On the product mean fitness and population growth in sexual and asexual populations

We examine situations that have frequently been invoked as advantageous for sex. In a constant environment with one diallelic locus determining viability that differs between the sexes, complete genotypic frequency dynamics are obtained in a symmetric case. The product of male and female mean fitnesses may not increase over time. In models with periodic or random environments, the numbers of sexuals and asexuals in pure populations of each can be compared. In agreement with previous studies, sexual populations are shown to grow at a faster rate than asexual populations.