The Role of Quenched Noise in the Evolution of Populations undergoing Range Expansions

Inferring or predicting evolutionary outcomes in populations growing on surfaces requires understanding the causes and consequences of genetic spatial structure, an area that has received much attention recently. However, much remains to be understood about the role that variability in the environment plays in the evolution of these growing populations, which may have far-reaching consequences, e.g., for the emergence of antibiotic resistance in bacterial colonies. To make progress, it is essential to understand the interplay between intrinsic demographic noise caused by genetic drift and extrinsic environmental noise that arises from interactions with landscape features, such as nutrient-rich regions of increased growth. To study the interactions between these two regimes of noise, we conduct multi-species Eden model simulations of population growth in heterogeneous landscapes, and we analyze the results through the "lenses" of population genetics and geometric optics. This allows us to characterize how repeated lensing effects from landscape features shapes the advancing colony front and creates a distinct genetic lineage structure. By connecting population genetic measures to the landscape heterogeneity, we distinguish between genetic drift and environmental noise signatures.