 Inbreeding, including self-fertilization in plants and automictic parthenogenesis (thelytoky) in hymenoptera, tends to lead to the harmful expression of deleterious recessive alleles (inbreeding depression).Cross-fertilization between unrelated individuals ordinarily leads to the masking of deleterious recessive alleles in progeny.Many studies have demonstrated that homozygous individuals are often disadvantaged with respect to heterozygous individuals.