Dissertation Research: Morphological Diversification and Phylogentic Systematics of the Plant Genus Weinmannia

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9706948 Schaal Graduate student Jason Bradford, under the direction of advisors Dr. Barbara Schaal at Washington University and Dr. Paul Berry at the Missouri Botanical Garden, is studying morphological evolution of the complex inflorescence structures in the tropical tree genus Weinmannia, of the Cunoniaceae family. Extensive field collecting has been done in parts of South America and in Madagascar, and additional collecting targets regions of high species diversity in Australasia. A major focus of the research is DNA sequencing of a nuclear ribosomal RNA gene, to generate data appropriate for constructing a phylogenetic framework of the genus from mutational differences among the species. About one-third of the estimated 150 species in the genus are to be analyzed for DNA variation. Studies of the position and complexity of the branched flowering axes, the inflorescences, will then be conducted, to distinguish structures that are likely the result of shared ancestry from those arising as convergent adaptations in different lineages. In a project focused on tropical woody plants, and bringing both molecular and morphological approaches to taxonomic study, Mr. Bradford will add field collecting in poorly researched areas of Melanesia and Polynesia to sample Weinmannia diversity across its southern-hemisphere range. The molecular phylogenetic data will augment general studies of dicot phylogeny ongoing in several laboratories in the world. The morphological analyses contribute to renewed study of modular growth patterns in flowering plants, where differences in timing (heterochrony) and in positioning (heterotopy) characterize vegetative and reproductive axes in related species.