Biotic resistance towards Hydrellia egeriae, a biological control agent for the aquatic weed Egeria densa, in South Africa
- Moffat, Rosali, van Noort, Simon, Coetzee, Julie A, Hill, Martin P
- Authors: Moffat, Rosali , van Noort, Simon , Coetzee, Julie A , Hill, Martin P
- Date: 2024
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451299 , vital:75038 , http://dx.doi.org/10.17159/2254-8854/2024/a15718
- Description: Egeria densa is a submerged aquatic weed that can grow into dense monocultures in rivers and dams in South Africa, which negatively affects ecosystem functioning and services. The biological control agent Hydrellia egeriae Rodrigues-Júnior (Diptera: Ephydridae) was first released against Egeria densa Planchon (Hydrocharitaceae) in South Africa in 2018. Biotic resistance in an introduced range can have negative impacts on the ability of a biological control agent to establish and exert top-down pressure. Dipteran and lepidopteran species that are used as biological control agents are often susceptible to higher levels of parasitism in their introduced range than biological control agents from other insect orders. In addition, ecological analogues that are present in South Africa, make H. egeriae particularly vulnerable to biotic resistance. Considering this, post-release surveys were conducted to investigate if native parasitoids will extend their host range to include H. egeriae. Chaenusa seminervata van Achterberg, C. anervata van Achterberg (Braconidae: Alysiinae: Dacnusini) and Ademon lagarosiphonae van Achterberg (Braconidae: Opiinae) were reared from field-collected H. egeriae pupae, within a year of its release. These braconid parasitoids were previously recorded from a native herbivore, Hydrellia lagarosiphon Deeming (Diptera: Ephydridae).
- Full Text:
- Date Issued: 2024
- Authors: Moffat, Rosali , van Noort, Simon , Coetzee, Julie A , Hill, Martin P
- Date: 2024
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451299 , vital:75038 , http://dx.doi.org/10.17159/2254-8854/2024/a15718
- Description: Egeria densa is a submerged aquatic weed that can grow into dense monocultures in rivers and dams in South Africa, which negatively affects ecosystem functioning and services. The biological control agent Hydrellia egeriae Rodrigues-Júnior (Diptera: Ephydridae) was first released against Egeria densa Planchon (Hydrocharitaceae) in South Africa in 2018. Biotic resistance in an introduced range can have negative impacts on the ability of a biological control agent to establish and exert top-down pressure. Dipteran and lepidopteran species that are used as biological control agents are often susceptible to higher levels of parasitism in their introduced range than biological control agents from other insect orders. In addition, ecological analogues that are present in South Africa, make H. egeriae particularly vulnerable to biotic resistance. Considering this, post-release surveys were conducted to investigate if native parasitoids will extend their host range to include H. egeriae. Chaenusa seminervata van Achterberg, C. anervata van Achterberg (Braconidae: Alysiinae: Dacnusini) and Ademon lagarosiphonae van Achterberg (Braconidae: Opiinae) were reared from field-collected H. egeriae pupae, within a year of its release. These braconid parasitoids were previously recorded from a native herbivore, Hydrellia lagarosiphon Deeming (Diptera: Ephydridae).
- Full Text:
- Date Issued: 2024
Demanding doctorability for abortion on request: a conversation analysis of pre-abortion counselling in public hospitals in the Eastern Cape, South Africa
- Du Toit, Ryan, Macleod, Catriona I
- Authors: Du Toit, Ryan , Macleod, Catriona I
- Date: 2024
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/460985 , vital:76071 , https://srh.bmj.com/content/50/4/278.citation-tools
- Description: Out-of-school comprehensive sexuality education (CSE) Re-search on abortion counselling generally uses retrospective interviewing regarding providers’ and users’ experiences. In this article we explore how requests for abortion are made and received in real time in (officially non-mandatory) pre-abortion counselling conducted by nurses and counsellors in South African public abortion clinics. To capture turn-by-turn interactions, we recorded, using consecutive sampling, 28 sessions at three abortion clinics in 2017/2018. No researcher was present. Conversation analysis, based on an ethnomethodological paradigm, was used to understand the conversational projects of the sessions and to outline how the provider and user oriented to the request for an abortion as a conversational task.
- Full Text:
- Date Issued: 2024
- Authors: Du Toit, Ryan , Macleod, Catriona I
- Date: 2024
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/460985 , vital:76071 , https://srh.bmj.com/content/50/4/278.citation-tools
- Description: Out-of-school comprehensive sexuality education (CSE) Re-search on abortion counselling generally uses retrospective interviewing regarding providers’ and users’ experiences. In this article we explore how requests for abortion are made and received in real time in (officially non-mandatory) pre-abortion counselling conducted by nurses and counsellors in South African public abortion clinics. To capture turn-by-turn interactions, we recorded, using consecutive sampling, 28 sessions at three abortion clinics in 2017/2018. No researcher was present. Conversation analysis, based on an ethnomethodological paradigm, was used to understand the conversational projects of the sessions and to outline how the provider and user oriented to the request for an abortion as a conversational task.
- Full Text:
- Date Issued: 2024
A Spectre Haunting a Journalist and a Devastated Land
- Authors: Baines, Gary F
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/450055 , vital:74879 , https://www.scielo.org.za/pdf/hist/v68n1/07.pdf
- Description: In 1986, British journalist Fred Bridgland published the first, and to date the only full-length English language biography of Jonas Savimbi, 1 the leader of UNITA (National Union for the Total Independence of Angola). The mammoth volume raised the profile of Savimbi and elevated the guerrilla to a pantheon that included his idol Mao Zedong and his reputed friend, Che Guevera. 2 Apparently unbeknown to Bridgland, Savimbi was already exhibiting the worst excesses of Mao: the elimination of all potential rivals to his ironclad control of the rebel armed group. What Bridgland could not have foreseen was that Savimbi was destined to die in the same undignified manner as Guevera with the reputation that he had helped cultivate in tatters (255).
