Species and space: role of volume in organizing coral reef fish assemblages in SE Cuba

A reliable species–area relationship holds true for a number of terrestrial systems. When species–area data are plotted on logarithmic axes, the slope bears strong consistency across taxa. This study examined effects of habitat space on the diversity of coral reef fish species. Because habitat space on coral reefs is 3-dimensional, we developed and employed a methodology that accounts for volume. A positive relationship was observed both between log species richness of fish and log area, and log species richness and log volume. Area explained 88 to 99% and volume explained 76 to 99% of the variation in species richness. The slopes of species–area curves observed here (z = 0.46 to 0.61) are considerably higher than for other taxa (average z-value of 0.26), but are similar to those observed in other 3-dimensional systems (fishes 0.43, carabid beetles 0.36, birds 0.61). Volume accounted for some of the observed difference, and factoring out volume reduced the slope of the curve by up to 18% (z = 0.38 to 0.52). An increase in suitable habitat (habitat diversity) has been proposed as an important factor explaining the noted increase in species relative to space. Habitat heterogeneity showed strong positive relationships with both area and volume. Canonical correspondence analysis indicated that habitat variables explained 66 to 76% of the variation in species richness at our sites at all spatial scales. The results of this study suggest that the relationship between species and space holds true for reef systems, and that habitat space and microhabitat diversity are good predictors of fish species richness.