Figure 4.

The spread of a fast-growing mutant in binary fission populations with age-related fitness costs. Plotted are histograms of the fold increase of the mutant fraction ($\frac{\mathrm{final}\mathrm{fraction}}{\mathrm{initial}\mathrm{fraction}}$, where the initial fraction is ${10}^{-3}$) for ${10}^3$ independent simulations experiencing different age-related fitness costs. The aging factor (the parameter b in Equation (1)) is the multiplicative factor by which reproductive time increases with age such that $1.05$ means a $5\%$ increase in reproductive time in the simulations. As the aging factor is increased the distribution shifts to the right indicating that the final mutant fraction increases in simulations. See Appendix C, Appendix D and Appendix E for robustness analyses and companion figures using different simulation parameters.