Browsing by Author "Wheat, Nicola M"

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    Assessment of the current population status, genetic diversity and phylogenetic affinities of the rare South African moss, Zygodon leptobolax
    (2006) Wheat, Nicola M; Hedderson, Terry A
    The rare moss Zygodon leptobolax is endemic to Table Mountain, where it is found growing on alien Quercus hosts. The present study aims to investigate this species, place it within a phylogenetic framework and answer the key questions I) what is the current status of Z. leptobolax? 2) what level of genetic diversity exists in the remaining populations? and 3) should these populations be afforded conservation status?
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    An ethnobotanical, phytochemical and metabolomics investigstion of plants from the Paulshoek Communal Area, Namaqualand
    (2014) Wheat, Nicola M; Gammon, David W; Hoffman, Timm; Chibale, Kelly
    The aim of this thesis is to investigate medicinal plants from different perspectives in an attempt to arrive at a new, integrated and streamlined method for the discovery of bioactive secondary metabolites of plant origin. This will be done through a focused study of the traditionally used medicinal plants of the Paulshoek region of Namaqualand and a demographic study of the people who use them. Trends in traditional medicinal plant choice will be investigated and methods of traditional knowledge acquisition and transfer will be examined. Additional assessment of bioactivity and trends in bioactivity will be conducted and a variety of physico-chemical and computational techniques will be used to determine the major metabolites present in selected plant species. These different approaches to medicinal plants will be brought together in a single holistic method put forward as a possible way of conducting future studies into discovering active metabolites for potential drug development.
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    Patterns of parasitism and emergence in the gall midge Dasineura Dielsii (Diptera: Cecidomyiidae) : a biological control agent of Acacia cyclops in South Africa
    (2004) Wheat, Nicola M; Richardson, David Mark; Hoffmann, John H
    Acacia cyclops A. Cunn. ex G. Don is an invasive alien plant that invades fynbos and coastal dunes. Several acacia species are grown commercially in South Africa and this has limited biocontrol agents to those that reduce only reproductive capacity. Dasineura dielsii was released in 2002 as a biocontrol agent for A. cyclops. This gall-forming midge destroys inflorescences and prevents seedpods from forming, but allows continued harvesting. Insects overwinter as larvae within their galls. This study examined the levels of parasitism experienced by dormant D. dielsii larvae, as well as the trigger that causes them to break dormancy. Gall clusters were sampled over autumn and early winter, and were dissected to determine occupancy. The effects of temperature and light on dormant larvae were also examined. Observations showed that as the season progressed, more D. dielsii larvae entered dormancy. At the same time, a greater proportion of dormant larvae were parasitized. Parasitism was highest, at 18.5%, at the end of the study period, but this level of parasitism is not enough to reduce the biocontrol power of D. dielsii. A positive relationship between mass of gall clusters and the number of galls they contain was established. Larval dormancy could not be artificially broken by either light or temperature, and it appears that neither factor alone can trigger a break in dormancy.