Effect of environmental heterogeneity on mutation-selection balance during range expansions

While mutation-selection balance has been extensively studied in well-mixed environments and populations undergoing range expansions in uniform environments, little is known about the effects of environmental structure on the interplay between mutation and selection and on the evolutionary fate of a population.

We consider a system with mutation and selection where individuals with deleterious alleles have an advantage in isolated patches, but a disadvantage everywhere else.

Simulations and theoretical analysis highlight that the deleterious allele can fix at the population front even when the density of patches is below the one guaranteeing spread via percolation. We are able to predict this regime using least-time arguments for front propagation.

Our findings are an example of two sub-critical processes assisting each other to achieve super-criticality. From an applied perspective, it highlights the role of landscape structure during evolution, for example on the emergence of pesticide resistance.