The evolution and genetics of migration in insects

Because areas suitable for growth and reproduction are often ephemeral, a primary selective force in the evolution of migratory behavior in insects is the need to colonize new habitats. However, both migration itself and flight capability reduce present reproductive success. Thus the long-term fitness benefit of migration, the colonization of new habitats, is balanced by a short-term reduction in fitness, the result being that variation for migratory ability is preserved in a population. Migration is but one component of a wide suite of functionally connected traits that together form a migratory syndrome. Genetic variation is found in all components of the migratory syndrome, and selection for migration results in a change in the frequency of expression of these components, which can be analyzed and predicted using the mathematics of quantitative genetics. We illustrate this evolutionary interplay with the example of the evolution of wing dimorphism in the sand cricket.