The monospecific genus
Hekistocarpa (Rubiaceae) is restricted to the rainforest region of Cameroon and Nigeria. Traditionally, it has been placed in the tribe
Hedyotideae, subfamily Rubioideae, from which it differs in the absence of raphides. Cladistic analyses of nucleotide sequences
from the
rbcL gene and the
rps16 intron support a group comprised of
Hekistocarpa,
Tamridaea, and
Virectaria (subfamily Ixoroideae s. l.). This clade is the sister group of
Sabicea plus
Pseudosabicea. Although
Sabicea,
Pseudosabicea,
Tamridaea and
Virectaria have been proposed to belong to a reformed tribe Sabiceeae; it is proposed here that Sabiceeae should be restricted to comprise
Sabicea and allies, and that
Hekistocarpa,
Tamridaea, and
Virectaria should be referred to an emended tribe Virectarieae. The tribes Virectarieae and Sabiceeae are more easily characterized morphologically
than a more broadly circumscribed tribe Sabiceeae (including
Virectaria,
Hekistocarpa, and
Tamridaea). A detailed description is given for
Hekistocarpa, including external morphology, reproductive anatomy, and pollen morphology.
Key words: Hekistocarpa, Virectarieae, Ixoroideae s. l., Rubiaceae, rbcL, rps16 intron, pollen morphology, seed anatomy.
Received January 25, 2001 Accepted June 20, 2001