A synoptic revision of the creeping herbaceous African species of Ardisia (Primulaceae or Myrsinaceae) with six new species from Cameroon and Gabon.

Currently 39 species of Ardisia are recognised from continental Africa, of which three (A. sadebeckiana Gilg, A. schlechteri Gilg, and A. ebo Cheek, each endemic to Cameroon and known from a single collection) are herbaceous, with creeping, horizontal, rooting herbaceous stems, the stem apex more or less ascending to up to c. 10 cm tall above the ground (decumbent). These species lack the distinctive plagiotropic (perpendicular and horizontal) aerial reproductive stems seen in most woody Ardisia species of Africa (instead sporadically producing rooting ascending stems from the horizontal stem) and have distichous leaves (not spiralled as in most species in Africa). Accordingly, they are proposed as a separate subgenus Kamardisia. Study of herbarium material revealed that six additional species exist which are described and illustrated in this paper, together with preliminary conservation assessments. These are: A. hansii (South Region, Cameroon and Belinga, Gabon), A. massaha (Belinga, Gabon), A. chaillu, A. minuta, A. waka (all Chaillu Massif, Gabon), A. ngounie (Ogooué-Maritime, Gabon). We provide a key to the identification of the nine herbaceous species, provide preliminary conservation assessments for each, and notes on shared characteristics of the African herbaceous species including the taxonomic value of leaf microcharacters (oil glands and trichomes). We also make a preliminary report on the possibility of bacterial colonisation of marginal leaf pores in some of these herbaceous species. All of the species are range restricted, the most wide-ranging with only three sites. All but one species is threatened, and almost all of those are Critically Endangered (provisional assessments). The two first published species have not been seen for more than 125 years, despite being in easily accessible, well-botanised locations, and are both feared extinct. We discuss actions to attempt to refind these species and safeguard the remainder.