Speciation - the process through which new species arise - remains one of the most controversial (and poorly understood) aspects of the study of animal diversity. Natural hybridization events between closely related species provide unique opportunities to investigate the genetic basis of species differences and the nature of the barriers to gene exchange that tend to keep species distinct. Information about the distribution and number of genes that contribute to genetic isolation can be gained from analysis of the distribution of genotypes within and adjacent to a hybrid zone. This project will document, at high resolution, patterns of genetic variation in a very well-characterized zone of hybridization between closely related insect species. These genetic analyses will be coupled with studies of both pre-mating and post-mating barriers to gene exchange (factors that cause reproductive isolation). The project will take advantage of recombinant DNA technology to identify a set of restriction fragment length polymorphisms (RFLPs), which will serve as the genetic markers to analyze the extent and direction of hybridization and backcrossing and the consequences for the flow of alleles from one species into the other. The discovery of RFLPs has provided an enormously useful set of markers for human geneticists studying inherited diseases and holds great promise for genetic studies of natural populations of other species as well. The approaches and understanding developed in the course of this study will be useful in a variety of contexts.
