Ecological impacts of photoautotrophic Euendoliths on South African mussel beds
- Dievart, Alexia Madeleine Angèle
- Authors: Dievart, Alexia Madeleine Angèle
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435650 , vital:73176 , DOI 10.21504/10962/435650
- Description: Aphytis lingnanensis was reared and tested in South Africa in the early 2000s for augmentation against red scale on citrus and was found to be ineffective. Aphytis melinus is now commercially available and it is important that the efficacy of augmentation thereof on red scale is determined locally. Field trials, fitness assessments and molecular identification on A. melinus from two insectaries were done. Field trials was done in seven, five and six pairs of comparable release and control orchards across the Eastern and Western Cape during the seasons of 2019/2020, 2020/2021 and 2021/2022 respectively. Red scale infestation was monitored and a sample of 20 infested fruit from each orchard was randomly collected every four weeks. Aphytis spp. responsible for parasitism were identified and the percentage parasitism recorded. Results of this study of field trials suggest that the augmentation of A. melinus did not significantly increase the level of parasitism above that of the untreated control. Five repetitions with six replicates of flight and longevity tests were performed with wasps from each insectary. Wasps in the longevity test from two insectaries were kept at 23 °C and 65% RH with honey. Flight tests were performed in tubes of 16 by 30 cm, with a light above a clear, sticky ceiling at 23 °C and 65% RH. On average in five replicates, 65%, 33% and 17% A. melinus wasps were alive on day one, five and 10 respectively. The overall sex ratio was 1.58 for females to males, but 1.05, 2.19 and 2.66 for non-flyers, non-crawlers, crawlers, and flyers respectively. In flight tests for both insectaries combined, only 36.97% of wasps could initiate flight in 24 h while 56.96% remained on the tube floor, and 6.05% attempted to crawl upwards. No significant differences in flight performance were recorded between the two insectaries. Wasps from the local insectary lived significantly longer during the longevity tests but were shorter in transit than wasps from the overseas insectary. COI genes were sequenced and compared against Genbank sequences using BLAST. Molecular identifications did not confirm morphological identifications for all species, indicating unexpected genetic complexity. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-04-05
- Authors: Dievart, Alexia Madeleine Angèle
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435650 , vital:73176 , DOI 10.21504/10962/435650
- Description: Aphytis lingnanensis was reared and tested in South Africa in the early 2000s for augmentation against red scale on citrus and was found to be ineffective. Aphytis melinus is now commercially available and it is important that the efficacy of augmentation thereof on red scale is determined locally. Field trials, fitness assessments and molecular identification on A. melinus from two insectaries were done. Field trials was done in seven, five and six pairs of comparable release and control orchards across the Eastern and Western Cape during the seasons of 2019/2020, 2020/2021 and 2021/2022 respectively. Red scale infestation was monitored and a sample of 20 infested fruit from each orchard was randomly collected every four weeks. Aphytis spp. responsible for parasitism were identified and the percentage parasitism recorded. Results of this study of field trials suggest that the augmentation of A. melinus did not significantly increase the level of parasitism above that of the untreated control. Five repetitions with six replicates of flight and longevity tests were performed with wasps from each insectary. Wasps in the longevity test from two insectaries were kept at 23 °C and 65% RH with honey. Flight tests were performed in tubes of 16 by 30 cm, with a light above a clear, sticky ceiling at 23 °C and 65% RH. On average in five replicates, 65%, 33% and 17% A. melinus wasps were alive on day one, five and 10 respectively. The overall sex ratio was 1.58 for females to males, but 1.05, 2.19 and 2.66 for non-flyers, non-crawlers, crawlers, and flyers respectively. In flight tests for both insectaries combined, only 36.97% of wasps could initiate flight in 24 h while 56.96% remained on the tube floor, and 6.05% attempted to crawl upwards. No significant differences in flight performance were recorded between the two insectaries. Wasps from the local insectary lived significantly longer during the longevity tests but were shorter in transit than wasps from the overseas insectary. COI genes were sequenced and compared against Genbank sequences using BLAST. Molecular identifications did not confirm morphological identifications for all species, indicating unexpected genetic complexity. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-04-05
