A multidisciplinary study to assess the ecology of the Cape sea urchin, Parechinus angulosus, and its emerging use as a bioindicator to monitor coastal resiliency
- Authors: Redelinghuys, Suzanne
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435691 , vital:73179 , DOI 10.21504/10962/435692
- Description: The resilience of marine species in the face of unpredictable climate change stands as a paramount concern for the maintenance of ecological stability. Under such fluctuating conditions, it is critical to understand how organisms mitigate these effects in physiological, genetic, and morphological terms. To that end, this thesis focused on the Cape sea urchin, Parechinus angulosus, employing a multidisciplinary approach encompassing morphology, genomics, and gut microbial diversity to assess its potential as a bioindicator species and elucidate its adaptive strategies in response to varying environmental conditions along the South African coastline. This was achieved through studying their anatomy in order to link observed variation to prevailing local environmental conditions, aided by the species’ wide distribution range which allows insight into adaptations across broad geographic regions and ecological settings. The first empirical chapter, Chapter 3, focusing on eight key morphometric traits of test, Aristotle’s lantern and spines, revealed distinct variation in the Cape sea urchin's morphology between the east and west coasts of South Africa, suggesting the presence of some level of local adaptation to the prevailing environmental factors found on the east and west coasts of South Africa. This points to potential bioindicator capabilities of the species, reflecting adaptive divergence amidst contrasting environmental conditions. Further analysis is however necessary in order to isolate specific physiological trends that may be associated with these morphometric differences, thereby enhancing and tightening their ecological implications. The second experimental chapter, Chapter 4, delved into the genetic structure of the Cape urchin by investigating genome-wide diversity, the presence of cryptic population structure, and spatial patterns of genomic diversity. Moderate genomic differentiation was detected among populations along the eastern and western coasts of South Africa by outlier loci that may undergo natural selection, which could indicate local adaptation to environmental conditions. This pattern hints at adaptive differentiation and cryptic genetic structures within the Cape sea urchin populations and emphasises the species' potential adaptive responses to localised (in this case regional) environmental pressures. Assigning functional significance to these genetic variations will require a comprehensive annotated reference genome, a limitation acknowledged in the current study. Chapter 5 explored the gut microbial diversity and revealed significant compositional variations between the east and west coast populations of South Africa, confirming regional and inter-regional variation. This chapter also highlighted the essential biochemical pathways critical to the survival of the host which is crucial for assessing the health of the urchin host. Together, the functional content of the gut bacteria and microbial diversity showcases its potential as a bioindicator for coastal ecosystem health. Logistical challenges and confounding factors like host physiology will need to be fully considered for its effective application. Overall, the findings of this doctoral research suggest that the Cape sea urchin displays promising characteristics as a bioindicator species due to its morphological, genetic, and gut microbial variations in response to environmental differences, providing a diverse array of means in which urchins could be used as bioindicators, from their uses to assess water quality and detect pollution, to ecosystem health monitoring and biodiversity studies in which sea urchin abundance, distribution, and presence are monitored. Further research, integrating these multidisciplinary approaches is recommended to validate and refine its bioindicator potential. Additionally, the development of a comprehensive annotated reference genome is imperative to harness the species' genetic information effectively. This study underscores the significance of integrating multiple disciplines in understanding how species respond to environmental change and their potentials contributions to monitor ecological resilience. The original multidisciplinary approach, combined with high computational outputs presents a promising framework for a comprehensive ecological monitoring in marine ecosystems. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
Developing biological control agents for the management of the invasive tree Robinia pseudoacacia
- Authors: Wolmarans, Abigail
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435717 , vital:73181 , DOI 10.21504/10962/435717
- Description: Robinia pseudoacacia (Fabaceae) is a deciduous tree native to the Appalachian Mountains of North America but has become naturalised and invasive in other countries such as temperate North America, Europe, Australia, and Southern Africa. In South Africa the tree is classified as a category 1B invasive alien under the National Environmental Management Act (NEMBA), which stipulates the species requires some form of control as it has already caused extensive negative ecological and economic impacts. In the invaded range the tree creates monocultures that displace native species and spreads rapidly from suckering roots, making it a proficient invader. The South Africa plant prioritisation system suggests R. pseudoacacia is in the top three species which should be considered for classical weed biological control in South Africa. This thesis investigates which insects known to be associated with tree should be prioritised as candidate agents, as well as offering interesting insights into prioritising insects for weed biological control and using plant phylogenies and available literature to predict insect specificity. To ensure that no candidate biological control agents were already present in South Africa as well as to prioritise which guilds of the tree to prioritise for potential biological control, pre-release surveys were conducted across nine sites where the tree has invaded South Africa. It was found that no insects from the native range of R. pseudoacacia were present in South Africa. Seed surveys revealed that generalist insects attack a sizable proportion (68 %) of the seeds on the trees. In combination with a low seed soil bank (15.8 %) this suggests that seed- feeding agents may be helpful, however, candidate agents which damage leaves should be prioritised due to R. pseudoacacia relying heavily upon vegetative reproduction and much less on sexual reproduction. Leaves may therefor reduce the spread of these invasive trees. The insect assemblages in the native range of R. pseudoacacia are well understood. In addition, several associated insects have unintentionally followed the tree on its global spread, where they are often regarded as pests. The third chapter is therefore aimed at prioritising the known insects associated with the tree in both the native and invaded range. Literature surveys and Harris (1973) prioritisation systems were used to prioritise close to 64 candidate biological control agents down to three foliage- feeding agents, namely Odontota dorsalis (Coleoptera, Chrysomelidae), Macrosaccus robiniella (Lepidoptera, Gracillariidae) and Obolodiplosis robiniae (Diptera, Cecidomyiidae). To further prioritise the six selected agents in Chapter 4, species distribution were modelled with known climatic variables. This was done by using the species known occurrence localities, from both the native and where applicable invaded ranges, to identify which species that would best match with South Africa’s climate. The study showed that O. dorsalis is best suited to survive in South Africa, followed by O. robiniae and then M. robiniella. Collected data aided in the introduction of the prioritised O. robiniae into South African quarantine facilities. Unfortunately, despite several attempts, cultures could not be established, making conventional host specificity testing impossible. Thus, in Chapter 5 we aimed to determine the potential host range of the midge using information from experts in the field of galling insects, literature surveys, agricultural pest lists, and social science platforms coupled with native and invaded range surveys. The list of non-target species to consider as potential hosts was refined by developing phylogenetic trees of closely related Fabaceae that share the same distribution (native and invaded) as R. pseudoacacia. Through the available information gathered, and field surveys of these species, O. robiniae has not been shown to utilise any species, other than those from the Robinoid clade. In addition, the midge has also never been recorded on a number of closely related leguminous fodder and horticultural species growing in close proximity at high densities to R. pseudoacacia - suggesting negligible risk to South African growers of the same species. Host-specificity assessments through field surveys can be regarded as one of the best indicators of the ecological host range, however, this information is difficult to quantify and infrequently available, thus seldom used when determining the safety of a candidate biocontrol agent. In this unique study, using the extensive data collected we are able to show that O. robiniae would be potentially safe for release in South Africa. However, open field tests exposing closely related non-target plant species under natural and semi-natural conditions are planned in Switzerland over the next two years aiming to confirm these conclusions. By identifying and prioritizing potential biological control agents, this research contributes to the development of a targeted and sustainable solution for managing R. pseudoacacia in South Africa. The economic implications of successful biological control include reduced costs associated with invasive species management and ecosystem restoration. Additionally, by mitigating the negative ecological impacts, the agricultural systems in affected regions stand to benefit from enhanced resilience and productivity. Furthermore, the study's approach of using plant phylogenies and available literature to predict insect specificity offers a valuable methodological contribution to the broader field of weed biological control. This methodology can be adapted and applied to other invasive species, providing a framework for efficient and informed decision-making in weed management strategies. In essence, this research not only addresses the specific challenges posed by R. pseudoacacia in South Africa but also provides a template for tackling similar issues in different geographical contexts, thereby contributing to global efforts in sustainable agriculture and environmental conservation. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
Genetic connectivity of the slinger Chrysoblephus puniceus among Marine Protected Areas and unprotected areas along the east coast of South Africa
- Authors: Ockhuis, Samantha Angelique Natasha
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435954 , vital:73215 , DOI 10.21504/10962/435954
