A MODEL FOR EVOLUTION AND EXTINCTION

We present a model for evolution and extinction in large ecosystems. T he model incorporates the effects of interactions between species and the influences of abiotic environmental factors. We study the properti es of the model by approximate analytic solution and also by numerical simulation, and use it to make predictions about the distribution of extinctions and species lifetimes that we would expect to see in real ecosystems. It should be possible to test these predictions against th e fossil record. The model indicates that a possible mechanism for mas s extinction is the coincidence of a large coevolutionary avalanche in the ecosystem with a severe environmental disturbance. (C) 1996 Acade mic Press Limited