Honorary Citation for the Conferment of Doctor of Laws honoris causa - Tandabantu Tennyson August
- Authors: Rhodes University , Martin, Tom
- Date: 2024-14-05
- Subjects: Uncatalogued
- Language: English
- Type: Speeches , Transcripts, speech , text
- Identifier: http://hdl.handle.net/10962/432591 , vital:72885
- Description: Rhodes University Honorary Doctorate Citation (5 April 2024) Tandabantu Tennyson August: 1980s. South Africa. In the Bantustans of the time, like the Transkei, the youth have little reason for hope. They have much reason for despair. Their choices seem limited to the politics of struggle or to crime, an attempt to gain some kind of advantage from the meagre and unacceptable options on offer. In those bleak times, what was needed was visionaries. People who could see beyond the current circumstances to a different future and imagine how best to prepare for it. Not as idealists, but as pragmatists. What would happen once circumstances change, once the struggle had succeeded? Would we be ready for it? What qualities would the youth need to have in order to both benefit from and participate in a new dispensation? One such visionary was Tandabantu Tennyson August, and it is my distinct pleasure to have the opportunity to tell you more about him. Born in 1948, Mr. August matriculated from Healdtown High School, before pursuing higher education at the University of Transkei, where obtained a Bachelor of Arts degree majoring in English and Geography. This was followed by Comparative Curriculum Studies at the University of South Africa, alongside obtaining teaching certificates from Lovedale and Cicira teacher training colleges, with majors in Physical Science, Mathematics, Science, and Mathematics. This solid educational foundation laid the groundwork for his impactful career in education. He taught at Wongalethu High, St Johns College and was deputy principal at Norwood, before taking up his first principalship, at Thanga High School in 1980. From 1984 to 1990 he was principal of Ndamase High School. During his tenure there, the matric pass rate never fell below 90%. From 1991 to 1995 he was principal Isivivane High School during which time the school was promoted from a primary to a high school. Following his distinguished service at schools, he worked at the Eastern Cape Department of Basic Education, first as a deputy chief education specialist (1996 – 2006) and then as chief education specialist (2006-2010). During that time, he played a pivotal role in establishing (in conjunction with Rhodes University) and being the provincial coordinator the Advanced Certificate in Education in English, followed by ACEs in mathematical literacy and life orientation. In 2016 he received a provincial teaching award for excellence. In 2017 he was awarded the Kade Asmal award for excellence in teaching. To this day, he remains an Executive member of the eastern cape Education advisory council. Quite a career. But there’s something I haven’t mentioned. He was also an accomplished rugby player of international standing. While at Lovedale College, he was selected to represent Border and then the South African African Rugby Board, playing England in Gqeberha in 1972, in a team that would later be known as the black springboks. He eventually received his green and gold springbok blazer as just recognition of his achievement. He incorporated his love of sport into his vision for the youth under his care, as part of his overriding mission of educating the whole person. He got everyone involved in sport, if not as a player, then as a supporter. Especially during his time as principal of Ndamase High School, I am led to believe, it was extremely intimidating for opposing teams to play them. Not only at Ndamase home games, but especially at their away games. There would be one bus for the team players, and six buses for the supporters. From 1986 – 1990: he was president of the Transkei schools` sports union (TSSU). But there’s yet another thing I haven’t mentioned. In 1981, just as his career as an educational leader was really taking off, he was involved in a terrible motor vehicle accident. It left him permanently disabled and, for much of his life, a wheelchair user. Rather than stopping him, it simply added another string to his bow, now as an advocate for the disabled. From 2012 – 2022: Chairperson Eastern Cape South African National Association For Special Education (SANASE): this organization cater for the education and wellbeing of learners with disabilities and special needs. In 2023, he was the national deputy president of the same organisation. From 2013 – to date: he is a Board Member on the National Council of & for persons with disabilities (NCPD). I had the pleasure of an extensive conversation with one of Mr August’s former pupils at Ndamase High, Professor Deyi Mbelani, the current director of Rhodes University’s Institute for the Study of Englishes in Africa. He told me many stories about Mr August’s leadership, that I only wish I had time to share with you now. I put it to Professor Mbelani that, having read about Mr August, the word that stood out for me was “dedication.” He agreed that “dedication” was the word, but that I must not leave out another: “vision”. It is Mr August’s status as a visionary that best defines him, he said. Going back over the above, I think he is right. Mr Chancellor I have the honour to request you to confer the degree of Doctor of Laws honoris causa on the Mr Tandabantu Tennyson August. *The above citation draws heavily on documents submitted as part of the honorary doctorate nomination process and others compiled by the Division of Communications and Advancement. - Tom Martin.
