Dietary fatty acids of spiders reveal spatial and temporal variations in aquatic-terrestrial linkages
- Chari, Lenin D, Richoux, Nicole B, Moyo, Sydney, Villet, Martin H
- Authors: Chari, Lenin D , Richoux, Nicole B , Moyo, Sydney , Villet, Martin H
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441919 , vital:73935 , https://doi.org/10.1016/j.fooweb.2020.e00152
- Description: Stream and riparian food webs can be strongly linked by inputs of aquatic emergent insect prey to terrestrial predators. However, quantifying these linkages and understanding how they vary in time and space is challenging. We investigated the dynamic width of a riverine trophic subsidy zone by determining the relationship between perpendicular distance from a river and dietary contributions of aquatic insect prey to web-building spiders' diets. To assess this relationship, riparian web-building spiders at two river sites were sampled during four seasons and analysed for the fatty acids 16:0, 16:1ω7 and 20:5ω3, their total ω3-fatty acid content and their ω3:ω6 ratio to evaluate trophic subsidies reaching them from an adjacent river. River-derived fatty acids generally declined with increased distance from the river, indicating a diffusion of aquatically derived subsidies into the riparian zone. While the river was only 16 m wide at its broadest, river-derived trophic subsidies were detected up to four times that distance from the river edge. Spiders at a downstream section of the river, characterised by generally higher emergence rates of aquatic insects, contained higher proportions of aquatic indicator fatty acids compared with spiders located upstream, where emergence rates were lower. Similarly, proportions of aquatic indicator fatty acids in spiders were lowest during winter when aquatic insect emergence rates were lowest. The fatty acid 20:5ω3 (eicosapentaenoic acid; EPA) held the best promise as a biomarker of aquatic-derived tropic subsidies and could be developed as a useful tool for riparian research and management.
- Full Text:
- Date Issued: 2020
- Authors: Chari, Lenin D , Richoux, Nicole B , Moyo, Sydney , Villet, Martin H
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441919 , vital:73935 , https://doi.org/10.1016/j.fooweb.2020.e00152
- Description: Stream and riparian food webs can be strongly linked by inputs of aquatic emergent insect prey to terrestrial predators. However, quantifying these linkages and understanding how they vary in time and space is challenging. We investigated the dynamic width of a riverine trophic subsidy zone by determining the relationship between perpendicular distance from a river and dietary contributions of aquatic insect prey to web-building spiders' diets. To assess this relationship, riparian web-building spiders at two river sites were sampled during four seasons and analysed for the fatty acids 16:0, 16:1ω7 and 20:5ω3, their total ω3-fatty acid content and their ω3:ω6 ratio to evaluate trophic subsidies reaching them from an adjacent river. River-derived fatty acids generally declined with increased distance from the river, indicating a diffusion of aquatically derived subsidies into the riparian zone. While the river was only 16 m wide at its broadest, river-derived trophic subsidies were detected up to four times that distance from the river edge. Spiders at a downstream section of the river, characterised by generally higher emergence rates of aquatic insects, contained higher proportions of aquatic indicator fatty acids compared with spiders located upstream, where emergence rates were lower. Similarly, proportions of aquatic indicator fatty acids in spiders were lowest during winter when aquatic insect emergence rates were lowest. The fatty acid 20:5ω3 (eicosapentaenoic acid; EPA) held the best promise as a biomarker of aquatic-derived tropic subsidies and could be developed as a useful tool for riparian research and management.
- Full Text:
- Date Issued: 2020
Do spotted hyaenas outcompete the big cats in a small, enclosed system in South Africa?:
- Comley, Jessica, Joubert, Christoffel J, Mgqatsa, Nokubonga, Parker, Daniel M
- Authors: Comley, Jessica , Joubert, Christoffel J , Mgqatsa, Nokubonga , Parker, Daniel M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150099 , vital:38940 , doi:10.1111/jzo.12772
- Description: Carnivores are adapted to kill, meaning sympatric carnivores can have particularly aggressive and harmful competitive interactions. The co‐existence of multiple carnivores in an ecosystem could be restricted by their similarity in ecological niches (e.g. dietary overlap); however, high prey abundances could facilitate their co‐existence. Although the development of small, enclosed reserves (over 400 km2) in South Africa has reduced human–carnivore conflict, these systems may increase the likelihood of carnivore intra‐guild competition due to the clumping of competing carnivores into these restricted spaces. Using carnivore scat and kill site analyses, we determined the dietary preferences and overlap of sympatric large carnivores in a small, enclosed reserve, Selati Game Reserve (Selati).
- Full Text:
- Date Issued: 2020
- Authors: Comley, Jessica , Joubert, Christoffel J , Mgqatsa, Nokubonga , Parker, Daniel M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150099 , vital:38940 , doi:10.1111/jzo.12772
- Description: Carnivores are adapted to kill, meaning sympatric carnivores can have particularly aggressive and harmful competitive interactions. The co‐existence of multiple carnivores in an ecosystem could be restricted by their similarity in ecological niches (e.g. dietary overlap); however, high prey abundances could facilitate their co‐existence. Although the development of small, enclosed reserves (over 400 km2) in South Africa has reduced human–carnivore conflict, these systems may increase the likelihood of carnivore intra‐guild competition due to the clumping of competing carnivores into these restricted spaces. Using carnivore scat and kill site analyses, we determined the dietary preferences and overlap of sympatric large carnivores in a small, enclosed reserve, Selati Game Reserve (Selati).
- Full Text:
- Date Issued: 2020
Examining intraspecific multiple predator effects across shifting predator sex ratios:
- 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: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150119 , vital:38941 , https://doi.org/10.1016/j.baae.2020.03.002
- Description: Predator-predator interactions, or “multiple predator effects” (MPEs), are pervasive in the structuring of communities and complicate predictive quantifications of ecosystem dynamics. The nature of MPEs is also context-dependent, manifesting differently among species, prey densities and habitat structures. However, there has hitherto been a lack of consideration for the implications of intraspecific demographic variation within populations for the strength of MPEs. The present study extends MPE concepts to examine intraspecific interactions among male and female predators across differences in prey densities using a functional response approach. Focusing on a copepod-mosquito model predator-prey system, interaction strengths of different sex ratio pairs of Lovenula raynerae were quantified towards larval Culex pipiens complex prey, with observations compared to both additive and substitutive model predictions.
