Figure 5.

The spread of a fast-growing mutant in budding populations with age-related fitness costs. (left) 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 of unicellular budding populations experiencing different age-related fitness costs (similar in structure to Figure 4). Increasing the aging factor shifts the distribution to the right elevating the final mutant fraction. (right) Plotted are another set of histograms similar to the left panel except for multicellular budding populations. Compared to the unicellular budding populations, the distributions are more bimodal. If we consider the higher mode of the distributions we find that again the aging factor increases the final mutant fraction but by a much greater amount than in the corresponding unicellular populations: $216.40\pm 0.82$ in a multicellular budding population for an aging factor of $1.1$ compared to $79.18\pm 5.64$ in the unicellular budding population. See Appendix C, Appendix D and Appendix E for robustness analyses and companion figures using different simulation parameters.