- Description: Marine Protected Areas (MPAs) are advocated worldwide for the conservation of biodiversity and fisheries management, as well as for adaptation and resilience in the face of climate change. Their effectiveness has been noted through increases in abundances, biomass, sizes and diversity of species, as well as the recovery of overexploited fisheries. For MPAs to realise their full potential, these benefits need to expand beyond their boundaries through larval dispersal and/or adult spillover. Connectivity between MPAs is critical for planning and placement of MPAs, as this promotes the persistence of metapopulations, their recovery from disturbance, as well as productivity in marine ecosystems. The effectiveness of MPAs in conserving biodiversity along the east coast of South Africa has been established; however, limited evidence is available on whether they offer benefits beyond their boundaries, enhancing biodiversity and fisheries in adjacent areas. The slinger Chrysoblephus puniceus, an endemic southern African sparid, is a major component of the commercial linefishery in KwaZulu-Natal (KZN), South Africa and southern Mozambique, and is also caught in the recreational ski-boat fishery in these regions. The spawning of slinger occurs in shoals on offshore reefs from southern Mozambique to the north of KZN, and larvae are likely transported southwards, assisted by the southward-flowing Agulhas Current and promoted by a relatively long larval duration. Slinger are relatively resident, but occasional northward migrations have been observed. These life history characteristics suggested that slinger would be a suitable biological model to test connectivity along the east coast, and particularly connectivity between MPAs. The aim of this study was therefore to investigate connectivity of slinger between MPAs and the surrounding areas along the east coast of South Africa, using restriction-site-associated DNA (RAD) sequencing. This formed part of the larger CAPTOR project investigating east coast MPA connectivity across a range of taxa and habitat types. A temporal comparison of genetic diversity in slinger spanning two sampling events (2012 and 2018) revealed no substantial changes in genetic diversity, as well as a lack of genetic structure along the KZN coast. Similarly, no substantial changes in effective population size (Ne) were found between 2012 and 2018 for microsatellites and Single Nucleotide Polymorphisms (SNPs). However, subtle, albeit non-significant, differences were observed both spatially and over time in the microsatellite data, indicating some instability along the KZN coast. A lack of genetic structure based on RAD sequencing was observed between east coast MPAs and the surrounding areas. This implies high connectivity along the coast - not only are east coast MPAs connected, the surrounding areas are also connected, and there is replenishment between all areas via larval dispersal and/or adult spillover. Analyses of multidirectional gene flow between MPAs, together with known spatial spawning patterns and prior particle dispersal modelling, identified the Richards Bay area as a key source of recruits. However, parentage analysis – a direct method to estimate connectivity – failed to match any parent-offspring pairs in this study; successful parentage assignments are highly dependent on intensive sampling of potential parents and are seldom feasible in marine systems, as most populations have large effective population sizes. Estimates of intergenerational effective population size for slinger in this study are considered large - >2 000 and infinite based on adults and juveniles, respectively. Population genetics revealed close genetic similarities between slinger adult and juvenile slinger sites, emphasizing genetic connectivity and the lack of structure between sites observed before. This was the first study on South African sparids to use RAD sequencing to assess genetic connectivity between MPAs along the east coast of South Africa. Overall, results provide evidence that MPAs along the east coast of South Africa are connected, and can readily replenish or be replenished by other sites along the east coast of South Africa, whether they are within MPAs or not. So too are the areas surrounding MPAs interconnected, and slinger forms a homogenous single population on the east coast of South Africa. This notwithstanding, it is important that east coast MPAs, particularly those that host spawning shoals of slinger, are well managed in order that they continue to provide recruits to sustain the population and support sustainable fisheries. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
Implications of Lantana camara invasion on rural livelihoods and native woody species in the Kavango Zambezi Transfrontier Conservation Area, Zimbabwe
- Authors: Francis, Buhle
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435896 , vital:73210 , DOI 10.21504/10962/435896
- Description: Lantana (Lantana camara Linn, Verbenaceae) is an invasive alien species found in many disturbed and conservation habitats worldwide. Much work has been conducted on the impacts that L. camara has on ecosystems and communities living in affected areas. In some localities, interventions to eradicate L. camara have been made to reduce the impacts, with follow-up assessments on the benefits of these restoration efforts at some locations. However, L. camara continues to spread globally, and the Zambezi Transfrontier Conservation Area (KAZA TFCA) in Zimbabwe has not been spared. The KAZA TFCA is an important area for biodiversity conservation, ecotourism, and enabling and encouraging regional peace, cooperation and socio-economic advancement. This study was carried out in the KAZA TFCA, covering the Hwange District in Zimbabwe, with the primary aim to ascertain the effects of L. camara on rural livelihoods, native woody species and the soil properties of KAZA TFCA, and whether the policy environment and passive restoration efforts have been effective in controlling it in the area. The study employed a mixed-methods approach using both qualitative and quantitative methodologies to resolve the research problem. Firstly, 102 plots were randomly established in the study areas where native woody species were recorded. In the first section of the Communal area, there were 60 plots in total comprising of 34 invaded and 8 uninvaded. In the other section of the Communal area, 21 plots were sampled, with 7 invaded, 7 control and the other 7 cleared. In the Victoria Falls National Park, 18 plots were established which comprised of 12 invaded and 6 uninvaded. In the Victoria Falls Rainforest area, 21 plots were established which comprised of 7 invaded, 7 cleared and 7 control. The criteria of selecting 102 plots was based on a number of factors which included; Research objectives, Randomisation, Historical data (From locals and Environmental Management Agency), Environmental variables, Spatial distribution if invasion, Accessibility, Budget and Time constraints. A total of 72 soil samples were collected for laboratory analysis of nitrogen, pH, organic carbon, phosphorous and potassium. The 72 soil samples were considered based on available funding for analysis. This soil samples collected samples were representative of the entire study site. In the Communal areas, 300 household questionnaires (representing approximately 12.35% of the total number of 2 430 households) were administered, two focus groups with elderly residents were conducted, and 11 key informant interviews were held. One-way ANOVAs and several multivariate tests were conducted to assess the impact of L. camara invasion on native woody species composition and soil properties. Descriptive statistics were used to conduct a cost-benefit analysis of the presence of L. camara in the study sites. This was coupled with a principal component analysis to assess vulnerability of respondents to invasion, based on variables such as age, gender and level of education. One-way ANOVAs and multivariate analysis were also used to assess if passive restoration contributed to the recovery of native woody vegetation and the improvement of soil properties. In invaded plots, restoration natural recovery occurred after removing the L. camara invasion with no further intervention done after the removal. Document and thematic analyses were conducted to evaluate perceptions and knowledge of policy and legislation pertaining to L. camara management. Lantana camara negatively affected the native woody species, as evidenced by a reduction in species richness, abundance, density, height and canopy cover. Lantana camara also altered soil properties such as texture, chemical composition, colour and porosity, as found by comparing invaded and non-invaded plots in both the Park and Communal areas. Once L. camara invades an area it tends to become dominant at the expense of native species, many of which are a source of livelihood for the local people. Thus, displacement of native species by L. camara potentially increases the vulnerability of local people, some of whom are already experiencing challenges, such as drought and human-wildlife conflict. The invasion of L. camara was found to date back over eight decades ago. Based on focus group discussions with elderly participants, the initial invasion of L. camara in the Ndlovu Communal area was approximated to 1942. This invasion was noted to have begun in ward 2 of Ndlovu Communal area and spread to the other four wards in the study area over 16 years. Despite the challenges of losses and costs induced by the invasion of L. camara, benefits and gains were reported in some areas. For example, in the protected areas, the fruits of L. camara are eaten by birds, while bees use the flowers for honey production. It is noted that L. camara seeds spread through bird droppings become a cost to the environment through further proliferation of the invasion. In some communal areas, households use L. camara for hedges, herbal medicine, cane for furniture, and as an ornament. The relative losses and gains associated with L. camara are context-specific and are dependent on several factors. In this study, the presence of L. camara resulted in negative impacts that included the reduced area of productive land for crops and grazing. Combined, the mean costs borne were US$ 483 household-1 year-1. Furthermore, the combined mean benefits of L. camara, such as use as live fencing around homesteads and fields, mosquito repellent, fruit, fire kindling and ornaments, protection of fowls from raptors, and the prevention of gully erosion along watercourses, were valued at US$ 716 household-1 year-1, thereby exceeding the costs by 48%. However, most (62%) households experienced a net negative cost-benefit ratio. The overall mean value across the sample indicates benefits outweigh costs because a minority of households experience large net benefits. Although L. camara is invasive in the area, communities have taken advantage of its presence to find uses that contribute to their day-to-day lives. Despite the use of L. camara by communities, efforts to remove it have been made in some parts of the Ndlovu Communal area as well as in the Parks (Victoria Falls and Rainforest). The study investigated the impact of passive restoration on native woody species and soil properties. The findings showed a significant improvement in species richness and diversity in cleared plots compared with invaded plots. The species composition differed in the cleared, invaded and uninvaded plots with specific species favouring the different types of “treatments”. This showed the relationship between invasion and associated species. Soil properties had visible differences due to passive restoration, with figures of cleared sites consistently being intermediates of invaded and uninvaded plots. Despite the passive restoration projects, an analysis of knowledge and management showed that most local respondents whose age ranged between 25- 93 years, did not consider L. camara to be invasive but viewed it as part of the vegetation in the area. They also took little responsibility for its management. A further analysis of documents and policies related to the management of invasive alien species found that there were legal instruments in place for the management of invasive alien plants in Zimbabwe, including L. camara. The key informant interviews and the questionnaire surveys showed conflicting views on perceptions and opinions about whose responsibility it was to manage L. camara, with communities saying it is the authority’s responsibility, while some of the authorities suggested that it was everyone’s responsibility. However, some of the key informants highlighted the need to review the policies, guided by empirical studies on of the impacts of L. camara. Currently, it appears the policies are adopted from international bodies as a means of alignment to global policies, but they are not contextualised to suit the dynamics in the country. Overall, the study showed that the presence of L. camara in the KAZA TFCA has notable negative impacts on the native woody vegetation, as well as on local livelihoods, but some households have adapted to using L. camara to benefit them. This, however, has implications for efforts to stop the spread of L. camara if its presence is considered a benefit by some and a cost by others. The efforts to remove L. camara show that the native woody vegetation recovered. The study showed the need to raise awareness of the invasive nature of L. camara because some respondents did not consider it invasive. Findings from this study have implications for the management of L. camara in KAZA TFCA and similar areas, and inferences can be made to assist in the management of other invasive alien plants. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2024
- Full Text:
Plankton and macroinvertebrate dynamics in the Khakhea–Bray transboundary aquifer region
- Authors: Mungenge, Chipo Perseverance
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435674 , vital:73178 , DOI 10.21504/10962/435674
