Hekistocarpa (Rubiaceae): a member of an emended tribe Virectarieae

The monospecific genus Hekistocarpa (Rubiaceae) is restricted to the rainfo rest region of Cameroon and Nigeria. Traditionally, it has been placed in t he tribe Hedyotideae, subfamily Rubioideae, from which it differs in the ab sence of raphides. Cladistic analyses of nucleotide sequences from the rbcL gene and the rps16 intron support a group comprised of Hekistocarpa, Tamri daea, and Virectaria (subfamily Ixoroideae s. I.). This clade is the sister group of Sabicea plus Pseudosabicea. Although Sabicea, Pseudosabicea, Tamr idaea and Virectaria have been proposed to belong to a reformed tribe Sabic eeae; it is proposed here that Sabiceeae should be restricted to comprise S abicea and allies, and that Hekistocarpa, Tamridaea, and Virectaria should be referred to an emended tribe Virectarieae. The tribes Virectarieae and S abiceeae are more easily characterized morphologically than a more broadly circumscribed tribe Sabiceeae (including Virectaria, Hekistocarpa, and Tamr idaea). A detailed description is given for Hekistocarpa, including externa l morphology, reproductive anatomy, and pollen morphology.