- Full Text:
- Date Issued: 2020
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Dick, Jaimie T A
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150119 , vital:38941 , https://doi.org/10.1016/j.baae.2020.03.002
- Description: Predator-predator interactions, or “multiple predator effects” (MPEs), are pervasive in the structuring of communities and complicate predictive quantifications of ecosystem dynamics. The nature of MPEs is also context-dependent, manifesting differently among species, prey densities and habitat structures. However, there has hitherto been a lack of consideration for the implications of intraspecific demographic variation within populations for the strength of MPEs. The present study extends MPE concepts to examine intraspecific interactions among male and female predators across differences in prey densities using a functional response approach. Focusing on a copepod-mosquito model predator-prey system, interaction strengths of different sex ratio pairs of Lovenula raynerae were quantified towards larval Culex pipiens complex prey, with observations compared to both additive and substitutive model predictions.
- Full Text:
- Date Issued: 2020
Fabrication of dye-sensitized solar cells based on push-pull asymmetrical substituted zinc and copper phthalocyanines and reduced graphene oxide nanosheet:
- Chindeka, Francis, Mashazi, Philani N, Britton, Jonathan, Oluwole, David O, Mapukata, Sivuyisiwe, Nyokong, Tebello
- Authors: Chindeka, Francis , Mashazi, Philani N , Britton, Jonathan , Oluwole, David O , Mapukata, Sivuyisiwe , Nyokong, Tebello
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149076 , vital:38802 , https://doi.org/10.1016/j.jphotochem.2020.112612
- Description: Dye sensitized solar cells (DSSCs) were fabricated by using 2(3,5-biscarboxyphenoxy), 9(10), 16(17), 23(24)-tri(tertbutyl) phthalocyaninato Cu (4) and Zn (5) complexes as dyes on the ITO-TiO2 photoanodes containing reduced graphene oxide nanosheets (rGONS) or nitrogen-doped rGONS (NrGONS). The evaluation of the assembled DSSCs revealed that using ITO-TiO2-NrGONS-CuPc photoanode had the highest fill factor (FF) and power conversion efficiency (ɳ) of 69% and 4.36% respectively. These results show that the asymmetrical phthalocyanine complexes (4) and (5) exhibit significant improvement on the performance of the DSSC compared to our previous work on symmetrical carboxylated phthalocyanines with ɳ = 3.19%.
- Full Text:
- Date Issued: 2020
- Authors: Chindeka, Francis , Mashazi, Philani N , Britton, Jonathan , Oluwole, David O , Mapukata, Sivuyisiwe , Nyokong, Tebello
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149076 , vital:38802 , https://doi.org/10.1016/j.jphotochem.2020.112612
- Description: Dye sensitized solar cells (DSSCs) were fabricated by using 2(3,5-biscarboxyphenoxy), 9(10), 16(17), 23(24)-tri(tertbutyl) phthalocyaninato Cu (4) and Zn (5) complexes as dyes on the ITO-TiO2 photoanodes containing reduced graphene oxide nanosheets (rGONS) or nitrogen-doped rGONS (NrGONS). The evaluation of the assembled DSSCs revealed that using ITO-TiO2-NrGONS-CuPc photoanode had the highest fill factor (FF) and power conversion efficiency (ɳ) of 69% and 4.36% respectively. These results show that the asymmetrical phthalocyanine complexes (4) and (5) exhibit significant improvement on the performance of the DSSC compared to our previous work on symmetrical carboxylated phthalocyanines with ɳ = 3.19%.
- Full Text:
- Date Issued: 2020
Lions do not change rivers: complex African savannas preclude top-down forcing by large carnivores
- Comley, Jessica, Joubert, Christoffel J, Mgqatsa, Nokubonga, Parker, Daniel M
- Authors: Comley, Jessica , Joubert, Christoffel J , Mgqatsa, Nokubonga , Parker, Daniel M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149215 , vital:38816 , https://doi.org/10.1016/j.jnc.2020.125844
- Description: Trophic cascade theories such as the ‘behaviourally-mediated trophic cascade hypothesis’ (BMTCH), have mainstreamed as ecological tools for conserving biodiversity and restoring ecosystems. The BMTCH relies on indirect negative effects of large carnivores through suppression of mesocarnivore activity and habitat use. Importantly, effects of top carnivores on mesocarnivores varies over time and space, is dependent on the species involved, and local context. In South Africa, there are very few free-ranging carnivores, as populations are often restricted to enclosed reserves. While predator-proof fences reduce human-wildlife conflict, they also influence space use within communities. We used an enclosed reserve with a relatively full complement of carnivores to test the generality of the BMTCH in the African context. Using single-species, multi-season occupancy models we investigated the spatial dynamics of multiple carnivores. We also investigated spatial partitioning by vegetation type and temporal partitioning.
- Full Text:
- Date Issued: 2020
- Authors: Comley, Jessica , Joubert, Christoffel J , Mgqatsa, Nokubonga , Parker, Daniel M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149215 , vital:38816 , https://doi.org/10.1016/j.jnc.2020.125844
- Description: Trophic cascade theories such as the ‘behaviourally-mediated trophic cascade hypothesis’ (BMTCH), have mainstreamed as ecological tools for conserving biodiversity and restoring ecosystems. The BMTCH relies on indirect negative effects of large carnivores through suppression of mesocarnivore activity and habitat use. Importantly, effects of top carnivores on mesocarnivores varies over time and space, is dependent on the species involved, and local context. In South Africa, there are very few free-ranging carnivores, as populations are often restricted to enclosed reserves. While predator-proof fences reduce human-wildlife conflict, they also influence space use within communities. We used an enclosed reserve with a relatively full complement of carnivores to test the generality of the BMTCH in the African context. Using single-species, multi-season occupancy models we investigated the spatial dynamics of multiple carnivores. We also investigated spatial partitioning by vegetation type and temporal partitioning.