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- Date Issued: 2024-14-05
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
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- Date Issued: 2024-04-05
A revised checklist of extant freshwater fishes of the Zambezian Lowveld Ecoregion, with taxonomic revision of the lowveld largescale yellowfish, Labeobarbus marequensis
- Authors: Ntokoane, Tholoana
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435943 , vital:73214
- Description: Access restricted. Expected release in 2025. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
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- Date Issued: 2024-04-05
A social realist account of the way academic managers exercise agency in monitoring students’ academic success in South African higher education
- Authors: Dwayi, Valindawo Valile Medicine
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435863 , vital:73207 , DOI 10.21504/10962/435863
- Description: The roots of this thesis lie in discourses which promote the use of academic monitoring strategies for student success in South African higher education. Although access to higher education widened for black South Africans following the first democratic election, this ‘formal’ access (Morrow, 1993) has not been matched by success with annual cohort studies showing that, regardless of the university at which they are registered, the subjects they are studying and the qualifications they hope to attain, black South Africans fare less well than their white peers. Monitoring performance and referring students on to academic support and development structures thus became a strategy identified as having the potential to address patterns in performance data. The study reports on an attempt to introduce a strategy for Academic Monitoring for Integrated Academic Development at a historically black university in South Africa’s Eastern Cape province. It draws on a metatheoretical framework developed from Bhaskar’s (1978, 1998) critical realism and Archer’s (1995, 1996) social realism to do this. More specifically, it focuses on the way managers at the institution exercised their agency in relation to the strategy and identifies the way social and structural conditions, developed from the time colonial settlers first arrived on the continent, worked to constrain the exercise of this agency. Although the focus of the study was on agency, the study revealed a system of necessary contradictions (Archer, 1995, 1996), a system of conflicting beliefs exacerbated by a lack of resources, that led to the implementation of the strategy not being as successful as intended. The study not only illuminates the conditions at one South African university but also adds to the body of work on management in higher education and to critiques of ‘managerialism’. , Eyona ngxam yale thisisi kukuphendla iindlela zokukhuthaza ukusetyenziswa kwamaqhinga ezemfundo okuqwalasela impumelelo yabafundi kumaziko emfundo ephakamileyo aseMzantsi Afrika. Nangona emva konyulo lokuqala lwedemokhrasi abemi abantsundu baseMzantsi Afrika bethe bavuleleka ukuba bafikelele kwimfundo ephakamileyo, olu fikelelo 'lusesikweni' (Morrow, 1993) khange luhambelane nempumelelo yaba bafundi, nanjengoko uphando olujolise kwimpumelelo yabafundi ngonyaka ngamnye lubonisa ukuba aba bafundi bathi nokuba bafunda kweyiphi iyunivesithi, befunda ziphi iikhosi bekwafundela waphi amakhono, abafundi abantsundu basoloko berhuqeka emva xa bethelekiswa nabo bamhlophe. Ukuqwalaselwa kwenkqubela nokudluliselwa kwabafundi kumacandelo enkxaso nophuhliso kwimiba yemfundo kube liqhinga elithe lachongwa njengelunokukwazi ukujongana neepateni zendlela abaqhuba ngayo abafundi. Olu phando lunika ingxelo malunga nenzame yokuza neqhinga lokuQwalaselwa kwemiba yeMfundo ukwenzela uPhuhliso kwiyunivesithi eyayisakuba yeyabantsundu kwiphondo leMpuma Koloni laseMzantsi Afrika. Luqamele ngesakhelo semethathiyori esakhelwe kwi-critical realism kaBhaskar (1978, 1979) kunye ne-social realism kaArcher (1995, 1996). Eyona nto lugxile kuyo yindlela abalawuli neenkokeli zeli zikomfundo eziwasebenzisa ngayo amagunya azo ngokunxulumene neli qhinga, lukwachonga indlela iimeko zentlalo nezeziko, ezamana ziphuhliswa ukususela oko kwathi kwafika abarhwaphilizi kweli lizwekazi, ezasebenza ngayo ekunqandeni ukusetyenziswa kwala magunya. Nangona ugxiliso lolu phando belusemagunyeni, luthe lwaveza uluhlu lwemiba echaseneyo eyimfuneko (Archer, 1995, 1996), uluhlu lweenkolelo ezingqubanayo ezihlutshezwa kukushokoxeka kwezixhobo, nolukhokelele ekubeni ukufezekiswa kweli qhinga kungabiyiyo le mpumelelo ibilindelekile. Olu phando aluphelelanga nje ekugqamiseni iimeko zale yunivesithi yaseMzantsi Afrika, koko lukongeza kumsebenzi osele wenziwe kwimfundo ephakamileyo lukwaphendla ‘ezolawulo’. , Thesis (PhD) -- Faculty of Education, Centre for Higher Education Research, Teaching and Learning, 2024
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- Date Issued: 2024-04-05
Augmentation of Aphytis melinus DeBach (Hymenoptera: Aphelinidae) for the control of California red scale Aonidiella aurantii Maskell (Hemiptera: Diaspididae) on citrus
- Authors: De Beer, Ernst Friedrich Ludwig
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435638 , vital:73175 , DOI 10.21504/10962/435638
