Developing biological control agents for the management of the invasive tree Robinia pseudoacacia
- Authors: Wolmarans, Abigail
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435717 , vital:73181 , DOI 10.21504/10962/435717
- Description: Robinia pseudoacacia (Fabaceae) is a deciduous tree native to the Appalachian Mountains of North America but has become naturalised and invasive in other countries such as temperate North America, Europe, Australia, and Southern Africa. In South Africa the tree is classified as a category 1B invasive alien under the National Environmental Management Act (NEMBA), which stipulates the species requires some form of control as it has already caused extensive negative ecological and economic impacts. In the invaded range the tree creates monocultures that displace native species and spreads rapidly from suckering roots, making it a proficient invader. The South Africa plant prioritisation system suggests R. pseudoacacia is in the top three species which should be considered for classical weed biological control in South Africa. This thesis investigates which insects known to be associated with tree should be prioritised as candidate agents, as well as offering interesting insights into prioritising insects for weed biological control and using plant phylogenies and available literature to predict insect specificity. To ensure that no candidate biological control agents were already present in South Africa as well as to prioritise which guilds of the tree to prioritise for potential biological control, pre-release surveys were conducted across nine sites where the tree has invaded South Africa. It was found that no insects from the native range of R. pseudoacacia were present in South Africa. Seed surveys revealed that generalist insects attack a sizable proportion (68 %) of the seeds on the trees. In combination with a low seed soil bank (15.8 %) this suggests that seed- feeding agents may be helpful, however, candidate agents which damage leaves should be prioritised due to R. pseudoacacia relying heavily upon vegetative reproduction and much less on sexual reproduction. Leaves may therefor reduce the spread of these invasive trees. The insect assemblages in the native range of R. pseudoacacia are well understood. In addition, several associated insects have unintentionally followed the tree on its global spread, where they are often regarded as pests. The third chapter is therefore aimed at prioritising the known insects associated with the tree in both the native and invaded range. Literature surveys and Harris (1973) prioritisation systems were used to prioritise close to 64 candidate biological control agents down to three foliage- feeding agents, namely Odontota dorsalis (Coleoptera, Chrysomelidae), Macrosaccus robiniella (Lepidoptera, Gracillariidae) and Obolodiplosis robiniae (Diptera, Cecidomyiidae). To further prioritise the six selected agents in Chapter 4, species distribution were modelled with known climatic variables. This was done by using the species known occurrence localities, from both the native and where applicable invaded ranges, to identify which species that would best match with South Africa’s climate. The study showed that O. dorsalis is best suited to survive in South Africa, followed by O. robiniae and then M. robiniella. Collected data aided in the introduction of the prioritised O. robiniae into South African quarantine facilities. Unfortunately, despite several attempts, cultures could not be established, making conventional host specificity testing impossible. Thus, in Chapter 5 we aimed to determine the potential host range of the midge using information from experts in the field of galling insects, literature surveys, agricultural pest lists, and social science platforms coupled with native and invaded range surveys. The list of non-target species to consider as potential hosts was refined by developing phylogenetic trees of closely related Fabaceae that share the same distribution (native and invaded) as R. pseudoacacia. Through the available information gathered, and field surveys of these species, O. robiniae has not been shown to utilise any species, other than those from the Robinoid clade. In addition, the midge has also never been recorded on a number of closely related leguminous fodder and horticultural species growing in close proximity at high densities to R. pseudoacacia - suggesting negligible risk to South African growers of the same species. Host-specificity assessments through field surveys can be regarded as one of the best indicators of the ecological host range, however, this information is difficult to quantify and infrequently available, thus seldom used when determining the safety of a candidate biocontrol agent. In this unique study, using the extensive data collected we are able to show that O. robiniae would be potentially safe for release in South Africa. However, open field tests exposing closely related non-target plant species under natural and semi-natural conditions are planned in Switzerland over the next two years aiming to confirm these conclusions. By identifying and prioritizing potential biological control agents, this research contributes to the development of a targeted and sustainable solution for managing R. pseudoacacia in South Africa. The economic implications of successful biological control include reduced costs associated with invasive