- Description: Temporary wetlands are prevalent in semi–arid and arid climates across the globe and harbour unique faunal assemblages that significantly contribute to regional aquatic biodiversity. This study aims to enhance our understanding of the ecological dynamics of temporary wetland ecosystems, focusing on plankton dynamics, large branchiopod diversity, trophic dynamics, water quality and the impacts of freshwater salinisation in temporary pans in the Khakhea Bray Transboundary aquifer region in the North west Province, South Africa. This body of work represents field, laboratory and writing components which span the period May 2021 to December 2023. The results from this study revealed seasonal patterns in plankton diversity with a winter peak in phytoplankton diversity dominated by Zygnematophyceae species, while Chlorophyceae were dominant in summer. Zooplankton diversity was high in summer as compared to winter, with both Rotifera and Copepoda dominant in both seasons. Six large branchiopod species were found in the region, and three of these were new distribution records for the North west Province, including the first record of Phallocryptus spinosa in the salt pan that was sampled in summer. Large branchiopod diversity was mainly influenced by water temperature and phosphorous in summer, while sediment sodium influenced the diversity in winter. The stable isotope analyses used to determine trophic dynamics in these temporary pans revealed that the food web had four trophic levels, with the top predators being the notonectids Anisops sp. The dominant consumers were predatory insects such as Sigara sp., Anisops sp., Lestes sp., Rhantus sp. and Cybister sp. adults and larvae, as well as detritivorous Tomopterna sp. tadpoles. High trophic niche overlaps were found between the notonectids and the dytiscids. These temporary pans are susceptible to anthropogenic impacts, and disturbed pans were found to have elevated pH, ammonium, phosphates and dissolved oxygen compared to the undisturbed pans. A strong positive relationship was observed between chl–a and temperature, pH, dissolved oxygen, phosphates and ammonium. Chlorophyll–a concentration increased as surface area and the distance from kraals, buildings and latrines decreased. Freshwater salinisation was found to cause notable shifts in abiotic factors and benthic phytoplankton communities, favouring the proliferation of saline–tolerant diatom species at the cost of more sensitive taxa. The study also revealed that in interaction with salinisation, time also exerted a notable influence on shaping the benthic phytoplankton community. Salinity levels of 2.5 ppt and above led to significant decreases in emergent taxa richness and abundance, with Spinicaudata and Ostracoda being the most sensitive taxa to high salinities. There was a limited effect on community hatching phenology dynamics from salinity. This suggests that the main impact of salinisation in these systems will be reductions in hatching success and, hence, reduced recruitment. The study highlights the vulnerability of temporary pan ecosystems to anthropogenic influences and the complexities of interactions of organisms and the environmental conditions in these systems. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
The impacts of bottom-up and top-down drivers in shaping the herbivore community in Pafuri, Kruger National Park, South Africa
- Authors: Walker, Gareth Alexander
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435703 , vital:73180 , DOI 10.21504/10962/435703
- Description: Globally, terrestrial mammal populations are facing critical population declines and range contractions owing to habitat fragmentation and destruction, wildlife overexploitation, and climate change driven by expansion of the human population. Mammalian herbivores are integral for maintaining ecosystem structure and functionality. They do this this through herbivory, by acting as prey and cycling soil nutrients. The impacts of herbivores on ecosystems, however, vary with their spatial occupancy which is influenced by interacting bottom-up and top-down factors. Modelling the drivers of herbivore communities is no trivial task given the myriad of potential bottom-up and top-down factors, and the interactions between the two, as well as the species-specific variations in intrinsic functional traits (e.g., foraging strategy, body size, metabolic rate, etc.) influencing herbivore responses (e.g., social structure, space-use, activity patterns, etc.) to these drivers. Consequently, few studies have attempted to model both bottom-up and top-down drivers in structuring herbivore communities, particularly in an African context where predator-prey guilds include multiple species, exposed to high levels of human activity. Therefore, the overarching aim of my research was to quantify the relative effects of both bottom-up and top-down factors driving the herbivore community in the northern Pafuri region of Kruger National Park, South Africa. I utilized a combination of field (i.e., camera trap and vegetation surveys) and analytical (i.e., stable carbon isotopes from faeces and plants) techniques in conjunction with geospatial data to evaluate the impacts of bottom-up (i.e., forage quantity, quality, and water availability) and top-down (i.e., predation and anthropogenic risks) factors on herbivore spatial occupancy and activity patterns. Herbivore responses to bottom-up and top-down factors were species-specific, even among members of the same feeding guild. Specifically, I found that herbivores (varying in body size and foraging strategy) displayed temporal, spatial and in some instances, dietary shifts that reflect species-specific, ecological trade-offs between resource acquisition, and predator and human avoidance. For example, kudu (Tragelaphus strepsiceros) displayed temporal and spatial avoidance of predators and humans, and exhibited previously undocumented levels of seasonal dietary shifts which suggests that the species traded forage acquisition for reduced predation and anthropogenic risks. Further, high levels of human activity appeared to eclipse the risks associated with natural predators resulting in human induced landscapes of fear. For example, warthogs (Phacochoerus africanus) and zebra (Equus quagga) occupied habitats with higher predation risks, but displayed spatial avoidance of nature reserve boundaries which were synonymous with high levels of bushmeat poaching. Most studies focussing on the impacts of bottom-up and top-down drivers neglect to consider the roles that humans play in structuring ecological communities. The results of my thesis, however, emphasize the importance of including anthropogenic drivers when investigating the roles that various bottom-up and top-down factors play in shaping ecological communities. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
A critical analysis of the factors influencing knowledge sharing in Indian family owned businesses in South Africa
- Authors: Sha, Shafeek
- Date: 2024-04-03
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/434817 , vital:73107 , DOI 10.21504/10962/434817
- Description: It is commonly believed that family businesses have formed the backbone of many economies around the globe and that they have been the predominant form of enterprise that has given rise to some of the most famous multinational enterprises. Family businesses contribute to the wealth creation in most economies and conservative estimates suggest that 65% to 80% of all businesses worldwide are owned and managed by families. In South Africa, Indian family owned businesses contribute more to employment than any other family business. There is a general perception amongst South Africans that Indian family owned businesses are more successful and that this success is continued from one generation to the next. Intrigued by this “phenomenon” for many years, the researcher decided to investigate it. The perspective adopted for this research was to look at the research problem from a knowledge management discipline viewpoint, in general, with a specific focus on knowledge sharing and Indian family owned businesses. The purpose of this study is to critically analyse the factors that influence the effectiveness of knowledge sharing in Indian family owned businesses. So the research answered the question: How do Indian family owned businesses in South Africa share their knowledge to ensure the continued success of their businesses through succeeding generations? A positivist research paradigm and philosophy was adopted for this research together with a quantitative research approach using survey research as the research strategy of choice. After conducting an extensive literature review, the next step was to develop and formulate a theoretical model, and flowing from the model and prior research, a research instrument was developed and administered to a qualifying sample of Indian family owned businesses in South Africa. Structural equation modelling was used as the principal mode of statistical analysis to measure the relationships amongst the variables in the model proposed in this study. After analysing the empirical data, the following key factors were identified as statistically significant in being determinants of knowledge sharing in Indian family owned businesses in South Africa: organisational culture, learning organisation, and leadership. These findings serve to contribute to the existing literature within the fields of knowledge management and family business. This study will richly contribute to research-based evidence of the factors that influence knowledge sharing in Indian family owned businesses. The outcomes will allow existing and emerging family businesses to ensure the future success of their enterprises from one generation to the next by embracing the empirical findings of this research and thus ultimately contribute to the future success of the family business as a whole. , Thesis (PhD) -- Faculty of Commerce, Management, 2024
- Full Text:
Dictionaries as pedagogic tools: a case study of selected schools in Makhanda, Eastern Cape
- Authors: Wababa, Zola Richman
- Date: 2024-04-03
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/434651 , vital:73093 , DOI 10.21504/10962/434656
- Description: The importance of dictionaries in society has been confirmed in relevant literature while their specific role in education is underlined by several studies focused on the use of dictionaries in teaching and learning. This study focuses on mother-tongue or first language (L1) isiXhosa learners and their use of dictionaries across subjects in the Intermediate Phase of primary schooling. The research sought to examine how dictionaries are used in teaching and learning and how they could be used more effectively in the teaching and learning processes, with a focus on isiXhosa L1 learners in the Makhanda area of the Sarah Baartman District of education, Eastern Cape. The general aim of this study was to improve the process and practice of using and producing Language for General Purpose (LGP) and Language for Specific Purpose (LSP) dictionaries across subjects. The study also sought to contribute to improving the functional value and user-friendliness of teaching support materials, such as dictionaries. The Curriculum and Assessment Policy Statement (CAPS) policy document states that dictionaries are essential in teaching and learning of both language and content subjects. In relation to language subjects, the CAPS is explicit about the use of dictionaries in the acquisition of vocabulary, meaning, spelling, pronunciation, and grammar, among other types of information that are integral in language attainment and learning. Nonetheless, the CAPS document does not clearly articulate the use of dictionaries in content subjects. The study draws on two branches of lexicography – namely, dictionary user research and dictionary criticism – to examine the extent to which dictionaries are problem-solving tools which assist users to meet their cognitive and communicative needs. Thus, the study seeks to influence policy and practice of the use of dictionaries as teaching and learning resource materials that could help teachers and learners better understand key concepts across subjects. A mixed-method approach was used to collect both quantitative and qualitative data using a variety of data collection instruments, viz., observation schedules, questionnaires, and interviews. The study found that although teachers were aware of dictionaries, they did not use them as a resource in teaching. Furthermore, teachers lacked skills in the use of dictionaries, therefore, they were not able to effectively integrate dictionaries in their lessons. The research also found that learners had little awareness of dictionaries and did not fully understand their role in language acquisition or content. Lastly, the study offered some insights on how dictionaries could be integrated in teaching and learning, and how their use could address some communicative and cognitive problems faced by non-mother tongue English speakers in a context where English dominates teaching and learning at the expense of learners’ L1. , Thesis (PhD) -- Faculty of Humanities, School of Languages and Literatures, 2024
- Full Text:
Electricity demand and supply in South Africa: is nuclear energy a feasible alternative to coal for baseload energy supply in South Africa?