- Full Text:
- Date Issued: 2023
- Authors: Baines, Gary F
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/450055 , vital:74879 , https://www.scielo.org.za/pdf/hist/v68n1/07.pdf
- Description: In 1986, British journalist Fred Bridgland published the first, and to date the only full-length English language biography of Jonas Savimbi, 1 the leader of UNITA (National Union for the Total Independence of Angola). The mammoth volume raised the profile of Savimbi and elevated the guerrilla to a pantheon that included his idol Mao Zedong and his reputed friend, Che Guevera. 2 Apparently unbeknown to Bridgland, Savimbi was already exhibiting the worst excesses of Mao: the elimination of all potential rivals to his ironclad control of the rebel armed group. What Bridgland could not have foreseen was that Savimbi was destined to die in the same undignified manner as Guevera with the reputation that he had helped cultivate in tatters (255).
- Full Text:
- Date Issued: 2023
Atypical HIV-vacuolar myelopathy: a case report :
- Mongezi, Tau, Sibi, Joseph, Jerry, George, Lourdes de Fátima, Ibañez Valdés, Tozama, Dubula, Humberto, Foyaca Sibat
- Authors: Mongezi, Tau , Sibi, Joseph , Jerry, George , Lourdes de Fátima, Ibañez Valdés , Tozama, Dubula , Humberto, Foyaca Sibat
- Date: 2021-06
- Subjects: South Africa HIV (Viruses) Cervical spondylotic myelopathy Article
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/7670 , vital:54741 , https://doi.org/10.1186/s40001-021-00483-0
- Description: Background: Here, we report an atypical HIV-vacuolar myelopathy and search the available medical literature about atypical presentations of human immunodefciency virus associate vacuolar myelopathy (HIV-VM) and immunoglobu‑ lin therapy response. Case: A 26-year-old lady who was 4 weeks postpartum presented to us with acute faccid quadriparesis, with no sen‑ sory level. Extensive workup ruled out other causes of myelopathy. She developed a stage 3 acute kidney injury, and MRI showed difuse cord atrophy involving the lower cervical and thoracic cord. The patient received IV-immunoglob‑ ulin, ARVs, and supportive therapy with inadequate response. Unfortunately, she developed nosocomial pneumonia and died. Discussion: In HIV-VM, there is spinal cord atrophy, which mainly involves the thoracic cord. In our case, this patho‑ logical process also afected the spinal cord’s cervical region, leading to faccid tetraplegia, with high CD4 level, with‑ out response to the treatment, including intravenous immunoglobulin. Keynotes: Vacuolar myelopathy, HIV, Immunoglobulin therapy, faccid tetraplegia, hypokalaemia. Renal failure. Keywords: Human immunodefciency virus, Associated lesions of the nervous system, Human immunodefciency virus-associated myelopathy, Intravenous immunoglobulin administration, Case report, HIV-vacuolar myelopathy
- Full Text:
- Date Issued: 2021-06
- Authors: Mongezi, Tau , Sibi, Joseph , Jerry, George , Lourdes de Fátima, Ibañez Valdés , Tozama, Dubula , Humberto, Foyaca Sibat
- Date: 2021-06
- Subjects: South Africa HIV (Viruses) Cervical spondylotic myelopathy Article
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/7670 , vital:54741 , https://doi.org/10.1186/s40001-021-00483-0
- Description: Background: Here, we report an atypical HIV-vacuolar myelopathy and search the available medical literature about atypical presentations of human immunodefciency virus associate vacuolar myelopathy (HIV-VM) and immunoglobu‑ lin therapy response. Case: A 26-year-old lady who was 4 weeks postpartum presented to us with acute faccid quadriparesis, with no sen‑ sory level. Extensive workup ruled out other causes of myelopathy. She developed a stage 3 acute kidney injury, and MRI showed difuse cord atrophy involving the lower cervical and thoracic cord. The patient received IV-immunoglob‑ ulin, ARVs, and supportive therapy with inadequate response. Unfortunately, she developed nosocomial pneumonia and died. Discussion: In HIV-VM, there is spinal cord atrophy, which mainly involves the thoracic cord. In our case, this patho‑ logical process also afected the spinal cord’s cervical region, leading to faccid tetraplegia, with high CD4 level, with‑ out response to the treatment, including intravenous immunoglobulin. Keynotes: Vacuolar myelopathy, HIV, Immunoglobulin therapy, faccid tetraplegia, hypokalaemia. Renal failure. Keywords: Human immunodefciency virus, Associated lesions of the nervous system, Human immunodefciency virus-associated myelopathy, Intravenous immunoglobulin administration, Case report, HIV-vacuolar myelopathy
- Full Text:
- Date Issued: 2021-06
An Application to Support end-users of wi-fi Hotspots in the Township of Makhanda
- Buwa, Lubabalo, Shibeshi, Zelalem S, Terzoli, Alfredo
- Authors: Buwa, Lubabalo , Shibeshi, Zelalem S , Terzoli, Alfredo
- Date: 2021
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429077 , vital:72558 , https://ieeexplore.ieee.org/abstract/document/9514200
- Description: Having access to the Internet is a powerful resource that can change one's life, but connectivity inequality continues to be a significant issue, especially for disadvantaged communities. The usage of Wi-Fi hotspots is becoming very useful for accommodating many people living in underprivileged areas to connect to the Internet. Primarily, these hotspots get deployed in public places like hotels, restaurants, etc. This paper discusses how such a system can be made to work as a solution for disadvantaged communities considering the user base in such communities and adhering to government regulations. The research is developed in collaboration with Khula Tech Solutions ISP that provides wireless Internet services in Makhanda (formally known as Grahamstown). Khula Tech Solutions is starting an initiative of installing Wi-Fi hotspots around the township of Makhanda and needs an application that will support users of the Wi-Fi hotspots. The research's result is a proof-of-concept mobile application developed through iterative and incremental software development techniques and mobile application technologies. With this research, the hope is that it is the beginning of further work for the users to become connected citizens.
- Full Text:
- Date Issued: 2021
- Authors: Buwa, Lubabalo , Shibeshi, Zelalem S , Terzoli, Alfredo
- Date: 2021
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429077 , vital:72558 , https://ieeexplore.ieee.org/abstract/document/9514200
- Description: Having access to the Internet is a powerful resource that can change one's life, but connectivity inequality continues to be a significant issue, especially for disadvantaged communities. The usage of Wi-Fi hotspots is becoming very useful for accommodating many people living in underprivileged areas to connect to the Internet. Primarily, these hotspots get deployed in public places like hotels, restaurants, etc. This paper discusses how such a system can be made to work as a solution for disadvantaged communities considering the user base in such communities and adhering to government regulations. The research is developed in collaboration with Khula Tech Solutions ISP that provides wireless Internet services in Makhanda (formally known as Grahamstown). Khula Tech Solutions is starting an initiative of installing Wi-Fi hotspots around the township of Makhanda and needs an application that will support users of the Wi-Fi hotspots. The research's result is a proof-of-concept mobile application developed through iterative and incremental software development techniques and mobile application technologies. With this research, the hope is that it is the beginning of further work for the users to become connected citizens.
