Department of Mathematics

In nature, populations expand into new habitat at different spatial and temporal scales, from bacterial cells forming a colony all the way to invasive species colonising new geographical regions. The expansion process can thereby affect the evolutionary path of the growing population, a topic that has gathered much interest recently. The effects of environmental heterogeneity on the evolutionary dynamics of such range expansions remains poorly understood so far - not least due to the large variety of environmental heterogeneity found in nature. To understand the effects of this heterogeneity, we use a combination of simulations, analytical theory, and experiments with microbial model systems.In a bottom-up approach we are seeking to first understand the effects of isolated inhomogeneities and then describe the evolution in complex heterogeneous environments. Specifically, we first consider the effects of isolated obstacles and hotspots as well as bumps in an otherwise flat habitat. The former two are regions which hinder and accelerate the invasion, respectively. We find that those structures have characteristic consequences for neutral genetic diversity (the distribution of individuals that are genetically different, but do not have a selective advantage or disadvantage). We observe an additional layer of ‘survival of the luckiest’ – complementary to, yet qualitatively different from, founder effects occurring in the presen