species management and ecosystem restoration. Additionally, by mitigating the negative ecological impacts, the agricultural systems in affected regions stand to benefit from enhanced resilience and productivity. Furthermore, the study's approach of using plant phylogenies and available literature to predict insect specificity offers a valuable methodological contribution to the broader field of weed biological control. This methodology can be adapted and applied to other invasive species, providing a framework for efficient and informed decision-making in weed management strategies. In essence, this research not only addresses the specific challenges posed by R. pseudoacacia in South Africa but also provides a template for tackling similar issues in different geographical contexts, thereby contributing to global efforts in sustainable agriculture and environmental conservation. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-04-05
- Authors: Wolmarans, Abigail
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435717 , vital:73181 , DOI 10.21504/10962/435717
- Description: Robinia pseudoacacia (Fabaceae) is a deciduous tree native to the Appalachian Mountains of North America but has become naturalised and invasive in other countries such as temperate North America, Europe, Australia, and Southern Africa. In South Africa the tree is classified as a category 1B invasive alien under the National Environmental Management Act (NEMBA), which stipulates the species requires some form of control as it has already caused extensive negative ecological and economic impacts. In the invaded range the tree creates monocultures that displace native species and spreads rapidly from suckering roots, making it a proficient invader. The South Africa plant prioritisation system suggests R. pseudoacacia is in the top three species which should be considered for classical weed biological control in South Africa. This thesis investigates which insects known to be associated with tree should be prioritised as candidate agents, as well as offering interesting insights into prioritising insects for weed biological control and using plant phylogenies and available literature to predict insect specificity. To ensure that no candidate biological control agents were already present in South Africa as well as to prioritise which guilds of the tree to prioritise for potential biological control, pre-release surveys were conducted across nine sites where the tree has invaded South Africa. It was found that no insects from the native range of R. pseudoacacia were present in South Africa. Seed surveys revealed that generalist insects attack a sizable proportion (68 %) of the seeds on the trees. In combination with a low seed soil bank (15.8 %) this suggests that seed- feeding agents may be helpful, however, candidate agents which damage leaves should be prioritised due to R. pseudoacacia relying heavily upon vegetative reproduction and much less on sexual reproduction. Leaves may therefor reduce the spread of these invasive trees. The insect assemblages in the native range of R. pseudoacacia are well understood. In addition, several associated insects have unintentionally followed the tree on its global spread, where they are often regarded as pests. The third chapter is therefore aimed at prioritising the known insects associated with the tree in both the native and invaded range. Literature surveys and Harris (1973) prioritisation systems were used to prioritise close to 64 candidate biological control agents down to three foliage- feeding agents, namely Odontota dorsalis (Coleoptera, Chrysomelidae), Macrosaccus robiniella (Lepidoptera, Gracillariidae) and Obolodiplosis robiniae (Diptera, Cecidomyiidae). To further prioritise the six selected agents in Chapter 4, species distribution were modelled with known climatic variables. This was done by using the species known occurrence localities, from both the native and where applicable invaded ranges, to identify which species that would best match with South Africa’s climate. The study showed that O. dorsalis is best suited to survive in South Africa, followed by O. robiniae and then M. robiniella. Collected data aided in the introduction of the prioritised O. robiniae into South African quarantine facilities. Unfortunately, despite several attempts, cultures could not be established, making conventional host specificity testing impossible. Thus, in Chapter 5 we aimed to determine the potential host range of the midge using information from experts in the field of galling insects, literature surveys, agricultural pest lists, and social science platforms coupled with native and invaded range surveys. The list of non-target species to consider as potential hosts was refined by developing phylogenetic trees of closely related Fabaceae that share the same distribution (native and invaded) as R. pseudoacacia. Through the available information gathered, and field surveys of these species, O. robiniae has not been shown to utilise any species, other than those from the Robinoid clade. In addition, the midge has also never been recorded on a number of closely related leguminous fodder and horticultural species growing in close proximity at high densities to R. pseudoacacia - suggesting negligible risk to South African growers of the same species. Host-specificity assessments through field surveys can be regarded as one of the best