- Full Text:
- Date Issued: 2020
Movement patterns of the epizoic limpet Lottia tenuisculpta on two host snails Omphalius nigerrimus and Reishia clavigera:
- Nakano, Tomoyuki, Okumura, Yousuke, Nakayama, Ryo, Seuront, Laurent
- Authors: Nakano, Tomoyuki , Okumura, Yousuke , Nakayama, Ryo , Seuront, Laurent
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160268 , vital:40429 , DOI: 10.1080/13235818.2020.1808280
- Description: The tiny epizoic limpet Lottia tenuisculpta lives on rocky surfaces and shells of the snails Omphalius nigerrimus and Reishia clavigera. The movement patterns of the limpet on host snails was observed during 24 h under controlled laboratory conditions. A specific behaviour, referred to as returning behaviour and reminiscent of homing behaviour, was observed in seven out of 20 individuals, and two out of 15 individuals on O. nigerrimus and R. clavigera, respectively.
- Full Text:
- Date Issued: 2020
- Authors: Nakano, Tomoyuki , Okumura, Yousuke , Nakayama, Ryo , Seuront, Laurent
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160268 , vital:40429 , DOI: 10.1080/13235818.2020.1808280
- Description: The tiny epizoic limpet Lottia tenuisculpta lives on rocky surfaces and shells of the snails Omphalius nigerrimus and Reishia clavigera. The movement patterns of the limpet on host snails was observed during 24 h under controlled laboratory conditions. A specific behaviour, referred to as returning behaviour and reminiscent of homing behaviour, was observed in seven out of 20 individuals, and two out of 15 individuals on O. nigerrimus and R. clavigera, respectively.
- Full Text:
- Date Issued: 2020
Non-material costs of wildlife conservation to local people and their implications for conservation interventions:
- Thondhlana, Gladman, Redpath, Stephen Mark, Vedeld, Pål Olav, Van Eeden, Lily, Pascual, Unai, Sherren, Kate, Murata, Chenai
- Authors: Thondhlana, Gladman , Redpath, Stephen Mark , Vedeld, Pål Olav , Van Eeden, Lily , Pascual, Unai , Sherren, Kate , Murata, Chenai
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150174 , vital:38946 , https://doi.org/10.1016/j.biocon.2020.108578
- Description: In assessment of costs (and benefits) of wildlife conservation, conventional economic valuation frameworks may inadequately address various non-tangible values and neglect social, cultural and political contexts of resources and their use. Correspondingly, there seems to be much more focus on quantifying the economic, material benefits and costs of wildlife conservation than the non-material aspects that also affect human well-being. In addition, current research on the costs of wildlife conservation tends to be discipline-focused which constrains comparability, often causing conceptual ambiguity. This paper is an attempt to address this ambiguity. While there is growing acknowledgement of the material costs of wildlife conservation, we contend that employing a broader, composite social well-being approach may provide better conceptual insights on—and practical options for—managing various non-material impacts of wildlife conservation for local people.
- Full Text:
- Date Issued: 2020
- Authors: Thondhlana, Gladman , Redpath, Stephen Mark , Vedeld, Pål Olav , Van Eeden, Lily , Pascual, Unai , Sherren, Kate , Murata, Chenai
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150174 , vital:38946 , https://doi.org/10.1016/j.biocon.2020.108578
- Description: In assessment of costs (and benefits) of wildlife conservation, conventional economic valuation frameworks may inadequately address various non-tangible values and neglect social, cultural and political contexts of resources and their use. Correspondingly, there seems to be much more focus on quantifying the economic, material benefits and costs of wildlife conservation than the non-material aspects that also affect human well-being. In addition, current research on the costs of wildlife conservation tends to be discipline-focused which constrains comparability, often causing conceptual ambiguity. This paper is an attempt to address this ambiguity. While there is growing acknowledgement of the material costs of wildlife conservation, we contend that employing a broader, composite social well-being approach may provide better conceptual insights on—and practical options for—managing various non-material impacts of wildlife conservation for local people.
- Full Text:
- Date Issued: 2020
Nuruddin Farah: variations on the theme of return
- Authors: Naicker, Kamil
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149643 , vital:38871 , https://www.ajol.info/index.php/tvl/article/view/196356
- Description: This article explores the role of the returnee protagonist in selected works of Nuruddin Farah. Nadine Gordimer described Farah as “one of the real interpreters” of Africa and this article argues that Farah’s returnees operate as interpreters themselves, their liminality working to mediate between international readers and “local” subject matter. However, it also observes that Farah, who spent decades in exile, is often as preoccupied with writing non-belonging as he is with rendering Somalia itself. Farah’s returnee narratives are, broadly, novels of redress, in which characters enact their return in an attempt to seek out the missing, rebuild the lost or reclaim the stolen, with imperfect results. In exploring these variations on homecoming, the paper investigates the ways in which Farah’s body of work reflects shifts in identity politics over time, and the unique pressures these shifts exert on the homecoming arc.
- Full Text:
- Date Issued: 2020
- Authors: Naicker, Kamil
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149643 , vital:38871 , https://www.ajol.info/index.php/tvl/article/view/196356
- Description: This article explores the role of the returnee protagonist in selected works of Nuruddin Farah. Nadine Gordimer described Farah as “one of the real interpreters” of Africa and this article argues that Farah’s returnees operate as interpreters themselves, their liminality working to mediate between international readers and “local” subject matter. However, it also observes that Farah, who spent decades in exile, is often as preoccupied with writing non-belonging as he is with rendering Somalia itself. Farah’s returnee narratives are, broadly, novels of redress, in which characters enact their return in an attempt to seek out the missing, rebuild the lost or reclaim the stolen, with imperfect results. In exploring these variations on homecoming, the paper investigates the ways in which Farah’s body of work reflects shifts in identity politics over time, and the unique pressures these shifts exert on the homecoming arc.
