The contribution of land tenure diversity to the spatial resilience of protected area networks
- de Vos, Alta, Cumming, George S
- Authors: de Vos, Alta , Cumming, George S
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416421 , vital:71347 , xlink:href="https://doi.org/10.1002/pan3.29"
- Description: The relationship between diversity and resilience is relatively well‐established for ecological systems, but remains much less explored for socio‐economic systems. Institutional diversity can have particular relevance for protected areas, whose managerial responses to environmental change depend on their legal basis, ability to make and enforce rules and socio‐political acceptance and endorsement. 2. Protected area expansion strategies are increasingly turning to private land con‐ servation to increase the configuration and connectivity of national protected area networks. Yet, we know little about the relative role of privately owned pro‐ tected areas in protecting threatened and poorly protected (under‐represented) habitats, and in the overall connectivity of the national protected area network. 3. We present an empirical assessment of protected area tenure diversity across South Africa.
- Full Text:
- Date Issued: 2019
- Authors: de Vos, Alta , Cumming, George S
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416421 , vital:71347 , xlink:href="https://doi.org/10.1002/pan3.29"
- Description: The relationship between diversity and resilience is relatively well‐established for ecological systems, but remains much less explored for socio‐economic systems. Institutional diversity can have particular relevance for protected areas, whose managerial responses to environmental change depend on their legal basis, ability to make and enforce rules and socio‐political acceptance and endorsement. 2. Protected area expansion strategies are increasingly turning to private land con‐ servation to increase the configuration and connectivity of national protected area networks. Yet, we know little about the relative role of privately owned pro‐ tected areas in protecting threatened and poorly protected (under‐represented) habitats, and in the overall connectivity of the national protected area network. 3. We present an empirical assessment of protected area tenure diversity across South Africa.
- Full Text:
- Date Issued: 2019
Ultrafast Photodynamics of the Indoline Dye D149 Adsorbed to Porous ZnO in Dye-Sensitized Solar Cells
- Rohwer, Egmont, Richter, Christoph, Heming, Nadine, Strauch, Kerstin, Litwinski, Christian, Nyokong, Tebello, Schlettwein, Derck, Schwoerer, Heinrich
- Authors: Rohwer, Egmont , Richter, Christoph , Heming, Nadine , Strauch, Kerstin , Litwinski, Christian , Nyokong, Tebello , Schlettwein, Derck , Schwoerer, Heinrich
- Language: English
- Type: Article
- Identifier: vital:7326 , http://hdl.handle.net/10962/d1020576
- Description: We investigate the ultrafast dynamics of the photoinduced electron transfer between surface-adsorbed indoline D149 dye and porous ZnO as used in the working electrodes of dye-sensitized solar cells. Transient absorption spectroscopy was conducted on the dye in solution, on solid state samples and for the latter in contact to a I−/I3− redox electrolyte typical for dye-sensitized solar cells to elucidate the effect of each component in the observed dynamics. D149 in a solution of 1:1 acetonitrile and tert-butyl alcohol shows excited-state lifetimes of 300±50 ps. This signature is severely quenched when D149 is adsorbed to ZnO, with the fastest component of the decay trace measured at 150±20 fs due to the charge-transfer mechanism. Absorption bands of the oxidized dye molecule were investigated to determine regeneration times which are in excess of 1 ns. The addition of the redox electrolyte to the system results in faster regeneration times, of the order of 1 ns. , Original publication is available at http://dx.doi.org/10.1002/cphc.201200715
- Full Text: false
- Authors: Rohwer, Egmont , Richter, Christoph , Heming, Nadine , Strauch, Kerstin , Litwinski, Christian , Nyokong, Tebello , Schlettwein, Derck , Schwoerer, Heinrich
- Language: English
- Type: Article
- Identifier: vital:7326 , http://hdl.handle.net/10962/d1020576
- Description: We investigate the ultrafast dynamics of the photoinduced electron transfer between surface-adsorbed indoline D149 dye and porous ZnO as used in the working electrodes of dye-sensitized solar cells. Transient absorption spectroscopy was conducted on the dye in solution, on solid state samples and for the latter in contact to a I−/I3− redox electrolyte typical for dye-sensitized solar cells to elucidate the effect of each component in the observed dynamics. D149 in a solution of 1:1 acetonitrile and tert-butyl alcohol shows excited-state lifetimes of 300±50 ps. This signature is severely quenched when D149 is adsorbed to ZnO, with the fastest component of the decay trace measured at 150±20 fs due to the charge-transfer mechanism. Absorption bands of the oxidized dye molecule were investigated to determine regeneration times which are in excess of 1 ns. The addition of the redox electrolyte to the system results in faster regeneration times, of the order of 1 ns. , Original publication is available at http://dx.doi.org/10.1002/cphc.201200715
- Full Text: false
Development of Graphene/CdSe Quantum Dots-Co Phthalocyanine Nanocomposite for Oxygen Reduction Reaction
- Nyoni, Stephen, Nyokong, Tebello
- Authors: Nyoni, Stephen , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7300 , http://hdl.handle.net/10962/d1020368
- Description: Nanocomposites containing CdSe quantum dots, tetra(4-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninatocobalt(II)) (CoPyPc) and reduced graphene nanosheets (rGNS) were devoloped and used for the modification of a glassy carbon electrode. Characterization of the nanocomposites was done by transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses. Cyclic voltammetry (CV) was used for electrochemical characterization of the prepared nanocomposite for oxygen reduction reaction. The oxygen reduction activity for rGNS/CdSe-CoPyPc nanocomposite was found to be superior over the individual nanomaterials in this study. The activity of the nanocomposite towards oxygen reduction was also tested for tolerance to methanol crossover effect using chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) studies. , Original publication is available at http://dx.doi.org/10.1002/elan.201400372
- Full Text: false
- Authors: Nyoni, Stephen , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7300 , http://hdl.handle.net/10962/d1020368
- Description: Nanocomposites containing CdSe quantum dots, tetra(4-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninatocobalt(II)) (CoPyPc) and reduced graphene nanosheets (rGNS) were devoloped and used for the modification of a glassy carbon electrode. Characterization of the nanocomposites was done by transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses. Cyclic voltammetry (CV) was used for electrochemical characterization of the prepared nanocomposite for oxygen reduction reaction. The oxygen reduction activity for rGNS/CdSe-CoPyPc nanocomposite was found to be superior over the individual nanomaterials in this study. The activity of the nanocomposite towards oxygen reduction was also tested for tolerance to methanol crossover effect using chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) studies. , Original publication is available at http://dx.doi.org/10.1002/elan.201400372
- Full Text: false
Deposition of CdS, CdS/ZnSe and CdS/ZnSe/ZnS shells around CdSeTe alloyed core quantum dots: effects on optical properties
- Adegoke, Oluwasesan, Nyokong, Tebello, Forbes, Patricia B C
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Language: English
- Type: Article
- Identifier: vital:7289 , http://hdl.handle.net/10962/d1020342
