A revision and phylogenetic analysis of Stapeliopsis (Apocynaceae)

Abstract

A survey of morphological characters is carried out for Stapeliopsis. The information obtained from this is combined with molecular data from the plastid trnL-F DNA region and ITS1 of the nuclear encoded 18S-26S rRNA cistron, to obtain a hypothesis of the evolutionary relationships among the species. It is shown that Stapeliopsis is monophyletic in a combined molecular and morphological analysis. Stapeliopsis is sister to a clade containing Huernia, Orbea and Tromotriche. The species of Stapeliopsis group into two clades. One contains S. khamiesbergensis, S. neronis and S. urniflora, and this is highly supported. The remaining species fall into an unsupported clade in which S. exasperata is sister to the others. The genera Hermanschwartzia Plowes and Neopectinaria Plowes are rejected. It is shown that a synapomorphy for Stapeliopsis is the laterally flattened inner corona-lobes, which touch the anthers only at their bases. Eight species of Stapeliopsis are recognized, with no subgeneric divisions. © 2005 The Linnean Society of London.