- Full Text:
- Date Issued: 2020
Patient acceptance of HIV testing services in rural emergency departments in South Africa
- Aditi Rao, Caitlin Kennedy, Pamela Mda, Thomas C. Quinn, David Stead, Bhakti Hansoti
- Authors: Aditi Rao , Caitlin Kennedy , Pamela Mda , Thomas C. Quinn , David Stead , Bhakti Hansoti
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/3270 , vital:43287 , https://doi.org/10.4102/sajhivmed.v21i1.1105
- Description: Background: South Africa faces the highest burden of HIV infection globally. The National Strategic Plan on HIV recommends provider-initiated HIV counselling and testing (HCT) in all healthcare facilities. However, HIV continues to overwhelm the healthcare system. Emergency department (ED)-based HCT could address unmet testing needs. Objectives: This study examines the reasons for accepting or declining HCT in South African EDs to inform the development of HCT implementation strategies. Method: We conducted a prospective observational study in two rural EDs, from June to September 2017. Patients presenting to the ED were systematically approached and offered a point-of-care test in accordance with national guidelines. Patients demographics, presenting compaint, medical history and reasons for accepting/declining testing, were recorded. A pooled analysis is presented. Results: Across sites, 2074 adult, non-critical patients in the ED were approached; 1880 were enrolled in the study. Of those enrolled, 19.7% had a previously known positive diagnosis, and 80.3% were unaware of their HIV status. Of those unaware, 90% patients accepted and 10% declined testing. The primary reasons for declining testing were ‘does not want to know status’ (37.6%), ‘in too much pain’ (34%) and ‘does not believe they are at risk’ (19.9%). Conclusions: Despite national guidelines, a high proportion of individuals remain undiagnosed, of which a majority are young men. Our study demonstrated high patient acceptance of ED-based HCT. There is a need for investment and innovation regarding effective pain management and confidential service delivery to address patient barriers. Findings support a routine, non-targeted HCT strategy in EDs. Keywords: HIV counselling and testing; South Africa; emergency department; patient acceptance; implementation research; linkage to care.
- Full Text:
- Date Issued: 2020
- Authors: Aditi Rao , Caitlin Kennedy , Pamela Mda , Thomas C. Quinn , David Stead , Bhakti Hansoti
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/11260/3270 , vital:43287 , https://doi.org/10.4102/sajhivmed.v21i1.1105
- Description: Background: South Africa faces the highest burden of HIV infection globally. The National Strategic Plan on HIV recommends provider-initiated HIV counselling and testing (HCT) in all healthcare facilities. However, HIV continues to overwhelm the healthcare system. Emergency department (ED)-based HCT could address unmet testing needs. Objectives: This study examines the reasons for accepting or declining HCT in South African EDs to inform the development of HCT implementation strategies. Method: We conducted a prospective observational study in two rural EDs, from June to September 2017. Patients presenting to the ED were systematically approached and offered a point-of-care test in accordance with national guidelines. Patients demographics, presenting compaint, medical history and reasons for accepting/declining testing, were recorded. A pooled analysis is presented. Results: Across sites, 2074 adult, non-critical patients in the ED were approached; 1880 were enrolled in the study. Of those enrolled, 19.7% had a previously known positive diagnosis, and 80.3% were unaware of their HIV status. Of those unaware, 90% patients accepted and 10% declined testing. The primary reasons for declining testing were ‘does not want to know status’ (37.6%), ‘in too much pain’ (34%) and ‘does not believe they are at risk’ (19.9%). Conclusions: Despite national guidelines, a high proportion of individuals remain undiagnosed, of which a majority are young men. Our study demonstrated high patient acceptance of ED-based HCT. There is a need for investment and innovation regarding effective pain management and confidential service delivery to address patient barriers. Findings support a routine, non-targeted HCT strategy in EDs. Keywords: HIV counselling and testing; South Africa; emergency department; patient acceptance; implementation research; linkage to care.
- Full Text:
- Date Issued: 2020
Playing with food: Detection of prey injury cues stimulates increased functional foraging traits in Xenopus laevis
- South, Josie, Botha, Taryn L, Wolmarans, Nico J, Wepener, Victor, Weyl, Olaf L F
- Authors: South, Josie , Botha, Taryn L , Wolmarans, Nico J , Wepener, Victor , Weyl, Olaf L F
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443386 , vital:74114 , https://hdl.handle.net/10520/EJC-1d75666653
- Description: Animal behavioural traits determine trophic interaction strength, which in turn structures ecological communities. Behavioural responses to prey cues can inform upon how prey are perceived and detected and therefore determine whether certain stimuli can increase or dampen predatory efficiency and therefore community structuring. We examined the functional foraging traits of an amphibian predator Xenopus laevis on mosquito larvae (Culex sp.), with regard to responses towards different prey cues. We assessed a suite of foraging behaviours exhibited when supplied with three abundances of live prey (2, 4 and 20); non-injury prey cues; prey injury kairomones from mechanically damaged prey in order to determine the importance of cues in stimulating foraging. High abundance of live prey caused frogs to visit the top of the arena significantly more than in the other treatments. This suggests that hydromechanical and visual cues alert X. laevis to prey items in different spatial zones, which results in foraging where the prey have aggregated, while the non-injury prey cue resulted in a decrease in foraging behaviours. The injury kairomone cue elicited a significantly farther distance travelled, and similar responses in terms of velocity of movement and duration of time spent moving when supplied with 20 live prey items. Previous work on X. laevis predation has focused on prey detection via lateral line sensitivity, however, the strength of response elicited by the prey injury kairomone treatment indicates that there are also complex olfactory pathways involved in detecting prey items. This is possibly related to abiotic context (i.e. turbid ponds) and high predator density in the wild.
