Diversity Patterns from Ecological Models at Dynamical Equilibrium

摘要

We study a dynamic model of ecosystems where immigration plays an essentialrole both in assembling the species community and in mantaining itsbiodiversity. This framework is particularly relevant for insular ecosystems.Population dynamics is represented either as an individual based model or as aset of deterministic equations for population abundances. Local extinctions andimmigrations balance in a statistically stationary state where biodiversityfluctuates around a constant mean value. At stationarity, biodiversityincreases as a power law of the immigration rate. Our model yields almost powerlaw species area relationships, with a range of effective exponents inagreement with that observed for biodiversity of whole archipelagos. We alsoobserve broad distributions for species abundances and species lifetimes and asmall number of trophic levels, limited by the immigration rate. These resultsare rather robust with respect to change of description level, as well aschange of population dynamic equations, from prey dependent to ratio dependent.