- Authors: Maqanda, Vuyani
- Date: 2024-04-03
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/434802 , vital:73106 , DOI 10.21504/10962/434802
- Description: Climate change mitigation has created pressure on the energy mix choices of all countries. Highly polluting energy sources are increasingly unpopular. Renewable energy options have emerged as preferred choices for the low-emissions transition. Proponents of nuclear power have promoted the technology as a low-emissions technology by focusing on the operational phase and ignoring the other polluting phases. South Africa generated about 83% of its electricity supply from coal in 2019 and was rated as the 12th most polluting country in the world. In addition to the high pollution levels, the ageing coal fleet suffered from poor maintenance that resulted in frequent power blackouts. One of the government’s energy plans from 2010 proposed the addition of 9 600 MW of nuclear capacity by 2030. However, this plan was not implemented. This study investigates why nuclear power historically never expanded beyond a single power facility in South Africa as well as the possible future role of nuclear power in alleviating South Africa’s current electricity supply constraints and emissions commitments in the period up to 2050. Qualitative analysis is used for this study with a focus on historical document analysis and interviews with energy experts. Two research methods, case studies, and expert opinions were used in this study with data sourced from policy documents, Statistics South Africa, the World Bank, and published articles from various platforms. The Hotelling model, focusing on the impact of price differentials on energy transitions, was used as a theoretical framework. The conclusion from applying the model was that nuclear power was more expensive than the other options even when internalisation of pollution externalities was considered and therefore nuclear power could not displace the cheaper alternatives like coal based on price factors alone. The Multi-Level Perspective, working through institutions, revealed that the institutional setting did not support a transition to nuclear energy. The lack of coordination of strategies derailed the transition. The comparative case study analysis of Germany, the UK, Australia, and India reaffirmed this as countries with better coordination succeeded in transitions. Energy experts offered differing views on the feasibility of nuclear power but many agreed that South Africa should focus on technologies it has better competencies in. , Thesis (PhD) -- Faculty of Commerce, Economics and Economic History, 2024
- Full Text:
An examination of the use and value of support systems for people living with HIV/AIDS in Makhanda
- Authors: Gorham, Catherine Margaret
- Date: 2023-10-13
- Subjects: HIV-positive persons South Africa Makhanda , AIDS (Disease) Patients South Africa Makhanda , Social networks , Diseases Social aspects , Health services accessibility , Narrative
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432411 , vital:72868 , DOI 10.21504/10962/432411
- Description: Through the experiences of five people, this study asks how support systems develop, are used and are valued for those faced with the everyday challenges of living with HIV. Additional evidence is found in accounts from those identified as essential sources of support. These are primarily friends, sometimes family. This perspective is rounded out by insights gathered from those working in local organisations and in the analysis of services offered by the state. The three women and two men at the centre of this study live in Makhanda in the Eastern Cape, South Africa. Makhanda (formerly Grahamstown) is characterised by extremes of poverty and wealth, reflected in low employment, expanding informal and low-income settlement areas but also in a high level of community activism and access to resources. Each of the five tested positive for HIV variously between 1998 and 2008. These years were pivotal in the development of the local and national epidemic. The rapid expansion of infection rates, contestation over forms of and access to treatment, followed by emphasis of a biomedical response, in equal measure bracket and cut across their experiences. To this point, research is less concerned with what individual experiences say about living through the HIV/AIDS epidemic. Preoccupations lie more generally with macro- or micro-level factors, with behaviour change, managing risk and so public health – not the processes linking individual circumstances and choices to opportunities and outcomes described by individual, community and structural, socio-economic contexts. Personal accounts and observations of a developing, community-based, local response to an unfolding epidemic are therefore considered against the analysis of available medical and nonmedical resources. This enables identification and investigation of social processes operating between proximal and distal conditions, determining possibilities for access to support. The focus of this study thus falls to the interrelations of structure, agency and action. It contributes to an empirical and theoretical understanding of what “support” is, what “coping” means and what unfolds where diagnosis with HIV disrupts and challenges existing ways of coping and forms of support. The accounts gathered for this study offer an “insider” perspective, focused on what follows from testing positive to identifying what resources hold significance. Connections between individual, community and society, through psycho-social, local and macro-level processes are explored. Along with the empirical study of individual accounts, the thesis offers a theoretical framework that uses a grounded-theory approach in conjunction with the tools of narrative analysis. These are critically adapted from a sociology of illness studies. Ideas of risk and response, of material and social capital, of the nature of HIV/AIDS as an experience that is inclusive of both chronic, everyday challenge and critical, life-threatening crisis disrupting a sense of time, biography and self, are brought together in the analysis. In this way the understanding of what support means, how it develops and is used (systematically or not), and of the links operating between structural and social conditions, individual agency and action, can be developed. What the thesis finds is that, beyond the medical system of hospitals and clinics, there is surprisingly little use of available resources. There is thus an absence of any systematic support for those faced with the physical, psychological, social and material impacts of HIV/AIDS. Given the nature of personal circumstances, embedded as they are within local conditions that reflect structural constraints of the broader economy and society, this should not be surprising. A system of support exists in only the most limited definition. Against this, what is novel in these findings is the role that psycho-social processes play in negotiating these conditions and how this works, determining what unfolds. A key finding is that it is more through chance than choice that people do find conventional forms of support. The reasons for this have to do not only with limitations to state and institutional capacity, but also with the impact on individuals of perceptions of themselves shaped by the impact of the epidemic and also the past. The result is that under the burden of HIV/AIDS, in the context of extreme inequalities and the absence of an adequate response from the state, already invisible individuals who do not “count” run the risk of becoming doubly invisible. It is through a process of personal adaptation in which shifts in identity and a sense of self are key that they must find their own way. This involves re-conceptualisations of identity, a sense of self and place in the world. The focus on five people and the community in which they live is a limit to the scope of study Yet it is this focus which allows for a new understanding of the social processes involved, and so the links operating between individuals and society. This is of significance beyond the study of HIV/AIDS alone, contributing to the broader sociological project of understanding what it means to “be human”. , Thesis (PhD) -- Faculty of Humanities, Sociology, 2023
- Full Text:
Beyond mastery: jazz, gender and power in postapartheid South Africa
- Authors: Williams, Ulagh
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432505 , vital:72876 , DOI 10.21504/10962/432512
- Description: This dissertation studies the musical lives of seven South African women who have built highprofile national and international careers as jazz musicians. Empirically it records self-reported experiences and actions that they have identified as relevant to their success within a notoriously patriarchal field. Drawing on feminist research methods and Interpretative Phenomenological Analysis the dissertation strives to develop an empathic yet critical epistemological framework attuned to the complexities of their lived experiences as women and as jazz musicians. Theoretically it investigates the power relations at play in the myriad ways they negotiate or have been impelled to negotiate gender and patriarchy as musicians. Chapter one draws attention to the ubiquity of patriarchy in South African and international jazz culture, and highlights the research participants’ numerous successes to date as performers, educators, composers, and bandleaders. Chapter two positions this study in relation to cognate work in South African jazz studies, international feminist jazz studies and feminist phenomenology. Chapters three to five successively consider the participants’ early enculturation as musical and gendered subjects, their agentic responses to structures of patriarchy and/or race as emerging and established professionals, and the ways these experiences have found expression in some of their musical utterances as performers and composers. Fusing art and activism, the participants challenge and transcend masculinist discourses of mastery that still dominate South African jazz as a field of production and aesthetic practice. , Thesis (PhD) -- Faculty of Humanities, Music and Musicology, 2023
- Full Text:
Click consonants in contact: a comparative sociohistorical analysis with special reference to Nama-Afrikaans contact
- Authors: Christie, Camilla Rose
- Date: 2023-10-13
- Subjects: Click consonant , Language contact , Sociohistorical linguistics , Sociolinguistics , Nama language , Khoekhoe , African languages , Linguistic borrowing
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432370 , vital:72865 , DOI 10.21504/10962/432370
