An advantage for the evolution of male haploidy and systems with similar genetic transmission

Abstract

In arthropods and rotifers a variety of genetic systems share the common property that males transmit only their mother's genome while females transmit genomes of both parents. Many of these have long been recognised because of the haploidy of males, but there are also some species in which males are diploid and yet transmit only the maternal genome. It is shown that the evolution of these maternal-genome-transmitting males (“haploid” males) is governed by the simple selective principle that maternal alleles occur at twice the frequency in gametes of haploid sons as in gametes of diploid sons. Under a simple constraint on the fitness of haploid males, selection favours mothers which produce haploid sons merely because they transmit maternal alleles at a greater rate than do diploid sons. The advantage to mothers in producing haploid sons is at the expense of the paternal genome, which is not transmitted by haploid sons. There is therefore counter-selection on fathers to produce diploid sons, and if the right genetic variation arises this countering selection will revert male haploidy to diploidy. These arguments apply to large, random-mating populations but not necessarily to inbred populations.