Abstract The Cape horse mackerel (Trachurus trachurus capensis ) has traditionally made an important contribution to the South African fishing industry and is a key component of the Benguela ecosystem. This thesis concerns the assessment and management of the South African horse mackerel resource. It starts with a brief review of the biology of the Cape horse mackerel and the history of the fishery, as well as of the Management Strategy Evaluation approach, which was applied in this work. Ass...
Abstract It is common to think of our universe according to the “block universe” idea, which says that spacetime consists of many “stacked” 3-surfaces varied as a function of some kind of proper time τ . Standard ideas do not distinguish past and future, but Ellis’ “evolving block universe” tries to make a fundamental distinction. One proposal for this proper time is the proper time measured along the timelike Ricci eigenlines, starting from the big bang. The main idea of this ...
The genus, Leucadendron, of the Cape Proteaceae family, is made up of over 70 dioecious species that vary in their degree of sexual dimorphism. Males are generally more highly ramified (branched) with smaller leaves compared to corresponding females. It has been hypothesised that sexual dimorphism in Leucadendrons is linked to serotiny (a fire-adapted reproductive strategy), where highly serotinous females may incur extra resource costs in order to keep their transpiring cones alive betwe...
ABSTRACT Stator limbatus is a generalist seed-feeding beetle (Coleoptera: Bruchidae) whose natural range extends from the southern USA to Latin America. Individuals have recently been collected in the Western Cape province of South Africa in seeds of the invasive alien plant species Acacia mearnsii and A. cyclops. This study conducted a preliminary examination of its oviposition preference, and development on, a number of indigenous and invasive alien Acacia species and the invasive alien Par...
Abstract Widdringtonia cedarbergensis is a critically endangered conifer restricted entirely to the Cederberg Mountain range in the Western Cape of South Africa. This study aimed to assess whether contemporary climate change could be a driver in the recently documented tenfold decline of W. cedarbergensis in the last 40 years. By building distribution models using Maxent bioclimatic modelling for pre- and post- 1970’s point occurrence data, the distribution of the species pre- and post-1970...
Abstract The need to come up with new and novel antibiotics that utilize unique mechanisms, to which bacteria cannot generate resistance, was the main motivation of this study. Tyrocidine peptides are non-selective antibiotics that have such properties. However, very limited information is available about their mechanism of action. The aim of this study was to determine the mechanism of action of tyrocidine peptides, tyrocidine A, tyrocidine B and tyrocidine C. Chapter 3 explored the structur...
ABSTRACT Ehrharta calycina J. E. Sm. (Poaceae) is a widespread and often abundant species whose core distribution lies within the Greater Cape Floristic Region (GCFR). Importantly, it shows a high degree of morphological and ploidy level variation. Based on observations of distinct forms co-occurring at multiple sites, the hypothesis that E. calycina comprises more than one species was tested. Morphological analysis of herbarium specimens using a multivariate approach found strong evidence fo...
Abstract This study investigates the diet of breeding Black Sparrowhawks (Accipiter melanoleucus) on the Cape Peninsula of South Africa. Macro-remains of prey were collected from below and around the vicinity of nests throughout the breeding seasons of 2012 and 2013. These prey items were then identified down to species where possible through the use of a museum reference collection. In both years 85.9% of the individual remains were those of Columbidae, which corresponds with the only other ...
Abstract Interest in commercial sea urchin aquaculture is growing worldwide. This is because sea urchins have good quality roe which is a delicacy in many countries. Since the quality of sea urchin roe is dependent on what the sea urchin eats, increased research is being carried out to understand sea urchin feeding preferences. Feeding preference is related to the attractiveness/palatability of the feed, which is thought to be based on its chemical composition. Since an unpalatable feed will ...
Abstract Phytoplankton community composition in the Southern Ocean (SO) determines levels of primary production, which support marine ecosystems and export of material to the deep sea. Nanoplankton (cell diameters 2-20 µm) are poorly resolved by traditional microscopy, and it is becoming apparent that unknown diversity and ecosystem functionality may be contained in this size class: for example, small diatoms (
Table of Content Acknowledgment Short Abstract General Abstract Chapter 1: Introduction Chapter 2: Stable isotope turnover in blood and toenails: A case study in captive African penguins Chapter 3: Insights from stable isotope into African penguins foraging behaviour during the pre-moult period Chapter 4: Temporal and spatial variation of Cape Gannet diets: lessons from stable isotopes Chapter 5: The pattern and location of moult in White-chinned Petrels Chapter 6: White-chinned Petrel...
Abstract Within the Cape Floristic Region many lineages are characterised by large floral diversity. The genus Erica is one of these lineages, making up -7% of the CFR. Surprisingly, even though pollinators have been suggested to be a driving force of floral morphology, the role of pollinators in the floral diversification and speciation of this genus is not yet well understood. Therefore the aim of this paper was to establish if Erica species can and do self-pollinate. Two Erica ...
ABSTRACT The yeast Saccharomyces cerevisiae is used extensively in many important industrial applications that often expose these organisms to a range of stresses. Consequently, a considerable amount research has focused on understanding the nature of stress response in yeast and the development of more stress resistant yeast. The stress protein Hsp12 has since garnered interest, as it is upregulated in response to a wide variety of environmental stresses. Using an Hsp12-GFP construct, we con...
Abstract The disturbance ecology and regeneration patterns of the emergent conifer, Widdringtonia whytei, and five broadleaved species, Aphloia theiformis, Rapanea melanophloeos, Maesa lanceolata, Maytenus accuminata and Psychotria mahonii, were inferred from population size structures in the mixed conifer-broadleaved forests of Mt. Mulanje, Malawi. The size-class structures of the emergent cedar populations were characterised by even-sized, disjunct frequency distributions. Seedling recruitm...
ABSTRACT Over the years, natural products have played a major role in the search for novel drugs or drug candidates. Secondary metabolites from nature especially those of fungal origin exhibit unique biological activities and research continue to meet the keen interests which have potential pharmaceutical value. Fungi constitute an important source of secondary metabolites such as penicillin. The present study analyzed the biological activities of a variety of compound mixtures from wood deca...