Abstract/Summary

Cistanche is a genus of 20-30 species of parasitic flowering plants in the family Orobanchaceae. Species of Cistanche are notable for their uses for medicine, particularly in China, and the genus is regarded as a taxonomically complex one in which species limits are poorly understood. This study reviewed the uses of species of Cistanche across its range, finding evidence of use in medicine and as food outside of China. Future uses and sustainable uses of Cistanche species will depend on a reliable taxonomy, and the remainder of the thesis describes taxonomic and molecular phylogenetic studies. A taxonomic revision for the genus Cistanche in Iraq was made, and it is shown that only one entity is present in Iraq. A justification for using the name C. tubulosa for this entity is presented. The most widely distributed species is Cistanche tubulosa s.l., with this name used from North Africa and the Middle East to India and China. A previously available phylogeny showed that the name is applied to plants that fall into more than one lineage. Which of these should be correctly referred to as C. tubulosa cannot be determined without reference to type material. It is shown that the type specimen of C. tubulosa is lost and so a specimen is identified as a neotype for this species. Molecular phylogenetic studies were carried out to further test species limits for C. tubulosa and its closest relatives. Ninety-six herbarium specimens were selected to represent the geographic distribution and morphological diversity of Cistanche species in the ‘Widespread clade’ that includes C. tubulosa, with emphasis on type specimens, including the candidate neotype identified here. Next generation sequencing used a set of universal Angiosperm baits. Phylogenetic reconstructions showed that species names as currently used do not map to monophyletic groups. The candidate neotype of C. tubulosa is in a strongly supported group with plants from Spain and North Africa, but these plants are not named C. tubulosa. Further molecular and taxonomic studies are needed before a revision of this taxonomically challenging genus can be presented.