Sample size assessments for thermal physiology studies: An R package and R Shiny application
- van Steenderen, Clarke J M, Sutton, Guy F, Owen, Candice A, Martin, Grant D, Coetzee, Julie A
- Authors: van Steenderen, Clarke J M , Sutton, Guy F , Owen, Candice A , Martin, Grant D , Coetzee, Julie A
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444455 , vital:74242 , https://doi.org/10.1111/phen.12416
- Description: Required sample sizes for a study need to be carefully assessed to account for logistics, cost, ethics and statistical rigour. For example, many studies have shown that methodological variations can impact the critical thermal limits (CTLs) recorded for a species, although studies on the impact of sample size on these measures are lacking. Here, we present ThermalSampleR; an R CRAN package and Shiny application that can assist researchers in determining when adequate sample sizes have been reached for their data. The method is particularly useful because it is not taxon specific. The Shiny application offers a user‐friendly interface equivalent to the package for users not familiar with R programming. ThermalSampleR is accompanied by an in‐built example dataset, which we use to guide the user through the workflow with a fully worked tutorial.
- Full Text:
- Authors: van Steenderen, Clarke J M , Sutton, Guy F , Owen, Candice A , Martin, Grant D , Coetzee, Julie A
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444455 , vital:74242 , https://doi.org/10.1111/phen.12416
- Description: Required sample sizes for a study need to be carefully assessed to account for logistics, cost, ethics and statistical rigour. For example, many studies have shown that methodological variations can impact the critical thermal limits (CTLs) recorded for a species, although studies on the impact of sample size on these measures are lacking. Here, we present ThermalSampleR; an R CRAN package and Shiny application that can assist researchers in determining when adequate sample sizes have been reached for their data. The method is particularly useful because it is not taxon specific. The Shiny application offers a user‐friendly interface equivalent to the package for users not familiar with R programming. ThermalSampleR is accompanied by an in‐built example dataset, which we use to guide the user through the workflow with a fully worked tutorial.
- Full Text:
A review of the biocontrol programmes against aquatic weeds in South Africa
- Coetzee, Julie A, Bownes, Angela, Martin, Grant D, Miller, Benjamin E, Smith, Rosalie, Weyl, Philip S R, Hill, Martin P
- Authors: Coetzee, Julie A , Bownes, Angela , Martin, Grant D , Miller, Benjamin E , Smith, Rosalie , Weyl, Philip S R , Hill, Martin P
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406965 , vital:70326 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a18"
- Description: Biological control (biocontrol) against invasive macrophytes is one of the longest standing programmes in South Africa, initiated in the 1970s against water hyacinth, Pontederia crassipes Mart. (Pontederiaceae). Since then, 15 agent species (13 insects, one mite and one pathogen) have been released against six weeds, most of which are floating macrophytes, with excellent levels of success. The release of the water hyacinth planthopper Megamelus scutellaris Berg (Hemiptera: Delphacidae) in particular, has improved biocontrol prospects for water hyacinth since 2018. In the last decade, however, a new suite of submerged and rooted emergent invasive macrophytes has been targeted. The first release against a submerged macrophyte in South Africa, and the first release against Brazilian waterweed, Egeria densa Planch. (Hydrocharitaceae), anywhere in the world, was achieved with the release of a leafmining fly, Hydrellia egeriae Rodrigues-Júnior, Mathis and Hauser (Diptera: Ephydridae). Yellow flag, Iris pseudacorus L. (Iridaceae) and Mexican waterlily, Nymphaea mexicana Zucc. (Nymphaeaceae), have also been targeted for biocontrol for the first time worldwide, and are in the early stages of agent development. Post-release evaluations, long term monitoring and controlled experiments have highlighted the need for a more holistic approach to managing aquatic invasive plants in South Africa, whose presence is largely driven by eutrophication, resulting in regime shifts between floating and submerged invaded states.
- Full Text:
- Authors: Coetzee, Julie A , Bownes, Angela , Martin, Grant D , Miller, Benjamin E , Smith, Rosalie , Weyl, Philip S R , Hill, Martin P
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406965 , vital:70326 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a18"
- Description: Biological control (biocontrol) against invasive macrophytes is one of the longest standing programmes in South Africa, initiated in the 1970s against water hyacinth, Pontederia crassipes Mart. (Pontederiaceae). Since then, 15 agent species (13 insects, one mite and one pathogen) have been released against six weeds, most of which are floating macrophytes, with excellent levels of success. The release of the water hyacinth planthopper Megamelus scutellaris Berg (Hemiptera: Delphacidae) in particular, has improved biocontrol prospects for water hyacinth since 2018. In the last decade, however, a new suite of submerged and rooted emergent invasive macrophytes has been targeted. The first release against a submerged macrophyte in South Africa, and the first release against Brazilian waterweed, Egeria densa Planch. (Hydrocharitaceae), anywhere in the world, was achieved with the release of a leafmining fly, Hydrellia egeriae Rodrigues-Júnior, Mathis and Hauser (Diptera: Ephydridae). Yellow flag, Iris pseudacorus L. (Iridaceae) and Mexican waterlily, Nymphaea mexicana Zucc. (Nymphaeaceae), have also been targeted for biocontrol for the first time worldwide, and are in the early stages of agent development. Post-release evaluations, long term monitoring and controlled experiments have highlighted the need for a more holistic approach to managing aquatic invasive plants in South Africa, whose presence is largely driven by eutrophication, resulting in regime shifts between floating and submerged invaded states.
