Leguminosae is the third largest family of flowering plants, and includes many ecologically and economically important species. To understand this great divesity it is necessary to describe the patterns of relationship and phylogeny linking the many species and genera to one another. Much work of this type has been done, and continues, using traditional characters such as morphology and chemistry. This study will focus on variation patterns at the DNA level, specifically emphasizing the chloroplast genome, which has proven to be of great utility as a source of characters for constructing phylogenetic hypotheses. Restriction site analysis and DNA sequencing will be used to survey genera representing all of the major tribes of the pivotal subfamilies Papilionoideae and Caesalpinioideae, the groups considered to represent the main radiation of the family. Results from these studies will be integrated with those of non-molecular studies progressing elsewhere in the community. The resulting phylogenetic hypotheses will be used to study the origins of nitrogen-fixing symbioses in the family, with emphasis on the development of the nuclear multigene families involved in nodulation.
