Speaker
Description
The rate of de novo mutations varies across species and is predicted to be dependent on parameters such as population size, the average generation time, and how far the population is from the fitness peak. Mutations that modify the mutation rate itself often emerge in bacterial evolution experiments, either increasing or decreasing the mutation rate of ancestral lineages. Previous theoretical approaches have delineated the conditions necessary for these modifiers of mutation rate to spread in the population, either by hitchhiking with beneficial mutations or by reducing the load of deleterious mutations. One implicit assumption in previous work is that the fractions of beneficial and deleterious mutations are identical in the modifier and ancestral lineages (which differ only in how often new mutations arise). Recent empirical work, however, has highlighted the fact that modifications of the mutation rate are often accompanied by changes in mutation bias, such that different types of mutations occur at different rates. This can dramatically alter the availability of beneficial and deleterious mutations for the modifier lineage. In this talk, I will present a stochastic model and computer simulations which explore the effect of mutations that modify both the mutation rate and the mutation bias, demonstrating how these two effects simultaneously play a role in the evolution of microbes.