- Full Text:
- Date Issued: 2021
Feasibility Study: Computing Confidence Interval (CI) for IBR Data Using Bootstrapping Technique
- Chindipha, Stones D, Irwin, Barry V W
- Authors: Chindipha, Stones D , Irwin, Barry V W
- Date: 2021
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427665 , vital:72454 , https://www.researchgate.net/profile/Barry-Ir-win/publication/358895311_Feasibility_Study_Computing_Confidence_Inter-val_CI_for_IBR_Data_Using_Bootstrapping_Technique/links/621bdc469947d339eb6e578b/Feasibility-Study-Computing-Confidence-Interval-CI-for-IBR-Data-Using-Bootstrapping-Technique.pdf
- Description: Statistical bootstrapping has been used in different fields over the years since it was introduced as a technique that one can use to simulate data. In this study, parametric and nonparametric bootstrapping techniques were used to create samples of different compositions from the baseline data. The bootstrap distribution of a point estimator of a population parameter has been used in the past to produce a bootstrapped confidence interval (CI) for the parameter’s true value, if the parameter is written as a function of the population’s distribution. Population parameters are estimated with many point estimators. The study used mean as the population parameter of interest from which bootstrap samples were created. This research was more interested in the CI side of bootstrapping and it is this aspect that this paper focused on. This is the case because the study wanted to offer a certain degree of assurance and reliability of IBR data to users who may not have access to a larger ’lens’ of a network telescope to allow them to monitor security threats in their network. The primary interest in the dataset were source and destination IP (DSTIP) addresses, thus the study selected different size pools of DSTIP addresses to simulate bootstrap samples.
- Full Text:
- Date Issued: 2021
- Authors: Chindipha, Stones D , Irwin, Barry V W
- Date: 2021
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427665 , vital:72454 , https://www.researchgate.net/profile/Barry-Ir-win/publication/358895311_Feasibility_Study_Computing_Confidence_Inter-val_CI_for_IBR_Data_Using_Bootstrapping_Technique/links/621bdc469947d339eb6e578b/Feasibility-Study-Computing-Confidence-Interval-CI-for-IBR-Data-Using-Bootstrapping-Technique.pdf
- Description: Statistical bootstrapping has been used in different fields over the years since it was introduced as a technique that one can use to simulate data. In this study, parametric and nonparametric bootstrapping techniques were used to create samples of different compositions from the baseline data. The bootstrap distribution of a point estimator of a population parameter has been used in the past to produce a bootstrapped confidence interval (CI) for the parameter’s true value, if the parameter is written as a function of the population’s distribution. Population parameters are estimated with many point estimators. The study used mean as the population parameter of interest from which bootstrap samples were created. This research was more interested in the CI side of bootstrapping and it is this aspect that this paper focused on. This is the case because the study wanted to offer a certain degree of assurance and reliability of IBR data to users who may not have access to a larger ’lens’ of a network telescope to allow them to monitor security threats in their network. The primary interest in the dataset were source and destination IP (DSTIP) addresses, thus the study selected different size pools of DSTIP addresses to simulate bootstrap samples.
- Full Text:
- Date Issued: 2021
Towards the Development of a Photovoltaic Array Fault Detection and Diagnosis (PVAFDD) System
- Ncube, Prince D N, Meyer, Edson L, Shibeshi, Zelalem S
- Authors: Ncube, Prince D N , Meyer, Edson L , Shibeshi, Zelalem S
- Date: 2021
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429105 , vital:72560 , https://ieeexplore.ieee.org/abstract/document/9698581
- Description: The perpetual increment in energy demand continues to put pressure on the South African Economy. Independent Power Producers (IPPs) have been contracted to relieve the strain by supplementing energy production using solar photovoltaic (PV) technologies. These IPPs are paid per megawatt they produce and face stiff penalties should they fail to deliver on contractual obligations. Naturally solar PV plants are susceptible to numerous PV faults that could lead to a negative return on investment. It therefore makes economic sense to adopt mechanisms that can be able to detect, localize and diagnose PV faults when they occur within a solar PV system. There exists an extensive literature on how to detect and diagnose PV faults, however, localizing PV faults is still in its infancy. This paper proposes to cater to the needs of the IPPs by developing an intelligent PV Array Fault Detection and Diagnostics (PVAFDD) system capable of localizing PV faults which can be embedded into the Supervisory Control and Data Acquisition (SCADA) system used to manage and control such PV systems. The PVAFDD system is based on a machine learning (ML) model implemented using logistic regression algorithm. The ML model is trained using meteorological data ranging over a period of eight years in Alice, Eastern Cape. Using simulations driven by real-life data scenarios, we have been able to train, validate and test the PVAFDD system. When the PVAFDD system detects a fault, a cascade of real-time PVA tests is undertaken to localize the PV fault. The system then carries out PVA fault diagnostics and gives recommendations on the PV fault classification. Corrective measures can therefore be implemented on the affected PVA swiftly reducing the downtime of the PV plant, ergo proving to be a cost-effective measure that offers a competitive edge to IPPs using the PVAFDD system.
