Phylogeny inferred from morphology and DNA data: characterizing well-supported groups in Vanguerieae (Rubiaceae)

The Vanguerieae is a species-rich tribe of the Rubiaceae with problematic generic circumscriptions. Here we address this issue by presenting a phylogeny in which strongly supported groups are identified. We use DNA sequence data from the nuclear ribosomal internal transcribed spacer (ITS) region, trnT-F sequences from the chloroplast genome, and 30 morphological characters. Over 70 taxa are sampled, representing 23 out of the 27 currently recognized genera. We also present a detailed discussion of the morphological variation present in the tribe, in which we focus on features that are taxonomically informative. We show that there are several strongly supported groups in the tribe, but that these rarely coincide with traditional genera. Canthium, Rytigynia, Tapiphyllum and possibly Pygmaeothamnus are polyphyletic, and Fadogia is paraphyletic. Keetia, Lagynias, and Multidentia are monophyletic with strong support, while the monophyly of Psydrax is weakly supported. Several morphological characters are mapped onto the phylogeny to visualize how these can be used to delimit monophyletic groups. Canthium subgenus Afrocanthium is given generic rank as Afrocanthium and 17 combinations for species in this genus are made. New combinations are also made for Canthium sensu stricto.