- Full Text:
- Date Issued: 2020
- Authors: South, Josie , Botha, Taryn L , Wolmarans, Nico J , Wepener, Victor , Weyl, Olaf L F
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443386 , vital:74114 , https://hdl.handle.net/10520/EJC-1d75666653
- Description: Animal behavioural traits determine trophic interaction strength, which in turn structures ecological communities. Behavioural responses to prey cues can inform upon how prey are perceived and detected and therefore determine whether certain stimuli can increase or dampen predatory efficiency and therefore community structuring. We examined the functional foraging traits of an amphibian predator Xenopus laevis on mosquito larvae (Culex sp.), with regard to responses towards different prey cues. We assessed a suite of foraging behaviours exhibited when supplied with three abundances of live prey (2, 4 and 20); non-injury prey cues; prey injury kairomones from mechanically damaged prey in order to determine the importance of cues in stimulating foraging. High abundance of live prey caused frogs to visit the top of the arena significantly more than in the other treatments. This suggests that hydromechanical and visual cues alert X. laevis to prey items in different spatial zones, which results in foraging where the prey have aggregated, while the non-injury prey cue resulted in a decrease in foraging behaviours. The injury kairomone cue elicited a significantly farther distance travelled, and similar responses in terms of velocity of movement and duration of time spent moving when supplied with 20 live prey items. Previous work on X. laevis predation has focused on prey detection via lateral line sensitivity, however, the strength of response elicited by the prey injury kairomone treatment indicates that there are also complex olfactory pathways involved in detecting prey items. This is possibly related to abiotic context (i.e. turbid ponds) and high predator density in the wild.
- Full Text:
- Date Issued: 2020
Privacy risk and the use of Facebook Apps: a gender-focused vulnerability assessment
- Van der Schyff, Karl, Flowerday, Stephen, Furnell, Steven
- Authors: Van der Schyff, Karl , Flowerday, Stephen , Furnell, Steven
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149054 , vital:38800 , https://doi.org/10.1016/j.cose.2020.101866
- Description: The surveillance and subsequent privacy risks (i.e., misuse of personal information) of Facebook App data constitute a persistent problem that affects millions of users. However, despite Facebook App research on specifics such as privacy concerns, value of information, and demographics, none of them has conducted vulnerability assessments on the use of Facebook Apps as influenced by specific factors such as age, gender, and information privacy attitudes. As such, the purpose of this study was to predict the extent to which these factors influence an individual's intention to continue using Facebook Apps as part of a gender-focused vulnerability assessment. We evaluate two hypotheses by way of ordinal logistic regression using data gathered from 621 respondents. The results are indicative of the following: First, females are particularly vulnerable to privacy risks as a function of continued use of Facebook Apps. More specifically, those risks related to Facebook's access to personal information. Second, results indicate that a user's age is nonsignificant in relation to the continued use of Facebook Apps. We conclude with several theoretical and practice-oriented information privacy recommendations.
- Full Text:
- Date Issued: 2020
- Authors: Van der Schyff, Karl , Flowerday, Stephen , Furnell, Steven
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149054 , vital:38800 , https://doi.org/10.1016/j.cose.2020.101866
- Description: The surveillance and subsequent privacy risks (i.e., misuse of personal information) of Facebook App data constitute a persistent problem that affects millions of users. However, despite Facebook App research on specifics such as privacy concerns, value of information, and demographics, none of them has conducted vulnerability assessments on the use of Facebook Apps as influenced by specific factors such as age, gender, and information privacy attitudes. As such, the purpose of this study was to predict the extent to which these factors influence an individual's intention to continue using Facebook Apps as part of a gender-focused vulnerability assessment. We evaluate two hypotheses by way of ordinal logistic regression using data gathered from 621 respondents. The results are indicative of the following: First, females are particularly vulnerable to privacy risks as a function of continued use of Facebook Apps. More specifically, those risks related to Facebook's access to personal information. Second, results indicate that a user's age is nonsignificant in relation to the continued use of Facebook Apps. We conclude with several theoretical and practice-oriented information privacy recommendations.
- Full Text:
- Date Issued: 2020
Quantifying the impacts of abrasion and bacterial transfer when fish are exposed to sand during a catch-and-release event:
- Foster, Ryan M, Childs, Amber-Robyn, Brooks, Margot, Farthing, Matthew W, Butler, Edward C, Potts, Warren M
- Authors: Foster, Ryan M , Childs, Amber-Robyn , Brooks, Margot , Farthing, Matthew W , Butler, Edward C , Potts, Warren M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160427 , vital:40445 , https://doi.org/10.2989/1814232X.2020.1792982
- Description: Best-practice guidelines to improve recreational fishers’ handling during catch-and-release (CandR) events are critical to improve the conservation and management of fish stocks worldwide. While best-practice research is growing, there are knowledge gaps, with the effects of sand exposure on fish mucous membranes understudied. This study aimed to determine the effects of exposing a fish to sand during a CandR event. A total of 360 juvenile (48–137 mm TL) Cape stumpnose Rhabdosargus holubi were subjected to a simulated CandR event during which they were either held: (i) with wet hands, or (ii) dry hands; or with wet hands and then placed on either (iii) wet sterilised sand, (iv) dry sterilised sand, (v) wet unsterilised sand, or (vi) dry unsterilised sand. Fish were maintained in a recirculating system for two weeks, euthanised and subjected to an examination of their mucous layer (bacterial counts, abrasion counts and percentage of abrasion area) and an internal biological assessment. Bacteria fro m fish mucous layers were cultivated on agar plates to count bacterial colonies.
- Full Text:
- Date Issued: 2020
- Authors: Foster, Ryan M , Childs, Amber-Robyn , Brooks, Margot , Farthing, Matthew W , Butler, Edward C , Potts, Warren M
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/160427 , vital:40445 , https://doi.org/10.2989/1814232X.2020.1792982
- Description: Best-practice guidelines to improve recreational fishers’ handling during catch-and-release (CandR) events are critical to improve the conservation and management of fish stocks worldwide. While best-practice research is growing, there are knowledge gaps, with the effects of sand exposure on fish mucous membranes understudied. This study aimed to determine the effects of exposing a fish to sand during a CandR event. A total of 360 juvenile (48–137 mm TL) Cape stumpnose Rhabdosargus holubi were subjected to a simulated CandR event during which they were either held: (i) with wet hands, or (ii) dry hands; or with wet hands and then placed on either (iii) wet sterilised sand, (iv) dry sterilised sand, (v) wet unsterilised sand, or (vi) dry unsterilised sand. Fish were maintained in a recirculating system for two weeks, euthanised and subjected to an examination of their mucous layer (bacterial counts, abrasion counts and percentage of abrasion area) and an internal biological assessment. Bacteria fro m fish mucous layers were cultivated on agar plates to count bacterial colonies.