- Description: In this work, we synthesized water-soluble L-cysteine-capped alloyed CdSeTe core quantum dots (QDs) and investigated the structural and optical properties of deposition of each of CdS, CdS/ZnSe and CdS/ZnSe/ZnS shell layers. Photophysical results showed that the overcoating of a CdS shell around the alloyed CdSeTe core [quantum yield (QY) = 8.4%] resulted in effective confinement of the radiative exciton with an improved QY value of 93.5%. Subsequent deposition of a ZnSe shell around the CdSeTe/CdS surface decreased the QY value to 24.7%, but an increase in the QY value of up to 49.5% was observed when a ZnS shell was overcoated around the CdSeTe/CdS/ZnSe surface. QDs with shell layers showed improved stability relative to the core. Data obtained from time-resolved fluorescence measurements provided useful insight into variations in the photophysical properties of the QDs upon the formation of each shell layer. Our study suggests that the formation of CdSeTe/CdS core/shell QDs meets the requirements of quality QDs in terms of high photoluminescence QY and stability, hence further deposition of additional shells are not necessary in improving the optical properties of the core/shell QDs. Copyright © 2015 John Wiley & Sons, Ltd. , Original publication is available at http://dx.doi.org/10.1002/bio.3013
- Full Text: false
- Date Issued: 2015
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Language: English
- Type: Article
- Identifier: vital:7289 , http://hdl.handle.net/10962/d1020342
- Description: In this work, we synthesized water-soluble L-cysteine-capped alloyed CdSeTe core quantum dots (QDs) and investigated the structural and optical properties of deposition of each of CdS, CdS/ZnSe and CdS/ZnSe/ZnS shell layers. Photophysical results showed that the overcoating of a CdS shell around the alloyed CdSeTe core [quantum yield (QY) = 8.4%] resulted in effective confinement of the radiative exciton with an improved QY value of 93.5%. Subsequent deposition of a ZnSe shell around the CdSeTe/CdS surface decreased the QY value to 24.7%, but an increase in the QY value of up to 49.5% was observed when a ZnS shell was overcoated around the CdSeTe/CdS/ZnSe surface. QDs with shell layers showed improved stability relative to the core. Data obtained from time-resolved fluorescence measurements provided useful insight into variations in the photophysical properties of the QDs upon the formation of each shell layer. Our study suggests that the formation of CdSeTe/CdS core/shell QDs meets the requirements of quality QDs in terms of high photoluminescence QY and stability, hence further deposition of additional shells are not necessary in improving the optical properties of the core/shell QDs. Copyright © 2015 John Wiley & Sons, Ltd. , Original publication is available at http://dx.doi.org/10.1002/bio.3013
- Full Text: false
- Date Issued: 2015
Behavior of Palladium Nanoparticles in the Absence or Presence of Cobalt Tetraaminophthalocyanine for the Electrooxidation of Hydrazine
- Maringa, Audacity, Nyokong, Tebello
- Authors: Maringa, Audacity , Nyokong, Tebello
- Date: 2014
- Language: English
- Type: Article
- Identifier: vital:7305 , http://hdl.handle.net/10962/d1020382
- Description: We report on the electrodeposition of palladium nanoparticles (PdNPs) on a glassy carbon electrode (GCE) and onto a poly-CoTAPc-GCE (CoTAPc=cobalt tetraamino phthalocyanine) surface. The electrodes are denoted as PdNPs-GCE and PdNPs/poly-CoTAPc-GCE, respectively. PdNPs/poly-CoTAPc-GCE showed the best activity for the oxidation of hydrazine at the lowest potential of −0.28 V and with the highest currents. The results were further supported by electrochemical impedance spectroscopy (EIS) which showed that there was less resistance to charge transfer for PdNPs/poly-CoTAPc-GCE compared to PdNPs-GCE. The catalytic rate constant for hydrazine oxidation was 6.12×108 cm3 mol−1 s−1 using PdNPs/poly-CoTAPc-GCE. , Original publication is available at http://dx.doi.org/10.1002/elan.201400028
- Full Text: false
- Date Issued: 2014
- Authors: Maringa, Audacity , Nyokong, Tebello
- Date: 2014
- Language: English
- Type: Article
- Identifier: vital:7305 , http://hdl.handle.net/10962/d1020382
- Description: We report on the electrodeposition of palladium nanoparticles (PdNPs) on a glassy carbon electrode (GCE) and onto a poly-CoTAPc-GCE (CoTAPc=cobalt tetraamino phthalocyanine) surface. The electrodes are denoted as PdNPs-GCE and PdNPs/poly-CoTAPc-GCE, respectively. PdNPs/poly-CoTAPc-GCE showed the best activity for the oxidation of hydrazine at the lowest potential of −0.28 V and with the highest currents. The results were further supported by electrochemical impedance spectroscopy (EIS) which showed that there was less resistance to charge transfer for PdNPs/poly-CoTAPc-GCE compared to PdNPs-GCE. The catalytic rate constant for hydrazine oxidation was 6.12×108 cm3 mol−1 s−1 using PdNPs/poly-CoTAPc-GCE. , Original publication is available at http://dx.doi.org/10.1002/elan.201400028
- Full Text: false
- Date Issued: 2014
Integrating chemical control with sterile insect releases in an integrated pest management programme for Thaumatotibia leucotreta
- Nepgen, Eugene, Moore, Sean D, Hill, Martin P
- Authors: Nepgen, Eugene , Moore, Sean D , Hill, Martin P
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423770 , vital:72092 , xlink:href="https://doi.org/10.1111/jen.12487"
- Description: False codling moth Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is an important indigenous pest of citrus in southern Africa. Successful control is dependent upon integration of area-wide sterile insect releases and other suppression methods. The aim of this work was to test pyrethroid and organophosphate-based insecticides (tau-fluvalinate and chlorpyrifos) for their residual effect on mortality of released irradiated T. leucotreta male moths. Both of these insecticides were effective in killing irradiated T. leucotreta for 7 days after application on leaves, after which degradation of the active ingredient resulted in a marked reduction in efficacy after 14 days and rendering them harmless. Mortality was found to be similar for irradiated and non-irradiated male T. leucotreta after treatment. Consequently, even though these insecticides might have an effect on moths in the field, ratios of sterile:wild moths should not be altered. Supporting field data from six sites in the Sundays River Valley over a season of sterile insect releases showed the conventional chemical crop protection programme to be as effective as an integrated pest management programme in facilitating effective control of T. leucotreta through sterile insect releases. The study also confirmed that the ratios of sterile:wild male moths in the commercial citrus orchards were not affected by the application of insecticides. These findings confirm the high potential of sterile insect releases for control of T. leucotreta in citrus.
- Full Text:
- Date Issued: 2018
- Authors: Nepgen, Eugene , Moore, Sean D , Hill, Martin P
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423770 , vital:72092 , xlink:href="https://doi.org/10.1111/jen.12487"
- Description: False codling moth Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is an important indigenous pest of citrus in southern Africa. Successful control is dependent upon integration of area-wide sterile insect releases and other suppression methods. The aim of this work was to test pyrethroid and organophosphate-based insecticides (tau-fluvalinate and chlorpyrifos) for their residual effect on mortality of released irradiated T. leucotreta male moths. Both of these insecticides were effective in killing irradiated T. leucotreta for 7 days after application on leaves, after which degradation of the active ingredient resulted in a marked reduction in efficacy after 14 days and rendering them harmless. Mortality was found to be similar for irradiated and non-irradiated male T. leucotreta after treatment. Consequently, even though these insecticides might have an effect on moths in the field, ratios of sterile:wild moths should not be altered. Supporting field data from six sites in the Sundays River Valley over a season of sterile insect releases showed the conventional chemical crop protection programme to be as effective as an integrated pest management programme in facilitating effective control of T. leucotreta through sterile insect releases. The study also confirmed that the ratios of sterile:wild male moths in the commercial citrus orchards were not affected by the application of insecticides. These findings confirm the high potential of sterile insect releases for control of T. leucotreta in citrus.
