Evolution of responses to relative homozygosity

Abstract

ACCORDING to the theory of kin selection first elaborated by Hamilton^1,2, all individual behaviour is selected to maximise the increment to inclusive fitness ΔW_i + ΣΔW_jr_ij, where ΔW_i is the effect of an act on the fitness of the actor, ΔW_j is the effect of the same act on the fitness of a conspecific, and r_ij is the coefficient of relationship between the actor and the conspecific. Acts that lower an individual's direct fitness can thus be favoured by natural selection if, by conferring benefits on relatives of the actor, they cause a positive increment to the actor's inclusive fitness^3,4. Since the average r_ij between an individual and the targets of its behaviour varies because of fluctuations in local population structure, an individual is most likely to secure a positive increment if its behaviour is conditioned on as accurate an estimate as possible of the particular local distribution of r_ij. I describe here a mechanism by which this estimate could be improved on the basis of information derived from the relative homozygosity of the individual's own genotype, in species with certain kinds of life histories.