- Full Text:
- Date Issued: 2020
Social capital reduces vulnerability in rural coastal communities of Solomon Islands:
- Malherbe, Willem, Sauer, Warwick H H, Aswani, Shankar
- Authors: Malherbe, Willem , Sauer, Warwick H H , Aswani, Shankar
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150230 , vital:38951 , https://doi.org/10.1016/j.ocecoaman.2020.105186
- Description: Rural island communities are generally regarded as the most vulnerable groups affected by climate change. This perception arises due to them often being in less developed areas with high levels of exposure to stressors, while reportedly lacking the means to cope with these stressors. Studies which use developed-country yardsticks, such as those used in past IPCC-based assessments, when measuring vulnerability in less developed states will however inevitably over-pronounce its effects in such areas. The sustainable livelihoods approach provides an alternate means of determining vulnerability using capital assets such as social capital. The presence of these assets enables communities to pursue diverse livelihood strategies which ultimately serve to reduce their vulnerability. This study seeks to measure attributes of social capital in five marine dependent communities of Solomon Islands.
- Full Text:
- Date Issued: 2020
- Authors: Malherbe, Willem , Sauer, Warwick H H , Aswani, Shankar
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150230 , vital:38951 , https://doi.org/10.1016/j.ocecoaman.2020.105186
- Description: Rural island communities are generally regarded as the most vulnerable groups affected by climate change. This perception arises due to them often being in less developed areas with high levels of exposure to stressors, while reportedly lacking the means to cope with these stressors. Studies which use developed-country yardsticks, such as those used in past IPCC-based assessments, when measuring vulnerability in less developed states will however inevitably over-pronounce its effects in such areas. The sustainable livelihoods approach provides an alternate means of determining vulnerability using capital assets such as social capital. The presence of these assets enables communities to pursue diverse livelihood strategies which ultimately serve to reduce their vulnerability. This study seeks to measure attributes of social capital in five marine dependent communities of Solomon Islands.
- Full Text:
- Date Issued: 2020
Bait collecting by subsistence and recreational fishers in Knysna Estuary may impact management and conservation
- Simon, C, du Toit, A N, Smith, M K S, Claassens, Louw, Smith, F, Smith, P
- Authors: Simon, C , du Toit, A N , Smith, M K S , Claassens, Louw , Smith, F , Smith, P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447056 , vital:74581 , https://hdl.handle.net/10520/EJC-1d75666653
- Description: To facilitate development of tailored management strategies for bait species within Knysna Estuary (South Africa), demand for bait, harvesting activity and perceptions around conservation among recreational and subsistence bait fishers were investigated. In 2015 and 2016, bait collectors were interviewed (n = 84) and observed (n = 167) during low tides at six sites during peak and off-peak holiday periods. Significant associations among subsistence and recreational fishers and their favoured bait species, collecting spots and method, frequency of collection, views on regulations and desired daily limit for mudprawns suggest differences that may warrant different management strategies. Furthermore, observed methods and duration of bait collecting differed according to site, suggesting spatial variation in baiting pressures. Subsistence fishers potentially collect more mudprawns more frequently than do recreational fishers and consequently have a greater impact on mudprawn populations. By contrast, recreational fishers collect more polychaete worms, but because they are mainly active during holidays, their impact on these species may be localised and not yet critical. Most subsistence fishers would like increased daily bag limits, to sell bait and would welcome a rotational zonation scheme to replace the current permanent exclusion zone. The merits and disadvantages of these management options and suggestions are discussed.
- Full Text:
- Date Issued: 2019
- Authors: Simon, C , du Toit, A N , Smith, M K S , Claassens, Louw , Smith, F , Smith, P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447056 , vital:74581 , https://hdl.handle.net/10520/EJC-1d75666653
- Description: To facilitate development of tailored management strategies for bait species within Knysna Estuary (South Africa), demand for bait, harvesting activity and perceptions around conservation among recreational and subsistence bait fishers were investigated. In 2015 and 2016, bait collectors were interviewed (n = 84) and observed (n = 167) during low tides at six sites during peak and off-peak holiday periods. Significant associations among subsistence and recreational fishers and their favoured bait species, collecting spots and method, frequency of collection, views on regulations and desired daily limit for mudprawns suggest differences that may warrant different management strategies. Furthermore, observed methods and duration of bait collecting differed according to site, suggesting spatial variation in baiting pressures. Subsistence fishers potentially collect more mudprawns more frequently than do recreational fishers and consequently have a greater impact on mudprawn populations. By contrast, recreational fishers collect more polychaete worms, but because they are mainly active during holidays, their impact on these species may be localised and not yet critical. Most subsistence fishers would like increased daily bag limits, to sell bait and would welcome a rotational zonation scheme to replace the current permanent exclusion zone. The merits and disadvantages of these management options and suggestions are discussed.
- Full Text:
- Date Issued: 2019
Bloodmeal analysis in Culicoides midges collected near horses, donkeys and zebras in the Eastern Cape, South Africa:
- Riddin, Megan A, Venter, G J, Labuschagne, K, Villet, Martin H
- Authors: Riddin, Megan A , Venter, G J , Labuschagne, K , Villet, Martin H
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140692 , vital:37910 , DOI: 10.1111/mve.12381
- Description: An upsurge in African horse sickness (AHS) in the Eastern Cape, South Africa, from 2006 led to an epidemiological reassessment of the disease there. Light trapping surveys carried out near horses, donkeys and zebras in 2014–2016 collected 39 species of Culicoides midge (Diptera: Ceratopogonidae) that are potential vectors of AHS. To establish if these midges fed on equids, DNA sequences were obtained from the gut contents of 52 female midges (35 freshly blood-fed, 13 gravid and four parous), representing 11 species collected across 11 sites. Culicoides leucostictus fed on all three equids. Culicoides bolitinos, Culicoides imicola and Culicoides magnus fed on both horses and donkeys. Culicoides onderstepoortensis fed on donkeys, and Culicoides similis and Culicoides pycnostictus fed on zebras. Bloodmeals from cows, pigs, warthogs, impalas and a domestic dog were also identified in various species, but none of the midges tested had fed on birds. These results contribute to knowledge of the vectorial capacity of several species of Culicoides with regard to AHS in the Eastern Cape and point to potential reservoir hosts, of which donkeys, zebras and domestic dogs have previously been found to harbour AHS. Blood-fed midges were also obtained throughout winter, indicating the potential for endemic AHS in the province.