- Full Text:
- Date Issued: 2018
Comparisons of isotopic niche widths of some invasive and indigenous fauna in a South African river
- Hill, Jaclyn M, Jones, Roy W, Hill, Martin P, Weyl, Olaf L F
- Authors: Hill, Jaclyn M , Jones, Roy W , Hill, Martin P , Weyl, Olaf L F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423711 , vital:72088 , xlink:href="https://doi.org/10.1111/fwb.12542"
- Description: Biological invasions threaten ecosystem integrity and bio-diversity, with numerous adverse implications for native flora and fauna. Established populations of two notorious freshwater invaders, the snail Tarebia granifera and the fish Pterygoplichthys disjunctivus, have been reported on three continents and are frequently predicted to be in di-rect competition with native species for dietary resources.
- Full Text:
- Date Issued: 2015
- Authors: Hill, Jaclyn M , Jones, Roy W , Hill, Martin P , Weyl, Olaf L F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423711 , vital:72088 , xlink:href="https://doi.org/10.1111/fwb.12542"
- Description: Biological invasions threaten ecosystem integrity and bio-diversity, with numerous adverse implications for native flora and fauna. Established populations of two notorious freshwater invaders, the snail Tarebia granifera and the fish Pterygoplichthys disjunctivus, have been reported on three continents and are frequently predicted to be in di-rect competition with native species for dietary resources.
- Full Text:
- Date Issued: 2015
Thaumatotibia leucotreta and the Navel orange: ovipositional preferences and host susceptibility
- Love, C N, Hill, Martin P, Moore, Sean D
- Authors: Love, C N , Hill, Martin P , Moore, Sean D
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423811 , vital:72095 , xlink:href="https://doi.org/10.1111/jen.12126"
- Description: False codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), presents a significant threat to the South African citrus industry. To limit income loss due to direct larval damage or from fruit rejection due to the phytosanitary status of this pest, additional pre-harvest control techniques are required for Navel oranges, which are known to be susceptible to T.leucotreta damage. A number of Navel orange cultivars have been developed, and differences in female T. leucotretaovi positional preference and susceptibility of cultivars to larval penetration are known to exist. Navel orange cultivars were grouped according to time of maturity (early, mid- and late season). Female T.leucotreta were subjected to choice and no-choice tests with these cultivars, measured by oviposition. Host susceptibility was tested by allowing neonate T. leucotreta larvae to penetrate the different Navel cultivars. In the early maturing group, Fischer Navels were least preferred for oviposition and the least susceptible to larval penetration. The mid- and late season maturing groupings showed limited differences in oviposition preference, although host susceptibility did appear to be an important factor in assessing the vulnerability of fruit to T. leucotreta. Despite being widely planted in South Africa, the mid-season Palmer Navels were highly susceptible to larval penetration, while for the late season cultivars, Cambria and Glen Ora Late were the least susceptible to T. leucotreta. As a result of these laboratory trials, it is recommended that farmers increase cultivation of Fischer Navels as the principal early season cultivar, avoid Palmer Navels in favour of other mid-season maturing cultivars and give preference to the late maturing Cambria and Glen Ora Late cultivars, to limit T. Leucotreta damage.
- Full Text:
- Date Issued: 2014
- Authors: Love, C N , Hill, Martin P , Moore, Sean D
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423811 , vital:72095 , xlink:href="https://doi.org/10.1111/jen.12126"
- Description: False codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), presents a significant threat to the South African citrus industry. To limit income loss due to direct larval damage or from fruit rejection due to the phytosanitary status of this pest, additional pre-harvest control techniques are required for Navel oranges, which are known to be susceptible to T.leucotreta damage. A number of Navel orange cultivars have been developed, and differences in female T. leucotretaovi positional preference and susceptibility of cultivars to larval penetration are known to exist. Navel orange cultivars were grouped according to time of maturity (early, mid- and late season). Female T.leucotreta were subjected to choice and no-choice tests with these cultivars, measured by oviposition. Host susceptibility was tested by allowing neonate T. leucotreta larvae to penetrate the different Navel cultivars. In the early maturing group, Fischer Navels were least preferred for oviposition and the least susceptible to larval penetration. The mid- and late season maturing groupings showed limited differences in oviposition preference, although host susceptibility did appear to be an important factor in assessing the vulnerability of fruit to T. leucotreta. Despite being widely planted in South Africa, the mid-season Palmer Navels were highly susceptible to larval penetration, while for the late season cultivars, Cambria and Glen Ora Late were the least susceptible to T. leucotreta. As a result of these laboratory trials, it is recommended that farmers increase cultivation of Fischer Navels as the principal early season cultivar, avoid Palmer Navels in favour of other mid-season maturing cultivars and give preference to the late maturing Cambria and Glen Ora Late cultivars, to limit T. Leucotreta damage.
- Full Text:
- Date Issued: 2014
The nocturnal larvae of a specialist folivore perform better on C hromolaena odorata leaves from a shaded environment
- Osariyekemwen O. Uyi, Costas Zachariades, Hill, Martin P, Conlong, Desmond
- Authors: Osariyekemwen O. Uyi , Costas Zachariades , Hill, Martin P , Conlong, Desmond
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424855 , vital:72189 , xlink:href="https://doi.org/10.1111/eea.12321"
- Description: Increasing evidence suggests that individuals of the same plant species occurring in different micro-habitats often show a degree of phenotypic and phytochemical variation. Consequently, insect herbivores associated with such plant species must deal with environment-mediated changes or variability in the traits of their host plants. In this study, we examined the effects of habitat condition (shadedvs. full-sun habitats) on plant traits and leaf characteristics of the invasive alien plant, Chromolaenaodorata (L.) King and Robinson (Asteraceae). In addition, the performance was evaluated in two generations of a specialist folivore, Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae: Arctiinae), on leaves obtained from both shaded and full-sun habitats. The study was done in an area where the insect was introduced as a biological control agent. Leaves growing in shade were less tough, had higher water and nitrogen content, and lower total non-structural carbohydrate, compared with leaves growing in full sun. Plants growing in shade had longer leaves and were taller, but above-ground biomass was significantly reduced compared with plants growing in full sun. In both generations (parents and offspring), P. insulata developed faster and had larger pupal mass, increased growth rate, and higher fecundity when reared on shaded foliage compared with full-sun foliage. Although immature survival and adult longevity did not differ between habitats, Maw’s host suitability index indicated that shaded leaves were more suitable for the growth and reproduction of P. insulata. We suggest that the benefits obtained by P.insulata feeding on shaded foliage are associated with reduced toughness and enhanced nitrogen and water content of leaves. These results demonstrate that light-mediated changes in plant traits and leaf characteristics can affect insect folivore performance.
