9629236 Hastings This project will use models to understand the dynamics of hybrid zones, locations where two species interbreed. The models improve on previous ones by including more realistic descriptions of movement (for example, the distribution of seeds around a plant) and of which individuals are likely to survive (including survival that depends on the frequency of other individuals). The methods include computer simulations and recent mathematical advances in understanding complex equations. The models will be used to estimate the amounts of selection and dispersal in natural hybrid zones. Hybrid zones are important because they are natural laboratories where the processes of natural selection are easier to study, since the interbreeding among different types produces novel types. Understanding natural selection in this way has societal importance for many issues, ranging from the preservation of biodiversity to plant and animal breeding.