Some Aspects of Natural Selection in Arrhenotokous Populations

SYNOPSIS. Obligate arrhenotoky is known to have evolved only eight times, once each in the rotifer order Monogonanta, the arachnid order Acarina, the insect orders Hymenoptera and Thysanoptera, and in two families of Homoptera (Coccidae and Aleyrodidae) and Coleoptera (Scolytidae and Micromalthidae). In this paper it is argued that in male haploids the population genetic parameter which is most nearly analogous to the average fitness in ordinary diploids is the geometric mean of the average fitness in the two sexes. The geometric mean fitness is maximized by selection in a random mating population, provided one takes into account the fact that the system of inheritance imposes constraints on the gene frequencies in males and females. Furthermore, under sufficiently small selection intensities, the rate of change in geometric mean fitness is approximately equal to the additive genetic variance infitness, where the additive variance is defined as the variance due to the regression on a model of gene action which assumes no dominance in females and complete dosage compensation in males. Some problems concerning the sex ratio in male haploids when there is extreme inbreeding are also discussed.