Abstract
M.Sc. (Botany)
Thesium is a large genus (ca. 350 species) of hemi-parasites, with a worldwide distribution. The centre of diversity is in South Africa, where approximately 170 species occur. The taxonomy of South African Thesium species was last comprehensively reviewed by Hill in 1925. Since 1925, ca. 38 new species have been described. Currently, no up-to-date key exists, considerable confusion surrounding species concepts remains and a continuum of characters between specimens makes the identification of species almost impossible. Thesium has consequently been identified as a high priority group for taxonomic research in South Africa and is in urgent need of revision. In addition, very little information is available on the ethnobotany of the genus, as well as the molecular relationships of South African species. As a first step towards addressing some of these knowledge gaps 1) a comprehensive taxonomic revision was completed for the T. goetzeanum complex, a group of 17 morphologically similar South African grassland species, 2) a literature review on the ethnobotany of Thesium was completed, 3) the morphology and anatomy of species in the T. goetzeanum complex were examined and previously used diagnostic characters and terminology were re-interpreted to clarify species delimitations, 4) species relationships based on morphology (cladistics analysis) were examined and 5) a preliminary investigation of the molecular relationships of the T. goetzeanum complex was completed using ITS and trnL-trnF gene regions.
In the first ethnobotanical literature review on the genus, which is presented here, Thesium was found to play an important role in local communities throughout Africa and Asia, and as a commercial product in China. Thesium species have numerous medicinal, and...