Integration of Local and Regional Perspectives on the Species Richness of Coral Assemblages

SYNOPSIS. We have evaluated the relationship between regionalspecies richness and the number of species occurring withinlocal, quantitatively sampled assemblages of scleractinian corals.Our data have been extracted from the published literature describingrichness patterns from over 100 locations around the world.In general, we find a positive relationship between local andregional richness. Local richness is not independent of regionalrichness as posited by conventional theory and there is no hardupper limit indicating saturation. Instead, local coral assemblagesare regionally enriched. This result suggests that these assemblagesare open to regional sources of species. The degree of regionalenrichment is geographically variable. In the Indo-Pacific,assemblages in speciose regions appear to be less open and muchmore sensitive to local depth and habitat gradients than thosein more depauperate regions. Other large-scale geographicaland historical effects on local richness in the Indo-Pacificinclude the degree of isolation from high-diversity regionsand distance from the equator. In contrast, local richness inthe relatively homogeneous and depauperate western Atlanticis insensitive to the large-scale variables we examined. Asin most ecological communities, membership in local assemblagesof corals is not absolutely limited (by biotic interactionsor local environmental factors) nor is it totally open to regionalpools of species. Understanding the dynamics of coral communitieswill require integrating the local ecological perspective withlarge-scale phenomena (i.e., physical TECO processes [Myers,1994] and evolutionary history [Hugueny et al. 1997]). Suchan integration will necessarily encompass multiple spatial andtemporal scales.