DISSERTATION RESEARCH: Systematic Biology of Costaceae(Zingiberales): Using Molecular and Morphological Data to Investigate Phylogenetics and Floral Evolution

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A grant has been awarded to Drs. Dennis Wm. Stevenson, W. John Kress, and Chelsea D. Specht at the New York Botanical Garden to study the systematics and evolution of Costaceae, a tropical plant family of approximately 130 species closely related to the economically important bananas and gingers as well as prominent ornamentals such as Heliconia and Strelitzia (Bird-of-Paradise). Also known for their ornamental appeal, Costaceae have showy flowers and floral structures with shapes and colors that are closely linked to the attraction of pollinators. The proposed research is designed to determine evolutionary relationships among species within the family and investigate the historical context in which Costaceae has achieved its current level of diversity. Approximately 2500kb of DNA sequence data will be generated for 75 species chosen to represent floral and biogeographic diversity within the family. These data will be analyzed along with morphological character data using contemporary phylogenetic techniques. In addition, the development of the different floral shapes will be studied to determine potential mechanisms involved in the evolution of floral form.Certain species in the genus Costus are pollinated by hummingbirds, while others are bee-pollinated. The genus has thus been divided into two groups based on these overall floral characteristics, however recent evidence has shown that these groupings are not reflective of evolutionary history. Rather, it seems as though individuals can switch back and forth between hummingbird and bee pollination, possibly based on environmental conditions such as pollinator availability or efficacy. Since similar floral forms are found in South American and African species, it may be concluded that common types of pollination pressures occur in these geographically distant forest, yielding similar shapes and colors in distinct lineages of plants. This study will increase our understanding of the forces that promote speciation and diversity in tropical plants. In addition, floral development studies may help to indicate how genetic factors are involved in the evolution of diverse forms, leading to a clearer understanding of the genetic basis for biodiversity.