Gene frequency clines at X-linked or haplodiploid loci.

The equations governing gene frequency clines at X-linked or haplodiploid loci are derived. Clines at X-linked loci will be identical to corresponding clines at autosomal loci only under three restrictive conditions (a) no dominance, (b) dispersal distance the same in each sex, (c) average effect of alleles same in each sex. If any of these conditions are not met then the males and females will have different gene frequencies. Clinal variation in colour morph frequency in the bumble bee Bombus melanopygusis analysed. It is concluded that a minimum selection intensity acting on the queens on the order of 1 per cent or less is sufficient to maintain the cline.