Coral Richness Research Articles

Species Richness of Reef-Building Corals Determined by Local and Regional Processes

Species richness in ecological communities has traditionally been explained in terms of species interactions, especially competition, operating within the local community over relatively short periods of time. Recently, it has become clear that ecological communities can be organized by a variety of processes operating at different spatial and temporal scales. Since local communities are imbedded within larger geographic regions, regional/historical phenomena and local processes may influence local richness jointly and should be analysed simultaneously. Here we perform such an analysis by comparing assemblages of hermatypic scleractinian corals from different regions sampled at over 100 sites around the world. Using multiple regression analysis, we find that local richness is as sensitive to regional richness as it is to each of two variables (depth and habitat) that subsume much of the local variability at a site. Our results indicate that although coral assemblages are believed to be intensely interactive, they are, nevertheless, regionally enriched and show no evidence of saturation. Multi-scale effects on local richness demand further investigation to clarify causal relationships, and to enlighten policy decisions over issues of biodiversity, habitat loss and fragmentation, and ecological restoration.

Coral and sea urchin assemblage structure and interrelationships in Kenyan reef lagoons

Patterns of hard coral and sea urchin assemblage structure (species richness, diversity, and abundance) were studied in Kenyan coral reef lagoons which experienced different types of human resource use. Two protected reefs (Malindi and Watamu Marine National Parks) were protected from fishing and coral collection, but exposed to heavy tourist use. One reef (Mombasa MNP) received protection from fishermen for one year and was exploited for fish and corals prior to protection and was defined as a ‘transitional reef’. Three reefs (Vipingo, Kanamai, and Diani) were unprotected and experienced heavy fishing and some coral collection. Protected and unprotected reefs were distinct in terms of their assemblage structure with the transitional reef grouping with unprotected reefs based on relative and absolute abundance of coral genera. Protected reefs had slightly higher (p 90% of the coral cover at sites with the highest sea urchin abundance. Effects of coral overcollection was only likely for the genusAcropora (staghorn corals). A combination of direct and indirect effects of human resource use may reduce diversity, species richness, and abundance of corals while increasing the absolute abundance of sea urchins and the relative cover ofPorites.