- Description: Aphytis lingnanensis was reared and tested in South Africa in the early 2000s for augmentation against red scale on citrus and was found to be ineffective. Aphytis melinus is now commercially available and it is important that the efficacy of augmentation thereof on red scale is determined locally. Field trials, fitness assessments and molecular identification on A. melinus from two insectaries were done. Field trials was done in seven, five and six pairs of comparable release and control orchards across the Eastern and Western Cape during the seasons of 2019/2020, 2020/2021 and 2021/2022 respectively. Red scale infestation was monitored and a sample of 20 infested fruit from each orchard was randomly collected every four weeks. Aphytis spp. responsible for parasitism were identified and the percentage parasitism recorded. Results of this study of field trials suggest that the augmentation of A. melinus did not significantly increase the level of parasitism above that of the untreated control. Five repetitions with six replicates of flight and longevity tests were performed with wasps from each insectary. Wasps in the longevity test from two insectaries were kept at 23 °C and 65% RH with honey. Flight tests were performed in tubes of 16 by 30 cm, with a light above a clear, sticky ceiling at 23 °C and 65% RH. On average in five replicates, 65%, 33% and 17% A. melinus wasps were alive on day one, five and 10 respectively. The overall sex ratio was 1.58 for females to males, but 1.05, 2.19 and 2.66 for non-flyers, non-crawlers, crawlers, and flyers respectively. In flight tests for both insectaries combined, only 36.97% of wasps could initiate flight in 24 h while 56.96% remained on the tube floor, and 6.05% attempted to crawl upwards. No significant differences in flight performance were recorded between the two insectaries. Wasps from the local insectary lived significantly longer during the longevity tests but were shorter in transit than wasps from the overseas insectary. COI genes were sequenced and compared against Genbank sequences using BLAST. Molecular identifications did not confirm morphological identifications for all species, indicating unexpected genetic complexity. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
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- Date Issued: 2024-04-05
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
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- Date Issued: 2024-04-05
Ecological impacts of photoautotrophic Euendoliths on South African mussel beds
- Authors: Dievart, Alexia Madeleine Angèle
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435650 , vital:73176 , DOI 10.21504/10962/435650
- Description: Aphytis lingnanensis was reared and tested in South Africa in the early 2000s for augmentation against red scale on citrus and was found to be ineffective. Aphytis melinus is now commercially available and it is important that the efficacy of augmentation thereof on red scale is determined locally. Field trials, fitness assessments and molecular identification on A. melinus from two insectaries were done. Field trials was done in seven, five and six pairs of comparable release and control orchards across the Eastern and Western Cape during the seasons of 2019/2020, 2020/2021 and 2021/2022 respectively. Red scale infestation was monitored and a sample of 20 infested fruit from each orchard was randomly collected every four weeks. Aphytis spp. responsible for parasitism were identified and the percentage parasitism recorded. Results of this study of field trials suggest that the augmentation of A. melinus did not significantly increase the level of parasitism above that of the untreated control. Five repetitions with six replicates of flight and longevity tests were performed with wasps from each insectary. Wasps in the longevity test from two insectaries were kept at 23 °C and 65% RH with honey. Flight tests were performed in tubes of 16 by 30 cm, with a light above a clear, sticky ceiling at 23 °C and 65% RH. On average in five replicates, 65%, 33% and 17% A. melinus wasps were alive on day one, five and 10 respectively. The overall sex ratio was 1.58 for females to males, but 1.05, 2.19 and 2.66 for non-flyers, non-crawlers, crawlers, and flyers respectively. In flight tests for both insectaries combined, only 36.97% of wasps could initiate flight in 24 h while 56.96% remained on the tube floor, and 6.05% attempted to crawl upwards. No significant differences in flight performance were recorded between the two insectaries. Wasps from the local insectary lived significantly longer during the longevity tests but were shorter in transit than wasps from the overseas insectary. COI genes were sequenced and compared against Genbank sequences using BLAST. Molecular identifications did not confirm morphological identifications for all species, indicating unexpected genetic complexity. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
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- Date Issued: 2024-04-05
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
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- Date Issued: 2024-04-05
Graphene derivatives and electrocatalysts as composite electrodes for selective detection of catecholamine neurotransmitters
- Authors: Luhana, Charles Benjamin
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435907 , vital:73211 , DOI 10.21504/10962/435907
