Population Dynamics of Metastable Growth Rates

Neo-Darwinian evolution provides a paradigm for population dynamics built on random mutations and selection with a clear separation of time-scales between single-cell mutation rates and the rate of reproduction. By studying the adaptation dynamics of genetically rewired yeast cells adapting to a severe regulatory challenge, we have uncovered a novel type of population dynamics in which intracellular processes seem to play a role in shaping the population structure. Under constant environmental conditions, we measure a wide distribution of growth rates that coexist in the population for very long durations (\textgreater 100 generations). Remarkably, the fastest growing cells do not take over the population on the time-scale dictated by the width of the growth-rate distributions and simple selection. In fact, the population-average growth rate plateaus and even decreases over the course of the adaptation, on intermediate time-scales of tens of generations. Our data show that the phenotypic state of the cells in a constant environment is metastable and varies on time-scales that reflect the importance of long-term intracellular processes in shaping the population structure. Moore LS, Stolovicki E, Braun E (2013) Population Dynamics of Metastable Growth-Rate Phenotypes. PLoS ONE 8(12):e81671.