DNA sequence data reveal polyphyly of Brexioideae (Brexiaceae; Saxifragaceae sensu lato)

Previous molecular phylogenetic analyses have demonstrated that Saxifragace ae sensu late are polyphyletic, with component lineages scattered throughou t the eudicots. As part of our effort to elucidate the relationships of mem bers of Engler and Prantl's Saxifragaceae s. 1., we undertook a molecular s ystematic study of subfamily Brexioideae, which comprises three genera: Bre xia, Ixerba, and Roussea. Not all taxonomic treatments have concurred, howe ver, in placing these genera together. To elucidate relationships among the se three genera as well as their relationships to other angiosperms we cons tructed large data sets of rbcL, 18S rDNA, and rbcL +18S rDNA sequences. Ou r phylogenetic analyses indicate clearly that Brexioideae are polyphyletic. Brexia is part of a celastroid clade that also includes Parnassia, Lepurop etalon, and Celastraceae. Ixerba appears as sister to a large eurosid I cla de; Roussea appears as part of Asterales. Molecular data, therefore, indica te that Brexioideae are a polyphyletic assemblage and component genera shou ld ultimately be incorporated into other groups. Our studies continue to de monstrate the polyphyly not only Saxifragaceae s. 1., but also of its const ituent subfamilies.