Using multiple plastid DNA regions to construct the first phylogenetic tree for Asian genera of Coffeeae (Ixoroideae, Rubiaceae)

Recent molecular phylogenetic studies in Coffeeae have resulted in a broader circumscription of the tribe, the reinstatement of Empogona and the inclusion of Psilanthus in Coffea. Despite these changes, further critical study of some genera of Coffeeae is still required. In this study, the monophyly of the Asian genera of Coffeeae (Diplospora, Discospermum and Xantonnea) was tested utilizing multiple plastid DNA (trnL-F, rpl16, accD-psa1 and petD) markers. A majority-rule consensus tree of the combined plastid DNA revealed novel relationships in Coffeeae. Diplospora is not monophyletic due to the inclusion of the Philippine Tricalysia negrosensis in the Diplospora clade and the placement of Diplospora sessilis and D. sorsogonensis in Octotropideae. Discospermum is not monophyletic due to the position of Xantonnea in the clade for this genus. Consultation of the protologues, type specimens and recent collections revealed that Xantonnea has the typical features of Discospermum. Thus, we here subsume Xantonnea under Discospermum and new combinations for Diplospora and Discospermum are provided.