Understanding the process by which new species evolve (speciation) is a fundamental question in biological sciences. A popular, but largely untested idea is that the formation of one species can catalyze the formation of other species within a community of interacting organisms (sequential speciation). Previous work has shown that a shift of the apple maggot fly from its native hawthorn host plant to the introduced domesticated apple about 150 years ago in the eastern US has induced a sequential host shift in the insect parasite community that attacks the flies. Specifically, as the fly shifts to attacking the fruits of a new host plant, the insect parasites that attack that fly shift in kind. What remains unknown is how general and rapid sequential speciation events are in nature. A powerful approach is to test the sequential speciation hypothesis in a more proximate case in the western US where the fly was recently introduced just 50 years ago. The proposed research will examine changes in the flies and their parasites in this new habitat to better evaluate the rate of speciation.
Understanding the origins of biodiversity is one of the central issues in biological sciences. In this regard, sequential speciation may be particular relevant for understanding biodiversity in general and in particular the astonishing levels of insect biodiversity (estimated 10-30 million species worldwide, the most diverse group of animals on the planet). Additionally, the apple maggot fly and several closely related species are major economic pests of several agricultural crops. Characterization of the origins of the parasitoid community can inform bio-control schemes to help farmers control the fly before it becomes a serious pest in the western United States.