The systematics of Knoxieae (Rubiaceae)-molecular data and their taxonomic consequences

The tribe Knoxieae consists of genera formerly included in (at least) four tribes of the Rubiaceae (the coffee family). Apart from Knoxia itself, which is mainly Indomalesian, the group is from Africa and Madagascar. Most genera are herbaceous or shrubby, but small trees are also present. They generally have fimbriate, colleter-tipped stipules and five-merous flowers with unequal calyx lobes. We present a molecular phylogeny of the group (based on two chloroplast markers, rps16 and trnT-F, and the nuclear ITS) and discuss the morphological support for the resulting groups and the taxonomic consequences of the phylogeny. Two hundred and sixty-one new sequences from 90 species have been obtained. Of the 19 genera of the Knoxieae, all but three (two monotypic and one with two species) are represented. The genera Calanda, Chlorochorion, Neopentanisia, and Paraknoxia are merged with Pentanisia. Pentas is shown to be not monophyletic and is split into the new genera Phyllopentas, Dolichopentas, and Rhodopentas. We also suggest the Pentas subgenera Megapentas and Chamaepentadoides be included in Chamaepentas. The genus Carphalea is also shown to be not monophyletic and for the African members of the genus (section Dirichletia) the name Dirichletia should be used. Placopoda is suggested to be merged with Dirichletia. Triainolepis is enlarged to include Paratriaina and Thyridocalyx. The tribal position of Lathraeocarpa is discussed. Twenty-nine new combinations for species and seven for infraspecific taxa are made. A key to the genera of Knoxieae is provided.