Stochastic exits from dormancy give rise to heavy-tailed distributions of descendants in bacterial populations

ABSTRACT

Variance in reproductive success is a major determinant of the degree of genetic drift in a population. While many plants and animals exhibit high variance in their number of progeny, far less is known about these distributions for microorganisms. We quantified the distribution of descendants arising from stochastically germinating Streptomyces spores by applying a novel and generalizable method. The distribution is heavy-tailed, with a few cells effectively “winning the jackpot” to become a disproportionately large fraction of the population. This not only decreases the effective population size by many orders of magnitude but can lead to its sub-linear scaling with the census population size. Furthermore, incorporating the empirically determined distribution into population genetics simulations reveals allele dynamics that differ substantially from classical population genetics models with matching effective population size. These results demonstrate that stochastic exists from dormancy can have a major influence on evolution in bacterial populations.