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

研究生芭芭拉·惠特洛克在哈佛大学大卫·鲍姆博士的指导下，正在研究可可或巧克力的来源——新热带植物可可属，以及它的近亲，以进行分类学和系统发育的研究。中美洲和南美洲的新藏品将增加植物标本馆的材料，并有助于提高对该群体形态和地理变化的理解。人们正在收集新的分子生物学证据，对叶绿体基因和核基因vicilinA进行DNA测序，这些基因被怀疑与可可的风味生物化学有关。DNA数据将用于推断c. 22种可可树及其近亲的系统发育树。反过来，这种家谱观点将指导进一步研究这一属和相关属的菜花的起源，沿着植物的主干和主干形成花（授粉后的果实），如可可可可，巧克力的商业来源。尽管种植可可具有重要的商业价值，但对可可的分类和系统发育的研究并不充分，新的分子方法应用于植物标本室和新采集的标本将有助于改进分类和发展该群体的系统发育。这些知识将有助于指导对影响热带植物花椰菜进化的遗传和生态因素的研究。

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.