Although the mimosoid legumes are an important component of tropical forests, especially in arid and semiarid regions, they have been understudied relative to the two other major legume groups, the papilionoid (pea-flowered) and caesalpinioid legumes. The most recent evolutionary study of the legume family incorporated only 7 samples from an estimated 4000 species of mimosoids. Proposed work by Dr. Melissa Luckow at Cornell University and colleagues is aimed at correcting the imbalance by intensive study of genera in the subfamily Mimosoideae. Specifically, the goals of this study are: 1) to construct an evolutionary tree for 39 genera of mimosoid legumes using data from both morphology and DNA sequences (from nuclear and plastid genes), and 2) to write a revision of these genera, complete with keys for identification and detailed descriptions. Field work will be undertaken to collect rare and unusual species in Africa, Madagascar, and South America. Molecular and morphological data will be employed in a phylogenetic analysis that will clarify the relationships among the genera and shed light on the evolution of nitrogen-fixation and characters associated with adaptation to arid climates. Interactive keys and descriptions will be constructed and incorporated into the Diversity of Life web site. The legume family is the third largest flowering-plant family, and second only to grasses in economic importance to mankind. The mimosoids are particularly important in tropical ecosystems as agroforestry and timber trees, providing wood and forage in marginal and arid regions of the world. Much effort is currently being expended to improve and exploit species of Prosopis (mesquite), Acacia, and Leucaena for food and fodder in arid habitats. Yet, currently there is little information on what the closest relative to Prosopis might be, or whether or not all species of Acacia in the New World are related to those in Africa and Australia. A phylogenetic context will be indispensable to the agricultural evaluation and development of species in these genera; reliable identification keys to the genera, with comprehensive descriptions, will be widely used by taxonomists, foresters, plant breeders, and ecologists. For example, most areas in Latin America lack comprehensive floras; legumes also tend to be one of the last groups to be worked on since the family is so large and diverse. Creating web-based keys and descriptions that can be downloaded will insure wide availability and affordability to users in developing countries. This format will also make it easy for instructors to integrate the material into their classrooms.