- Full Text:
- Date Issued: 2021
- Authors: Ncube, Prince D N , Meyer, Edson L , Shibeshi, Zelalem S
- Date: 2021
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429105 , vital:72560 , https://ieeexplore.ieee.org/abstract/document/9698581
- Description: The perpetual increment in energy demand continues to put pressure on the South African Economy. Independent Power Producers (IPPs) have been contracted to relieve the strain by supplementing energy production using solar photovoltaic (PV) technologies. These IPPs are paid per megawatt they produce and face stiff penalties should they fail to deliver on contractual obligations. Naturally solar PV plants are susceptible to numerous PV faults that could lead to a negative return on investment. It therefore makes economic sense to adopt mechanisms that can be able to detect, localize and diagnose PV faults when they occur within a solar PV system. There exists an extensive literature on how to detect and diagnose PV faults, however, localizing PV faults is still in its infancy. This paper proposes to cater to the needs of the IPPs by developing an intelligent PV Array Fault Detection and Diagnostics (PVAFDD) system capable of localizing PV faults which can be embedded into the Supervisory Control and Data Acquisition (SCADA) system used to manage and control such PV systems. The PVAFDD system is based on a machine learning (ML) model implemented using logistic regression algorithm. The ML model is trained using meteorological data ranging over a period of eight years in Alice, Eastern Cape. Using simulations driven by real-life data scenarios, we have been able to train, validate and test the PVAFDD system. When the PVAFDD system detects a fault, a cascade of real-time PVA tests is undertaken to localize the PV fault. The system then carries out PVA fault diagnostics and gives recommendations on the PV fault classification. Corrective measures can therefore be implemented on the affected PVA swiftly reducing the downtime of the PV plant, ergo proving to be a cost-effective measure that offers a competitive edge to IPPs using the PVAFDD system.
- Full Text:
- Date Issued: 2021
"Knowing With": New Rhodes Board Navigates Collaboration, Intimacy, and Solidarity
- Baasch, Rachel M, Fọlárànmí, Stephen, Koide, Emi, Kakande, Angelo, Simbao, Ruth K
- Authors: Baasch, Rachel M , Fọlárànmí, Stephen , Koide, Emi , Kakande, Angelo , Simbao, Ruth K
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147514 , vital:38645 , https://doi.org/10.1162/afar_a_00523
- Description: Rhodes University (or UCKAR), based in Makhanda, South Africa, joined the African Arts editorial consortium in 2016 and its first journal issue—vol. 50, no. 2—was published in 2017. Initially the board was run by Ruth Simbao, with the aim of developing collaborations with other scholars, particularly those based on the African continent and within the global south (Simbao 2017: 1). For the second Rhodes issue (Summer 2018), Simbao worked with Guest Board Member Amanda Tumusiime from Makerere University, and for the third Rhodes issue (Summer 2019) she collaborated with Stephen Folárànmí from Obáfémi Awólówò University, Ilé-Ifè, Nigeria, who at the time was a Postdoctoral Fellow at Rhodes.
- Full Text:
- Date Issued: 2020
- Authors: Baasch, Rachel M , Fọlárànmí, Stephen , Koide, Emi , Kakande, Angelo , Simbao, Ruth K
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147514 , vital:38645 , https://doi.org/10.1162/afar_a_00523
- Description: Rhodes University (or UCKAR), based in Makhanda, South Africa, joined the African Arts editorial consortium in 2016 and its first journal issue—vol. 50, no. 2—was published in 2017. Initially the board was run by Ruth Simbao, with the aim of developing collaborations with other scholars, particularly those based on the African continent and within the global south (Simbao 2017: 1). For the second Rhodes issue (Summer 2018), Simbao worked with Guest Board Member Amanda Tumusiime from Makerere University, and for the third Rhodes issue (Summer 2019) she collaborated with Stephen Folárànmí from Obáfémi Awólówò University, Ilé-Ifè, Nigeria, who at the time was a Postdoctoral Fellow at Rhodes.
- Full Text:
- Date Issued: 2020
Absent fathers: psychological and socio-economic implications for black children and directions for future research
- Magqamfana, Simnikiwe H, Bazana, Sandiso
- Authors: Magqamfana, Simnikiwe H , Bazana, Sandiso
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/163443 , vital:41038 , DOI: 10.1080/14330237.2020.1744299
- Description: This study investigated fathers’ absence influences on the self-perceptions of South African young adults. Informants were five black university students (two females, three males; age range 20 to 28 years). They responded to semi-structured face-to-face interviews on self-perceptions from having matured in the absence of their biological fathers. Thematic analysis of the data revealed that the informants consider the father-absence when they grapple with material well-being shortage. Participants had mixed perceptions about the psychosocial effects on them from father-absence, with some believing to be thriving despite a history of father-absence. Overall, the findings suggest a need for caution in pathologising young adults with a history of father-absence as necessarily deprived.
- Full Text:
- Date Issued: 2020
- Authors: Magqamfana, Simnikiwe H , Bazana, Sandiso
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/163443 , vital:41038 , DOI: 10.1080/14330237.2020.1744299
- Description: This study investigated fathers’ absence influences on the self-perceptions of South African young adults. Informants were five black university students (two females, three males; age range 20 to 28 years). They responded to semi-structured face-to-face interviews on self-perceptions from having matured in the absence of their biological fathers. Thematic analysis of the data revealed that the informants consider the father-absence when they grapple with material well-being shortage. Participants had mixed perceptions about the psychosocial effects on them from father-absence, with some believing to be thriving despite a history of father-absence. Overall, the findings suggest a need for caution in pathologising young adults with a history of father-absence as necessarily deprived.
- Full Text:
- Date Issued: 2020
Alternative prey impedes the efficacy of a natural enemy of mosquitoes
- Cuthbert, Ross N, Dalu, Tatenda, Wasserman, Ryan J, Weyl, Olaf L F, Froneman, P William, Callaghan, Amanda, Coughlan, Neil E, Dick, Jaimie T A
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Coughlan, Neil E , Dick, Jaimie T A
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467148 , vital:76831 , https://doi.org/10.1016/j.biocontrol.2019.104146
- Description: Adaptive foraging behaviour in the presence of multiple prey types may mediate stability to predator-prey relationships. For biological control agents, the presence of alternative prey may thus reduce ecological impacts towards target organisms, presenting a key challenge to the derivation of agent efficacies. Quantifications of non-target effects are especially important for generalist biocontrol agents in their regulation of pests, vectors and invasive species. We examined the predatory impact of the notonectid Anisops debilis towards larvae of the vector mosquito complex Culex pipiens in the presence of varying densities of alternative daphniid prey. Experimentally, we quantified functional responses of A. debilis towards target mosquito prey under different background daphniid compositions, and also tested for prey switching propensities by the notonectid predator.
