INBREEDING, SELF-FERTILIZATION, LETHAL GENES AND GENOMIC COALESCENCE

A deterministic computer model was used to investigate the elevation in frequency of coalesced genomic heterozygotes, i.e. heterozygotes with reduced numbers of independently assorting supergenic units at meiosis, in inbred populations in which every supergenic unit carried a recessive lethal gene. Inbreeding was manipulated in terms of s, the proportion of self-fertilizations per generation, and F, Wright's Inbreeding Coefficient which measures the degree of relatedness between individuals within a population. It was found that where F was greater than about 0.19, coalesced heterozygotes were lifted to high frequencies (> 50 per cent) in the population in the absence of self-fertilization. Coalesced heterozygotes were lifted to high frequencies in populations with F less than 0.19 by appropriate levels of self-fertilization. Populations with fewer independently segregating supergenic units at meiosis were more sensitive to the effects of inbreeding than those with larger numbers of such units. The possible significance of these observations in terms of the evolution of genetic systems and in conservation practice is briefly discussed.