Figure 1 .

Joint relative reproductive rate at a neutral autosomal marker locus induced by two autosomal factors in the absence of physical linkage. Each of the horizontal axes represents the fitness (relative viability or fertility) of female carriers of an autosomal factor (σ_f,i, i = 1, 2), with the fitness of a male carrier given by σ_m,i = 1 − σ_f,i. The saddle-shaped surface represents the relative reproductive rate at the marker locus induced by the two factors jointly and the relatively flat surface the rate under the multiplicative expectation. Thick lines indicate the intersection between the actual and expected barriers.