View Program - 2022 Population, Evolutionary, and Quantitative Genetics Conference

Mutations can affect both the immediate fitness of an organism and the rates and benefits of future mutations. While numerous examples of these evolvability modifiers have been identified, their favorability has been difficult to predict in rapidly evolving asexual populations, where large numbers of mutations compete simultaneously. Here we calculate the fixation probability of a mutation that modifies the rates and benefits of future mutations, demonstrating how this quantity depends on parameters like the population size and amount of concurrent genetic diversity in the population. We show that competition between linked mutations can exponentially influence the fixation probability of modifiers to the magnitude of fitness effects of beneficial mutations, providing a comparatively larger contribution to the fixation probability than modifiers to the rate of beneficial mutations. We find that evolvability modifiers that increase or decrease the magnitude of fitness effects of beneficial mutations respectively suppress or amplify an associated direct fitness cost. By considering deleterious mutations, we also demonstrate that modifiers to the magnitude of fitness effects of beneficial mutations can be exponentially favored to fix in a population even when they reduce the rate of adaptation by orders of magnitude.

Evolution of Evolvability In Rapidly Adapting Asexual Populations