- Full Text:
- Date Issued: 2020
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Coughlan, Neil E , Dick, Jaimie T A
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467148 , vital:76831 , https://doi.org/10.1016/j.biocontrol.2019.104146
- Description: Adaptive foraging behaviour in the presence of multiple prey types may mediate stability to predator-prey relationships. For biological control agents, the presence of alternative prey may thus reduce ecological impacts towards target organisms, presenting a key challenge to the derivation of agent efficacies. Quantifications of non-target effects are especially important for generalist biocontrol agents in their regulation of pests, vectors and invasive species. We examined the predatory impact of the notonectid Anisops debilis towards larvae of the vector mosquito complex Culex pipiens in the presence of varying densities of alternative daphniid prey. Experimentally, we quantified functional responses of A. debilis towards target mosquito prey under different background daphniid compositions, and also tested for prey switching propensities by the notonectid predator.
- Full Text:
- Date Issued: 2020
Assessing sediment particle-size effects on benthic algal colonisation and total carbohydrate production
- Dalu, Tatenda, Cuthbert, Ross N, Chavalala, Tiyisani L, Froneman, P William, Wasserman, Ryan J
- Authors: Dalu, Tatenda , Cuthbert, Ross N , Chavalala, Tiyisani L , Froneman, P William , Wasserman, Ryan J
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466815 , vital:76789 , https://doi.org/10.1016/j.scitotenv.2019.136348
- Description: Increased sedimentation and siltation associated with anthropogenic environmental change may alter microbial biofilms and the carbohydrates they produce, with potential bottom-up effects in these ecosystems. The present study aimed to examine to what extent carbohydrate (associated with biofilm exopolymer) concentration and benthic algal biomass vary among different sediment types (size-structure categories) using a microcosm experiment conducted over a period of 28 days. Substrate treatment and time had a significant effect on the total chlorophyll-a concentrations, whilst a significant interaction was present in the case of total sediment carbohydrates. Total sediment carbohydrates did not relate significantly to chlorophyll-a concentrations overall, nor for any substrate treatments owing to a non-significant ‘chlorophyll-a × substrate’ interaction term. The diatom community characteristics across sediment sizes were unique for each treatment in our study, with unique dominant diatom taxa compositions within each sediment size class. The finest sediment particle-size (greater than 63 μm) may be the least stable, most likely due to lower binding. We anticipate that the current study findings will lead to a better understanding of how different sediment types due to sedimentation and siltation will impact on primary productivity and the composition of diatom communities in aquatic systems.
- Full Text:
- Date Issued: 2020
- Authors: Dalu, Tatenda , Cuthbert, Ross N , Chavalala, Tiyisani L , Froneman, P William , Wasserman, Ryan J
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466815 , vital:76789 , https://doi.org/10.1016/j.scitotenv.2019.136348
- Description: Increased sedimentation and siltation associated with anthropogenic environmental change may alter microbial biofilms and the carbohydrates they produce, with potential bottom-up effects in these ecosystems. The present study aimed to examine to what extent carbohydrate (associated with biofilm exopolymer) concentration and benthic algal biomass vary among different sediment types (size-structure categories) using a microcosm experiment conducted over a period of 28 days. Substrate treatment and time had a significant effect on the total chlorophyll-a concentrations, whilst a significant interaction was present in the case of total sediment carbohydrates. Total sediment carbohydrates did not relate significantly to chlorophyll-a concentrations overall, nor for any substrate treatments owing to a non-significant ‘chlorophyll-a × substrate’ interaction term. The diatom community characteristics across sediment sizes were unique for each treatment in our study, with unique dominant diatom taxa compositions within each sediment size class. The finest sediment particle-size (greater than 63 μm) may be the least stable, most likely due to lower binding. We anticipate that the current study findings will lead to a better understanding of how different sediment types due to sedimentation and siltation will impact on primary productivity and the composition of diatom communities in aquatic systems.
- Full Text:
- Date Issued: 2020
Counting waterbirds on holiday: a snapshot for one Eastern Cape estuary
- Mullins, R Lorraine G, Craig, Adrian J F K
- Authors: Mullins, R Lorraine G , Craig, Adrian J F K
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/449375 , vital:74815 , https://doi.org/10.2989/00306525.2020.1783383
- Description: Over a ten-year period, each December the same observer counted waterbirds on the same stretch of the Kariega River in the Eastern Cape, South Africa. The site surveyed is dominated by waders, with variable numbers of other feeding guilds. Piscivorous birds in particular are poorly represented. Differences in the numbers of birds and species recorded, both within a single month and between years, are only partly explicable by environmental conditions on this permanently open estuary. From our comparison with nearby sites, we conclude local movements between rivers and pans in the region must occur regularly over short time intervals.
- Full Text:
- Date Issued: 2020
- Authors: Mullins, R Lorraine G , Craig, Adrian J F K
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/449375 , vital:74815 , https://doi.org/10.2989/00306525.2020.1783383
- Description: Over a ten-year period, each December the same observer counted waterbirds on the same stretch of the Kariega River in the Eastern Cape, South Africa. The site surveyed is dominated by waders, with variable numbers of other feeding guilds. Piscivorous birds in particular are poorly represented. Differences in the numbers of birds and species recorded, both within a single month and between years, are only partly explicable by environmental conditions on this permanently open estuary. From our comparison with nearby sites, we conclude local movements between rivers and pans in the region must occur regularly over short time intervals.
- Full Text:
- Date Issued: 2020
Growth of centimeter scale carbon wires using in-liquid AC arc discharge:
- Jankowski, Krzysztof, Ostafin, Agnes, Tomasik, Mikolaj, Nyokong, Tebello, Britton, Jonathan
- Authors: Jankowski, Krzysztof , Ostafin, Agnes , Tomasik, Mikolaj , Nyokong, Tebello , Britton, Jonathan
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149956 , vital:38914 , https://0-doi.org.wam.seals.ac.za/10.1007/s42452-020-2881-2
- Description: A novel observation of the formation of carbon wire in a carbon-based liquid solvent, using in liquid high voltage AC arc discharge is described. The authors describe the observed phenomenon, technical equipment needed to achieve the effect and preliminary qualitative results of obtained material. The wire consisted of well packed layers of carbon elements. The arc-discharge method is a simple, low cost method for the production of three dimensional carbon structures. A further research is needed to get a thorough understanding of the phenomenon.
