Clines are regions of blending between geographically abutting populations with different genetic makeup. Powerful theoretical and statistical methods are available to study the evolutionary forces that maintain natural clines. Here we demonstrate that clines also provide a powerful manipulative tool for the experimental study of dispersal and selection. We develop a new model of non-equilibrium cline dynamics that is suitable for studying rapid evolutionary changes. We use the model to study dispersal and natural selection in insecticide resistance in the Colorado potato beetle, a major defoliator of potato crops. We will create resistance clines in replicate potato fields in Massachusetts and Maine, and use them to test hypotheses about adaptation to spatially varying habitats, including dispersal patterns and the strength of selection. New 'refuge'-based strategies to slow the rate that pesticide resistance evolves also depend on knowledge of dispersal.
Our measurements of dispersal apply directly to new management strategies to slow the rate that resistance to pesticides evolves in potato beetles, and our new methods can be applied to other crop-pest systems. Our results will be shared with potato growers, who will directly benefit.