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The enemy release hypothesis and beyond: Lagarosiphon major invasion dynamics and management options for New Zealand using native natural enemies from South Africa
Get PDFNumerous 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, 202
The Economic Freedom Fighters and Politics of Populism: Enhancing Political Participation, or a Threat to Democracy?
No full textThis study presents a novel approach to understanding the economic freedom fighters (EFF) role in South African politics. The party has been called populist, fascist, and a threat to South Africa's democracy. This study was conducted through virtual ethnography research on the role of the EFF in South Africa's politics and presents the research findings here to understand if the EFF is merely populist, a threat to democracy, or encouraging citizens' political participation. The study's findings indicate that the EFF uses populist stances to attract supporters and voters to the party. But unlike the views of some commentators and scholars, the study presents different findings regarding the EFF's populist attitudes in the country's democracy. While some see such populist stances as a threat to democracy, the study views it as the party's advantage, among others, to encourage citizen political participation
South Africa-Africa trade: Continental Free Trade Area
Get PDFSouth Africa-Africa trade was examined for 2001-2021 and results show that Africa is an important market for South Africa's manufactured products and there is ease of market access for these products; its trade with Africa is highly complementary; and it has strong trade linkages with Africa's regional groups. Current South Africa-Africa trade is a foundation South Africa could utilise to consolidate, broaden and strengthen its role in intra-Africa trade with the AfCFTA in place as more complementary trade opportunities emerge; markets open more and current trade linkages with regional groups strengthen as trade barriers are reduced further; and regional value chains and production clusters initiatives emerge as market access improves with new and dynamic comparative advantages emerging
Experiences of Rural Secondary School Teachers in the Integration of Technology during Emergency Remote Teaching during the COVID-19 Pandemic in Namibia: An Exploratory Study’
Get PDFThis study explored the experiences of rural secondary school teachers in Namibia during emergency remote teaching (ERT) owing to the COVID-19 pandemic. The TPACK framework and sociocultural theory were used. Semi-structured interviews and focus group discussions with 26 rural teachers revealed that despite the availability of technological tools such as laptops, smartphones, and radio and television channels, integrating these into the teaching process posed significant challenges. A lack of technological knowledge among teachers coupled with infrastructure issues and inadequate institutional support hampered the smooth execution of ERT. Despite these challenges, teachers employed innovative methods to engage their students remotely. However, the findings underline the need for increased digital literacy, better ICT resource allocation, and adequate teacher training to successfully navigate a technology-driven teaching environment. This study provides insights into educational practice, policy initiatives, and future research toward a resilient and technology-enhanced educational system
Interrelated transformative process dynamics in the face of resource nexus challenges an invitation towards cross case analysis
Get PDFThe need for more attention to the social and human dimensions in global change sciences and natural resources management requires in-depth understandings of transformative approaches and processes. More inclusive and systemic approaches are needed that embrace complexity and support transformative learning, shifts in power relations, collective and relational agency and structural transformations for adaptive and innovative governance. Scientific understanding of how such change can be brought about is still limited. In this paper, which sets the scene for this Special Issue, we develop a conceptual framework for analyzing transformative processes across a range of diverse cases. Aspects of the conceptual framework are applied, tested and elaborated in three following papers in the Special Issue, deepening understanding of how transformative change in complex social-ecological systems may originate at nexus boundary zones such as that portrayed by the water-food-energy nexus. Specifically, the paper conceptually elaborates four iteratively related dynamics of transformative learning, transforming power relations, transformative agency and transforming structures which intersect in transformation processes. The perspectives offer tools for cross case analysis in the longer term, but also tools for supporting co-engaged, generative research processes
The feasibility of task-shifting prolonged exposure for Primary Care (PE-PC) for PTSD within a low resource community in the Eastern Cape
