Fish species Diversity on Model and Natural Reef Patches: Experimental Insular Biogeography

Fish communities associated with model and natural reef patches were studied to determine the effects of heterogeneity, area, and isolation on the number of fish species in these systems. The effects of season and succession on the structure of these communities were also examined. Species turnover was estimated to determine if numbers of fish species on small reefs can be viewed as a balance between immigration and local extinction. Interspace size diversity, one facet of reef heterogeneity, was not positively correlated with the number of fish species on either model or natural reefs. In addition, interspace size diversity had no significant effects on species composition. In most of the cases examined reef height, another aspect of reef heterogeneity, was positively correlated with the number of fish species and species diversity, H', on natural reefs. Observations of selected fish species inhabiting model reefs support the hypothesis that vertical zonation is a means of resource partitioning in these fish communities. A negative correlation was found between reef isolation and number of fish species on patch reefs. This correlation was strongest during periods when fish population sizes were lowest. Season had more of an effect on the structure of fish communities on model reefs than did succession. Immigration and local extinction of fish species occurred on model reefs throughout the study. Patterns of immigration and extinction approximated the predictions of the MacArthur-Wilson equilibrium model of insular zoogeography when species turnover was highest.