- Description: In this thesis, we investigated the development of electrochemical sensing electrodes based on graphene derivatives and the electrocatalyst composites of metallophthalocyanines and metal oxides towards the selective and sensitive detection of catecholamine neurotransmitters (NTs). The graphene and its derivatives offer excellent electron conductivity and hence their use as base electrode materials. Metallophthalocyanines are N4-macrocyclic metal organic complexes that have structural modification flexible and 18-π electrons with excellent electrocatalytic properties. They can incorporate transition metal ions at the centre of the macrocycle ring, and this further enhances their electrocatalytic activity. Transition metal oxides are of interest as these also offer excellent redox properties and pH sensitivity. A pH sensitive electrochemical sensor based on aminated graphene quantum dots (AmGQDs) and cobalt tetra carboxyphenoxy phthalocyanine (CoTCPhOPc) covalent conjugates onto the pre-grafted isophthalic acid (IPA) gold electrode was fabricated. It displayed excellent analytical performance towards the detection of dopamine (DA), norepinephrine (NOR) and epinephrine (EP). The electrochemical sensor exhibited good ability to suppress the background current due to ascorbic acid (AA), a major interference in the detection catecholamine NTs. The carboxylic acid functional group of cobalt phthalocyanine induced the pH sensitivity of the thin film and electrostatic repulsion of the negatively charged ascorbate (AA-) anion at physiological pH. In addition, the electrode could screen-off biological molecules in the newborn calf serum as a representative of a real sample. An electrochemically reduced graphene oxide–based cobalt phthalocyanine polymer (polyCoTAPc) composite electrochemical sensor was fabricated on glassy carbon electrode, GCE-ERGO/polyCoTAPc. The GCE-ERGO/polyCoTAPc could detect dopamine and paracetamol simultaneously as co-existing analytes in buffer and synthetic urine samples. We observed, (i) very strong absorption of the materials, (ii) increase in the electrode surface area, (iii) excellent conductivity, and (iv) electrocatalytic activity of the ERGO/polyCoTAPc composite surface. Furthermore, a simple ultrasensitive electrochemical sensor based on nickel hydroxide thin film electrodeposited onto reduced graphene oxide-molybdenum disulfide (RGO/MoS2) composite resulted in the electrochemical sensor that can selectively and simultaneously detect ascorbic acid, dopamine, and uric acid. A distinct peak potential separation was observed with excellent electrocatalytic oxidation currents. The electrochemical sensors developed in this work exhibited high sensitivity, selectivity, stability, and low detection limits suitable for the detection and determination of catecholamine NTs. , Thesis (PhD) -- Faculty of Science, Chemistry, 2024
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- Date Issued: 2024-04-05
Identification of Mycobacterium tuberculosis DnaK substrates – towards inhibiting DnaK as a novel drug target for the treatment of tuberculosis
- Authors: Tonui, Ronald
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435975 , vital:73217
- Description: Access restricted. Expected release in 2026. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2024
- Full Text:
- Date Issued: 2024-04-05
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:
- Date Issued: 2024-04-05
Keychains and preferential fuzzy sets with applications
- Authors: Mahlasela, Zuko
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435933 , vital:73213 , DOI 10.21504/10962/435935
- Description: In this thesis, we study the preferentiality behaviour of choices under uncertainties using keychains, where a keychain is defined as an (n+ 1)-tuple of non-increasing real numbers in the unit interval, I= [0, 1]. We look at the representations of uncertainties or sets defined by vague properties using the idea of keychains, pins and pinned flags. We then apply the ideas of preferential fuzzy sets to voting patterns, economics and decision making. For voting patterns, we simulate mock trials to investigate the behaviours of choices of different individuals, the outcomes of such voting and make specific conclusions about voting strategies. It can be argued that preferentiality in voting can enhance the democratic processes in national elections. This thesis contains various representations of keychains such as binary digits, weight order, lattice and simplex representations. Another useful aspect of keychains and preferential fuzzy sets is to study the outcomes of decision making linking it to the study of keychains and finite fuzzy sets. We envisage that this study will throw light on computational aspects of any countable situations. , Thesis (PhD) -- Faculty of Science, Mathematics, 2024
- Full Text:
- Date Issued: 2024-04-05
Phthalocyanine-based bio-functional conjugates: photodynamic therapy and photoantimicrobial chemotherapeutic efficacy evaluation in-vitro
- Authors: Magadla, Aviwe
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435918 , vital:73212 , DOI 10.21504/10962/435918