Genetic connectivity of the slinger Chrysoblephus puniceus among Marine Protected Areas and unprotected areas along the east coast of South Africa
- Ockhuis, Samantha Angelique Natasha
- Authors: Ockhuis, Samantha Angelique Natasha
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435954 , vital:73215 , DOI 10.21504/10962/435954
- Description: Marine Protected Areas (MPAs) are advocated worldwide for the conservation of biodiversity and fisheries management, as well as for adaptation and resilience in the face of climate change. Their effectiveness has been noted through increases in abundances, biomass, sizes and diversity of species, as well as the recovery of overexploited fisheries. For MPAs to realise their full potential, these benefits need to expand beyond their boundaries through larval dispersal and/or adult spillover. Connectivity between MPAs is critical for planning and placement of MPAs, as this promotes the persistence of metapopulations, their recovery from disturbance, as well as productivity in marine ecosystems. The effectiveness of MPAs in conserving biodiversity along the east coast of South Africa has been established; however, limited evidence is available on whether they offer benefits beyond their boundaries, enhancing biodiversity and fisheries in adjacent areas. The slinger Chrysoblephus puniceus, an endemic southern African sparid, is a major component of the commercial linefishery in KwaZulu-Natal (KZN), South Africa and southern Mozambique, and is also caught in the recreational ski-boat fishery in these regions. The spawning of slinger occurs in shoals on offshore reefs from southern Mozambique to the north of KZN, and larvae are likely transported southwards, assisted by the southward-flowing Agulhas Current and promoted by a relatively long larval duration. Slinger are relatively resident, but occasional northward migrations have been observed. These life history characteristics suggested that slinger would be a suitable biological model to test connectivity along the east coast, and particularly connectivity between MPAs. The aim of this study was therefore to investigate connectivity of slinger between MPAs and the surrounding areas along the east coast of South Africa, using restriction-site-associated DNA (RAD) sequencing. This formed part of the larger CAPTOR project investigating east coast MPA connectivity across a range of taxa and habitat types. A temporal comparison of genetic diversity in slinger spanning two sampling events (2012 and 2018) revealed no substantial changes in genetic diversity, as well as a lack of genetic structure along the KZN coast. Similarly, no substantial changes in effective population size (Ne) were found between 2012 and 2018 for microsatellites and Single Nucleotide Polymorphisms (SNPs). However, subtle, albeit non-significant, differences were observed both spatially and over time in the microsatellite data, indicating some instability along the KZN coast. A lack of genetic structure based on RAD sequencing was observed between east coast MPAs and the surrounding areas. This implies high connectivity along the coast - not only are east coast MPAs connected, the surrounding areas are also connected, and there is replenishment between all areas via larval dispersal and/or adult spillover. Analyses of multidirectional gene flow between MPAs, together with known spatial spawning patterns and prior particle dispersal modelling, identified the Richards Bay area as a key source of recruits. However, parentage analysis – a direct method to estimate connectivity – failed to match any parent-offspring pairs in this study; successful parentage assignments are highly dependent on intensive sampling of potential parents and are seldom feasible in marine systems, as most populations have large effective population sizes. Estimates of intergenerational