Molecular systematics of the temperate IR-lacking Clade of Papilionoid Legumes (Leguminosae) and the Evolution of Nod Factor Receptor Genes

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The legumes (plant family Leguminosae) are second only to the grasses in agricultural and economic importance, with a large number of species planted as horticultural varieties or harvested as crops for food, forage, fiber, fuel, oils, timber, medicines, and chemicals. Within the "papilionoid" subfamily many of the familiar domesticated species grown for food and forage, including Medicago (alfalfa), Cicer (chick pea), Lens (lentil), Pisum (pea), Trifolium (clover), Vicia (faba bean), are members of a group technically known as the inverted repeat lacking clade or "IRLC". The IRLC, with ca. 50 genera and more than 4,350 species (23% of all legumes), contains the vast majority of herbaceous legumes that are geographically widespread and often ecologically dominant in temperate regions of the world, especially North America and Eurasia. This group also contains a number of species used as model plant systems for the study of genetics and genomics (Medicago truncatula, Pisum sativum) and symbiotic nitrogen fixation (Medicago and Trifolium species), as well as several large genera that serve as examples of adaptive radiation or diversification. In spite of the number of biologically interesting, agriculturally, and ecologically important species in this group, relatively few broad-level systematic studies on this group have been undertaken and many issues related to the taxonomy and evolutionary relationships among its members remain unresolved. The primary goals of this project are 1) the clarification of relationships in the IRLC using phylogenies (or trees) based on sequences of multiple plastid and nuclear genes; 2) to construct an up-to-date classification of this group at the generic level that reflects their phylogenetic relationships; and 3) to use the phylogeny to study interesting and potentially useful questions about the biology, ecology, and evolution of this group, such as estimating rates and patterns of species diversification, and the evolution of genes essential to establishment of the symbiotic relationship between legumes and nitrogen-fixing rhizobial bacteria. An important outcome of this project will be a much-improved understanding of the history and biodiversity of this group of papilionoid legumes, which includes almost one quarter of all species in the family. Furthermore, these results will promote a greater understanding of a number of fundamental biological questions that have implications for the entire family, such as the conservation and evolution of genes required for the specific recognition of nitrogen-fixing bacteria by their legumes hosts. This project will foster collaborations among US and international collaborators, while graduate and undergraduate students will receive training in contemporary systematic biology as well as current techniques of DNA sequencing, phylogeny reconstruction, and bioinformatics through participation in all phases of the project. Results will be widely disseminated to both the general public and the scientific community through presentations at meetings, publications, contributions to legume information websites (e.g., ILDIS, LIS) and publicly accessible databases (Genbank, Tree of Life Project, TreeBASE), in addition to the creation of a dedicated website to serve as an comprehensive resource for information on the biodiversity, phylogeny, and agro-economic importance of this group of legumes.