A STOCHASTIC-MODEL FOR THE SPECIES-AREA RELATIONSHIP

A model is introduced which leads to the power law for the species number-area relationship of island biogeography. Starting from the equilibrium theory, populations are modelled by stochastic birth and death processes which include demographic and environmental noise. Essential factors for producing the power law are sufficient similarity of the species and of the islands, and the inclusion of interspecific competition. An exponential decrease of species number with distance of the island from the species pool is derived too. Species number-abundance frequency distributions are found to which lognormal distributions can be fitted.