Survival of a Mutation under Mixed Positive Assorative and Random Mating. I. One Locus, Two Alleles without Dominance

Abstract

Deterministic and stochastic linear branching models represent populations carrying one wild and one mutant allele at a single autosomal locus when mixed positive assortative and random mating is practised. Self-fertilization is assumed possible. As required, the time-independence of mutant characteristics or the occurrence of specific offspring distributions is assumed. In the absence of population density-dependent selection, 'absolute,' not 'relative' population parameters determine the fate of a mutation. For 'basic' populations tbe probability of survival of a mutation introduced by a single heterozygote is calculated. When there occurs heterozygote superiority over the mutant homozygote, this survival probability is an increasing function of the degree of positive assortative mating practised. When there occurs homozygote superiority, this probability can be an increasing, decreasing, or constant function of the degree of assortative mating. The survival probability is always an increasing function of parameters termed 'fitnesses' of the mutant genotypes. Stochastic resuilts obtained generalize predictions given without proof by Bartlett [19681.