Population stability and the evolution of dispersal in a heterogeneous environment

A model is presented which demonstrates that a stable polymorphism for dispersal tendency can be generated under a wide range of conditions. These conditions include both different genetic models and different "dispersal probability" functions. It is shown that individual selection for or against dispersers may result in a stable polymorphism which depresses population numbers and prevents population fitness from being maximized. Changes in the genotypic probabilities of dispersal may lead to very large changes in other parameters both with regard to their means and their spatial distribution. The effect of increasing environmental stability does not effect the proportion of dispersers maintained in the population in identical ways; the effect depends upon the parameter altered and the genetic model used.