indicators of the ecological host range, however, this information is difficult to quantify and infrequently available, thus seldom used when determining the safety of a candidate biocontrol agent. In this unique study, using the extensive data collected we are able to show that O. robiniae would be potentially safe for release in South Africa. However, open field tests exposing closely related non-target plant species under natural and semi-natural conditions are planned in Switzerland over the next two years aiming to confirm these conclusions. By identifying and prioritizing potential biological control agents, this research contributes to the development of a targeted and sustainable solution for managing R. pseudoacacia in South Africa. The economic implications of successful biological control include reduced costs associated with invasive species management and ecosystem restoration. Additionally, by mitigating the negative ecological impacts, the agricultural systems in affected regions stand to benefit from enhanced resilience and productivity. Furthermore, the study's approach of using plant phylogenies and available literature to predict insect specificity offers a valuable methodological contribution to the broader field of weed biological control. This methodology can be adapted and applied to other invasive species, providing a framework for efficient and informed decision-making in weed management strategies. In essence, this research not only addresses the specific challenges posed by R. pseudoacacia in South Africa but also provides a template for tackling similar issues in different geographical contexts, thereby contributing to global efforts in sustainable agriculture and environmental conservation. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-04-05
Analysis of the role and regulation of HOP1a and HOP1b splice variants in cancer biology
- Authors: Schwarz, Kelly
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432240 , vital:72854
- Description: Restricted access. Expected lease date in 2025. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Schwarz, Kelly
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432240 , vital:72854
- Description: Restricted access. Expected lease date in 2025. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2023-10-13
Exploring the interplay between foundation phase learners’ home and school literacy practices
- Authors: Magxala, Xoliswa Patience
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431587 , vital:72788 , DOI 10.21504/10962/431587
- Description: The thesis looked at Foundation Phase children’s early home literacy practices and examined how these literacy practices are adopted at school in Libode, Eastern Cape Province, South Africa, a rural area. The purpose of the study was to determine how early literacy practices at home are adopted in classrooms. The study aimed to determine the relationship between home and school literacy. To understand the literacy practices used at home and school by four Foundation Phase children and four Foundation Phase teachers, an interpretive ethnographic study design was used. Participants who spoke isiXhosa as their first language participated in data collection using structured observations, video and audio recordings, field notes, and unstructured interviews. The study’s framework, the Cultural Historical Activity Theory, was used as a tool to collect, examine, and interpret data through its various components. Themes were identified, arranged, and categorized. The findings revealed children from low socioeconomic backgrounds have rich literacy practices. Teachers do not acknowledge or recognize the contributions that these children’s cultural backgrounds make. The study recommends that schools start acknowledging the advantages that children’s environments have for them. It also suggests that teachers build on the knowledge that children bring from home, as this will have an impact on how they behave in class because students bring their family’s literacy habits, which serve as the foundation for their academic literacy habits, to school. , Thesis (PhD) -- Faculty of Education, Institute for the Study of Englishes in Africa, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Magxala, Xoliswa Patience
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431587 , vital:72788 , DOI 10.21504/10962/431587
- Description: The thesis looked at Foundation Phase children’s early home literacy practices and examined how these literacy practices are adopted at school in Libode, Eastern Cape Province, South Africa, a rural area. The purpose of the study was to determine how early literacy practices at home are adopted in classrooms. The study aimed to determine the relationship between home and school literacy. To understand the literacy practices used at home and school by four Foundation Phase children and four Foundation Phase teachers, an interpretive ethnographic study design was used. Participants who spoke isiXhosa as their first language participated in data collection using structured observations, video and audio recordings, field notes, and unstructured interviews. The study’s framework, the Cultural Historical Activity Theory, was used as a tool to collect, examine, and interpret data through its various components. Themes were identified, arranged, and categorized. The findings revealed children from low socioeconomic backgrounds have rich literacy practices. Teachers do not acknowledge or recognize the contributions that these children’s cultural backgrounds make. The study recommends that schools start acknowledging the advantages that children’s environments have for them. It also suggests that teachers build on the knowledge that children bring from home, as this will have an impact on how they behave in class because students bring their family’s literacy habits, which serve as the foundation for their academic literacy habits, to school. , Thesis (PhD) -- Faculty of Education, Institute for the Study of Englishes in Africa, 2023
