The proposed research will use comparative evidence from the ontogeny of flowers to address phylogeny of legumes. Polarization methods will use outgroup comparison. Preliminary trees based on 33 taxa representing major tribes of the three subfamilies of Leguminosae and 30 traditional characters from mature flower and vegetative structure were developed for comparative purposes. To date, 17 qualitative ontogenetic characters with discrete character states have been derived based on direct observation of floral ontogenies with SEM; most are heterochronic. Preliminary results show some unexpected relationships among tribes and subfamilies that need to be assessed in terms of characters used: i.e., caesalpinioids Gleditsia and Ceratonia are a basal sister group to the rest of the legumes; and Caesalpiniodeae appears non- monophyletic. The research will also test the hypothesis that specialized character states are first expressed late in floral ontogeny, using species of Sophora, a papilionoid with diverse pollinators. In addition, presumably different development pathways leading to convergent floral structure will be documented in three caesalpinioid genera (Cassia s. str., Chamaecrista, Senna) that are strikingly alike in specialized character states.
