integrated in order to gain an understanding of the evolutionary perspective. Depending upon the scale of population considered, reef communities may operate as both individualistic assemblages of taxa with similar requirements, and as more tightly integrated ecological entities.