SYSTEMATICS AND PHYLOGENY OF THE SATYRIUM-ERECTUM GROUP (ORCHIDACEAE), WITH DESCRIPTIONS OF 2 NEW SPECIES FROM THE KAROO REGION OF SOUTH-AFRICA

Two spectacular new orchid species from the semi-arid Karoo region of South Africa are described here. Both have been confused with Satyrium erectum Sw. in the past, yet have clear diagnostic characters which j ustify their recognition as distinct species. Satyrium pulchrum S. Joh nson & Kurzweil sp. nov., known only from an isolated granite inselber g in Namaqualand, appears to be the sister taxon to S. erectum, wherea s Satyrium pallens S. Johnson & Kurzweil sp. nov., known from several populations along the southern margins of the Karoo, has closer affini ties to Satyrium longicolle Lindl. These four species form a distinct monophyletic group characterized by several synapomorphies. The allopa tric distribution pattern and considerable divergence in floral charac ters of the sister species suggest that speciation involved shifts in the pollination system of geographically isolated populations. (C) 199 8 The Linnean Society of London.