- Description: Despite their ubiquity across southern Africa, click consonants are among the world’s most poorly understood speech sounds. Details of their phonological behaviour during language contact remain unclear, in large part because of the under-documentation of contact events of marginalised languages in rural contexts. Working within a sociohistorical linguistic framework with reference to material socioeconomic theories of language contact, this thesis compares and contrasts the diachronic phonological outcomes of various click loan events. The primary event under investigation is the donation of loanwords from an endangered click language, Nama, via substrate interference with the lexicon of a socially dominant clickless language, Afrikaans, in the Namaqualand region of the Northern Cape. The phonological adaptations employed to integrate donated lexical material into a host grammar ought ordinarily to be fairly regular, but the cross-linguistic rarity of click consonants complicates this process. The twenty click consonants expected of Nama undergo phonemic neutralisation when realised in Namaqualand Afrikaans, such that contrast embedded in click ‘type’ and click ‘accompaniment’ is collapsed. Speakers of Namaqualand Afrikaans employ any click type when uttering any click word, and may even use different click types in different tokens of the same lexical item. This unpredictability neutralises contrast. Nonetheless, there is some evidence of a diachronic trend from the unpredictable use of multiple click types and accompaniments toward the stable use of only the linguopulmonic dental click. When these novel data are set against the phonological outcomes of other contact events between a click language and a clickless languages across southern Africa, the normal outcome of click loan under is shown to be the collapse of ‘type’ contrasts. An important outlier is the large ‘type’-contrasting click inventory still shared by isiXhosa and isiZulu long after the extinction of donor click languages in the Khoekhoe branch, suggesting that this contact event must historically have entailed sustained community-wide bilingualism. These comparative observations are used to develop a cross-linguistic typology of click loan events that aims to improve our understanding of the precolonial linguistic landscape of southern Africa. The improved documentation of click consonants in rural language varieties is urgently recommended. , Thesis (PhD) -- Faculty of Humanities, Linguistics and Applied Language Studies, 2023
- Full Text:
Computational studies in human African trypanosomiasis
- Authors: Muronzi, Tendai
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431883 , vital:72812 , DOI 10.21504/10962/431885
- Description: Human African trypanosomiasis (HAT) is a neglected tropical disease (NTD) caused by two subspecies of the parasite, namely Trypanosoma brucei (Tb) gambiense (g-HAT) and rhodesiense (r-HAT). HAT is endemic in sub-Saharan countries, where the parasite transmission vectors, tsetse flies, breed. An estimated 70 million people remain at risk of contracting the disease, where the infection is classified as acute or chronic for g-HAT and r-HAT, respectively, with both forms ending in fatal meningoencephalitis when left untreated. Both g-HAT and r-HAT are responsible for widespread fatal epidemics throughout sub-Saharan African history, resulting from the complex molecular interplay between trypanosomes and humans through unique, innate immunity evasion mechanisms. Of interest, the Tbr subspecies expresses a serum resistance-associated protein (SRA), which binds to human serum lytic factor, apolipoprotein L1 (ApoL1), nullifying any trypanocidal activity. In response, ApoL1 (G1 and G2) variants found in humans of sub-Saharan African lineage have been cited for conferring resistance to the r-HAT infection in an interaction that is not fully elucidated In the event of successful infection, current HAT chemotherapeutics are plagued with complexity of administration, poor efficacy, toxicity, and potential drug resistance, highlighting a need for improved approaches. The parasite folate pathway provides a strategic target for alternative anti-trypanosomal drug development as trypanosomatids are folate auxotrophs, requiring host folate for growth and survival. Validated drug targets pteridine reductase (TbPTR1) and dihydrofolate reductase (TbDHFR) are essential for salvaging cofactors folate and folate biopterin crucial to parasite survival, making them viable targets for anti-folate investigation. The overall aims of this thesis were to a) provide insights into the molecular and dynamic basis of the SRA and ApoL1 interplay in HAT infection and b) identify safer and more efficient anti-folate anti-trypanosomal drug alternatives through in silico approaches. To achieve our first aim, in silico structure prediction was applied to generate 3D models of ApoL1 C-terminal variants G0, G1, G1G/M, G2 and G1G2, and four SRA variants retrieved from the NCBI database. The SRA and ApoL1 structures were inspected dynamically to identify the effect of the variants through molecular dynamics (MD) simulations. Dynamic residue network (DRN) analysis of MD trajectories was fundamental in identifying residues playing a vital role in the intramolecular communication of both proteins in the presence of mutations. Protein-protein docking was then applied to calculate plausible SRA-ApoL1 C-terminal wild-type complex structures to further elucidate the nature of SRA-mediated infection. Through MD simulations, twelve SRA-ApoL1 dimeric structures were narrowed down from five to two energetically sound complexes. The two feasible SRA-ApoL1 complexes (1 and 2) exhibited favourable communication observed through DRN analysis, including the retaining key communication residues identified in prior monomer DRN calculations. ApoL1 C-terminal variants were additionally incorporated into SRA-ApoL1 complexes 1 and 2 for further complex dynamics analysis This investigation into the nature of SRA-ApoL1 binding resulted in five primary outcomes: 1) highlighting the intramolecular effects ApoL1 variants have on the stability of the protein, 2) the identification of crucial SRA and ApoL1 communication residues in both monomeric or dimeric form, 3) the isolation of feasible SRA-ApoL1 complexes determined through global and local structural analyses 4) identification of residues crucial to the complex formation and maintenance of SRA-ApoL1, overlapping with those identified in (1), and 5) the minimal dissociative role of the G1 mutations in the complex, but compounding effect of the G2 deletion mutation. Computational modelling and drug repurposing were employed to achieve the thesis's second aim as they drastically cut down the costs involved in drug discovery and provide a more time-efficient screening method through numerous drug candidates. Using high throughput virtual screening, a subset of 2089 approved DrugBank compounds were screened against TbPTR1. The outputs were filtered to 24 viable compounds in 54 binding poses using binding energy and molecular interactions. Through subsequent MD simulations of 200ns, thirteen potential hit compounds were identified. The resultant hit compounds were subjected to further blind docking against TbDHFR and molecular dynamics to identify compounds with the potential for dual inhibition. The filtered subset was also tested in in vitro single concentration and dose-response bioassays to assess inhibitory properties against Trypanosoma brucei, complementing in silico findings. Post-molecular dynamics, four compounds exhibited high stabilities and molecular interactions with both TbPTR1 and TbDHFR, with two presenting favourable results in the in vitro assays. Three compounds additionally shared common structural moieties. In all, the in silico repurposing highlighted drugs characterised by favourable interactions and stabilities in TbPTR1, thus providing (1) a framework for further studies investigating anti-folate HAT compounds and (2) modulatory scaffolds based on identified moieties that can be used for the design of safe anti-folate trypanosomal drugs. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
- Full Text:
Exploring the drivers of co-occurring multiple non-native fish assemblages within an invaded and flow-modified African river system
- Authors: Mpopetsi, Pule Peter
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431871 , vital:72810 , DOI 10.21504/10962/431871
- Description: Globally, there is growing concern on the negative impacts of species invasions and habitat disturbance because these have been shown to have the potential to disrupt native community structure and function. In some instances, these two stressors can occur in concert, such as in river systems associated with inter-basin water transfer (IBWT) schemes. The Great Fish River in the Eastern Cape, South Africa, is an example of a system affected by both habitat modification and multiple fish invasions largely because of an IBWT scheme. The opening of the Orange-Fish IBWT, which transfers water from the Orange River to the Great Fish River, modified the latter’s natural flow regime from irregular seasonal to perennial. In addition, the IBWT facilitated translocations of five fish species from the Gariep Dam (Orange River system) into the Great Fish River system. Proliferation of these non-native fish species, along with that of other fish species introduced for angling and biological control, raise questions on the mechanisms facilitating their existence within this highly modified river system. This thesis explored mechanisms associated with co-occurrences of these multiple non-native fishes within the Great Fish River. A comparison of historical and contemporary records on the ichthyofauna of the Great Fish River revealed that, of the 11 non-native fishes reported in this system, seven have established successfully, three have failed to establish and the status of one was uncertain. The Orange-Fish IBWT and angling were the main vectors of these invasions, accounting for 36% and 46%, respectively. The study also found that most established non-native fish species were large sized, had high longevity and wide habitat tolerance. Trait-based approaches were employed to investigate the role of functional diversity of non-native and native fishes in relation to their composition, distribution and environmental relationships. Although considerable interspecific variation in body morphology-related functional traits among species were observed, there was no clear distinction in these traits between native and non-native fish assemblages on a trait-ordination space. Furthermore, there were weak species-trait-environment relationships, suggesting that environmental filtering was less plausible in explaining the occurrence patterns of these fishes. Stable isotope-based trophic relationships were evaluated in three invaded sections: the upper (UGFR) mainstem sections of the Great Fish River; and lower (LGFR) mainstem sections of the Great Fish River; and its tributary, the Koonap River. It was observed that native and non-native fish assemblages exhibited variation in isotopic diversity typified by low isotopic diversity overlaps in UGFR and Koonap River, whereas the LGFR was characterised by high isotopic diversity overlap. Within the invaded sections, non-native fishes were found to have isotopic niches characterised by variable isotopic niche sizes and were more isotopically dissimilar with propensity towards trophic differentiation within the UGFR and Koonap River but were mostly characterised by high isotope niche overlaps in the LGFR. Overall, these results provided evidence of trophic niche differentiation as a probable mechanism associated with the