effective population size for slinger in this study are considered large - >2 000 and infinite based on adults and juveniles, respectively. Population genetics revealed close genetic similarities between slinger adult and juvenile slinger sites, emphasizing genetic connectivity and the lack of structure between sites observed before. This was the first study on South African sparids to use RAD sequencing to assess genetic connectivity between MPAs along the east coast of South Africa. Overall, results provide evidence that MPAs along the east coast of South Africa are connected, and can readily replenish or be replenished by other sites along the east coast of South Africa, whether they are within MPAs or not. So too are the areas surrounding MPAs interconnected, and slinger forms a homogenous single population on the east coast of South Africa. This notwithstanding, it is important that east coast MPAs, particularly those that host spawning shoals of slinger, are well managed in order that they continue to provide recruits to sustain the population and support sustainable fisheries. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-04-05
- Authors: Ockhuis, Samantha Angelique Natasha
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435954 , vital:73215 , DOI 10.21504/10962/435954
- Description: Marine Protected Areas (MPAs) are advocated worldwide for the conservation of biodiversity and fisheries management, as well as for adaptation and resilience in the face of climate change. Their effectiveness has been noted through increases in abundances, biomass, sizes and diversity of species, as well as the recovery of overexploited fisheries. For MPAs to realise their full potential, these benefits need to expand beyond their boundaries through larval dispersal and/or adult spillover. Connectivity between MPAs is critical for planning and placement of MPAs, as this promotes the persistence of metapopulations, their recovery from disturbance, as well as productivity in marine ecosystems. The effectiveness of MPAs in conserving biodiversity along the east coast of South Africa has been established; however, limited evidence is available on whether they offer benefits beyond their boundaries, enhancing biodiversity and fisheries in adjacent areas. The slinger Chrysoblephus puniceus, an endemic southern African sparid, is a major component of the commercial linefishery in KwaZulu-Natal (KZN), South Africa and southern Mozambique, and is also caught in the recreational ski-boat fishery in these regions. The spawning of slinger occurs in shoals on offshore reefs from southern Mozambique to the north of KZN, and larvae are likely transported southwards, assisted by the southward-flowing Agulhas Current and promoted by a relatively long larval duration. Slinger are relatively resident, but occasional northward migrations have been observed. These life history characteristics suggested that slinger would be a suitable biological model to test connectivity along the east coast, and particularly connectivity between MPAs. The aim of this study was therefore to investigate connectivity of slinger between MPAs and the surrounding areas along the east coast of South Africa, using restriction-site-associated DNA (RAD) sequencing. This formed part of the larger CAPTOR project investigating east coast MPA connectivity across a range of taxa and habitat types. A temporal comparison of genetic diversity in slinger spanning two sampling events (2012 and 2018) revealed no substantial changes in genetic diversity, as well as a lack of genetic structure along the KZN coast. Similarly, no substantial changes in effective population size (Ne) were found between 2012 and 2018 for microsatellites and Single Nucleotide Polymorphisms (SNPs). However, subtle, albeit non-significant, differences were observed both spatially and over time in the microsatellite data, indicating some instability along the KZN coast. A lack of genetic structure based on RAD sequencing was observed between east coast MPAs and the surrounding areas. This implies high connectivity along the coast - not only are east coast MPAs connected, the surrounding areas are also connected, and there is replenishment between all areas via larval dispersal and/or adult spillover. Analyses of multidirectional gene flow between MPAs, together with known spatial spawning patterns and prior particle dispersal