Evolution and the stochastic description of simple ecosystems

A stochastic description of the population dynamics of a predator-prey ecosystem is developed and the behaviour of small mutant populations studied. Expressions for their probability of survival are found and the results generalized to arbitrary ecosystems. The results of their calculations reveal the importance of neutral or near neutral mutations, and indicate the limited ability of 'selection' to eliminate less effective members of the population. Evolution appears as a complex dialogue between mutation and selective forces where neither is necessarily dominant and both the extremes of Neo-Darwinism and of Neutral drift are refuted. A calculation of the non-linear effects of the spatial interaction between individuals of a mutant population, shows how altruism and a division of labour can evolve because of spatial inhomogeneity, and how the 'unit' of selection can thereby change from individuals to social groups. © 1983.SCOPUS: ar.j