Systematic Studies of Perennial Species of Sunflowers (Helianthus)

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Systematic studies of perennial species of Helianthus will follow two major lines of research. One is to use data from analysis of chloroplast DNA restriction site mutations to clarify several phylogenetic problems. These include the relationship of Helianthus to the putatively related genus, Phoebanthus, the relationships among the infrageneric groups of Helianthus (sects. Helianthus, Ciliares, and Atrorubentes), and the relationships of two enigmatic species, H. porteri and H. agrestis. A second major line of research will be to use data from chemistry, chloroplast DNA and nuclear ribosomal DNA restriction site analysis and isozymes to clarify selected situations that involve hybridization or polyploidy in species of the genus that occur in the southeastern United States. The results of the project will be to provide a firm phylogeny for Helianthus as a basis to understand topics such as biogeography and chemical evolution in the genus, and to clarify the systematics of the genus in the southeastern United States.