Résumé
Dispersal evolves under the action of opposing forces. Some factors, like the cost of dispersal, select against dispersal. Several other factors, however, select for dispersal. In this chapter we focus on three main factors: (1) the temporal variability of the environment will often select for dispersal; (2) dispersal may also be adaptive if it reduces competition between relatives; and (3) dispersal may represent a way to escape the cost of inbreeding.