The retreat of the less fit allele in a population-controlled model for population genetics.

It is shown that the solutions of a single-locus diploid model with population control for the spatial and temporal interaction of the three genotypes approach a constant-density equilibrium in which only the more fit allele is present, provided the density dependent birth rate and fitnesses have certain properties. The speed at which this phenomenon spreads is at least as great as that of the linearization of the corresponding Fisher equation. A larger upper bound for this speed is also obtained.