Figure 3.

Expected allele frequency distribution under three biallelic population genetics models. Shaded boxes: polymorphic sites having arisen through an AT → CG mutation. Open boxes: polymorphic sites having arisen through a CG → AT mutation. Models M₁ (nonstationary) and M₂ (nonneutral) differ from M₀ largely in that the expected distributions are asymmetric. Expectations under M₁ and M₂ are similar but distinct. For instance, with the parameter values chosen here for illustration, the less probable allele frequency is 5 under M₁, but 6 under M₂.