- Description: This thesis reports on the syntheses and characterisation of symmetrical and asymmetrical phthalocyanines (Pcs) with different ring substituents derived to form either cationic styryl pyridine, cationic styryl pyridine triphenylphosphonium (TPP+)-based, benzothiazole, cationic pyridyl-dihydrothiazole and other closely related groups. The starting Pc complex of the synthesised Pc derivatives was typically obtained through the cyclotetramerisation of a substituted phthalonitrile. Then, depending on the desired final complex, the desired complexes were synthesised through the Knoevenagel condensation, alkylation reaction, and Schiff base reaction. Furthermore, silica nanoparticles (SiNPs) were also used to encapsulate Pcs. Following aminopropyl triethoxysilane amino (APTES) functionalisation of the surface of the Pc@SiNPs-APTES, biomolecules such as gallic acid, folic acid, and ampicillin were covalently attached to the surface. Additionally, Pc@SiNPs-APTES is protonated with 1,3-propanesultone. The pair of synthesised asymmetric Pcs is attached to ciprofloxacin (CIP) via an amide bond. Different analytical methods were used to characterise the Pcs and their conjugates. The photophysics and photochemistry of the Pcs both by themselves and in their conjugate form when doped with SiNPs. The cationic Pcs were able to produce sufficient singlet oxygen on their own in most cases. This is explained by the Pcs greater solubility in water. Since singlet oxygen is produced from the triplet state, singlet oxygen quantum yield (Δ) values complement triplet quantum yield (T) values. Low Δ values could be attributed to ineffective energy transfer; screening effects may have prevented the excited triplet state of the Pcs from interacting with the ground state molecular oxygen, lowering the Δ values. In other instances, the Pcs' protection by the SiNPs could be credited with extending the triplet lifetime. The direct connection of Pcs with CIP increased the formation of T and Δ in ABSTRACT comparison to Pcs alone. Both in planktonic and biofilm form, the cationic Pcs and conjugates showed enhanced bacterial elimination. The Pcs and conjugates demonstrated significant activity in photodynamic therapy treatment (PDT) experiments at the tested doses. In both PDT and photodynamic antimicrobial chemotherapy (PACT) treatment, the cationic Pcs outperformed the neutral Pc in terms of biological activity. , Thesis (PhD) -- Faculty of Science, Chemistry, 2024
- Full Text:
- Date Issued: 2024-04-05
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:
- Date Issued: 2024-04-05
Review of the systematics and regional diversity of the diploid barbs (Enteromius Cope, 1867) of southern Africa
- Authors: Scheepers, Martinus Johannes
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435966 , vital:73216
- Description: Access restricted. Expected release in 2025. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-04-05
The enemy release hypothesis and beyond: Lagarosiphon major invasion dynamics and management options for New Zealand using native natural enemies from South Africa
- Authors: Baso, Nompumelelo Catherine
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435627 , vital:73174 , DOI 10.21504/10962/435627
- Description: Numerous scientific investigations have demonstrated the destructive impact that exotic species can have on ecosystem services beyond a specific threshold. There are many explanations for why introduced plants are likely to be more successful outside their native range. One such explanation is offered by the Enemy Release Hypothesis (ERH), which states that plants automatically become superior competitors outside of their natural range due to release from top-down stressors (herbivory, parasites, and diseases) that is evident in the absence of their natural enemies. The underlying assumption of the ERH is that natural enemies are important regulators of plant species populations, and that the pressures from these natural enemies are felt more readily by native species compared to alien plants. Consequently, in the absence of such pressures, the ERH assumes that exotic plants can allocate more resources towards growth and reproduction, while effectively maintaining accumulated biomass. Classical biological control has previously been cited as evidence for the enemy release hypothesis. Therefore, the overarching aim and theme of this thesis was to investigate the role of ERH on the invasiveness of Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae) in New Zealand. Firstly, a literature search and a meta-analysis was used to synthesize existing studies in order to test for general applicability of this hypothesis to aquatic plant invasions. Furthermore, an empirical investigation was conducted in order to directly quantify enemy release in L. major populations invaded areas of New Zealand. To achieve this, various plant parameters of this plant, overall macrophyte and invertebrate diversity were measured and compared between sites in the native range in South Africa and the invaded areas in New Zealand. Although the meta-analysis showed variable evidence for this hypothesis depending on various modulating factors such as study type, plant growth form and measured parameters, for L. major, there was strong evidence of enemy release. The biogeographical comparisons showed that L. major exhibited increased fitness in most of the invaded sites, marked by elevated biomass accumulation, significantly higher shoot production, and the displacement of native plant species. The observed fitness advantages were directly correlated to a decrease in herbivory diversity and pressure upon the plant's introduction to New Zealand. Unlike the native populations, which contend with the presence of at least four co-occurring herbivores, including specialist herbivores, the invaded range had a substantially lower herbivore diversity, with only Hygraula nitens Butler (Lepidoptera: Crambidae) syn. Nymphula nitens, significantly damaging L. major. These findings emphasize the importance of understanding invasion ecology and theories such as ERH in order to advance aquatic plant management and also