- Full Text:
- Date Issued: 2015
- Authors: Osariyekemwen O. Uyi , Costas Zachariades , Hill, Martin P , Conlong, Desmond
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424855 , vital:72189 , xlink:href="https://doi.org/10.1111/eea.12321"
- Description: Increasing evidence suggests that individuals of the same plant species occurring in different micro-habitats often show a degree of phenotypic and phytochemical variation. Consequently, insect herbivores associated with such plant species must deal with environment-mediated changes or variability in the traits of their host plants. In this study, we examined the effects of habitat condition (shadedvs. full-sun habitats) on plant traits and leaf characteristics of the invasive alien plant, Chromolaenaodorata (L.) King and Robinson (Asteraceae). In addition, the performance was evaluated in two generations of a specialist folivore, Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae: Arctiinae), on leaves obtained from both shaded and full-sun habitats. The study was done in an area where the insect was introduced as a biological control agent. Leaves growing in shade were less tough, had higher water and nitrogen content, and lower total non-structural carbohydrate, compared with leaves growing in full sun. Plants growing in shade had longer leaves and were taller, but above-ground biomass was significantly reduced compared with plants growing in full sun. In both generations (parents and offspring), P. insulata developed faster and had larger pupal mass, increased growth rate, and higher fecundity when reared on shaded foliage compared with full-sun foliage. Although immature survival and adult longevity did not differ between habitats, Maw’s host suitability index indicated that shaded leaves were more suitable for the growth and reproduction of P. insulata. We suggest that the benefits obtained by P.insulata feeding on shaded foliage are associated with reduced toughness and enhanced nitrogen and water content of leaves. These results demonstrate that light-mediated changes in plant traits and leaf characteristics can affect insect folivore performance.
- Full Text:
- Date Issued: 2015
The importance of long-term post-release studies in classical biological control: Insect–plant monitoring and public awareness of water hyacinth management (Pontederia crassipes) in Dique Los Sauces, Argentina
- Faltlhauser, Ana C, Jiménez, Nadia L, Righetti, Tomas, Visintin, Andrés M, Torrens, Javier, Salinas, Nicolás A, Mc Kay, Fernando, Hill, Martin P, Cordo, Hugo A, Sosa, Alejandro J
- Authors: Faltlhauser, Ana C , Jiménez, Nadia L , Righetti, Tomas , Visintin, Andrés M , Torrens, Javier , Salinas, Nicolás A , Mc Kay, Fernando , Hill, Martin P , Cordo, Hugo A , Sosa, Alejandro J
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424828 , vital:72187 , xlink:href="https://doi.org/10.1111/eea.13355"
- Description: Several components of classical biological control (CBC) programmes are necessary to assess the success of the management strategy (e.g., post-release monitoring) and also help prevent reintroductions or resurgences of invasive species (e.g., public awareness). Water hyacinth, Pontederia (= Eichhornia) crassipes (Mart.) Solms (Pontederiaceae) is an aquatic plant naturally distributed in the north-eastern region of the Del Plata basin in Argentina. In the 1960s it was introduced into the Dique Los Sauces reservoir located outside of its native range in La Rioja Province, in western Argentina, where it became invasive. The natural enemy, Neochetina bruchi Hustache (Coleoptera: Curculionidae), was intentionally introduced in 1974 to control the weed. To assess the success of this CBC programme, a long-term post-release study was conducted. Between 1965 and 2023, we monitored plant coverage, estimated N. bruchi densities, and quantified the associated damage by reanalysing previously published data and incorporating new sampling. We also conducted an online survey to analyse public knowledge and perception about this programme. Water hyacinth coverage fluctuated from its first record in 1965 (maximum coverage 90%) until the control of germinated plants (coverage 0%) in 2018. The plant decline was accompanied by an increase in the weevil population. In our survey, out of 325 respondents only a small group of mostly middle-aged and elderly people knew that the restoration had been achieved through a management strategy and even fewer were aware of the biocontrol approach taken. Respondents who had a positive approach to biological control were more aware of the management plan than respondents who had neutral or negative opinions. Neochetina bruchi has played a key factor in the control of P. crassipes. The intrinsic dynamics of these populations, the dormant seed bank, and the lack of public awareness support the need for long post-release evaluations including outreach campaigns to make a sustainable successful management programme.
- Full Text:
- Date Issued: 2023
- Authors: Faltlhauser, Ana C , Jiménez, Nadia L , Righetti, Tomas , Visintin, Andrés M , Torrens, Javier , Salinas, Nicolás A , Mc Kay, Fernando , Hill, Martin P , Cordo, Hugo A , Sosa, Alejandro J
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424828 , vital:72187 , xlink:href="https://doi.org/10.1111/eea.13355"
- Description: Several components of classical biological control (CBC) programmes are necessary to assess the success of the management strategy (e.g., post-release monitoring) and also help prevent reintroductions or resurgences of invasive species (e.g., public awareness). Water hyacinth, Pontederia (= Eichhornia) crassipes (Mart.) Solms (Pontederiaceae) is an aquatic plant naturally distributed in the north-eastern region of the Del Plata basin in Argentina. In the 1960s it was introduced into the Dique Los Sauces reservoir located outside of its native range in La Rioja Province, in western Argentina, where it became invasive. The natural enemy, Neochetina bruchi Hustache (Coleoptera: Curculionidae), was intentionally introduced in 1974 to control the weed. To assess the success of this CBC programme, a long-term post-release study was conducted. Between 1965 and 2023, we monitored plant coverage, estimated N. bruchi densities, and quantified the associated damage by reanalysing previously published data and incorporating new sampling. We also conducted an online survey to analyse public knowledge and perception about this programme. Water hyacinth coverage fluctuated from its first record in 1965 (maximum coverage 90%) until the control of germinated plants (coverage 0%) in 2018. The plant decline was accompanied by an increase in the weevil population. In our survey, out of 325 respondents only a small group of mostly middle-aged and elderly people knew that the restoration had been achieved through a management strategy and even fewer were aware of the biocontrol approach taken. Respondents who had a positive approach to biological control were more aware of the management plan than respondents who had neutral or negative opinions. Neochetina bruchi has played a key factor in the control of P. crassipes. The intrinsic dynamics of these populations, the dormant seed bank, and the lack of public awareness support the need for long post-release evaluations including outreach campaigns to make a sustainable successful management programme.