co-occurrences of the non-native fishes. However, mechanisms facilitating these co-occurrences within the invaded sections appears to be complex, context-specific and, in some cases, unclear. Lastly, machine learning techniques, boosted (BRT) and multivariate (MRT) regression trees, revealed that the flow-disturbed habitats were invaded by multiple non-native species, whereas the non-disturbed headwaters remained invasion free. In addition, non-native species were predicted to co-occur with native species within the mainstem and large tributary sections of the Great Fish River system. Thus, the IBWT-disturbed mainstem sections were predicted to be more prone to multiple invasions compared to undisturbed headwater tributaries. , Tlhaselo ka mefuta ya diphoofolo-tsa-matswantle (non-native species), ha mmoho le phetolo/tsenyehelo ya bodulo ba diphoofolo-tsa-lehae (native species), di nkuwa ele tse pedi tsa tse kgolo ka ho fetisisa hara ditshoso tse kgahlanong le paballo kapa tshireletso ya diphoofolo-tsa-lehae tse phelang dinokeng kapa metsing. Maemong a mang, dikgatello tsena tse pedi dika etsahala ka nako e le nngwe, jwalo ka dinokeng tseo di amanang le maano a ho fetisa/tsamaisa metsi pakeng tsa dinoka tse fapa-fapaneng (IBWT). Enngwe ya dinoka tse jwalo, ke noka e bitswang ka Great Fish River, e fumanehang Kapa-Botjabela (Eastern Cape) ka hara naha ya Afrika Borwa (South Africa). Noka ena ya Great Fish River e angwa ke tshenyehelo ya bodulo ba ditlhapi-tsa-lehae, ha mmoho le tlhaselo ya tsona ka ditlhapi-tsa-matswantle. Tsena di etsahala hahololo ka lebaka la morero kapa leano la phepelo ya metsi le bitswang Orange-Fish IBWT, leo lona le ileng la fetola phallo ya tlhaho ya metsi a Great Fish River. Ho feta moo, leano lena la phephelo yametsi, Orange-Fish IBWT, le entse hore ho be bonolo ho fetisetswa ha mefuta e mehlano ya ditlhapi-tsa-matswantle ho tloha letamong le bitswang Gariep Dam, hoya kena ka hara noka ya Great Fish River. Ditla morao tsa tsena tsohle, ebile ho ata ha mefuta e mengata ya ditlhapi-tsa-matswantle ka hara noka ya Great Fish River. Ho ata hona ha ditlapi-tsa-matswantle ka hara noka ena ya Great Fish River, ho hlahisa dipotso mabapi le mekgwa e bebofatsang ho phela ha ditlhapi tsena tsa matswantle ka hara noka ena; hore ana ebe diphela jwang ka hara noka ya Great Fish River? Ka hona, sepheo le merero wa thuto ena ke ho phuputsa mekgwa e bebofatsang ho phela ha mefuta ena e fapaneng ya ditlhapi-tsa-matswantle ka hara noka ya Great Fish River. Dipheto tsa diphuputso di hlalosa hore, ha jwale, ka hara noka ena ya Great Fish River, hona le ditlhapi-tsa-matswantle tse leshome le motso o mong (11). Bosupa (7) ba tsona di phela ka katleho, ha tse tharo di hlolehile ho theha (3), mme e le nngwe (1) boemo ba teng ha bo hlake. Hare lekola hore ke efeng mekgwa e amanang le ho ata ha ditlhapi-tsa-matswantle ka hara Great Fish River, re fumana hore leano la phephelo ya metsi la Orange-Fish IBWT ka 36%, ha mmoho le boithapollo ba ho tshwasa ditlhapi (angling) ka 46%, ene ele tsona tsela tsa ho kena ha ditlhapi-tsa-matswantle ka hara Great Fish River, tse ka sehlohong. Re fumantsha hape hore katleho ya ditlhapi-tsa-matswantle e amahangwa le hore di boholo bo bokae, le hore diphela nako e ka kang. Mohlala, ditlhapi tse kgolo tse phelang nako etelele ka tlhaho ya tsona, di amahangwa le katleho ya ho theha ka hara noka ena. Ha tseo tse phelang nako e kgutshwanyane tsona disa amahangwe leho atleha ka hara noka ena. Tse ding tsa dipheto di hlalosa hore, ditlhapi-tsa-lehae le ditlhapi-tsa-matswantle, ka karolelano, hadi fapane haholo ka dibopeho tsa mmele, dihlopa tsena tse pedi diya tshwana. Re fumantsha hape hore dihlopa tsena tse pedi tsa ditlapi dija mefuta e fapaneng ya dijo. Eleng engwe ya dintho tse netefatsang katleho ya ditlhapi-tsa-matswantle ka hara noka ena ya Great fish river. Hona keka lebaka la hore, dihlopa tsena tse pedi hadi bakisane dijo, empa di phela ka mefuta e fapaneng ya dijo. Hare phethela, re fumantsha hore mefuta e fapafapaneng ya ditlhapi-tsa-matswantle e fumaneha feela ka hara madulo a amahangwang le phethoho ya phallo ya metsi (flow alteration), madulo asa amahangwang le phetoho ya phallo ya metsi ona ane a hloka ditlhapi-tsa-matswantle. Sena se bolela hore phetolo ya phallo ya metsi ya Great Fish River, ka lebaka la Orange-Fish IBWT, e fokoditse matla a noka ena ho lwantsha tlhaselo ya ditlhapi-tsa-matswantle. Ka hona, ho bobebe hore ditlhapi-tsa-matswantle di thehe ka katleho ka hara noka ena. Tsena tsohle keka baka la phetolo ya phallo ya metsi a Great Fish River e bakilweng ke leano la phephelo ya metsi la Orange-Fish IBWT. , Thesis (PhD) -- Faculty of Science, Faculty of Science, Ichthyology and Fisheries Science, 2023
- Full Text:
InVisible freedom fighter: a critical analysis of portrayals of women in archival photographs, independence monuments and contemporary art in Zambia (Northern Rhodesia) and Zimbabwe (Southern Rhodesia)
- Authors: Kalichini, Gladys Melina
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432433 , vital:72870 , DOI 10.21504/10962/432433
- Description: This doctoral dissertation in art history develops a notion of invisibility by critically analysing processes in which narratives about women are either concealed or uncovered in visual portrayals relating to the independence of Zambia (former Northern Rhodesia) and Zimbabwe (previously Southern Rhodesia). This study concentrates on three main visual categories that include archival photographs, national monuments, and visual art. It critically engages with concepts of memory and history through a framework of gender. The concept of invisibility developed in this thesis articulates a dynamic process in which independence narratives evolve over time, sometimes revealing memories associated with women and at other times rendering women invisible. National liberation in many African states is dominantly accredited to the political parties that were in power at the time of independence. In Zambia, the United National Independence Party (UNIP) is acknowledged for spearheading efforts to overthrow the colonial administration, while in Zimbabwe it is the Zimbabwe African National Union – Patriotic Front (ZANU – PF). Both political parties were headed by men, and the majority of their memberships was also comprised of men; as such, the dominant narratives largely illuminate the stories of men associated with these political parties. The overarching argument of this doctoral dissertation is that there is a gender bias inherent in dominant independence struggles narratives that are communicated through cultural heritage sites such as monuments and archives. In this study, art and art making inform theory as the methodological approach takes the direction in which selected artworks and visual materials are employed as a starting point of considering concepts that relate to the visibilities of stories about women. This approach cogitates the function of art, visual culture, and art history in the production of knowledges that foster in-depth understandings of concepts that explain social phenomena such as historical erasure. This doctoral dissertation in art history is divided into two parts, A and B, that conceptually complement each other. In section A which comprises of chapters one and two, the study develops an alternative visual archive that surveys the involvements of six specific women in the attainment of national independence in their respective countries, and critically analyses the Freedom Statue in Zambia and the National Heroes Acre in Zimbabwe as monuments dedicated to commemorating the independence struggle in the two countries. In Chapters three to five which form the second section of this dissertation, the emphasis of the discussion is on how selected visual artworks of three selected artists disrupt, counter or engage with dominant historical accounts that either exclude or marginalise narratives about women. The three artists include myself, Gladys Kalichini, and Zimbabwean born artists Kudzanai Chiurai and Gresham Tapiwa Nyaude. This thesis offers a culturally rich conversation about visual representations of social, political and cultural roles women performed in the colonial times in Northern and Southern Rhodesia and gives insight into the evolution of the luminosity of contemporary performances of women’s social collectives in Zambia and Zimbabwe. , Thesis (PhD) -- Faculty of Humanities, Fine Art, 2023
- Full Text:
Jazz pedagogical strategies: an A/R/Tographic investigation into the implementation of the South African jazz CAPS syllabus
- Authors: Rungan, Natalie
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432488 , vital:72875 , DOI 10.21504/10962/432488
- Description: The Jazz stream of the Curriculum and Assessment Policy Statement Further Education and Training music curriculum was introduced in South Africa in 2012 (DBE, 2011a). Despite the intentions of the government to promote diversity, social transformation, and inclusion, subject music is still weighted towards Western Art Music, perpetuating past biases of a Eurocentric model for music education. This study, which uses a mixed-method approach, seeks to create strategies to advance Jazz education in South Africa through an a/r/tographic analysis of the author’s Jazz pedagogical methods at Durban High School in KwaZulu Natal, South Africa. Key approaches include curriculum theory, currere, a/r/tography, among others. After reviewing Jazz pedagogy in the U.S.A. and South Africa as a starting point, using Pinar’s (1994) method of currere, the author demonstrates how past personal music educational processes have led to present Jazz pedagogical methods. Six original compositions were written that outline the influences that infused these methods and added to the creative output related to this research. Interviews were conducted with key stakeholders in the Jazz community to gain perspective about the current state of Jazz education, and with students to provide insight into their reactions to the Jazz stream of CAPS. This presents new information about the curriculum from a learners’ perspective. Ethical clearance for research with children was sought and received (Appendix A). Findings show that the ability of learners to recognise the value in, and identity relating to, their African culture through Jazz points to a pivotal departure from previous Eurocentric music education models. However, despite South Africa being positioned as one of the only countries offering Jazz as a subject choice to high school learners, the selection of Jazz in the subject of Music remains underutilised. This study concludes that for Jazz education to advance in South African high schools, there needs to be intentional engagement with Jazz professionals at the high school level. , Thesis (PhD) -- Faculty of Humanities, Music and Musicology, 2023
- Full Text:
Revisionist narratives: locating six Black artist-teachers onto the map of twentieth-century modern art in Zimbabwe
- Authors: Muvhuti, Tichapera Barnabas
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432444 , vital:72871 , DOI 10.21504/10962/432444