modelling, identified the Richards Bay area as a key source of recruits. However, parentage analysis – a direct method to estimate connectivity – failed to match any parent-offspring pairs in this study; successful parentage assignments are highly dependent on intensive sampling of potential parents and are seldom feasible in marine systems, as most populations have large effective population sizes. Estimates of intergenerational effective population size for slinger in this study are considered large - >2 000 and infinite based on adults and juveniles, respectively. Population genetics revealed close genetic similarities between slinger adult and juvenile slinger sites, emphasizing genetic connectivity and the lack of structure between sites observed before. This was the first study on South African sparids to use RAD sequencing to assess genetic connectivity between MPAs along the east coast of South Africa. Overall, results provide evidence that MPAs along the east coast of South Africa are connected, and can readily replenish or be replenished by other sites along the east coast of South Africa, whether they are within MPAs or not. So too are the areas surrounding MPAs interconnected, and slinger forms a homogenous single population on the east coast of South Africa. This notwithstanding, it is important that east coast MPAs, particularly those that host spawning shoals of slinger, are well managed in order that they continue to provide recruits to sustain the population and support sustainable fisheries. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-04-05
Identification of Mycobacterium tuberculosis DnaK substrates – towards inhibiting DnaK as a novel drug target for the treatment of tuberculosis
- Authors: Tonui, Ronald
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435975 , vital:73217
- Description: Access restricted. Expected release in 2026. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2024
- Full Text:
- Date Issued: 2024-04-05
- Authors: Tonui, Ronald
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435975 , vital:73217
- Description: Access restricted. Expected release in 2026. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2024
- Full Text:
- Date Issued: 2024-04-05
Ingqiqo yamanina kuxanduva lokusiphula neengcambu ugonyamelo nokuxhatshazwa: Uhlalutyo lweetekisi ZesiXhosa ezicatshulwe kuncwadi olubhalwe ngamanina (1976-2015)
- Authors: Bilatyi, Katy Nomthandazo
- Date: 2024-04-04
- Subjects: Uncatalogued
- Language: Xhosa
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435582 , vital:73170 , DOI 10.21504/10962/435582
- Description: Uphando luza kuqwalasela ingqiqo yamanina kuxanduva lokusiphula neengcambu ugonyamelo nokuxhatshazwa kwawo ngamadoda. Ingxoxo iza kugxila kubabhali abangamanina beencwadi zesiXhosa ezicatshulweyo kolu phando, nalapho kuqwalaselwa indlela ababazoba ngayo abalinganiswa babo abangamanina. Kule ngxoxo kuqwalaselwa indlela ababhali abangamanina abafana noBelebesi (1976), Dazela (1988), Magadla (1992) Madolo (1998), Mayosi (2003), Magqashela (2006) kunye noBuzani (2015) abathe babazoba ngayo abalinganiswa abangamanina kwiincwadi zesiXhosa ezicatshuliweyo. Oku kukutyhila ubukrelekrele bababhali ekusebenziseni uncwadi ukuzisa izisombululo kwimingeni ajamelene nayo amanina efana nogonyamelo kunye noxhatshwazo. Obu bukrelekrele baba babhali bujongwa ngokweembali ezimbini, imbali yaphambi kozuzo lwenkululeko emva kongenelelo lobuKoloniyali kunye neyasemva kozuzo lwenkululeko yaseMzantsi Afrika. Iincwadi ezikhethiweyo zibhalwe phakathi kweminyaka ye-1976 ukuya kwiminyaka yama-2015. Uphando luya kujonga ukuba lungaba lukhona utshintsho kusini na kwindlela la manina ababazoba ngayo abalinganiswa ngokwezi mbali zahlukileyo kananjalo naxa bezotywa ngababhali abangamadoda. Uphando luya kutyhila kananjalo imixholo nemixholwana abayikhethayo nedlulisa iimvakalelo zabo bengamanina kumbandela wogonyamelo olukhatshwa yipatriyakhi kunye noxhatshazo abalufumana kumadoda. Xa kuphendlwa le mixholo yaba babhali bahlukileyo baneemvelaphi ezahlukileyo ngokwemontlalo bebhala ngokwamaxesha okanye iimbhali ezahlukileyo, kuya kucaca ukuba amava abo ayafana nokuba linina okanye ibhinqa. Loo mava abo anele ukuba bajikeleze kwimixholo ebizwa ngokuba yifeminist themes nakubeni izimbo zabo zokubhala zahlukile nje. Injongo kukubonisa ukuba nangona amanina aphila phantsi kweemeko neemontlalo ezahlukileyo nje, iinzima