- Full Text:
- Date Issued: 2023
Two in one: cryptic species discovered in biological control agent populations using molecular data and crossbreeding experiments
- Paterson, Iain D, Mangan, Rose, Downie, Douglas A, Coetzee, Julie A, Hill, Martin P, Burke, Ashley M, Downey, Paul O, Henry, Thomas J, Compton, Stephen G
- Authors: Paterson, Iain D , Mangan, Rose , Downie, Douglas A , Coetzee, Julie A , Hill, Martin P , Burke, Ashley M , Downey, Paul O , Henry, Thomas J , Compton, Stephen G
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424877 , vital:72191 , xlink:href="https://doi.org/10.1002/ece3.2297"
- Description: There are many examples of cryptic species that have been identified through DNA-barcoding or other genetic techniques. There are, however, very few confirmations of cryptic species being reproductively isolated. This study presents one of the few cases of cryptic species that has been confirmed to be reproductively isolated and therefore true species according to the biological species concept. The cryptic species are of special interest because they were discovered within biological control agent populations. Two geographically isolated populations of Eccritotarsus catarinensis (Carvalho) [Hemiptera: Miridae], a biological control agent for the invasive aquatic macrophyte, water hyacinth, Eichhornia crassipes (Mart.) Solms [Pontederiaceae], in South Africa, were sampled from the native range of the species in South America. Morphological characteristics indicated that both populations were the same species according to the current taxonomy, but subsequent DNA analysis and breeding experiments revealed that the two populations are reproductively isolated. Crossbreeding experiments resulted in very few hybrid offspring when individuals were forced to interbreed with individuals of the other population, and no hybrid offspring were recorded when a choice of mate from either population was offered. The data indicate that the two populations are cryptic species that are reproductively incompatible. Subtle but reliable diagnostic characteristics were then identified to distinguish between the two species which would have been considered intraspecific variation without the data from the genetics and interbreeding experiments. These findings suggest that all consignments of biological control agents from allopatric populations should be screened for cryptic species using genetic techniques and that the importation of multiple consignments of the same species for biological control should be conducted with caution.
- Full Text:
- Date Issued: 2016
- Authors: Paterson, Iain D , Mangan, Rose , Downie, Douglas A , Coetzee, Julie A , Hill, Martin P , Burke, Ashley M , Downey, Paul O , Henry, Thomas J , Compton, Stephen G
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424877 , vital:72191 , xlink:href="https://doi.org/10.1002/ece3.2297"
- Description: There are many examples of cryptic species that have been identified through DNA-barcoding or other genetic techniques. There are, however, very few confirmations of cryptic species being reproductively isolated. This study presents one of the few cases of cryptic species that has been confirmed to be reproductively isolated and therefore true species according to the biological species concept. The cryptic species are of special interest because they were discovered within biological control agent populations. Two geographically isolated populations of Eccritotarsus catarinensis (Carvalho) [Hemiptera: Miridae], a biological control agent for the invasive aquatic macrophyte, water hyacinth, Eichhornia crassipes (Mart.) Solms [Pontederiaceae], in South Africa, were sampled from the native range of the species in South America. Morphological characteristics indicated that both populations were the same species according to the current taxonomy, but subsequent DNA analysis and breeding experiments revealed that the two populations are reproductively isolated. Crossbreeding experiments resulted in very few hybrid offspring when individuals were forced to interbreed with individuals of the other population, and no hybrid offspring were recorded when a choice of mate from either population was offered. The data indicate that the two populations are cryptic species that are reproductively incompatible. Subtle but reliable diagnostic characteristics were then identified to distinguish between the two species which would have been considered intraspecific variation without the data from the genetics and interbreeding experiments. These findings suggest that all consignments of biological control agents from allopatric populations should be screened for cryptic species using genetic techniques and that the importation of multiple consignments of the same species for biological control should be conducted with caution.
- Full Text:
- Date Issued: 2016
Thermal plasticity and microevolution enhance establishment success and persistence of a water hyacinth biological control agent
- Griffith, Tamzin C, Paterson, Iain D, Owen, Candice A, Coetzee, Julie A
- Authors: Griffith, Tamzin C , Paterson, Iain D , Owen, Candice A , Coetzee, Julie A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424866 , vital:72190 , xlink:href="https://doi.org/10.1111/eea.12814"
- Description: Aspects of the thermal physiology of the water hyacinth biological control agent Eccritotarsus catarinensis Carvalho (Hemiptera: Miridae) have been extensively investigated over the past 20 years to understand and improve post-release establishment in the field. Thermal physiology studies predicted that the agent would not establish at a number of cold sites in South Africa, where it has nonetheless subsequently established and thrived. Recently, studies have begun to incorporate the plastic nature of insect thermal physiology into models of agent establishment. This study determined whether season and locality influenced the thermal physiology of two field populations of E. catarinensis, one collected from the hottest site where the agent has established in South Africa, and one from the coldest site. The thermal physiology of E. catarinensis was significantly influenced by season and site, demonstrating a degree of phenotypic plasticity, and that some post-release local adaptation to climatic conditions has occurred through microevolution. We then determined whether cold acclimation under laboratory conditions was possible. Successfully cold-acclimated E. catarinensis had a significantly lower critical thermal minimum (CTmin) compared to the field cold-acclimated population. This suggests that cold acclimation of agents could be conducted in the laboratory before future releases to improve their cold tolerance, thereby increasing their chance of establishment at cold sites and allowing further adaptation to colder climates to occur in the field. Although the thermal tolerance of E. catarinensis is limited by local adaptations to climatic conditions in the native range, the plastic nature of the insect's thermal physiology has allowed it to survive in the very different climatic conditions of the introduced range, and there has been some adaptive change to the insect's thermal tolerance since establishment. This study highlights the importance of plasticity and microevolutionary processes in the success of biological control agents under the novel climatic conditions in the introduced range.
- Full Text:
- Date Issued: 2019
- Authors: Griffith, Tamzin C , Paterson, Iain D , Owen, Candice A , Coetzee, Julie A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424866 , vital:72190 , xlink:href="https://doi.org/10.1111/eea.12814"
- Description: Aspects of the thermal physiology of the water hyacinth biological control agent Eccritotarsus catarinensis Carvalho (Hemiptera: Miridae) have been extensively investigated over the past 20 years to understand and improve post-release establishment in the field. Thermal physiology studies predicted that the agent would not establish at a number of cold sites in South Africa, where it has nonetheless subsequently established and thrived. Recently, studies have begun to incorporate the plastic nature of insect thermal physiology into models of agent establishment. This study determined whether season and locality influenced the thermal physiology of two field populations of E. catarinensis, one collected from the hottest site where the agent has established in South Africa, and one from the coldest site. The thermal physiology of E. catarinensis was significantly influenced by season and site, demonstrating a degree of phenotypic plasticity, and that some post-release local adaptation to climatic conditions has occurred through microevolution. We then determined whether cold acclimation under laboratory conditions was possible. Successfully cold-acclimated E. catarinensis had a significantly lower critical thermal minimum (CTmin) compared to the field cold-acclimated population. This suggests that cold acclimation of agents could be conducted in the laboratory before future releases to improve their cold tolerance, thereby increasing their chance of establishment at cold sites and allowing further adaptation to colder climates to occur in the field. Although the thermal tolerance of E. catarinensis is limited by local adaptations to climatic conditions in the native range, the plastic nature of the insect's thermal physiology has allowed it to survive in the very different climatic conditions of the introduced range, and there has been some adaptive change to the insect's thermal tolerance since establishment. This study highlights the importance of plasticity and microevolutionary processes in the success of biological control agents under the novel climatic conditions in the introduced range.
- Full Text:
- Date Issued: 2019
Field-based ecological studies to assess prospective biological control agents for invasive alien plants: An example from giant rat's tail grass
- Sutton, Guy F, Canavan, Kim N, Day, Michael M, Paterson, Iain D
- Authors: Sutton, Guy F , Canavan, Kim N , Day, Michael M , Paterson, Iain D
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423756 , vital:72091 , xlink:href="https://doi.org/10.1111/1365-2664.13834"
- Description: Biological control (biocontrol) of invasive alien plants is a widely utilised weed management tool. Prospective biocontrol agents are typically assessed through host specificity testing and pre-release efficacy studies performed in quarantine. However, rearing of the potential biocontrol agents and/or test plants is often difficult or impossible under quarantine conditions. Moreover, practitioners may attain laboratory artefacts in quarantine, which may result in the potential agent being needlessly rejected. Field-based studies in the weed's indigenous distribution could overcome these issues.
