Figure 4.

Sign epistasis is less likely to occur between mutations with large effects. (a) Examples of a smooth landscape with paths of monotonically increasing fitness (left) and a rugged landscape characterized by reciprocal sign epistasis (right). (b) Experimentally measured probability of observing sign epistasis as a function of the log growth of two single knockouts with similar effects (G₀₁ = G₁₀ within 20%, G = mean(G₀₁, G₁₀)). The blue shaded area is the standard error of the mean computed by bootstrap.