The role of hybridization in the formation of new species, particularly at the diploid level, is a central problem of plant evolution. Graduate student Andrea Wolfe, under the direction of faculty advisor Wayne Elisens at University of Oklahoma, proposes to test various hypotheses of homoploid hybrid speciation in a complex of four species of herbaceous perennials in the genus Penstemon, using molecular and genetic markers. Individual plants sampled throughout the range of each species will be surveyed for isozyme (protein) variation and for mutational differences in chloroplast DNA and in nuclear ribosomal DNA. Because these data provide genetic markers which minimize problems of character intermediacy and dominance, they are especially appropriate for testing hypotheses about hybridization and introgression, and the origin of new species from stabilized hybrid recombinants. The study represents a unique opportunity to test two examples of hybrid speciation in a group of closely related plants. Because one purported parental species, Penstemon centranthifolius, has numerous diagnostic molecular and genetic markers which distinguish it from other members of this hybrid complex, the group of species also offers an excellent system to test models of introgressive hybridization, the "leakage" of genes from one species into another.
