Dissertation Research: Phylogenetic Systematics of Cacao and its Relatives (Byttnerieae: Sterculiaceae)

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9700876 Baum Graduate student Barbara Whitlock, under the direction of Dr. David Baum of Harvard University, is studying the neotropical plant genus Theobroma, the source of cocoa or chocolate, and its relatives of the tribe Byttnerieae of the Sterculiaceae family, for taxonomic and phylogenetic purposes. New collections in Central and South America will augment herbarium materials, and help improve understanding of morphological and geographic variation in the group. New molecular biology evidence is being gathered, from DNA sequencing of a chloroplast gene and of a nuclear gene, vicilinA, suspected to be involved in the flavor biochemistry of cocoa. The DNA data will be used to infer a phylogenetic tree for the c. 22 species of Theobroma and its close relatives. In turn, that genealogical perspective will guide further study of the origins of cauliflory in this and related genera, the formation of flowers (and fruits after pollination) along the trunk and main stems of the plant, as in Theobroma cacao, the commercial source of chocolate. Despite the commercial importance of cultivated cocoa, the taxonomy and phylogeny of the several species of Theobroma are not well studied, and new molecular methods applied to herbarium and freshly collected specimens will help improve classification and develop a phylogeny for the group. That knowledge will then help guide studies of the genetic and ecological factors affecting the evolution of cauliflory in tropical plants.