- Full Text:
- Date Issued: 2023-10-13
Kenyan comedy: transmogrifying stereotypes and fashioning a ‘Kenyanness’ of aesthetic escapism
- Authors: Lumasia, Patrick Chesi
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432477 , vital:72874 , DOI 10.21504/10962/432477
- Description: Despite the proliferation of stereotypes in Kenyan comedy, little research exists to show the two intersect to shape a peculiar notion of ‘Kenyanness’. Indeed, Kenyan comedy, besides reproducing and playing on the quotidian and the historical, is heavily invested with ethnic and gender stereotypes that reflect the Kenyan milieu as it intersects with the global. This comedy is oftentimes seen by some critics as detrimental to Kenyan society because it supposedly shapes and reinforces ethnic and/or gender relations in the country. However, this study contends that Kenyan comedy is open to multiple interpretations and meaning contestations that are not necessarily clear to the comedians and audiences due to the asymmetry that abounds between the production and consumption ends of the comedy’s spectrum. The comedy is therefore ambivalent. This research seeks to demonstrate that Kenyan comedy—as a form of entertainment and critique of society—does not seek to fix and reify Kenyan identities. Instead, the comedy frees these identities from the presumed vice-hold, constricting world of stereotypes by disrupting the linearity of the stereotypes, thereby unsettling the hierarchical structure of hegemonic ideology embedded in them through postmodern humour: a form of humour amenable to postmodern sensibilities. To this end, the comedy offers Kenyans momentary escape into a comedic utopia, through which, they address pertinent issues affecting their nationhood, even as they endeavor to fashion a ‘Kenyanness’ of aesthetic escapism that is celebratory of the country’s rich socio-cultural diversity. The study employs Jörg Schweinitz’s (2011) stereotype theory and the postpositivist realist theory of identity in its study of stand-up, scripted episodic and topical comedy as transposed on to YouTube. Specifically, the thesis considers: the Churchill Show (2012 – 2022) that aired on NTV; 2012–2022; The Real Househelps of Kawangware (2014–2021) on KTN/NTV; Auntie Boss (2016–2021) on NTV; The Wicked Edition and The Trending Trend Talkers (2014–). , Thesis (PhD) -- Faculty of Humanities, Literary Studies in English, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Lumasia, Patrick Chesi
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432477 , vital:72874 , DOI 10.21504/10962/432477
- Description: Despite the proliferation of stereotypes in Kenyan comedy, little research exists to show the two intersect to shape a peculiar notion of ‘Kenyanness’. Indeed, Kenyan comedy, besides reproducing and playing on the quotidian and the historical, is heavily invested with ethnic and gender stereotypes that reflect the Kenyan milieu as it intersects with the global. This comedy is oftentimes seen by some critics as detrimental to Kenyan society because it supposedly shapes and reinforces ethnic and/or gender relations in the country. However, this study contends that Kenyan comedy is open to multiple interpretations and meaning contestations that are not necessarily clear to the comedians and audiences due to the asymmetry that abounds between the production and consumption ends of the comedy’s spectrum. The comedy is therefore ambivalent. This research seeks to demonstrate that Kenyan comedy—as a form of entertainment and critique of society—does not seek to fix and reify Kenyan identities. Instead, the comedy frees these identities from the presumed vice-hold, constricting world of stereotypes by disrupting the linearity of the stereotypes, thereby unsettling the hierarchical structure of hegemonic ideology embedded in them through postmodern humour: a form of humour amenable to postmodern sensibilities. To this end, the comedy offers Kenyans momentary escape into a comedic utopia, through which, they address pertinent issues affecting their nationhood, even as they endeavor to fashion a ‘Kenyanness’ of aesthetic escapism that is celebratory of the country’s rich socio-cultural diversity. The study employs Jörg Schweinitz’s (2011) stereotype theory and the postpositivist realist theory of identity in its study of stand-up, scripted episodic and topical comedy as transposed on to YouTube. Specifically, the thesis considers: the Churchill Show (2012 – 2022) that aired on NTV; 2012–2022; The Real Househelps of Kawangware (2014–2021) on KTN/NTV; Auntie Boss (2016–2021) on NTV; The Wicked Edition and The Trending Trend Talkers (2014–). , Thesis (PhD) -- Faculty of Humanities, Literary Studies in English, 2023
- Full Text:
- Date Issued: 2023-10-13
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