Dynamics and Organization of a Rocky Intertidal Fish Assemblage: The Persistence and Resilience of Taxocene Structure

Abstract

This paper examines characteristics of a rocky intertidal fish taxocene in central California. Seasonal and annual changes in taxocene structure, diversity, and recruitment were described and attempts were made to correlate these parameters with environmental variables. In addition, the persistence and resilience of taxocene structure were examined to determine whether this assemblage was regulated through deterministic or stochastic processes. A series of tidepools were defaunated 15 times over 29 mo. Sampling did not grossly affect taxocene structure in the study site and recolonization from surrounding areas was rapid. Three types of abundance patterns were observed: (1) species present year round (residents), (2) species present seasonally, and (3) species occasionally present. Productivity appeared to be the main environmental factor affecting taxocene structure because there were significant correlations between it and: (1) diversity, (2) species richness, (3) numerical abundance, and (4) recruitment to the assemblage. Wave action and temperature played a lesser role in explaining variations in taxocene parameters. The test of taxocene persistence and resilience showed that this assemblage was both persistent and resilient over the course of the study, despite repeated defaunation. These results are consistent with the predictions of the deterministic model of community organization and contradict those of the stochastic model. Consequently, this taxocene is probably successional or persistent. This result is surprising because studies of algal and invertebrate assemblages occupying this habitat indicate that these assemblages are stochastically regulated. Thus, the environmental pressures affecting the evolution of assemblage regulation have had different effects on these three taxocenes. This demonstrates that the relationship of environment to community organization is complex and dependent upon the evolutionary and ecological characteristics of the taxa examined.