Evolutionary Dynamics of Branching Cellular Populations

Branching cellular populations, such as the cells of developing kidney ducts, mammary glands, certain microbial colonies, and others, present a unique challenge for evolutionary dynamics: Each branching event increases the effective dividing population size, while branch terminations will prevent propagation of portions of the cellular population. In this work, we develop a basic theory of the evolutionary dynamics of branching populations with tip-driven growth. We compare the theory to simulations of branching tissue and show that branch bifurcations tend to enhance survival probabilities of strains within the population, independently of the details of the bifurcation process. Conversely, branch terminations lead to increased extinction. Our model predicts an optimal branch rate at which mutations arising within the population are more likely to survive as the population grows.