The pantropical family Capparaceae comprises approximately 40 genera and 800 species. Capparaceae are well suited for systematic and evolutionary inquiries. Not only are Capparaceae in need of cladistically based phylogenetic hypotheses, but the diversity of floral form exhibited by the group make the family a model system to examine evolution of floral forms. It has been almost universally agreed that Capparaceae have a very close phylogenetic relationship with Brassicaceae, including the model species Arabidopsis thaliana. Recent morphological and molecular analyses indicate that Cleome (Capparaceae) are more closely related to Brassicaceae than to other Capparaceae. However these studies have sampled a maximum of four taxa from Capparaceae and typically have used only two. The goal of this study was to clarify the relationships between these two families by using evidence from DNA sequences of two regions of the chloroplast, ndhF and trnL-trnF, and by increasing sampling of Capparaceae to include most traditionally circumscribed groups. We sampled over 10 genera of Capparaceae, 10 species of Brassicaceae, and outgroups chosen from previous analyses of Capparales. Three monophyletic groups were supported: Brassicaceae, Cleomoideae, and Capparoideae, the last two clades corresponding to subfamilies of Capparaceae. Within the Capparaceae, Capparis is paraphyletic. This is not surprising given that more than one-half of the species of this family are placed in two genera, Capparis and Cleome; suggesting that plants with extreme morphological traits have been segregated out. Surprisingly, the genus Forchhammeria (Capparaceae) appears to be either sister to the rest of the Capparaceae and Brassicaceae clade or sister to other families in the Capparales such as Pentadiplandraceae. The chloroplast DNA phylogeny is used to assess floral character evolution within Capparaceae and Brassicaceae. New nomenclatural possibilities of naming Brassicaceae and Capparaceae will be evaluated based on these data.

Key words: Arabidopsis , Brassicaceae, Capparaceae, chloroplast DNA, phylogenetics