- Full Text:
- Date Issued: 2021
- Authors: Sutton, Guy F , Canavan, Kim N , Day, Michael M , Paterson, Iain D
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423756 , vital:72091 , xlink:href="https://doi.org/10.1111/1365-2664.13834"
- Description: Biological control (biocontrol) of invasive alien plants is a widely utilised weed management tool. Prospective biocontrol agents are typically assessed through host specificity testing and pre-release efficacy studies performed in quarantine. However, rearing of the potential biocontrol agents and/or test plants is often difficult or impossible under quarantine conditions. Moreover, practitioners may attain laboratory artefacts in quarantine, which may result in the potential agent being needlessly rejected. Field-based studies in the weed's indigenous distribution could overcome these issues.
- Full Text:
- Date Issued: 2021
Performance and field host range of the life stages of Cornops aquaticum, a biological control agent of water hyacinth
- Franceschini, M Celeste, Hill, Martin P, Fuentes-Rodríguez, Daniela, Gervazoni, Paula B, Sabater, Lara M, Coetzee, Julie A
- Authors: Franceschini, M Celeste , Hill, Martin P , Fuentes-Rodríguez, Daniela , Gervazoni, Paula B , Sabater, Lara M , Coetzee, Julie A
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424814 , vital:72186 , xlink:href="https://doi.org/10.1111/eea.13354"
- Description: Host specificity determination of weed biocontrol agents has historically relied on evidence generated through quarantine trials in the region of introduction. These trials could give ‘false positive’ results due to a maximum type I error probability, and where possible, more research under field conditions should be conducted in the region of origin. The oligophagous, semiaquatic grasshopper, Cornops aquaticum Bruner (Orthoptera: Acrididae, Tetrataeniini), was released in South Africa for the biological control of Pontederia crassipes Pellegrini and Horn (Pontederiaceae). The aim of this study was to assess how the performance and field host range of C. aquaticum varies according to its stages of development, and how this contributes to the understanding of the relationship between the fundamental (laboratory-based) and the ecological (field-based) host range of this grasshopper, and its implications for water hyacinth biocontrol. We conducted post-release laboratory no-choice trials, confining early instars (instars 1 and 2), later instars (instars 3–6), and adult females and males in mesh cages, to determine insect performance on wetland plants growing in sympatry with P. crassipes. Also, gut analysis from field-collected C. aquaticum was done to determine the ecological host range of this insect, identifying epidermal tissue of consumed plants. In no-choice trials, survival rates of the later instars and adult C. aquaticum were similar on Pistia stratiotes L. (Araceae), Oxycaryum cubense (Poepp. and Kunth) Lye (Cyperaceae), and P. crassipes. However, under field conditions, P. crassipes and the congeneric Pontederia azurea Sw. were the only plant contents in the guts of early instars and the most abundant species in later instars and adults. The results support the hypothesis that C. aquaticum is an oligophagous insect on the genus Pontederia, and that different life stages should be considered when conducting host-specificity trials in externally feeding mobile herbivore species. Diet composition of field-collected insects thus could help detect false positives in laboratory trials, being an additional and realistic approach in understanding and predicting the selection processes of the insect in the new environment. Retrospective analysis of potential agents that were rejected due to lack of host-specificity, using the methods from this study, could add a suite of additional agents to programs where invasive weeds remain unmanaged.
- Full Text:
- Date Issued: 2023
- Authors: Franceschini, M Celeste , Hill, Martin P , Fuentes-Rodríguez, Daniela , Gervazoni, Paula B , Sabater, Lara M , Coetzee, Julie A
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424814 , vital:72186 , xlink:href="https://doi.org/10.1111/eea.13354"
- Description: Host specificity determination of weed biocontrol agents has historically relied on evidence generated through quarantine trials in the region of introduction. These trials could give ‘false positive’ results due to a maximum type I error probability, and where possible, more research under field conditions should be conducted in the region of origin. The oligophagous, semiaquatic grasshopper, Cornops aquaticum Bruner (Orthoptera: Acrididae, Tetrataeniini), was released in South Africa for the biological control of Pontederia crassipes Pellegrini and Horn (Pontederiaceae). The aim of this study was to assess how the performance and field host range of C. aquaticum varies according to its stages of development, and how this contributes to the understanding of the relationship between the fundamental (laboratory-based) and the ecological (field-based) host range of this grasshopper, and its implications for water hyacinth biocontrol. We conducted post-release laboratory no-choice trials, confining early instars (instars 1 and 2), later instars (instars 3–6), and adult females and males in mesh cages, to determine insect performance on wetland plants growing in sympatry with P. crassipes. Also, gut analysis from field-collected C. aquaticum was done to determine the ecological host range of this insect, identifying epidermal tissue of consumed plants. In no-choice trials, survival rates of the later instars and adult C. aquaticum were similar on Pistia stratiotes L. (Araceae), Oxycaryum cubense (Poepp. and Kunth) Lye (Cyperaceae), and P. crassipes. However, under field conditions, P. crassipes and the congeneric Pontederia azurea Sw. were the only plant contents in the guts of early instars and the most abundant species in later instars and adults. The results support the hypothesis that C. aquaticum is an oligophagous insect on the genus Pontederia, and that different life stages should be considered when conducting host-specificity trials in externally feeding mobile herbivore species. Diet composition of field-collected insects thus could help detect false positives in laboratory trials, being an additional and realistic approach in understanding and predicting the selection processes of the insect in the new environment. Retrospective analysis of potential agents that were rejected due to lack of host-specificity, using the methods from this study, could add a suite of additional agents to programs where invasive weeds remain unmanaged.
- Full Text:
- Date Issued: 2023
Cryptic species of a water hyacinth biological control agent revealed in South Africa: host specificity, impact, and thermal tolerance
- Paterson, Iain D, Coetzee, Julie A, Weyl, Philip, Griffith, Tamzin C, Voogt, Nina, Hill, Martin P
- Authors: Paterson, Iain D , Coetzee, Julie A , Weyl, Philip , Griffith, Tamzin C , Voogt, Nina , Hill, Martin P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423982 , vital:72113 , xlink:href="https://doi.org/10.1111/eea.12812"
- Description: The discovery that cryptic species are more abundant than previously thought has implications for weed biological control, as there is a risk that cryptic species may be inadvertently released with consequences for the safety of the practice. A cryptic species of a biological control agent released for the control of the invasive alien macrophyte, water hyacinth, Eichhornia crassipes (C. Mart.) Solms. (Pontederiaceae), was recently discovered in South Africa. The two species were considered a single species prior to genetic analysis and interbreeding experiments. The original biological control agent retains the name Eccritotarsus catarinensis (Carvalho) (Heteroptera: Miridae) whereas the new species has been described as Eccritotarsus eichhorniae Henry. In this study, we compared the host specificity, efficacy, and thermal physiologies of the two species. The host specificity of the two species within the Pontederiaceae was very similar and both are safe for release in South Africa. Comparison of the per capita impact of the two species indicated that E. eichhorniae was the more damaging species but this is likely to be influenced by temperature, with E. catarinensis being more effective under lower temperatures and E. eichhorniae being more effective under higher temperatures. Releasing the correct species for the thermal environment of each release site will improve the level of control of water hyacinth in South Africa. This example highlights the need to keep populations of biological control agents from different native range collection localities separate, and to screen for host specificity and efficacy.
