Phylogenetic relationships of the northeastern South American Brownea clade of tribe detarieae (Leguminosae: Caesalpinioideae) based on morphology and molecular data

The legume subfamily Caesalpinioideae is a paraphyletic grade, within which are nested the monophyletic subfamilies Mimosoideae and Papilionoideae. Although higher level relationships within Caesalpinioideae are now better understood, few studies have examined generic and species level relationships. A morphological and molecular phylogenetic analysis of selected members of the Brownea clade (Detarieae: Caesalpinioideae) is presented here, focusing on relationships within and among the genera Elizabetha, Heterostemon, Paloveopsis, and Paloue. Morphological characters (125) and DNA sequence data from the plastid trnL intron and nuclear ITS were used to reconstruct phlogenetic relationships. These results indicate that (1) Heterostemon is monophyletic; (2) the majority of Elizabetha species form a poorly supported, monophyletic group sister to Paloue; and (3) Paloveopsis is nested within Paloue. Intergeneric hybridization between species of Paloue and Elizabetha has been identified and traditional generic, species, and intraspecies boundaries are assessed and reevaluated using the results of the combined phylogenetic analysis.