A Thesis submitted to the Faculty of Science, University of the Witwatersrand, in
fulfilment of the requirement for the degree of Doctor of Philosophy.
Johannesburg March 2016 / This study aims to provide a comprehensive description of the Flora, biogeography and
diversity of the serpentine outcrops of Barberton Greenstone Belt in Mpumalanga, South
Africa in order to set conservation priorities for these areas. About 30 large and many
smaller serpentine outcrops form part of the Barberton Greenstone Belt and consist of
various combinations of serpentinized minerals. Seven outcrops were selected to be
studied in detail.
A floristic analysis recorded 744 species and subspecies, 319 genera and 94 families.
The flora includes 33 taxa endemic to serpentine soils and six taxa, which are
hyperaccumulators of nickel. The endemic taxa make up 41 % of the endemics of the
Barberton Centre of Endemism. The serpentine flora was found to be different to the
surrounding non-serpentine vegetation in terms of numbers of species per family, the
ratios of dicotyledons to monocotyledons and familial composition. The Asteraceae and
the Anacardiaceae support a higher number of endemics than expected, which suggests
genetic pre-adaptation within these families and specifically within the genera Berkheya,
Helichrysum and Ozoroa. Most of the endemic taxa exhibit long-range dispersal
suggesting gene flow between populations on different outcrops. The endemics
represent a mix of neo-endemics and paleoendemics.
Non-parametric species richness estimators used to predict the species richness of each
site, indicated that five serpentine outcrops have higher species richness than the
surrounding non-serpentine areas. Indices of diversity calculated showed similar patterns
to those of the species richness estimates. The Barberton Greenstone Belt serpentine
outcrops show relatively high plant diversity when compared to some other serpentine
outcrops around the world. Beta diversity calculated for each site was not correlated with
altitude and weakly correlated with the size of outcrops. Species turnover between
outcrops is high and is positively correlated with the geographical distance between
outcrops. Diversity at higher taxonomic levels were calculated, and results suggest that
genera have some potential for facilitating the ranking of outcrops in terms of biological
richness to select sites for conservation planning. Less than 30% of serpentine outcrops
are adequately conserved. Species and genus richness and endemism were used to select
five outcrops that have high conservation priority / MT2016
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/21069 |
| Date | 19 September 2016 |
| Creators | Williamson, Sandra Doris |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (236 pages), application/pdf |
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