- Full Text:
- Date Issued: 2019
- Authors: Paterson, Iain D , Coetzee, Julie A , Weyl, Philip , Griffith, Tamzin C , Voogt, Nina , Hill, Martin P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423982 , vital:72113 , xlink:href="https://doi.org/10.1111/eea.12812"
- Description: The discovery that cryptic species are more abundant than previously thought has implications for weed biological control, as there is a risk that cryptic species may be inadvertently released with consequences for the safety of the practice. A cryptic species of a biological control agent released for the control of the invasive alien macrophyte, water hyacinth, Eichhornia crassipes (C. Mart.) Solms. (Pontederiaceae), was recently discovered in South Africa. The two species were considered a single species prior to genetic analysis and interbreeding experiments. The original biological control agent retains the name Eccritotarsus catarinensis (Carvalho) (Heteroptera: Miridae) whereas the new species has been described as Eccritotarsus eichhorniae Henry. In this study, we compared the host specificity, efficacy, and thermal physiologies of the two species. The host specificity of the two species within the Pontederiaceae was very similar and both are safe for release in South Africa. Comparison of the per capita impact of the two species indicated that E. eichhorniae was the more damaging species but this is likely to be influenced by temperature, with E. catarinensis being more effective under lower temperatures and E. eichhorniae being more effective under higher temperatures. Releasing the correct species for the thermal environment of each release site will improve the level of control of water hyacinth in South Africa. This example highlights the need to keep populations of biological control agents from different native range collection localities separate, and to screen for host specificity and efficacy.
- Full Text:
- Date Issued: 2019
The status and distribution of a newly identified endemic galaxiid in the eastern Cape Fold Ecoregion, of South Africa
- Chakona, Gamuchirai, Swartz, Ernst R, Chakona, Albert
- Authors: Chakona, Gamuchirai , Swartz, Ernst R , Chakona, Albert
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/425492 , vital:72250 , xlink:href="https://doi.org/10.1002/aqc.2850"
- Description: DNA-based studies have uncovered cryptic species and lineages within almost all freshwater fishes studied thus far from the Cape Fold Ecoregion (CFE) of South Africa. These studies have changed the way the CFE is viewed, as almost all stream fishes that were previously consid-ered to be of low conservation priority, because they were perceived to have broad geographical ranges, con-tain multiple historically isolated lineages, many of which are narrow-range endemics.
- Full Text:
- Date Issued: 2018
- Authors: Chakona, Gamuchirai , Swartz, Ernst R , Chakona, Albert
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/425492 , vital:72250 , xlink:href="https://doi.org/10.1002/aqc.2850"
- Description: DNA-based studies have uncovered cryptic species and lineages within almost all freshwater fishes studied thus far from the Cape Fold Ecoregion (CFE) of South Africa. These studies have changed the way the CFE is viewed, as almost all stream fishes that were previously consid-ered to be of low conservation priority, because they were perceived to have broad geographical ranges, con-tain multiple historically isolated lineages, many of which are narrow-range endemics.
- Full Text:
- Date Issued: 2018
Electrode Modification Using Alkynyl Substituted Fe(II) Phthalocyanine via Electrografting and Click Chemistry for Electrocatalysis
- Nxele, Siphesihle R, Mashazi, Philani N, Nyokong, Tebello
- Authors: Nxele, Siphesihle R , Mashazi, Philani N , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7284 , http://hdl.handle.net/10962/d1020329
- Description: In this work, tetrakis(5-hexyn-oxy)Fe(II) phthalocyanine was synthesised in order to perform a click reaction between the terminal alkyne groups and an azide group on a glassy carbon electrode (GCE) surface. An azide group was formed on the electrode surface following electrografting using 4-azidobenzene diazonium tetrafluoroborate by electrochemical reduction. The Cu(I) catalyzed alkyne-azide Huisgen cycloaddition reaction was then employed in order to react the terminal alkyne groups on the phthalocyanine with the azide groups on the GCE surface. The modified electrode was employed to catalyse the oxidation of hydrazine. The electrode showed good electrocatalytic ability towards the detection of hydrazine with a sensitivity of 15.38 µA mM−1 and a limit of detection of 1.09 µM. , Original publication is available at http://dx.doi.org/10.1002/elan.201500212
- Full Text: false
- Authors: Nxele, Siphesihle R , Mashazi, Philani N , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7284 , http://hdl.handle.net/10962/d1020329
- Description: In this work, tetrakis(5-hexyn-oxy)Fe(II) phthalocyanine was synthesised in order to perform a click reaction between the terminal alkyne groups and an azide group on a glassy carbon electrode (GCE) surface. An azide group was formed on the electrode surface following electrografting using 4-azidobenzene diazonium tetrafluoroborate by electrochemical reduction. The Cu(I) catalyzed alkyne-azide Huisgen cycloaddition reaction was then employed in order to react the terminal alkyne groups on the phthalocyanine with the azide groups on the GCE surface. The modified electrode was employed to catalyse the oxidation of hydrazine. The electrode showed good electrocatalytic ability towards the detection of hydrazine with a sensitivity of 15.38 µA mM−1 and a limit of detection of 1.09 µM. , Original publication is available at http://dx.doi.org/10.1002/elan.201500212
- Full Text: false
Iodine-Doped Cobalt Phthalocyanine Supported on Multiwalled Carbon Nanotubes for Electrocatalysis of Oxygen Reduction Reaction
- Nyoni, Stephen, Mashazi, Philani N, Nyokong, Tebello
- Authors: Nyoni, Stephen , Mashazi, Philani N , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7242 , http://hdl.handle.net/10962/d1020246
- Description: 4-(4,6-Diaminopyrimidin-2-ylthio) phthalocyaninatocobalt(II) (CoPyPc) was iodine doped, and its electrocatalytic properties explored. Physical characterization techniques such as UV-vis, X-ray photoelectron, electron paramagnetic resonance and infra-red spectroscopy were used. Cyclic voltammetry, electrochemical impedance spectroscopy and rotating disk electrode were used for electrochemical characterization of electrodes modified with the prepared phthalocyanine and its nanocomposites. The electrocatalytic effect of a new iodine-doped cobalt phthalocyanine derivative supported on multiwalled carbon nanotubes was then investigated towards oxygen reduction reaction. The electrocatalytic activity of the iodine-doped cobalt phthalocyanine was found to be superior in terms of current over the undoped phthalocyanine nanocomposite. , Original publication is available at http://dx.doi.org/10.1002/elan.201400499
- Full Text: false
- Authors: Nyoni, Stephen , Mashazi, Philani N , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7242 , http://hdl.handle.net/10962/d1020246
