Fig 5. A beneficial allele goes to fixation faster in populations with high Cra expression noise.

(A-B) Frequency of a beneficial allele competing with another allele in an environment that switches between glucose (yellow) and acetate (grey) every two days. The Cra dissociation constants have values of 0.07 and 0.05 mmol g⁻¹ for the beneficial and the wild-type Cra allele respectively. Both alleles occur in cells that have the same Cra expression noise, which is given by η² = 10 in (A), and η² = 0.01 in (B). Each plot show trajectories for 50 replicate population simulations. (C) Time until fixation of the beneficial allele (N = 50 replicates except for η² = 0.01, N = 49). Yellow diamonds and lines show the sample mean and one standard deviation. (D) The time the beneficial allele requires to go to fixation decreases with increasing fitness relative to its competitor (Spearman’s ρ = −0.77, p < 0.001). Circles are coloured according to Cra expression noise. The square (arrow) marks the one replicate where the fitter allele was lost from the population.