Two layers of chance associated with spatially expanding populations: How demographic noise and environmental heterogeneity shape genetic diversity

In nature, populations expand into new habitat at different spatial and temporal scales. The expansion process can thereby affect the evolutionary path of the growing population, a topic that gathered much interest recently. The effect 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. We here study the effect of environmental heterogeneity or landscape structure using a combination of theory, simulations, and experiments.

In particular, we consider isolated obstacles and hotspots, regions which hinder and accelerate the invasion, respectively, as well as bumps in an otherwise flat habitat. We find that those structures have characteristic effects on genetic diversity. We observe an additional layer of ‘survival of the luckiest’ – complementary to, yet qualitatively different from founder effects occurring in the presence of ‘spatial bottlenecks’. Our findings and experimental assays we currently develop suggest a way forward to study the evolutionary consequences of more complex large-scale structures.   

Host: Dr Edward Wallace