Assembly dynamics for a coral-associated reef community: spatial and temporal patterns, and a test of priority effects
The foundational goal of community ecology is to understand the drivers of variation in communities over spatial and temporal scales. This research combined nondestructive, observational studies of the natural variation within a coral-associated reef community over spatial and temporal scales, with a community manipulation to directly test the impacts of potential key species on community assembly processes. The observational components of this research characterized the composition of these reef communities and investigated patterns in variation relative to colony and regional scale environmental gradients. The results showed that colony scale parameters influence the composition of these communities more than regional scale parameters over both spatial and temporal scales. Colony size, depth, and percent live coral tissue were all correlated with changes in community composition in space and time. In addition to depicting patterns associated with colony scale parameters, species-specific responses to gradients in wave height and chlorophyll-a were observed over spatial scales. The composition of communities was more consistent in time than in space when comparing intra-colony and inter-colony community dissimilarity metrics. Spatial surveys depicted non-random co-occurrence patterns between some of the commonly observed community members. By modeling probabilities of arrival and departure for specific species relative to the presence of taxonomically similar species, temporal surveys of focal communities reinforced the importance of species interactions in structuring coral-associated reef communities and added a directional component to potential species interactions. Community manipulations directly quantified the effects of two commonly observed coral host protection mutualist species on the formation and maintenance components of community assembly. The results showed that these two species have inhibitory effects on the composition of the coral-associated community. These effects were driven by species-specific responses to each of the mutualist species. This dissertation provides fundamental details about the natural variation in coral-associated communities, incorporates a community manipulation to directly test community assembly processes, and provides a template of analyses for characterizing spatial and temporal patterns in other communities.