9407144 Campbell The main purpose of this research is to test models for the maintenance of plant hybrid zones. Clines along hybrid zones can be explained by several mechanisms that differ in the form of selection. Direct tests of these models will be conducted in a hybrid zone between 2 flowering plants, Ipomopsis aggregata and I. tenuituba. The study has two major goals. The first goal is to characterize the overall form of selection to distinguish among the proposed models. Controlled crosses will be used to produce hybrid seed, followed by reciprocal transplants to determine relative fitness of parental species and offspring hybrids at several sites along the hybrid zone. The second goal is to determine the form and mechanism of selection directly on those floral traits that exhibit clines. Quantitative, molecular and observational methods will be used to address this second goal.