Get PDFAlthough high levels of trauma exposure potentiate an alarming prevalence of PTSD, increasing the need for trauma-focused treatment, the South African health system is unable to care for the population. The South African healthcare system contains a range of systemic and structural inefficiencies, including suboptimal care and shortages of healthcare professionals. PE-PC offers a resource-constrained mental healthcare system solution by integrating an evidence-based intervention (EBI) in primary care settings. Likewise, the present study acknowledges the ratio of mental healthcare professionals to patients in low- and middle-income countries (LMIC). It explores task shifting to expand mental healthcare to primary care settings. The study follows qualitative healthcare design research to explore the experiences and perceptions of the two cohorts of trauma support workers (TSW) from Rhode University and the Joza community in Makhanda. The feasibility of the PE-PC intervention in Makhanda was illustrated through the data obtained from the TSWs' experiences and perceptions of the intervention's utility. The present study presents an essential contribution to the sparse research conducted on treating PTSD in LMIC with shortages in healthcare professionals. The thematic findings look at the trauma support workers (TSWs) role, including some of its challenges, to explore the feasibility of interventions. Some of the themes highlighted unpack the perceived utility of task-shifting in low-resource contexts, the limitations thereof and considerations for future research. Notwithstanding the challenges, the data from the present study indicates that PE-PC can be feasibly task-shifted in low-resource contexts such as Makhanda.Thesis (MA) -- Faculty of Humanities, Psychology, 202
To yoga or not to yoga? The effect of yoga on sustained attention: an fNIRS Study
Get PDFDeficits in sustained attention are ubiquitous across numerous neuropsychological disorders. Besides being critical in learning, memory, and general cognitive capacity, sustained attention is thought to be the primary foundation for ‘higher’ cognitive functions including, divided, selective, and focused attention. Despite the above, sustained attention remains the lesser-researched form of attention. Sustained attention is thought to be regulated by the default mode network and the central executive network, the latter of which is situated in the dorsolateral prefrontal cortex (DLPFC), a brain region typically associated with sustained attention. Given the contributions of sustained attention in overall cognitive functioning, alternative and natural methods used to enhance this type of executive function are important. One alternative method is yoga exercise, where yoga is thought to place the body into the most favourable state to enhance sustained attention capacity. This study found a significant (p = 0.018) difference between the yoga and control group in incongruent response accuracy scores in the SCWT. However, no statistically significant differences (p < 0.05) were observed in fNIRS individual and group analyses, SCWT congruent and incongruent reaction time, as well as congruent response accuracy. This suggests that short-term yoga practice may improve behavioural markers for sustained attention, at least in terms of cognitive interference.Thesis (MA) -- Faculty of Humanities, Psychology, 202
Insights: elucidation of squalene monooxygenase inhibitors for lowering cholesterol in cardiovascular diseases
Get PDFStatins have been used to lower high cholesterol levels in the past few decades. However, several studies have shown that some people taking statins experience side effects over time, especially elderly patients, women of childbirth possibility, and children. Several studies have shown that the majority of people with underlying cardiovascular complications caused by high cholesterol are at a greater risk of fatality due to COVID-19, regardless of age and sex. The literature suggests that antimycotic squalene monooxygenase inhibitors, terbinafine and its derivatives, and anticholesterolemic squalene monooxygenase (SM) inhibitors could be another option and a safer remedy for lowering cholesterol in mammals. Molecular docking calculations, molecular dynamics (MD) simulations, molecular mechanics generalized born surface area (MM-GBSA) calculations, quantum mechanics/molecular mechanics calculations (QM/MM), and density functional theory (DFT) calculations were used in this study. An early stage in drug discovery, in which small molecular hits from high- throughput screening (HTS) are evaluated and undergo limited optimization to identify promising lead compounds, is referred to as lead generation. To address the first step of lead generation, the number of compounds to be tested was narrowed down, and the hit compounds that could be taken for further tests were obtained. Thus, the molecular docking technique was taken advantage of, which assisted us in identifying the antimycotic ligand SDZ 18, which had a good