present valuable insights for developing effective strategies to mitigate the impact of invasive alien species on aquatic ecosystems. Specifically, results from the empirical investigation provide evidence in support of the ERH and highlight the suitability of implementing biological control strategies to manage the L. major invasion in New Zealand. Previous studies have shown the suitability of two specialist herbivores, Hydrellia lagarosiphon Deeming (Diptera: Ephydridae), and Polypedilum tuburcinatum Andersen (Diptera: Chironomidae), as potential biological control agents. This control strategy presents a sustainable and ecologically responsible approach, promoting coexistence between exotic plants and native species rather than displacement through competitive exclusion. With the apparent dominance of L. major at various New Zealand localities, the subsequent objective of this thesis was to investigate the competitive interactions between L. major and another invasive Hydrocharitaceae, Egeria densa Planchon, as driven by herbivory. Combinations of two host specific Ephydrid flies, H. lagarosiphon and H. egeriae, were used at eight different factorial combination of planting densities. The analysis of plant parameters and the application of inverse linear models revealed that L. major often exhibits relatively higher fitness, especially in low monoculture treatments when the two insects were isolated. However, multiple inverse linear models revealed that actual competitive outcomes are dependent on factors such as initial plant density and herbivory regime, with competitive interactions generally being mild. Nevertheless, the presence of H. lagarosiphon resulted in facilitation of E. densa growth. Thus, even at lower densities, these insects still had an impact on the observed interactions, further emphasizing suitability as damaging biological control agents. Lastly, focusing on the abiotic component of L. major invasion, Species Distribution Models (SDMs) were employed to map potential suitable habitat for this species, as well as predict the consequences of climate change on this. Correlative and mechanistic modelling was also used to simulate suitable habitat for potential biological control agents, thus addressing the potential for mismatches between host plant distribution and insect suitable range. The Maximum Entropy Species Distribution Modelling (MaxEnt) algorithm revealed that more than 90% of all freshwater ecosystems in New Zealand are susceptible to L. major invasion, with suitability projected to expand further under future climate scenarios. Moreover, correlative modelling using this method suggests limited suitable habitat for both herbivores. However, degree-day modelling, which also takes into account the physiological requirements, showed that H. lagarosiphon has the potential to produce viable populations in several parts of New Zealand. Overall, this thesis explored the intricate web of biotic and abiotic factors influencing the success of L. major outside its native range. The results emphasize the potential impacts of climate change on the invasion potential and management strategies for L. major. The findings also advocate for the implementation of sustainable and ecologically sound management solutions, such as biological control, to manage this species. , Thesis (PhD) -- Faculty of Science, Botany, 2024
- Full Text:
- Date Issued: 2024-04-05
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:
- Date Issued: 2024-04-05
The influence of the physical environment on invertebrate larval transport, settlement and recruitment with insights on early-stage physiological performance
- Authors: Duna, Oliver Olwethu
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435663 , vital:73177 , DOI 10.21504/10962/435663
- Description: Most marine benthic organisms have a biphasic life cycle whereby the larvae are pelagic, and their distribution, transport and settlement are largely controlled by environmental factors. Among these factors, hydrodynamics have key direct effects. Nearshore water hydrodynamics are strongly influenced by wind. This study investigated whether wind indirectly affects the distribution, settlement and recruitment of invertebrate marine larvae. Additionally, larvae are exposed to a more constant, benign environment than they will experience after settlement, and therefore the possible effects of larval thermal history on the physiological plasticity of settled organisms was also estimated for possible long-term insights into population dynamics. Four sites, two on the western and two on the eastern side of Algoa Bay in Gqeberha (formerly known as Port Elizabeth), South Africa, were chosen for larval collection. Sites at opposite ends of the bay were selected as they were towards either side of the dominant wind directions in this region. At each site, two sampling stations were identified at 300 and 900 metres offshore, with station replicates 300 metres apart. Sampling of marine invertebrate larvae was conducted after two days of westerly or easterly winds at either of the two western or eastern sites. The number of hours of unidirectional wind determined the prevalent wind on the two days prior to sampling. Samples were collected with a plankton pump at three depths; surface, mid-depth and bottom. Simultaneously with plankton sampling, water properties (fluorescence, temperature, zonal and meridional flow, salinity and oxygen) were measured. Settlement/recruitment samples of mussels and barnacles were