Ecological diversification of rapidly adapting populations

Microbial populations, owing to their large size, continually produce new mutations. Some mutations influence the competitive fitness of individuals, which compete with each other in a process known as clonal interference. Other mutations allow the population to diversify into distinct ecological niches, as has been directly observed in laboratory experiments. However, despite the empirical relevance of both clonal interference and ecological diversification in microbial populations, their interplay is not well understood theoretically. To address this gap, we study the dynamics of a simple class of consumer resource models in which individuals acquire mutations that alter their resource uptake rates. We focus on large, clonally interfering populations, where ecological and evolutionary timescales cannot be fully separated. In this regime, we find that the few highly fit individuals that dominate the future population are strongly influenced by the ecological environment set by the bulk population. This delayed feedback between evolutionary and ecological processes manifests as a dynamical "priority effect" for resident ecotypes, impeding diversification.