OEDIPAL MATING AS A FACTOR IN SEX ALLOCATION IN HAPLODIPLOIDS

Most theoretical work on brood sex ratio bias is based on life histori es involving potential sibmating, where inseminated females colonize a habitat producing progeny that mate randomly among themselves. Howeve r, another type of life history can favour female biased broods; it in volves mother-son matings and is uniquely accessible to haplodiploids. Colonization is accomplished by immature stages (mating is postdisper sal) and female bias is favoured at low colonization densities by the fact that, unlike isolated males, isolated females are not lost to the gene pool because they can mate with their parthenogenetically produc ed sons. We present a mathematical model of the life history including parameters describing colonization density, degree of aggregation, th e penalty incurred when a female must wait to mate with her parthenoge netically produced son, and inbreeding. Low colonization density favou rs female bias as does increased aggregation; a high penalty associate d with waiting for maturation of a son with which to mate means that s ome proportion of males among progeny will be favoured even at very lo w colonization densities. Life histories that fit the model are known in nematodes and mites.