- Full Text:
- Date Issued: 2019
- Authors: Riddin, Megan A , Venter, G J , Labuschagne, K , Villet, Martin H
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140692 , vital:37910 , DOI: 10.1111/mve.12381
- Description: An upsurge in African horse sickness (AHS) in the Eastern Cape, South Africa, from 2006 led to an epidemiological reassessment of the disease there. Light trapping surveys carried out near horses, donkeys and zebras in 2014–2016 collected 39 species of Culicoides midge (Diptera: Ceratopogonidae) that are potential vectors of AHS. To establish if these midges fed on equids, DNA sequences were obtained from the gut contents of 52 female midges (35 freshly blood-fed, 13 gravid and four parous), representing 11 species collected across 11 sites. Culicoides leucostictus fed on all three equids. Culicoides bolitinos, Culicoides imicola and Culicoides magnus fed on both horses and donkeys. Culicoides onderstepoortensis fed on donkeys, and Culicoides similis and Culicoides pycnostictus fed on zebras. Bloodmeals from cows, pigs, warthogs, impalas and a domestic dog were also identified in various species, but none of the midges tested had fed on birds. These results contribute to knowledge of the vectorial capacity of several species of Culicoides with regard to AHS in the Eastern Cape and point to potential reservoir hosts, of which donkeys, zebras and domestic dogs have previously been found to harbour AHS. Blood-fed midges were also obtained throughout winter, indicating the potential for endemic AHS in the province.
- Full Text:
- Date Issued: 2019
Employing the Processing Capability of Mixing Consoles and Audio Interfaces to Spatialize Sound:
- Authors: Foss, Richard
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426758 , vital:72389 , https://www.aes.org/e-lib/browse.cfm?elib=22211
- Description: Many audio interfaces and all mixing consoles have signal mixing capabilities. This paper describes an immersive sound system that employs these capabilities in order to spatialise sound sources, where these sources could be any of the inputs to these mix-capable devices. Graphic spatialisation control is provided on client devices, and 3D coordinates are sent to a server. The server uses these coordinates and speaker positions to render mix level and reverb parameter values. These values are sent to the mixer device using a control protocol. Advantages of this approach are that all inputs can be spatialised, and low-level processing is offloaded from the computer.
- Full Text:
- Date Issued: 2019
- Authors: Foss, Richard
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/426758 , vital:72389 , https://www.aes.org/e-lib/browse.cfm?elib=22211
- Description: Many audio interfaces and all mixing consoles have signal mixing capabilities. This paper describes an immersive sound system that employs these capabilities in order to spatialise sound sources, where these sources could be any of the inputs to these mix-capable devices. Graphic spatialisation control is provided on client devices, and 3D coordinates are sent to a server. The server uses these coordinates and speaker positions to render mix level and reverb parameter values. These values are sent to the mixer device using a control protocol. Advantages of this approach are that all inputs can be spatialised, and low-level processing is offloaded from the computer.
- Full Text:
- Date Issued: 2019
Environmental niche patterns of native and non-native fishes within an invaded African river system
- Kadye, Wilbert T, Booth, Anthony J
- Authors: Kadye, Wilbert T , Booth, Anthony J
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124407 , vital:35605 , https://doi.10.1111/jfb.13988
- Description: To test ecological niche theory, this study investigated the spatial patterns and the environmental niches of native and non-native fishes within the invaded Great Fish River system, South Africa. For the native fishes, there were contrasting environmental niche breadths that varied from being small to being large and overlapped for most species, except minnows that were restricted to headwater tributaries. In addition, there was high niche overlap in habitat association among fishes with similar distribution. It was therefore inferred that habitat filtering-driven spatial organization was important in explaining native species distribution patterns. In comparison, most non-native fishes were found to have broad environmental niches and these fishes showed high tolerance to environmental conditions, which generally supported the niche opportunity hypothesis. The proliferation of multiple non-native fishes in the mainstem section suggest that they form a functional assemblage that is probably facilitated by the anthropogenic modification of flow regimes through inter-basin water transfer. Based on the distribution patterns observed in the study, it was inferred that there was a likelihood of negative interactions between native and nonnative fishes. Such effects are likely to be exacerbated by altered flow regime that was likely to have negative implications for native ichthyofauna.
- Full Text:
- Date Issued: 2019
- Authors: Kadye, Wilbert T , Booth, Anthony J
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124407 , vital:35605 , https://doi.10.1111/jfb.13988
- Description: To test ecological niche theory, this study investigated the spatial patterns and the environmental niches of native and non-native fishes within the invaded Great Fish River system, South Africa. For the native fishes, there were contrasting environmental niche breadths that varied from being small to being large and overlapped for most species, except minnows that were restricted to headwater tributaries. In addition, there was high niche overlap in habitat association among fishes with similar distribution. It was therefore inferred that habitat filtering-driven spatial organization was important in explaining native species distribution patterns. In comparison, most non-native fishes were found to have broad environmental niches and these fishes showed high tolerance to environmental conditions, which generally supported the niche opportunity hypothesis. The proliferation of multiple non-native fishes in the mainstem section suggest that they form a functional assemblage that is probably facilitated by the anthropogenic modification of flow regimes through inter-basin water transfer. Based on the distribution patterns observed in the study, it was inferred that there was a likelihood of negative interactions between native and nonnative fishes. Such effects are likely to be exacerbated by altered flow regime that was likely to have negative implications for native ichthyofauna.
