Current evolutionary research focuses on problems associated with genetic changes that accompany the formation of new species and the maintenance of the integrity of species in the face of hybridization with closely related species. In order to understand processes involved in genetic differentiation, a pattern of evolutionary relationships must be constructed and the traits under study must be viewed with reference to this pattern. Evolutionary relationships have in the past proven difficult to construct for newly formed (very closely related) species but new techniques are available which allow the collection of data from the most variable DNA gene regions. These techniques are used in this research. The insect species known as the periodical cicadas have proved to be ideal study organisms to address problems of evolutionary tree construction and species divergence; they are easy to work with and the six species have a unique set of distributional patterns within which are various degrees of spatial isolation, temporal isolation, and genetic variability. Results from previous work established higher level evolutionary relationships, identified differences in genetic variability among species, discovered areas where hybridization is likely, and provided genetic evidence for life cycle plasticity which has important implications for evolutionary theory. The proposed research will examine suspected areas of hybridization among otherwise isolated groups and will extend phylogenetic analyses to the closely related, unstudied year classes which we suggest represent incipient species. What is learned about the usefulness of particular gene regions for constructing evolutionary relationships will be directly applicable to the study of relationships among other animals and plants and will lead to a better understanding of rates and mechanisms of evolution at the DNA level.