- Description: 4-(4,6-Diaminopyrimidin-2-ylthio) phthalocyaninatocobalt(II) (CoPyPc) was iodine doped, and its electrocatalytic properties explored. Physical characterization techniques such as UV-vis, X-ray photoelectron, electron paramagnetic resonance and infra-red spectroscopy were used. Cyclic voltammetry, electrochemical impedance spectroscopy and rotating disk electrode were used for electrochemical characterization of electrodes modified with the prepared phthalocyanine and its nanocomposites. The electrocatalytic effect of a new iodine-doped cobalt phthalocyanine derivative supported on multiwalled carbon nanotubes was then investigated towards oxygen reduction reaction. The electrocatalytic activity of the iodine-doped cobalt phthalocyanine was found to be superior in terms of current over the undoped phthalocyanine nanocomposite. , Original publication is available at http://dx.doi.org/10.1002/elan.201400499
- Full Text: false
Polyamide nanofiber membranes functionalized with zinc phthalocyanines
- Goethals, Annelies, Mugadza, Tawanda, Arslanoglu, Yasin, Zugle, Ruphino, Antunes, Edith M, Hulle, Stijn W H Van, Nyokong, Tebello, Clerck, Karen De
- Authors: Goethals, Annelies , Mugadza, Tawanda , Arslanoglu, Yasin , Zugle, Ruphino , Antunes, Edith M , Hulle, Stijn W H Van , Nyokong, Tebello , Clerck, Karen De
- Language: English
- Type: Article
- Identifier: vital:7313 , http://hdl.handle.net/10962/d1020539
- Description: Electrospinning is an efficient method for the production of polyamide nanofiber membranes that are suitable for water filtration. Previous studies have shown that nanofiber membranes have high clean water permeability. The pathogen removal efficiency can be improved by functionalization with (organic) biocides. However, these membranes, like other membranes, are vulnerable to fouling which reduces the filtration efficiency. Therefore the present article investigates the potential of zinc phthalocyanines, which can produce singlet oxygen in the presence of visible light, as a functionalizing agent. The polyamide nanofiber membranes were functionalized with phthalocyanines using both a pre-functionalizing and post-functionalizing method. Only the post-functionalization method shows to result in nanofiber membranes capable of producing singlet oxygen. After 30 min 45% of 1,2-diphenylisobenzofuran (DPBF), used as an oxygen quencher, was removed by reaction with singlet oxygen. This resulted in a removal rate of 0.33 mol DBPF mol−1Zn min−1. During short term leaching tests, phthalocyanines could not be detected. , Original publication is available at http://dx.doi.org/10.1002/app.40486
- Full Text: false
- Authors: Goethals, Annelies , Mugadza, Tawanda , Arslanoglu, Yasin , Zugle, Ruphino , Antunes, Edith M , Hulle, Stijn W H Van , Nyokong, Tebello , Clerck, Karen De
- Language: English
- Type: Article
- Identifier: vital:7313 , http://hdl.handle.net/10962/d1020539
- Description: Electrospinning is an efficient method for the production of polyamide nanofiber membranes that are suitable for water filtration. Previous studies have shown that nanofiber membranes have high clean water permeability. The pathogen removal efficiency can be improved by functionalization with (organic) biocides. However, these membranes, like other membranes, are vulnerable to fouling which reduces the filtration efficiency. Therefore the present article investigates the potential of zinc phthalocyanines, which can produce singlet oxygen in the presence of visible light, as a functionalizing agent. The polyamide nanofiber membranes were functionalized with phthalocyanines using both a pre-functionalizing and post-functionalizing method. Only the post-functionalization method shows to result in nanofiber membranes capable of producing singlet oxygen. After 30 min 45% of 1,2-diphenylisobenzofuran (DPBF), used as an oxygen quencher, was removed by reaction with singlet oxygen. This resulted in a removal rate of 0.33 mol DBPF mol−1Zn min−1. During short term leaching tests, phthalocyanines could not be detected. , Original publication is available at http://dx.doi.org/10.1002/app.40486
- Full Text: false
Effects of Redox Mediators on the Catalytic Activity of Iron Porphyrins towards Oxygen Reduction in Acidic Media
- He, Qinggang, Wu, Gang, Liu, Ke, Khene, M Samson, Li, Qing, Mugadza, Tawanda, Deunf, Elise, Nyokong, Tebello, Chen, Shaowei W
- Authors: He, Qinggang , Wu, Gang , Liu, Ke , Khene, M Samson , Li, Qing , Mugadza, Tawanda , Deunf, Elise , Nyokong, Tebello , Chen, Shaowei W
- Language: English
- Type: Article
- Identifier: vital:7291 , http://hdl.handle.net/10962/d1020354
- Description: The effects of different redox mediators on the oxygen reduction reaction (ORR) catalyzed by an iron porphyrin complex, iron(III) meso-tetra(N-methyl-4-pyridyl)porphine chloride [FeIIITMPyP], in 0.1 M triflic acid were investigated by cyclic voltammetry (CV) and spectroelectrochemistry in conjunction with density functional theory (DFT) calculations. The formal potentials of the FeIIITMPyP catalyst and the redox mediators, as well as the half-wave potentials for the ORR, were determined by CV in the absence and presence of oxygen in acidic solutions. UV/Vis spectroscopic and spectroelectrochemical studies confirmed that only the 2,2′-azino-bis(3-ethylbenzothiazioline-6-sulfonic acid)diammonium salt (C18H24N6O6S4) showed effective interactions with FeIIITMPyP during the ORR. DFT calculations suggested strong interaction between FeIIITMPyP and the C18H24N6O6S4 redox mediator. The redox mediator caused lengthening of the dioxygen iron bond, which thus suggested easier dioxygen reduction. Consistent results were observed in electrochemical impedance spectroscopic measurements for which the electron-transfer kinetics were also evaluated. , Original publication is available at http://dx.doi.org/10.1002/celc.201402054
- Full Text: false
- Authors: He, Qinggang , Wu, Gang , Liu, Ke , Khene, M Samson , Li, Qing , Mugadza, Tawanda , Deunf, Elise , Nyokong, Tebello , Chen, Shaowei W
- Language: English
- Type: Article
- Identifier: vital:7291 , http://hdl.handle.net/10962/d1020354
- Description: The effects of different redox mediators on the oxygen reduction reaction (ORR) catalyzed by an iron porphyrin complex, iron(III) meso-tetra(N-methyl-4-pyridyl)porphine chloride [FeIIITMPyP], in 0.1 M triflic acid were investigated by cyclic voltammetry (CV) and spectroelectrochemistry in conjunction with density functional theory (DFT) calculations. The formal potentials of the FeIIITMPyP catalyst and the redox mediators, as well as the half-wave potentials for the ORR, were determined by CV in the absence and presence of oxygen in acidic solutions. UV/Vis spectroscopic and spectroelectrochemical studies confirmed that only the 2,2′-azino-bis(3-ethylbenzothiazioline-6-sulfonic acid)diammonium salt (C18H24N6O6S4) showed effective interactions with FeIIITMPyP during the ORR. DFT calculations suggested strong interaction between FeIIITMPyP and the C18H24N6O6S4 redox mediator. The redox mediator caused lengthening of the dioxygen iron bond, which thus suggested easier dioxygen reduction. Consistent results were observed in electrochemical impedance spectroscopic measurements for which the electron-transfer kinetics were also evaluated. , Original publication is available at http://dx.doi.org/10.1002/celc.201402054
- Full Text: false