- Full Text:
- Date Issued: 2019
Impacts of gum-resin harvest and Lantana camara invasion on the population structure and dynamics of Boswellia serrata in the Western Ghats, India
- Soumya, Kori V, Shackleton, Charlie M, Setty, Siddappa R
- Authors: Soumya, Kori V , Shackleton, Charlie M , Setty, Siddappa R
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/177549 , vital:42832 , https://doi.org/10.1016/j.foreco.2019.117618
- Description: Assessing the effects of harvesting on the population dynamics of important non-timber forest products (NTFPs) species is important for informing species conservation options, guiding sustainable harvesting practices and offtake and supporting local livelihoods. However, harvesting is rarely the only pressure on NTFP populations, and it is vital that the effects of interactive pressures be considered. This applies to Boswellia serrata, an NTFP tree species which is widely harvested for gum-resin used in religious practices. However, in many settings populations are in decline, presumably due to heavy harvesting, but other factors may play a role, such as altered fire regimes and invasive species. Here we report on the effects of harvesting and invasion by Lantana camara on B. serrata populations in three protected areas in the Western Ghats biodiversity hotspot in southern India. We considered tree and juvenile density, size class distribution, and growth, mortality, and recruitment rates in harvested and unharvested populations over two years.
- Full Text:
- Date Issued: 2019
- Authors: Soumya, Kori V , Shackleton, Charlie M , Setty, Siddappa R
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/177549 , vital:42832 , https://doi.org/10.1016/j.foreco.2019.117618
- Description: Assessing the effects of harvesting on the population dynamics of important non-timber forest products (NTFPs) species is important for informing species conservation options, guiding sustainable harvesting practices and offtake and supporting local livelihoods. However, harvesting is rarely the only pressure on NTFP populations, and it is vital that the effects of interactive pressures be considered. This applies to Boswellia serrata, an NTFP tree species which is widely harvested for gum-resin used in religious practices. However, in many settings populations are in decline, presumably due to heavy harvesting, but other factors may play a role, such as altered fire regimes and invasive species. Here we report on the effects of harvesting and invasion by Lantana camara on B. serrata populations in three protected areas in the Western Ghats biodiversity hotspot in southern India. We considered tree and juvenile density, size class distribution, and growth, mortality, and recruitment rates in harvested and unharvested populations over two years.
- Full Text:
- Date Issued: 2019
Knowledge and knowledge sources on the importance of fruits for nutritional security are unaffected by deforestation status in Cameroon
- Ijang, T N P, Shackleton, Charlie M, Degrande, A
- Authors: Ijang, T N P , Shackleton, Charlie M , Degrande, A
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/177454 , vital:42823 , DOI: 10.17660/th2019/74.6.2
- Description: The Congo basin forest is experiencing increasing rate of deforestation, and is prone to inconsistent food supply and sporadic food shortages with corresponding high levels of malnutrition. Maintenance or planting of fruit trees can help mitigate deforestation while supplying fruits for home consumption. However, data on rates of fruit consumption are lacking for many developing countries, including Cameroon.
- Full Text:
- Date Issued: 2019
- Authors: Ijang, T N P , Shackleton, Charlie M , Degrande, A
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/177454 , vital:42823 , DOI: 10.17660/th2019/74.6.2
- Description: The Congo basin forest is experiencing increasing rate of deforestation, and is prone to inconsistent food supply and sporadic food shortages with corresponding high levels of malnutrition. Maintenance or planting of fruit trees can help mitigate deforestation while supplying fruits for home consumption. However, data on rates of fruit consumption are lacking for many developing countries, including Cameroon.
- Full Text:
- Date Issued: 2019
Modeling top-down and bottom-up drivers of a regime shift in invasive aquatic plant stable states
- Strange, Emily F, Landi, Pietro, Hill, Jaclyn M, Coetzee, Julie A
- Authors: Strange, Emily F , Landi, Pietro , Hill, Jaclyn M , Coetzee, Julie A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444732 , vital:74263 , https://doi.org/10.3389/fpls.2019.00889
- Description: The evidence for alternate stable states characterized by dominance of either floating or submerged plant dominance is well established. Inspired by an existing model and controlled experiments, we conceptually describe a dynamic that we have observed in the field using a simple model, the aim of which was to investigate key interactions of the shift between invasive floating and invasive submerged plant dominance, driven by the rapid decomposition of floating plants as a consequence of herbivory by biological control agents. This study showed that the rate of switch between floating and submerged invasive plant dominance, and the point in time at which the switch occurs, is dependent on the nutrient status of the water and the density of biological control agents on floating plant populations. Therefore, top-down invasive plant biological control efforts using natural enemies can affect systems on a wider scale than the intended agent – plant level, and can be significantly altered by bottom-up changes to the system, i.e., nutrient loading. The implications of this are essential for understanding the multiple roles invasive plants and their control have upon ecosystem dynamics. The results emphasize the importance of multi-trophic considerations for future invasive plant management and offer evidence for new pathways of invasion. The model outputs support the conclusion that, after the shift and in the absence of effective intervention, a submerged invasive stable state will persist.
- Full Text:
- Date Issued: 2019
- Authors: Strange, Emily F , Landi, Pietro , Hill, Jaclyn M , Coetzee, Julie A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444732 , vital:74263 , https://doi.org/10.3389/fpls.2019.00889
- Description: The evidence for alternate stable states characterized by dominance of either floating or submerged plant dominance is well established. Inspired by an existing model and controlled experiments, we conceptually describe a dynamic that we have observed in the field using a simple model, the aim of which was to investigate key interactions of the shift between invasive floating and invasive submerged plant dominance, driven by the rapid decomposition of floating plants as a consequence of herbivory by biological control agents. This study showed that the rate of switch between floating and submerged invasive plant dominance, and the point in time at which the switch occurs, is dependent on the nutrient status of the water and the density of biological control agents on floating plant populations. Therefore, top-down invasive plant biological control efforts using natural enemies can affect systems on a wider scale than the intended agent – plant level, and can be significantly altered by bottom-up changes to the system, i.e., nutrient loading. The implications of this are essential for understanding the multiple roles invasive plants and their control have upon ecosystem dynamics. The results emphasize the importance of multi-trophic considerations for future invasive plant management and offer evidence for new pathways of invasion. The model outputs support the conclusion that, after the shift and in the absence of effective intervention, a submerged invasive stable state will persist.
- Full Text:
- Date Issued: 2019