9701092 Jansen Graduate student Anne Hansen, under the direction of Profs. Robert Jansen and Lawrence Gilbert at the University of Texas, is studying plants of the tropical passion flower genus, Passiflora, in South America. The genus is large and taxonomically difficult, with over 475 species; the subgenus Passiflora with an estimated 100 species is the main target for study. Field work in Brazil will augment materials collected from other regions of the neotropics, complementing herbarium holdings. The general goals include improved species classification, with description of reliable and stable characters for identification, and the construction of a phylogeny for the group, from new molecular data derived from restriction site mapping of the chloroplast genome and from DNA sequencing of nuclear ribosomal genes. The widely cultivated edible passion fruit, Passiflora edulis, is a member of this subgenus, and a related goal is determination of the closest relatives of the cultivated species and the likely area of origin in South America. Considerable ecological work has been done on the interactions between Passiflora host plants and herbivorous insects of the butterfly genus Heliconius, in the American tropics. Many insects are specific to particular Passiflora species, and some are thought to sequester noxious plant compounds from their host plants (alkaloids, cyanogenic compounds) as potential chemical defenses of their own. Further research on this ecological interaction is limited by the lack of a phylogeny of the Passiflora species; it is not known whether closely related insect species feed on closely related plant species, or whether host switching is unconstrained by genealogical relationship. The project will improve the taxonomy of Passiflora species, and facilitate future ecological research by providing a reliable phylogeny for the plants.
