Evolutionary Genetics and Genetic Variation of Haplodiploids and X-linked Genes

The evolutionary genetics of haplodiploids and X-linked genes share many features and are different from diploid (autosomal) genes in many respects. For example, the conditions for a stable polymorphism, the amount of genetic load, and the effective population size are all expected to be quite different between haplodiploids or X-linked genes and diploids. From experimental data, the genetic load for X-linked genes is much less than autosomal genes and appears less for haplodiploids than for diploids. The observed amount of molecular variation for haplodiploids is much less than that for diploids, even more so than predicted from the differences in effective population size. Extensive recently published data suggest that the differences in variation for X-linked and autosomal genes for Drosophila, mice, and humans are consistent with the differences predicted theoretically based on the relative effective population sizes.