The study will determine the roles of a number of population-level processes, including genetic drift, migration, and local population extinction and recolonization, in determining the patterns of genetic differentiation among populations in nature. Population demographic data will be compared with genetic data to test theories concerning the effects of these various factors. The study animal is the swallow bug Oeciacus vicarius an ectoparasite exclusively of cliff swallows in Nebraska. Populations of swallow bugs undergo regular cycles of local population growth and extinction due to the ephemeral use of colony sites by the cliff swallow host. They are thus ideally suited for studies of the population genetic effects of dynamic factors such as extinction and recolonization. A longterm (10-year) database is available which details colony site usage and migration patterns for the cliff swallow hosts. The east with which important population parameters for these bugs may be estimated makes possible a population genetic unusual in both its precision and broad scope. The study will expand basic understanding of the fundamental process of genetic differentiation in natural populations, and will empirically test classical static (equilibrium) theories of population genetic structure against more recently proposed dynamic models. At a practical level, the study will provide general insights into the importance of various natural effects, such as local population extinction, in determining the overall level of genetic diversity for a species. This information is of considerable importance to conservation biologists as a guide in formulating effective strategies for maintaining species genetic diversity in the wild.