neentlungu zawo azisombulula ngendlela efanayo ngokusebenzisa usiba. Le ngxoxo ikhatshwa ziithiyori ezifana nefemayinizimu, ngakumbi ifemayinizimu yaseAfrika kunye kunye nangokoMzantsi Afrika iquka iMotherism kunye nenkcubeko ephehlelelwe phantsi kwePatriyakhi. Ezi thiyori ziludondolo lokuphendla nokuhlalutya ezi ncwadi zikhethiweyo zesiXhosa ukuze sicacelwe yeyona ndima idlalwa ngamanina kuluntu nanjengoko sisazi ukuba apha eMzantsi Afrika adlale eyona ndima yokuncedisa ekuziseni utshintsho kwimibandela yengcinezelo nasekuzuzweni kwenkululeko. Yiyo loo nto kufuneka nawo abonakale exhamla ngokulinganayo namadoda kwinkululeko ayisebenzeleyo ngokususa ugonyamelo, uxhatshazo nokubulawa kwawo ngamadoda. , Thesis (PhD) -- Humanities, School of Languages and Literatures, 2024
- Full Text:
- Date Issued: 2024-04-04
- Authors: Bilatyi, Katy Nomthandazo
- Date: 2024-04-04
- Subjects: Uncatalogued
- Language: Xhosa
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435582 , vital:73170 , DOI 10.21504/10962/435582
- Description: Uphando luza kuqwalasela ingqiqo yamanina kuxanduva lokusiphula neengcambu ugonyamelo nokuxhatshazwa kwawo ngamadoda. Ingxoxo iza kugxila kubabhali abangamanina beencwadi zesiXhosa ezicatshulweyo kolu phando, nalapho kuqwalaselwa indlela ababazoba ngayo abalinganiswa babo abangamanina. Kule ngxoxo kuqwalaselwa indlela ababhali abangamanina abafana noBelebesi (1976), Dazela (1988), Magadla (1992) Madolo (1998), Mayosi (2003), Magqashela (2006) kunye noBuzani (2015) abathe babazoba ngayo abalinganiswa abangamanina kwiincwadi zesiXhosa ezicatshuliweyo. Oku kukutyhila ubukrelekrele bababhali ekusebenziseni uncwadi ukuzisa izisombululo kwimingeni ajamelene nayo amanina efana nogonyamelo kunye noxhatshwazo. Obu bukrelekrele baba babhali bujongwa ngokweembali ezimbini, imbali yaphambi kozuzo lwenkululeko emva kongenelelo lobuKoloniyali kunye neyasemva kozuzo lwenkululeko yaseMzantsi Afrika. Iincwadi ezikhethiweyo zibhalwe phakathi kweminyaka ye-1976 ukuya kwiminyaka yama-2015. Uphando luya kujonga ukuba lungaba lukhona utshintsho kusini na kwindlela la manina ababazoba ngayo abalinganiswa ngokwezi mbali zahlukileyo kananjalo naxa bezotywa ngababhali abangamadoda. Uphando luya kutyhila kananjalo imixholo nemixholwana abayikhethayo nedlulisa iimvakalelo zabo bengamanina kumbandela wogonyamelo olukhatshwa yipatriyakhi kunye noxhatshazo abalufumana kumadoda. Xa kuphendlwa le mixholo yaba babhali bahlukileyo baneemvelaphi ezahlukileyo ngokwemontlalo bebhala ngokwamaxesha okanye iimbhali ezahlukileyo, kuya kucaca ukuba amava abo ayafana nokuba linina okanye ibhinqa. Loo mava abo anele ukuba bajikeleze kwimixholo ebizwa ngokuba yifeminist themes nakubeni izimbo zabo zokubhala zahlukile nje. Injongo kukubonisa ukuba nangona amanina aphila phantsi kweemeko neemontlalo ezahlukileyo nje, iinzima neentlungu zawo azisombulula ngendlela efanayo ngokusebenzisa usiba. Le ngxoxo ikhatshwa ziithiyori ezifana nefemayinizimu, ngakumbi ifemayinizimu yaseAfrika kunye kunye nangokoMzantsi Afrika iquka iMotherism kunye nenkcubeko ephehlelelwe phantsi kwePatriyakhi. Ezi thiyori ziludondolo lokuphendla nokuhlalutya ezi ncwadi zikhethiweyo zesiXhosa ukuze sicacelwe yeyona ndima idlalwa ngamanina kuluntu nanjengoko sisazi ukuba apha eMzantsi Afrika adlale eyona ndima yokuncedisa ekuziseni utshintsho kwimibandela yengcinezelo nasekuzuzweni kwenkululeko. Yiyo loo nto kufuneka nawo abonakale exhamla ngokulinganayo namadoda kwinkululeko ayisebenzeleyo ngokususa ugonyamelo, uxhatshazo nokubulawa kwawo ngamadoda. , Thesis (PhD) -- Humanities, School of Languages and Literatures, 2024
- Full Text:
- Date Issued: 2024-04-04
The influence of electronic-consumer experience (e-CX) on consumer post-purchase outcomes of South African e-commerce retail organisations
- Authors: Williams, Alyssa Shawntay
- Date: 2024-04-03
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/434828 , vital:73108
- Description: Access restricted. Expected release in 2026. , Thesis (PhD) -- Faculty of Commerce, Management, 2024
- Full Text:
- Date Issued: 2024-04-03
- Authors: Williams, Alyssa Shawntay
- Date: 2024-04-03
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/434828 , vital:73108
- Description: Access restricted. Expected release in 2026. , Thesis (PhD) -- Faculty of Commerce, Management, 2024
- Full Text:
- Date Issued: 2024-04-03
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