Phylogenetic Relationships and the Diversification of Photosynthetic Pathways in Eleocharis (Cyperaceae)

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The flowering plant genus Eleocharis is a large and taxonomically difficult group of sedges (Cyperaceae) including more than 250 described species distributed worldwide. Dr. Eric H. Roalson and Dr. Maurice Ku at Washington State University propose to conduct a thorough evolutionary study of this diverse group of sedges. As these plants are critical ecological components of riparian, lake, and fresh and brackish marsh habitats worldwide but are poorly understood, particularly in tropical areas, determining species differences and evolutionary patterns is critical to defining the functionality of the species in these ecosystems. Of particular interest are the patterns of diversification of the major lineages in the genus and the origins of adaptive characteristics in the group. Eleocharis species are known to capture energy in photosynthesis through multiple physiological mechanisms, commonly referred to as C3, C4, and C3-C4 intermediate. In addition, some species are able to change the mechanism used for fixing carbon through photosynthesis depending on their growing conditions. The origins of these adaptive characteristics are unclear and will be explored as a part of this project. Drs. Roalson and Ku will use DNA variation and physical and anatomical characteristics to study the pattern of diversification in physiological processes and the origins of leaf-anatomical innovations in the genus. These studies will also lead to a revision of the classification and identification methods in the group, which will allow for more accurate determination of species distributions and characteristics.This proposal will involve training of undergraduate, graduate, and postgraduate students in studies of DNA variation, plant anatomy, and biochemical research applied to systematic and evolutionary questions. Having a better understanding of the ability of some Eleocharis species to change their biochemistry and method of photosynthesis depending on their growing conditions provides an excellent opportunity for the future exploration of the genetics that control photosynthesis. This could have an enormous impact on current efforts in crop plants to increase productivity through selection and genetic modification. Finally, the results will be disseminated to the wider scientific and general audience communities through scientific publication, presentation of results at national and international meetings, and the development of web-based resources.