| Among the legumes, subfamily Caesalpinioideae is a paraphyletic grade within which are nested the subfamilies Mimosoideae and Papilionoideae. Recent work within the Caesalpinioideae has focused on higher level phylogenetic questions with relatively little emphasis on generic or species level phylogenies. The Brownea clade, contained in the tribe Detarieae (Caesalpinioideae), is composed of approximately eight genera, four of which are the focus of this dissertation and found predominately in the Guiana Shield region. This study is a phylogenetic analysis of selected members of the Brownea clade concentrating on generic and species level relationships of Elizabetha, Paloue, Paloveopsis, and Heterostemon and explores the phylogenetic relationships and character evolution among these closely related genera.; Chapter one is a morphological based on 125 morphological, anatomical, and floral characters. The characters used by the noted legume systematist Richard Cowan to define generic and species boundaries are compared to those found to be phylogenetically informative. Chapter two is a description of a new species of Paloue from Kaieteur Falls, Guyana, South America. While most Paloue species are lowland, riparian trees, this new species is the only one found at high elevations. Characters that distinguish this highland species are the presence of five sub-equal petals and leaves that are coriaceous with prominent, brochidromous venation on the underside of the lamina. Chapter three is a combined morphological and molecular phylogenetic analysis of the Brownea clade. This analysis includes the morphological data set combined with trnL plastid and nuclear ITS sequences. Traditional generic, species, and intra-species boundaries are assessed and reevaluated using the results of the combined analysis, and updated generic and species boundaries are suggested. According to the result, it is necessary to combine Elizabetha, Paloue, and Paloveopsis into a single genus. Character and character state evolution are explored in a phylogenetic context and hypotheses of character evolution are discussed.; The final chapter utilizes the results from the combined analysis to revise the taxonomy of the genus Paloue to include the genera Elizabetha and Paloveopsis. This is the first complete revisionary work published on Paloue s.s. and valuable field observations have been incorporated into the updated species descriptions. |