- Description: Job Kekana (1916-1995) was a South African sculptor and teacher who moved to Zimbabwe in 1944, where he founded the Kekana School of Art and Craft in the early 1960s. There were also a few Black Zimbabwean artist-teachers, namely, Sam Songo (1929-1977), Cornelius Manguma (b. 1935), Lazarus Khumalo (1930-2015), Joram Mariga (1927-2000) John Hlatywayo (b. 1928), who were either working with missionaries Canon Edward Paterson (1895-1974) and Father John Groeber (1903-1973) at the Cyrene and Serima workshops respectively and later on at the Mzilikazi Arts and Crafts Centre, or with Frank McEwen (1907- 1994) at the National Gallery school. This thesis examines the relative invisibility of Kekana and the selected Black artist-teachers in the dominant discourse of the history and development of modern art in Zimbabwe. Employing the biographical approach as a methodology, and modernism as an analytical tool and foregrounding African thinkers like Chika Okeke-Agulu Elizabeth Georgis, Emma Wolukau- Wanambwa and Salah Hassan, this research exposes the possible reasons for their exclusion from the canon, which are rooted in a gatekeeping culture shown by actors in the local art scene, including art historians and scholars, as well as cultural workers in institutions like the National Gallery of Zimbabwe who have not sufficiently questioned and possibly shaken the enshrined legacies of Paterson, Groeber and McEwen. Canons mostly tend to tell a story that privileges and excludes others from the art narrative of a nation. With the arrival of Frank McEwen on the scene in the late 1950s the stone sculpture tradition rose to prominence in such a way that it overshadowed other forms of art produced in the two mission schools or workshops at Serima and Cyrene. In the process, Kekana and his students at the Kekana School of Art and Craft were relegated to the peripheries of the canon as they carved in wood and tended to work in a more representational style. While there is literature acknowledging the role of the missionaries in laying the foundation of modern art in Zimbabwe, local artists-cum-teachers working with them are only recognised as a footnote on the nation’s map of modern art. Recognising that canons are always evolving and shifting, and without discrediting the work of the three mentioned expatriates – and to an extent that of Tom Blomefield of the Tengenenge Workshop – this thesis attempts to expand the canon by arguing for the inclusion of the critiqued overlooked six. Citing the efforts of researchers, scholars and curators in multicultural South Africa to bring the previously marginalised generation of Black modernists into the mainstream, this thesis demonstrates that it is possible to spotlight the narratives of the Black artists and teachers who continue to occupy peripheral space in the history of Zimbabwe. This comparative analysis is done bearing in mind the temptation of falling into the trap of glorifying ‘South African exceptionalism’. In analysing the Black artist-teachers’ contributions as a counter-narrative, this research proposes a more heterogeneous modernism and revisionist art history. , Thesis (PhD) -- Faculty of Humanities, Fine Art, 2023
- Full Text:
Status and potential of green infrastructure to support urban resilience in Zomba City, Malawi
- Authors: Likongwe, Patrick Jeremy
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431821 , vital:72806 , DOI 10.21504/10962/431821
- Description: Small and medium towns with less than one million inhabitants are regarded to be the fastest growing urban centres globally, absorbing the bulk of the urban population growth. This urban growth drives the diminishing natural capital within the urban settings, resulting in compromised ecosystem services delivery, thereby rendering urban dwellers and systems less resilient to hazards and shocks. It is known that urban resilience discourse is rooted in robust, empirical assessments of the nature, composition and distribution of urban green infrastructure. Using the concept of green infrastructure, a mechanism for the delivery of ecosystem services that are multi-functional, well connected, and that integrate the grey-green infrastructure while providing room for social inclusion, anchored the research in a small city of Zomba, Malawi, which is a fast-growing city facing natural resource and ecosystem service degradation. The research therefore was set to understand the status of urban green infrastructure in Zomba over space and time as the basis for enhancing urban resilience. This was facilitated by an understanding of the spatial and temporal quantity, quality, diversity and distribution of urban greenspaces and the composition, structure, diversity and distributional differences of urban trees within different urban greenspace classes. Further to this was an investigation on the perceptions of and preferences for urban greenspaces among the different socio-demographic groups and finally the role of residents, institutions and institutional frameworks in building urban resilience through the delivery of ecosystem services. To achieve these objectives, the study used a suite of methods. First was geographical information system and remote sensing to understand the spatial and temporal changes in greenspaces within the city in terms of quantity and distribution. Ecological methods of assessing the tree species composition, diversity, population structure and distribution were also employed. To gauge the perceptions of and preferences for urban greenspaces, a survey was done, targeting users found within the urban greenspaces plus residents that claimed to have patronised the urban greenspaces. Finally, to understand the role of nature and the relevant urban ecosystem services provided towards building urban resilience, remote sensing and key informant interviews were done to enrich the literature searches on a case study of urban community efforts involved in managing Sadzi hill to reverse ecosystem disservices versus Chiperoni hill that was not managed. A general impression of declining urban green infrastructure was verified through the study. The city has indeed lost 14 % tree cover between 1998 and 2018 due to increased housing and creation of agricultural land to support the growing urban population. The city has 168 tree species with 65 % of them being indigenous. Residential areas were dominated by exotic trees, mainly due to the abundance of exotic fruit trees like Mangifera indica. Generally, the city has a good tree diversity score but unequally distributed, with the formal residential areas, where the colonial masters settled, having more trees than the mixed and informal residential areas. Nine urban greenspace types were identified, but there was a low per capita urban greenspace area of 11.6 m2 per person, slightly above the minimum standard set by World Health Organisation. From the preferences for and perceptions of urban greenspaces, patronage to these greenspaces (treated as parks) was highest among the educated youth, a majority being from the high housing density areas where there are no urban parks. Walking to the nearest urban greenspace took more than 10 minutes for 85 % of the respondents. With the available by-laws in support for the governance of greenspaces within the city and the role of residents towards the same, restoration efforts that targeted Sadzi hill yielded positive results through reversing ecosystem disservices that were being experienced by the community members around the hill. The community enjoys several ecosystem services that have also contributed towards building their resilience to climatic and environmental hazards. The results of this study have unveiled several green infrastructure attributes that can contribute towards building urban social ecological resilience like the presence of high proportion of indigenous tree species, healthy urban forest, high proportion of fruit trees, high diversity scores, unparalleled demand for urban greenspaces for cultural and regulatory ecosystem services, the willingness to pay and work towards managing and conserving greenspaces and the social capital available from the urban communities. However, the study also unveiled several green infrastructure related attributes that if not checked will continue to undermine efforts towards building urban resilience. These included the continued drop in tree and greenspace cover, poor governance of the available public greenspaces, unequal distribution of trees and urban greenspaces, poor management of greenspaces, bare river banks, lack of park amenities and a lack of a clear strategy, policy or an urban plan that clearly outlines green infrastructure. Efforts towards addressing these will mean acknowledging the role of green infrastructure in supporting urban social ecological resilience. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2023
- Full Text:
Towards a better understanding of small-scale fishing decisions and their consequences in Northern Mozambique
- Authors: Heckendorn, Katrina Ann
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431797 , vital:72805 , DOI 10.21504/10962/431797
- Description: This study investigates the relationship between the interacting social and ecological systems within the Pemba Bay fishery, in Northern Mozambique, as mediated by fishing decisions. All ecosystems in the world are affected by human behaviours in some way. In many cases, human effects on ecosystems are detrimental to many other species and can cause shifts in the entire system. In fisheries, the connections between human behaviours and ecosystems are obvious, as fishers extract wild populations of marine species. Human behavioural plasticity and sometimes rapid cultural evolution allow human behaviours to change and adapt faster than many other species can respond which often allows fishers to overexploit marine ecosystems. Many fisheries in the world are fully, or over exploited. Managing these fisheries often focuses on changing those highly adaptable human behaviours. Fishers’ motivations for making different fishing decisions as well as attitudes towards the fishery can be used to understand human interactions with ecosystems when the dependence between the two is direct, as well as allowing managers to tailor interventions that account for fishers’ motivations and attitudes. Most fisheries’ management projects assume that behaviours are motivated by profit maximization. This study investigates this assumption by comparing the compatibility of interview responses and fishing behaviours with rational actor theory, which assumes profit maximization is the only goal. Responses are also compared with prospect theory, which emphasizes reliability of outcomes; descriptive norms, which focuses on social interactions; habitual behaviour, which assumes most decision are automatic based on habit; and theory of planned behaviour, which allows attitudes to be shaped by economic or non-economic motivations, as well as peer opinion and incorporates perceived behavioural control in making decisions. These behavioural theories span a variety of potential fisher motivations which could affect fishing decisions. The study then investigates the state of the social and ecological systems which have resulted, at least in part, from those fishing decisions, and makes recommendations on possible