collected at six sites, two at either edge of the bay and two within the center of the bay. Plastic scouring pads and PVC plastic plates covered with safety-walk, placed at least 30 cm from each other, were used to collect settlers/recruits of mussels and barnacles, respectively. The pads and plates were replaced on a monthly basis for 14 months to quantify monthly settlement/recruitment. At four of the six sites used for quantifying settlement/recruitment, settlers and recruits were collected to measure the physiological responses of these two ontogenetic stages (settlers and recruits) to acute temperature variations which they might experience in the intertidal zone. Three temperature loggers were used to record real time temperature variation at each site over the period (one month) in which the artificial collectors were in position. Factorial ANOVA was used to investigate the effects of wind, depth, site, and distance from the shore on the abundance of larvae in the water column, as well as the effects of month and site on settlement/recruitment. Additionally, multiple regression analyses were used to investigate the effects of physical parameters, including upwelling and dissipation of turbulent kinetic energy, on the abundance of both larvae, settlers and recruits. Distance-based linear models and redundancy analyses were also carried out on the abundances of invertebrate larvae. Correlation analyses were performed to investigate the effect of the number of hours of directional wind on settlement. Lastly, correlation analyses between wind and currents were carried out. The results revealed a link between winds and currents, with wind speed directly proportional to surface current speed, which, as expected, decreased with depth. Current direction was, however, not perfectly aligned with wind direction. Larval distribution, settlement and recruitment were largely associated with the nearshore dissipation of turbulent kinetic energy and upwelling. Thus, overall larval, settler and recruit abundances were indirectly affected by wind. Physiologically, there was no significant difference in oxygen consumption between the juvenile ontogenetic stages (settlers and recruits) of mussels. Recruits exposed to average and maximum temperatures, however, consumed more oxygen than those exposed to low temperatures. Wind and wind-mediated currents as well as temperature have been shown to shape the distribution and shore supply of larvae, and this study contributes to the broad knowledge of population dynamics and replenishment, and the tight relation of abiotic factors affecting biological processes on the shore. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-04-05
Wild edible plants in rural home gardens: livelihoods, perceptions, economic value & traditional knowledge
- Authors: Mothupi, Frans Makwena
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435885 , vital:73209 , DOI 10.21504/10962/435885
- Description: The prevalence of hunger and malnutrition has been steadily increasing in the world over the past decades. The rate of food insecurity was further exacerbated by the COVID 19 pandemic which plunged millions more into hunger as a result of a recovering economy and high food prices. These challenges are mostly experienced in Africa and are estimated to worsen in this region already affected by conflict, poor healthcare, and natural disasters such as floods and droughts. The green revolution in the 1960’s elevated agricultural production to play a pivotal role in the provision of food. However, production focused mainly on the cultivation of staple crops such as rice, wheat, and maize. The reliance on these crops has contributed to the lack of micronutrient intake and consumption of non-diverse diets. Wild edible plants (WEPs) which previously formed a significant part of indigenous people’s diet, have been regarded as an important food source crucial for the alleviation of malnutrition and micronutrient deficiencies. Despite their nutritional qualities, they are often ignored, overlooked, and undermined by agricultural programmes and food security interventions. Additionally, WEPs are largely absent in modern diets, they are often surrounded by negative perceptions, they are economically undervalued, and the indigenous knowledge of these species is under threat. As a result, this study regards WEPs as important resources that can significantly contribute to improved livelihood outcomes such as income, food security and good health. Using the Sustainable Livelihoods Framework, this study evaluated the contribution of WEPs to sustaining livelihoods, providing economic value, and examined how WEPs are perceived as well as the relationship between their knowledge and consumption in rural areas. This study was conducted in rural villages that are under the jurisdiction of the Moletjie and Matlala tribal authorities in the Polokwane and Aganang local municipalities, South Africa. Qualitative and quantitative research methods were employed for data collection. A total of 356 participants were interviewed for this study. Firstly, in-depth interviews were conducted with 20 elderly participants (Chapter 2). Semi-structured interviews were conducted with a total of 120 participants stratified by age, gender, and income groups (Chapter 3). A total of 96 household surveys were conducted in selected villages, this was complemented by direct observations and field surveys of the home gardens (Chapter 4). Questionnaires and freelists were administered