A problem in determining fitness differences.

Although differential contributions to the next generation have frequently been used to measure differences in fitness, a t genetic equilibrium there will be no such differences among genotypes with balanced polymorphism. For a single locus the frequencies, after selection, of the three genotypes, AA, Aa, aa, will be: qlp2/K 2W,,pq/W and W,, q2/v, where v = w,, p2 + 2W,, pq + tyz2 pa. To estimate the contribution of any genotype to the next generation, the average fitness of the offspring can be calculated from the frequencies of possible matings for that genotype and the average fitness of the offspring of each mating. For the AA genotype the average fitness of the offspring will be (K1p2/W) W,, + (2 W,,pdP) (0.5 K + 0.5%~) + (%2 a 2 / W K2