Variation in gene presence for different pathway length. Changes in peak variation in gene presence shown as a function of the pathway length n. Each data point shows the maximum value of 1 − x0−x
attained in the course of the numerical process, for the given parameter values. The shading at each point indicates the position of the equilibrium state: black indicates pathway acquired (x
>0.95), white indicates pathway absent (x0>0.95), and grey indicates the equilibrium is more than 0.05 from each extreme. The transfer rates used were γ1 = 10−3(high) and 10−9(low), and clustering κ = 1.0(high) and 0.1 (low). Throughout, fitness cost c, fitness benefit b and deletion rate δare fixed at c = 0.005, b = 0.1and δ = 10−9.