A model of the structure and dynamics of benthic marine invertebrate communities

Abstract

The species abundance distributions of many benthic marine invertebrate communities may not satisfactorily conform to either the log-normal or log-series models that are central to theories of community structure. Benthic communities usually have dominance-diversity curves that are concave, rather than linear (log-series) or sinusoidal (log-normal), with a progressive increase in the number of rare species, singleton species outnumber doubletons and so on. There is no mode in the species abundance distributions. An alternative theory is presented to offer an explanation for these observed species abundance distributions. The theory is explained by use of a model of benthic marine community dynamics based on established principles of population regulation, notably recruitment behavior, competition and mortality. The model simulates several previously recognized features of community development. A non-interactive stage of colonization is followed by an interactive stage where, because of competitive interactions, environmental stability leads to an increase in dominance which depresses the diversity of the community and the number of species. Intermediate levels of disturbance maintain an increased diversity and a larger number of species by ensuring that dominance by any 1 sp. is only temporary and a stable climax is never reached. The model consistently predicts the products of the interactions between population growth, competition and mortality to be communitites with dominance-diversity curves similar in shape to those of natural communities. The model also suggests that while many species have the potential for geometric population growth some species do not achieve this because of mortality and competitive exclusion and, within an area of study, some species may have only an arithmetic potential for population growth.