- Full Text:
- Date Issued: 2020
- Authors: Jankowski, Krzysztof , Ostafin, Agnes , Tomasik, Mikolaj , Nyokong, Tebello , Britton, Jonathan
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149956 , vital:38914 , https://0-doi.org.wam.seals.ac.za/10.1007/s42452-020-2881-2
- Description: A novel observation of the formation of carbon wire in a carbon-based liquid solvent, using in liquid high voltage AC arc discharge is described. The authors describe the observed phenomenon, technical equipment needed to achieve the effect and preliminary qualitative results of obtained material. The wire consisted of well packed layers of carbon elements. The arc-discharge method is a simple, low cost method for the production of three dimensional carbon structures. A further research is needed to get a thorough understanding of the phenomenon.
- Full Text:
- Date Issued: 2020
Mapping subtidal estuarine habitats with a remotely operated underwater vehicle (ROV):
- Wasserman, J, Claassens, Louw, Adams, Janine B
- Authors: Wasserman, J , Claassens, Louw , Adams, Janine B
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150163 , vital:38945 , DOI: 10.2989/1814232X.2020.1731598
- Description: Subtidal habitats have not yet been accounted for in habitat maps of South African estuaries. In this study, a novel method for mapping subtidal estuarine habitats, using a remotely operated underwater vehicle (ROV) piloted from a boat, was developed and tested in the Knysna Estuary. Video footage was recorded along 48 transects across the width of the estuary, and then reviewed to identify, classify and map habitats. Using the method developed in this study, 21 hours of footage was recorded over 15 days of sampling, and about 30 hours of post-processing was carried out to map an area exceeding 850 ha. This study has produced the first baseline dataset of subtidal habitats for a South African estuary. Additionally, the study revealed the previously unknown distribution of the invasive red seaweed Asparagopsis taxiformis, and the underestimation in previous studies of the estuary of area cover of eelgrass Zostera capensis by 130 ha.
- Full Text:
- Date Issued: 2020
- Authors: Wasserman, J , Claassens, Louw , Adams, Janine B
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150163 , vital:38945 , DOI: 10.2989/1814232X.2020.1731598
- Description: Subtidal habitats have not yet been accounted for in habitat maps of South African estuaries. In this study, a novel method for mapping subtidal estuarine habitats, using a remotely operated underwater vehicle (ROV) piloted from a boat, was developed and tested in the Knysna Estuary. Video footage was recorded along 48 transects across the width of the estuary, and then reviewed to identify, classify and map habitats. Using the method developed in this study, 21 hours of footage was recorded over 15 days of sampling, and about 30 hours of post-processing was carried out to map an area exceeding 850 ha. This study has produced the first baseline dataset of subtidal habitats for a South African estuary. Additionally, the study revealed the previously unknown distribution of the invasive red seaweed Asparagopsis taxiformis, and the underestimation in previous studies of the estuary of area cover of eelgrass Zostera capensis by 130 ha.
- Full Text:
- Date Issued: 2020
Radio and X-ray detections of GX 339–4 in quiescence using MeerKAT and Swift:
- Tremou, E, Corbel, S, Fender, R P, Woudt, P A, Miller-Jones, J C A, Motta, S E, Heywood, I, Armstrong, R P, Groot, P, Horesh, A, Van der Horst, A J, Koerding, E, Mooley, K P, Rowlinson, A, Wijers, R A M
- Authors: Tremou, E , Corbel, S , Fender, R P , Woudt, P A , Miller-Jones, J C A , Motta, S E , Heywood, I , Armstrong, R P , Groot, P , Horesh, A , Van der Horst, A J , Koerding, E , Mooley, K P , Rowlinson, A , Wijers, R A M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149862 , vital:38907 , https://0-doi.org.wam.seals.ac.za/10.1093/mnrasl/slaa019
- Description: The radio–X-ray correlation that characterizes accreting black holes at all mass scales – from stellar mass black holes in binary systems to supermassive black holes powering active galactic nuclei – is one of the most important pieces of observational evidence supporting the existence of a connection between the accretion process and the generation of collimated outflows – or jets – in accreting systems. Although recent studies suggest that the correlation extends down to low luminosities, only a handful of stellar mass black holes have been clearly detected, and in general only upper limits (especially at radio wavelengths) can be obtained during quiescence. We recently obtained detections of the black hole X-ray binary (XRB) GX 339–4 in quiescence using the Meer Karoo Array Telescope (MeerKAT) radio telescope and Swift X-ray Telescope instrument on board the Neil Gehrels Swift Observatory, probing the lower end of the radio–X-ray correlation. We present the properties of accretion and of the connected generation of jets in the poorly studied low-accretion rate regime for this canonical black hole XRB system.
- Full Text:
- Date Issued: 2020
- Authors: Tremou, E , Corbel, S , Fender, R P , Woudt, P A , Miller-Jones, J C A , Motta, S E , Heywood, I , Armstrong, R P , Groot, P , Horesh, A , Van der Horst, A J , Koerding, E , Mooley, K P , Rowlinson, A , Wijers, R A M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149862 , vital:38907 , https://0-doi.org.wam.seals.ac.za/10.1093/mnrasl/slaa019
- Description: The radio–X-ray correlation that characterizes accreting black holes at all mass scales – from stellar mass black holes in binary systems to supermassive black holes powering active galactic nuclei – is one of the most important pieces of observational evidence supporting the existence of a connection between the accretion process and the generation of collimated outflows – or jets – in accreting systems. Although recent studies suggest that the correlation extends down to low luminosities, only a handful of stellar mass black holes have been clearly detected, and in general only upper limits (especially at radio wavelengths) can be obtained during quiescence. We recently obtained detections of the black hole X-ray binary (XRB) GX 339–4 in quiescence using the Meer Karoo Array Telescope (MeerKAT) radio telescope and Swift X-ray Telescope instrument on board the Neil Gehrels Swift Observatory, probing the lower end of the radio–X-ray correlation. We present the properties of accretion and of the connected generation of jets in the poorly studied low-accretion rate regime for this canonical black hole XRB system.
- Full Text:
- Date Issued: 2020
String diagrams for modelling functional programming
- Authors: Motara, Yusuf, M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429022 , vital:72554 , https://ieeexplore.ieee.org/abstract/document/9334072
- Description: It is currently impossible to model functional programs in the same way that UML is used to model object-oriented programs: no analogous graphical notation exists. Unlike object-oriented programs, however, functional programming is built on a solid mathematical basis and it may be possible to adapt graphical notation from the mathematical domain for such modelling. This work examines string diagrams as a way to model certain functional abstractions. A proposed notation is demonstrated in the contexts of equational reasoning and descriptive modelling, and is found to be suitable for both.