to a total of 120 participants also stratified by age, gender, and income groups to collect data on indigenous knowledge of WEPs (Chapter 5). Thematic analysis were performed for interview data (Chapter 2) and data were summarised, descriptive statistics, chi square tests (Chapter 3), Kruskal-Wallis tests (Chapter 4), ANOVA tests and correlation tests (Chapter 5) were performed using SPSS software. The findings show that there has been a major nutrition transition characterised by changed meal composition, patterns, and frequency relating to the consumption of WEPs. The changes can be attributed to increasing western influence characterised by rising urbanisation, western lifestyle of church, school, and employment in an income-based economy dependent on retail stores to fulfil their daily dietary needs. Despite this, WEPs are still valuable to rural people, this is indicated by the fact that traditional foods are made optional at some modern and traditional celebrations. Overall, most of perceptions (65.6%) regarding the consumption of WEPs were positive. The overwhelming majority of respondents agreed or strongly agreed that preparations from the local WEPs are relatively more tasty (98.3%), healthy (96.6%), nutritious (86.7%), and better represent the traditional foods (94.1%). Additionally, participants perceived WEPs to have health benefits in that they have medicinal properties to help prevent diseases, are a good source of energy, highly nutritious and they give strength. Despite these benefits and positive perceptions, most participants expressed doubt over the commercial success of WEPs if they were to compete with cultivated crops in the market. As a result, they perceive the future of WEPs to be bleak as 95% of participants believe that their consumption is in decline. This can be largely attributed to deagrarianisation, climate change, and preference of cultivated foods by the youth. The study also showed that a diversity fruits and vegetables are available in rural home gardens, with cultivated fruits grown in abundance and WEPs available in almost all households (98%). WEPs represented 34% of the total estimated economic value of plants available in rural home gardens. Most of the home gardens produce food to supplement household food supply with only a few households engaged in trading. The trading of WEPs was recorded in 9% of the home gardens while 16% sold cultivated fruits and/or vegetables. Challenges such as lack of water and poor rainfall are shocks which affect the availability, richness, and abundance of home garden produce. WEPs are generally well known in rural areas as participants listed an average of 8.4±2.4 species. There was a significant statistical difference between the number of species listed by age group (p = 0.009) with the elderly listing a higher average number of species (9.3±2.6) compared to adults (8.1±2.5) and the youth (7.8±1.7). Vangueria infausta, Sclerocarya caffra, Ximenia caffra, Amaranthus retroflexus L. retroflexus, Citrullus lanatus,and Cleome gynadra where among the top listed species. There was also a significant positive correlation between the number of listed fruits with number of listed vegetables. The study also found a positive correlation between knowledge of WEPs and consumption. Most of the knowledge about WEPs was learned from a family member (89%), own observation (86%), a village elder (75%). This knowledge was mostly acquired from childhood through oral tradition (63%) and through participation (21%), and consumption (12%). , Thesis (PhD) -- Faculty of Science, Environmental Science, 2024
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- Date Issued: 2024-04-05
A battle of values: analysing the changing attitudes towards African refugees in Europe
- Authors: Mannion, Megan Kate
- Date: 2024-04-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/435525 , vital:73165
- Description: Cosmopolitanism is a moral perspective that stresses the importance that every human being is an equal and ultimate unit of moral concern. These principles make cosmopolitanism more concerned for and accommodative towards outsiders to a political community. Against the abstraction and universalism of cosmopolitanism, communitarianism emphasizes the role communities play in shaping our individual identities and sees it as justified that the interests and well-being of community members receive priority over those of outsiders. Both these value systems are present in Europe. The question is about which direction the trend has moved in recent decades. This dissertation examines the changing values that inform attitudes toward African refugees in Europe to get at this issue. Have attitudes towards African refugees shifted in a cosmopolitan or a communitarian direction in recent decades? This dissertation examines newspaper articles from The Guardian between 1990 and 2022 to track changes in value. The analysis of these articles uncovered that communitarian values were the most prevalent and stayed the most prevalent from 1990 to 2022. These findings indicate that communitarian values are higher than cosmopolitan values regarding African refugees within the general European context. These findings add to the growing body of knowledge regarding attitude shifts, and they provide a timeline for value changes that can help predict future values and be used in future comparative studies. , Thesis (MA) -- Faculty of Humanities, Political and International Studies, 2024
- Full Text:
- Date Issued: 2024-04-04