Diversity loss as a function of colony morphology*

Studies in cellular aggregates such as cancer and microbial colonies have shown that the dynamics of evolution play out very differently in populations that have spatial structure as compared to well-mixed populations. However, much of the theoretical work on spatially organized populations has focused on 1D systems or other models with simple spatial structure, ignoring the effects of mechanics as well as metabolism, which can play an important role in aggregate morphology. We study a stochastic model for microbial colony morphology that includes nutrient dynamics and a growth instability, and observe how different colony morphologies affect genetic drift. We compare rough and flat colony fronts and find that rough fronts exhibit two regimes of diversity loss, a transient regime in which diversity is lost much quicker than flat fronts and a long-time regime in which the diversity loss is more similar.