- Full Text:
- Date Issued: 2020
- Authors: Motara, Yusuf, M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429022 , vital:72554 , https://ieeexplore.ieee.org/abstract/document/9334072
- Description: It is currently impossible to model functional programs in the same way that UML is used to model object-oriented programs: no analogous graphical notation exists. Unlike object-oriented programs, however, functional programming is built on a solid mathematical basis and it may be possible to adapt graphical notation from the mathematical domain for such modelling. This work examines string diagrams as a way to model certain functional abstractions. A proposed notation is demonstrated in the contexts of equational reasoning and descriptive modelling, and is found to be suitable for both.
- Full Text:
- Date Issued: 2020
Additive multiple predator effects of two specialist paradiaptomid copepods towards larval mosquitoes
- Cuthbert, Ross N, Dalu, Tatenda, Wasserman, Ryan J, Weyl, Olaf L F, Froneman, P William, Callaghan, Amanda, Dick, Jaimie T A
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Dick, Jaimie T A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467137 , vital:76828 , https://doi.org/10.1016/j.limno.2019.125727
- Description: Interactions between multiple predators can profoundly affect prey risk, with implications for prey population stability and ecosystem functioning. In austral temporary wetlands, arid-area adapted specialist copepods are key predators for much of the hydroperiod. Limited autoecological information relating to species interactions negates understandings of trophic dynamics in these systems. In the present study, we examined multiple predator effects of two key predatory paradiaptomid copepods which often coexist in austral temporary wetlands, Lovenula raynerae Suárez-Morales, Wasserman and Dalu 2015 and Paradiaptomus lamellatus Sars, 1985. Predation rates towards larval mosquito prey across different water depths were quantified.
- Full Text:
- Date Issued: 2019
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Dick, Jaimie T A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467137 , vital:76828 , https://doi.org/10.1016/j.limno.2019.125727
- Description: Interactions between multiple predators can profoundly affect prey risk, with implications for prey population stability and ecosystem functioning. In austral temporary wetlands, arid-area adapted specialist copepods are key predators for much of the hydroperiod. Limited autoecological information relating to species interactions negates understandings of trophic dynamics in these systems. In the present study, we examined multiple predator effects of two key predatory paradiaptomid copepods which often coexist in austral temporary wetlands, Lovenula raynerae Suárez-Morales, Wasserman and Dalu 2015 and Paradiaptomus lamellatus Sars, 1985. Predation rates towards larval mosquito prey across different water depths were quantified.
- Full Text:
- Date Issued: 2019
An oversimplification of physiological principles leads to flawed macroecological analyses
- Boyles, Justin G, Levesque, Danielle L, Nowack, Julia, Wojciechowski, Michal S, Stawski, Clare, Fuller, Andrea, Smit, Ben, Tattersall, Glenn J
- Authors: Boyles, Justin G , Levesque, Danielle L , Nowack, Julia , Wojciechowski, Michal S , Stawski, Clare , Fuller, Andrea , Smit, Ben , Tattersall, Glenn J
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440505 , vital:73788 , https://doi.org/10.1002/ece3.5721
- Description: In light of the rapidly changing climate, there is an urgent need to develop a mechanistic understanding of how physiological functioning mediates ecological patterns. Recently, there has been a spate of papers using analyses that scale up from a standard physiological model, the Scholander–Irving model, to make predictions about range constraints on endothermic vertebrates (Buckley, Khaliq, Swanson, and Hof, 2018; Fristoe et al., 2015; Khaliq, Böhning‐Gaese, Prinzinger, Pfenninger, and Hof, 2017; Khaliq, Hof, Prinzinger, Böhning‐Gaese, and Pfenninger, 2014). Here, we argue that oversimplifications of the Scholander–Irving model and the use of questionable datasets lead to questionable macrophysiological analyses. Many of these problems have been addressed elsewhere, directly and indirectly (eg, McKechnie, Coe, Gerson, and Wolf, 2017; Mitchell et al., 2018), although the focus has largely been on the applicability of the Scholander–Irving model to warm environmental temperatures, which are often seen as more relevant to climate change. However, one specific aspect of the Scholander–Irving model, the assumption that energy expenditure of an endotherm below the thermoneutral zone (TNZ) can be described by basic Newtonian physics, has been used incorrectly in several papers. While not the only paper based on this assumption, the recent work by Buckley et al.(2018) reinvigorated discussions among physiologists about improper interpretations of the Scholander–Irving model. Our concerns are not new and have been voiced repeatedly in the past (Calder and Schmidt‐Nielsen, 1967; King, 1964; Tracy, 1972), but many of these ideas seem to have been buried by time.
- Full Text:
- Date Issued: 2019
- Authors: Boyles, Justin G , Levesque, Danielle L , Nowack, Julia , Wojciechowski, Michal S , Stawski, Clare , Fuller, Andrea , Smit, Ben , Tattersall, Glenn J
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440505 , vital:73788 , https://doi.org/10.1002/ece3.5721
- Description: In light of the rapidly changing climate, there is an urgent need to develop a mechanistic understanding of how physiological functioning mediates ecological patterns. Recently, there has been a spate of papers using analyses that scale up from a standard physiological model, the Scholander–Irving model, to make predictions about range constraints on endothermic vertebrates (Buckley, Khaliq, Swanson, and Hof, 2018; Fristoe et al., 2015; Khaliq, Böhning‐Gaese, Prinzinger, Pfenninger, and Hof, 2017; Khaliq, Hof, Prinzinger, Böhning‐Gaese, and Pfenninger, 2014). Here, we argue that oversimplifications of the Scholander–Irving model and the use of questionable datasets lead to questionable macrophysiological analyses. Many of these problems have been addressed elsewhere, directly and indirectly (eg, McKechnie, Coe, Gerson, and Wolf, 2017; Mitchell et al., 2018), although the focus has largely been on the applicability of the Scholander–Irving model to warm environmental temperatures, which are often seen as more relevant to climate change. However, one specific aspect of the Scholander–Irving model, the assumption that energy expenditure of an endotherm below the thermoneutral zone (TNZ) can be described by basic Newtonian physics, has been used incorrectly in several papers. While not the only paper based on this assumption, the recent work by Buckley et al.(2018) reinvigorated discussions among physiologists about improper interpretations of the Scholander–Irving model. Our concerns are not new and have been voiced repeatedly in the past (Calder and Schmidt‐Nielsen, 1967; King, 1964; Tracy, 1972), but many of these ideas seem to have been buried by time.