binding affinity of about -8,4 kcal mol−1. Another widely employed strategy, the molecular mechanics-generalized born surface area (MM-GBSA), was used to investigate the binding free energies of the protein-ligand complexes to validate the binding affinities obtained from molecular docking. Despite the excellent docking results, it must be emphasized that the stability of the ligand in the binding pocket must be investigated. To address this, the protein-ligand complexes were then taken through molecular dynamics for 100 ns simulations calculations which showed that the inhibitors stayed in the binding pocket with the RMSD values below 3.5 Å for most systems. This provided insight into a realistic model because the docked complexes were placed in conditions closer to the physiological environment at 300 K and 1.01325 bar, and in an explicitly solvated dynamic environment. Density functional theory (DFT) at the B3LPY level of theory using the standard 6-31G(d,p) basis set was used to assess the reactivity and other properties of the SM inhibitors. ONIOM calculations were performed to explain what was happening at the microscopic level by calculating the total energy of the complex. The aim of this project was to efficiently uncover the non-physical aspects of SM inhibitors with the help of computational techniques to identify new drugs that can lower high cholesterol levels. From a theoretical perspective, the results obtained from docking indicated that the antimycotic ligands SDZ SBA 586 18 and TNSA 84 (trisnor-squalene alcohol ) have good binding affinities, and the MM-GBSA method provided free energy calculations. MD results indicated that the stability of the ligand in the binding pocket was achieved during the 100 ns simulations. The HOMO-LUMO energy gaps obtained from DFT calculations provided information on the reactivity of the ligands. Other insights into the protein-ligand complexes were obtained from a hybrid ONIOM QM/MM study.Thesis (MSc) -- Faculty of Science, Chemistry, 202
Yield curve and business cycle dynamics in South Africa: new evidence from a Markov switching model
Get PDFGlobally, several empirical studies have demonstrated the ability of the yield spread to predict a recession in a country. In South Africa, previous studies have not only shown the yield curve's predictive power but have further demonstrated that it outperforms other commonly used variables, such as the growth rate of real money supply, changes in stock prices, and the index of leading economic indicators. However, some recent studies have shown that the yield spread (the spread between 10-year bonds and 3-month Treasury bills) gave false signals of recession. In this study, we explore the possible reasons for the false signals of the yield spread by addressing the following questions. Does the yield spread used matter? Does the measure of the business cycle used matter? And do the estimation techniques used matter? To address the first question, unlike the previous studies, this paper uses four different yield spreads- depicting short-term, medium-term, and long-term government bonds against the backdrop of a changing structure of bond holding, which reflects the increasing risk eversion of investors in South Africa. Second, the paper used different measures of business cycles, namely industrial production index, lagging, coincident, and leading economic indicators. The empirical models were estimated using both univariate and multivariate Markov switching models. As economic theory suggests, the univariate Markov switching model was used to determine if each variable exhibits a significant regime switching. The multivariate Markov switching model was estimated for each business cycle and yield spread variable, with each of the other variables serving as a non-switching explanatory variable, thereby addressing potential endogeneity concerns and the predictive power of the explanatory variable. Finally, the multivariate Markov switching model was estimated for three monthly sample periods, a full sample for 1986 to 2022, and two sub-samples – 1986 to 2009 and 2010 to 2022. This analysis consistently reveals significant regime-switching behavior across all the series thus, affirming the superiority of the regime switching model over the standard model used in previous studies. By analyzing the transition probabilities and the expected durations between these regimes, we find that including the spreads in the business cycle model improves the models’ predictability, with the medium-term bonds spread performing better than the usual long-term spread. The smoothed regime probability of the best-performing models is compared with the SARB recession dates; the two closely resemble each other, proving that the Markov switching model can help predict the turning points in the business cycle in South Africa.Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 202
Honorary Citation for the Conferment of Doctor of Laws honoris causa - Tandabantu Tennyson August
No full textRhodes 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