The evolution of mate choice copying by indirect selection

A two-locus, two-allele population genetic model is used to study whether an allele for mate choice copying can become fixed in a population when it has no direct fitness benefit and there is therefore no cost due to choice. All females have an intrinsic preference for males with a certain trait. If they have the copying allele, they modify this preference on the basis of observations of an older cohort's mating patterns. Our specific model suggests a general rule: copying alleles spread when copying causes females to mate males that have higher total lifetime fitness. It is therefore possible for copying to evolve both when females have preexisting preferences for high-viability males (good genes) and when females are copying a preference for a trait that impairs male survival. Copying can spread through the force of indirect selection even when there is mild direct selection against the copying allele.