interventions to improve the system based on better understanding of fishers’ attitudes and motivations. The study tests the hypothesis that fishers are motivated primarily by profit maximization and, therefore, rational actor theory is most compatible with fishers’ stated motivations for fishing, or alternatively, that one of the other behavioural theories better explains fisher responses. This section used categorized interview responses based on their agreement, or not, with assumed responses if a particular behavioural theory were compatible. The results indicate that four of the five theories are most compatible with responses for at least one fisher, but that the theory of planned behaviour is the most consistent with the data overall, not rational actor theory. Specifically, fishers seem concerned with behavioural control as well as some non-catch related characteristics of the fishery, such as collective action and sustainability. The second hypothesis is that prospect theory is more compatible with current fishing behaviours than rational actor theory. Prospect theory states that people prefer more reliable outcomes, even if slightly less profitable, than outcomes which are more profitable on average, but also more variable. This section used catch data, and changes in relative use of different fishing methods to address this hypothesis. This hypothesis is confirmed for some aspects of fishery data, but not all. Fishers prefer methods which are more reliable and these methods are increasing in relative use. However, neither catch value nor reliability increases fishers’ opinions of their fishing method, but fisher characteristics which increase options do. This again indicates that behavioural control is important in determining fishers’ attitudes towards fishing. The third question addresses the social system within the fishery. It investigates whether fishing in Pemba Bay is a chosen profession or a livelihood of desperation from the poorest individuals. The study hypothesizes that fishers are as well-off as their non-fishing neighbours, and fishers who use more reliable or profitable methods are better off than those using less reliable/profitable methods and, as such, are more committed to fishing as a way of life. This section used fisher interview responses and household surveys to compare subjective and material wellbeing of fishers and non-fishers around Pemba Bay. The first part of the hypothesis is partly supported. Fishers using most methods have material standards of living comparable to non-fishers. However, they report lower subjective well-beings. Most measures of wellbeing are not affected by the reliability or profitability of the fishing method used, which does not support the second part of the hypothesis. Additionally, fishers using more profitable or reliable methods do not indicate more commitment to fishing as a way of life. The fourth and final section investigates the marine ecosystem. Based on conversations with fishers and local researchers, it is assumed that the Pemba fishery is overexploited. As such, the study hypothesizes that marine biomass, individual size of marine species, and functional diversity are lower in Pemba Bay than in other sites around Northern Mozambique, Vamizi Island, Situ Island, and Nuarro, due to high fishing pressure, and that direct removal of species by fishing has a dominant effect. This final section used baited remote underwater videos (BRUVs) to compare species composition and indices of abundance from the different locations. Again, there is support for part of this hypothesis. Marine species biomass and sizes are lower in Pemba Bay than other sites in Northern Mozambique; however, functional diversity is not different. In these data, changes in biomass and size are not correlated with amount of catch, so direct removal by fishing may not be the dominant source of change in the Pemba fishery. Together, these data indicate that the Pemba fishery may be unsustainable based on social and ecological indications. The importance of behavioural control in understanding fishing decisions indicates that any interventions to mitigate problems in the fishery will need to work with fishers to increase empowerment and allow experimentation to find locally relevant solutions to problems. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
- Full Text:
A native weevil and an exotic planthopper: investigating potential biological control agents for nymphaea mexicana zuccarini (nymphaeaceae) and its hybrids in South Africa
- Authors: Reid, Megan Kim
- Date: 2023-03-31
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/422554 , vital:71957 , DOI 10.21504/10962/422554
- Description: Nymphaea mexicana Zuccarini (Nymphaeaceae) is an invasive plant originating from southern USA and Mexico that has become problematic in South Africa, invading several water bodies around the country. Manual removal of this plant is very labour intensive and is not cost efficient or effective for long term control, while the use of herbicides is damaging to the environment and expensive. Consequently, this plant is a desirable candidate for biological control, which takes advantage of enemy release of the target weed and aims to re-establish population suppression induced by host specific natural enemies. Initiating biological control requires that several steps are followed to maximise the success of the programme, and the first few of these, including overseas surveys in the native range of the plant, have already been completed. This thesis aimed to continue biological control research for this species to take further steps at effectively managing the plant. Firstly, pre-release surveys in the invaded range are necessary to: determine what factors (including enemy release) contribute to the invasiveness of the target weed; establish a baseline of information to allow for comparison after biological control agents have been released; and identify any insect herbivores that may already be present in the country. The pre-release surveys conducted in this study revealed useful information about N. mexicana invasions in South Africa and provided evidence that enemy release is applicable to this case. However, these studies determined that a native weevil, Bagous longulus Gyllenhal (Coleoptera: Curculionidae), has expanded its host range to include the exotic N. mexicana at three sites, and may thus have potential for management of the species through augmentative releases. The invasion of N. mexicana in South Africa is further complicated by the presence of several Nymphaea hybrids originating from a complex history of horticultural trade. Although previous research has shown that several hybrid groups are present in South Africa, their parentage is not known. As biological control requires the use of host specific insects adapted to overcome the unique chemical and morphological defences utilised by plant species, hybrids are notoriously difficult to manage because they possess intermediate characters inherited from parent species to which natural enemies may not have adapted. Although biological control of hybrids is challenging, other case studies have demonstrated that it is possible to find suitable agents, but the chances of success are increased if putative parents of the hybrids are known so that they can be surveyed for natural enemies. Further molecular studies including possible parents of the Nymphaea hybrids in South Africa were thus carried out in this thesis to focus future surveying efforts. Two main hybrid groups were identified with genetic similarity to two tested putative Nymphaea parents, and this will allow further investigations of these species to improve the chances of successfully managing these hybrid groups. Some of the tested hybrids showed genetic contributions from multiple groups, some of which were unidentified, so it is necessary to prioritise the most problematic hybrids for biological control. With more insight into the genetic makeup of the Nymphaea hybrids in South Africa, investigations into the host specificity of potential biological control agents can be conducted. The ideal biological control agent should have a broad enough host range to impact and survive on both N. mexicana and its hybrids, but without a host range so broad that it would pose risk to native South African species. Host specificity trials are thus necessary to determine the suitability of potential agents. The identification of B. longulus feeding on N. mexicana during pre-release surveys motivated further investigations to determine the natural distribution, field host range, and host specificity of B. longulus in experimentally controlled conditions. Further surveys were therefore conducted at native Nymphaea sites around South Africa in addition to host specificity trials using the native Nymphaea nouchali Burm. f. (Nymphaeaceae), two populations of N. mexicana, and a cultivated hybrid. Results from the surveys and host specificity tests suggest that B. longulus is widely distributed across South Africa, is specific to Nymphaea with no observed preference between N. mexicana and the native N. nouchali, and does not perform well on Nymphaea hybrids. Hence, B. longulus is promising for use in new association biological control through augmentative releases but is not suitable for management of hybrids. In addition to the potential use of the South African B. longulus, it is necessary to conduct host specificity trials for natural enemies from the native range of N. mexicana that were prioritised in previous studies. Megamelus toddi Beamer (Hemiptera: Delphacidae) is one such species that was imported into quarantined laboratory conditions from Florida, USA. Host specificity trials were conducted using the same test plants as described for the studies on B. longulus, in addition to multigeneration trials to determine how long M. toddi could survive on non-target host plants. As with the B. longulus studies, no statistically significant differences in preference were observed between N. mexicana and N. nouchali, but M. toddi could not complete development on the test hybrid, indicating that this species is also unsuitable for the management of Nymphaea hybrids. Despite suboptimal plant health, M. toddi completed development for three generations on the native N. nouchali. This lack of host specificity deems M. toddi unsafe for release in South Africa but highlights the importance of following predefined steps to develop a biological control programme. The concluding chapter of this thesis discusses the aforementioned findings in a broader context by considering the driving forces of plant invasions in general and specifically for N. mexicana in South Africa. Case studies are also consulted to provide insight into how to proceed with managing Nymphaea hybrids in South Africa, while the factors governing host specificity and host range expansion are also discussed and considered in the context of B. longulus and M. toddi. Finally, after a consideration of the limitations of these studies, recommendations are made to continue the development of biological control for N. mexicana in South Africa. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2023
- Full Text: