Kin Competition, the Cost of Inbreeding and the Evolution of Dispersal

Dispersal is often presented as a mechanism to avoid competition among relatives and inbreeding depression. However, the formal analysis of the effects of both these factors on the evolution of dispersal has only been conducted in few studies with strong restrictive assumptions. In this paper, I first derive the evolutionary stable dispersal rate as a function of three parameters: (1) the cost of dispersal, c, (2) the coefficient of relatedness among randomly chosen offspring, R, and (3) the cost of inbreeding, δ. In a second step, relatedness is used as a dynamical variable for the derivation of the evolutionarily stable dispersal rate. Finally, in a third step, relatedness and the cost of inbreeding are assumed to be dynamical variables. This allows to analyse the more realistic situation where dispersal, relatedness and the cost of inbreeding are coevolving simultaneously. Several subcases are considered depending on the genetic determinism (haploid or diploid), the control of the dispersal strategy (parent or offspring control of dispersal) and the plasticity of dispersal with sexes (with or without sex-specific dispersal rates). This analysis clarifies the role of the cost of inbreeding and kin competition on the evolution of dispersal (in particular on the evolution of sex-biased dispersal rates) and leads to quantitative and testable predictions.