- Full Text:
- Date Issued: 2019
Busy as a Bee: Breeding Industrious Bees in Malawi
- Kasumba, Arnold M, Pullanikkatil, Deepa
- Authors: Kasumba, Arnold M , Pullanikkatil, Deepa
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/433537 , vital:72982 , ISBN 978-3-319-75580-9 , https://link.springer.com/chapter/10.1007/978-3-319-75580-9_14
- Description: A trial and error venture at beekeeping by Arnold Kasumbu in central Malawi, is now a successful integrated farming enterprise incorporating 160 beehives and producing honey for customers in Malawi and Kenya. It is also a site for educational visits for university students learning about agriculture. Arnold’s parents were tobacco farmers living in the Mitundu area of Lilongwe District in central Malawi. He recalls that his childhood was steeped in poverty as he observed his father put in a lot of effort in his farm with diminutive returns. Being the eldest of three children in the household, Arnold was forced to end his schooling in Standard 8, as his family could not afford the school fees. Resolving that he would not do tobacco farming, he began exploring other means of income generation that would entail fewer struggles. He wanted to become wealthy and take care of his family. Through his integrated farm and beekeeping, he has done exactly that! This is Arnold’s life story.
- Full Text:
- Date Issued: 2019
- Authors: Kasumba, Arnold M , Pullanikkatil, Deepa
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/433537 , vital:72982 , ISBN 978-3-319-75580-9 , https://link.springer.com/chapter/10.1007/978-3-319-75580-9_14
- Description: A trial and error venture at beekeeping by Arnold Kasumbu in central Malawi, is now a successful integrated farming enterprise incorporating 160 beehives and producing honey for customers in Malawi and Kenya. It is also a site for educational visits for university students learning about agriculture. Arnold’s parents were tobacco farmers living in the Mitundu area of Lilongwe District in central Malawi. He recalls that his childhood was steeped in poverty as he observed his father put in a lot of effort in his farm with diminutive returns. Being the eldest of three children in the household, Arnold was forced to end his schooling in Standard 8, as his family could not afford the school fees. Resolving that he would not do tobacco farming, he began exploring other means of income generation that would entail fewer struggles. He wanted to become wealthy and take care of his family. Through his integrated farm and beekeeping, he has done exactly that! This is Arnold’s life story.
- Full Text:
- Date Issued: 2019
Could enemy release explain invasion success of Sagittaria platyphylla in Australia and South Africa?.
- Kwong, Raelene M, Sagliocco, Jean Louis, Harms, Nathan E, Butler, Kym L, Martin, Grant D, Green, Peter T
- Authors: Kwong, Raelene M , Sagliocco, Jean Louis , Harms, Nathan E , Butler, Kym L , Martin, Grant D , Green, Peter T
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76881 , vital:30633 , https://doi.org/10.1016/j.aquabot.2018.11.011
- Description: Sagittaria platyphylla (delta arrowhead) is an emergent aquatic macrophyte native to southeastern United States of America that has been introduced into Australia and South Africa as an ornamental pond and aquarium plant. Compared to plants in the native range, S. platyphylla in the introduced range have greater reproductive capacity and form extensive infestations that dominate shallow waterbodies. One explanation for the invasive success of S. platyphylla in introduced countries is that plants are devoid of biotic pressures that would regulate population abundance in their native range (the enemy release hypothesis). We previously reported on field surveys that documented the number of pathogens and insect herbivores associated with S. platyphylla in native and introduced ranges. Here, we quantify the damage caused by these natural enemies to S. platyphylla in the two ranges. As predicted, damage to plants caused by pathogens and insect herbivores was much greater in the native than the introduced range at both the plant and population level. In introduced regions herbivory was low (less than 10%) in every plant part, while in North America insect damage to fruiting heads was 46% (of fruiting heads attacked), damage to leaves was between 33 to 57%, and internal herbivore damage to petioles and the inflorescence scapes was 56% and 43% respectively. Pathogen damage to leaves was between 39 to 57% of leaves per plant affected, compared to 9% in Australia and 8% in South Africa. This lack of biotic resistance from herbivores and disease may have facilitated S. platyphylla invasion in Australia and South Africa.
- Full Text:
- Date Issued: 2019
- Authors: Kwong, Raelene M , Sagliocco, Jean Louis , Harms, Nathan E , Butler, Kym L , Martin, Grant D , Green, Peter T
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76881 , vital:30633 , https://doi.org/10.1016/j.aquabot.2018.11.011
- Description: Sagittaria platyphylla (delta arrowhead) is an emergent aquatic macrophyte native to southeastern United States of America that has been introduced into Australia and South Africa as an ornamental pond and aquarium plant. Compared to plants in the native range, S. platyphylla in the introduced range have greater reproductive capacity and form extensive infestations that dominate shallow waterbodies. One explanation for the invasive success of S. platyphylla in introduced countries is that plants are devoid of biotic pressures that would regulate population abundance in their native range (the enemy release hypothesis). We previously reported on field surveys that documented the number of pathogens and insect herbivores associated with S. platyphylla in native and introduced ranges. Here, we quantify the damage caused by these natural enemies to S. platyphylla in the two ranges. As predicted, damage to plants caused by pathogens and insect herbivores was much greater in the native than the introduced range at both the plant and population level. In introduced regions herbivory was low (less than 10%) in every plant part, while in North America insect damage to fruiting heads was 46% (of fruiting heads attacked), damage to leaves was between 33 to 57%, and internal herbivore damage to petioles and the inflorescence scapes was 56% and 43% respectively. Pathogen damage to leaves was between 39 to 57% of leaves per plant affected, compared to 9% in Australia and 8% in South Africa. This lack of biotic resistance from herbivores and disease may have facilitated S. platyphylla invasion in Australia and South Africa.
- Full Text:
- Date Issued: 2019