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 here 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 upon established principles of population regulation, notably recruitment behaviour, competition and mortality. The model sinlulates several previously recognised features of community development. A 'non-interactive' stage of colonisation is followed by a n 'interactive' stage where, because of competitive interactions, environmental stab~lity leads to a n increase in dominance which depresses the diversity of the community and the number of species. Intermediate levels of disturbance maintain a n increased divers~ty and a larger number of specles by ensuring that dominance by any one species is only temporary and a stable 'climax' is never reached. The model consistently predicts the products of the interactions between population growth, competitlon and mortality to be communitites with dominance-divers~ty 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 specles may have only an anthmetic potential for population growth.