- Full Text:
Biological control of South African plants that are invasive elsewhere in the world: A review of earlier and current programmes
- Olckers, Terence, Coetzee, Julie A, Egli, Daniella, Martin, Grant D, Paterson, Iain D, Sutton, Guy F, Wood, Alan
- Authors: Olckers, Terence , Coetzee, Julie A , Egli, Daniella , Martin, Grant D , Paterson, Iain D , Sutton, Guy F , Wood, Alan
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/414336 , vital:71137 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a21"
- Description: South Africa supports a rich floral diversity, with 21 643 native plant taxa that include a high proportion (76.3%) of endemic species, and many of these favoured as ornamentals, both locally and globally. Consequently, South Africa has contributed substantially to global plant invasions, with 1093 native taxa (5% of all species) naturalized in other countries. At least 80 taxa are invasive in natural or semi-natural ecosystems elsewhere, while an additional 132 taxa are potentially invasive. Of the global naturalized flora, 8.2% originate from South Africa and largely comprise species of Poaceae, Asteraceae, Iridaceae and Fabaceae. Australia, in particular, but also Europe and North America are major recipients of South African weeds. However, few countries have targeted South African plants for biological control (biocontrol), with most efforts undertaken by Australia. Previous and current targets have involved only 26 species with 17 agents (15 insects, one mite and one rust fungus) of South African origin released on five target species in Australia and the United States of America. South Africa’s history of weed biocontrol, together with a large cohort of active scientists, is currently facilitating several internationally funded programmes targeting invasive plants of South African origin. In particular, the recently inaugurated Centre for Biological Control at Rhodes University and the University of KwaZulu-Natal have provided the impetus for novel efforts on five new target species and renewed efforts on four previously targeted species. In this contribution, we review the history of earlier biocontrol programmes against weeds of South African origin and the status of projects currently in progress in South Africa.
- Full Text:
- Authors: Olckers, Terence , Coetzee, Julie A , Egli, Daniella , Martin, Grant D , Paterson, Iain D , Sutton, Guy F , Wood, Alan
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/414336 , vital:71137 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a21"
- Description: South Africa supports a rich floral diversity, with 21 643 native plant taxa that include a high proportion (76.3%) of endemic species, and many of these favoured as ornamentals, both locally and globally. Consequently, South Africa has contributed substantially to global plant invasions, with 1093 native taxa (5% of all species) naturalized in other countries. At least 80 taxa are invasive in natural or semi-natural ecosystems elsewhere, while an additional 132 taxa are potentially invasive. Of the global naturalized flora, 8.2% originate from South Africa and largely comprise species of Poaceae, Asteraceae, Iridaceae and Fabaceae. Australia, in particular, but also Europe and North America are major recipients of South African weeds. However, few countries have targeted South African plants for biological control (biocontrol), with most efforts undertaken by Australia. Previous and current targets have involved only 26 species with 17 agents (15 insects, one mite and one rust fungus) of South African origin released on five target species in Australia and the United States of America. South Africa’s history of weed biocontrol, together with a large cohort of active scientists, is currently facilitating several internationally funded programmes targeting invasive plants of South African origin. In particular, the recently inaugurated Centre for Biological Control at Rhodes University and the University of KwaZulu-Natal have provided the impetus for novel efforts on five new target species and renewed efforts on four previously targeted species. In this contribution, we review the history of earlier biocontrol programmes against weeds of South African origin and the status of projects currently in progress in South Africa.
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The establishment and rapid spread of Sagittaria Platyphylla in South Africa:
- Ndlovu, Mpilonhle S, Coetzee, Julie A, Nxumalo, Menzi M, Lalla, Reshnee, Shabalala, Ntombifuthi, Martin, Grant D
- Authors: Ndlovu, Mpilonhle S , Coetzee, Julie A , Nxumalo, Menzi M , Lalla, Reshnee , Shabalala, Ntombifuthi , Martin, Grant D
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149788 , vital:38884 , https://doi.org/10.3390/w12051472
- Description: Sagittaria platyphylla Engelm. (Alismataceae) is a freshwater aquatic macrophyte that has become an important invasive weed in freshwater systems in South Africa, New Zealand, Australia, and recently China. In South Africa, due to its rapid increase in distribution and ineffective control options, it is recognised as one of the country’s worst invasive aquatic alien plants. In this paper, we investigate the spread of the plant since its first detection in 2008, and the management strategies currently carried out against it. Despite early detection and rapid response programmes, which included chemical and mechanical control measures, the plant was able to spread both within and between sites, increasing from just one site in 2008 to 72 by 2019. Once introduced into a lotic system, the plant was able to spread rapidly, in some cases up to 120 km within 6 years, with an average of 10 km per year. The plant was successfully extirpated at some sites, however, due to the failure of chemical and mechanical control, biological control is currently being considered as a potential control option.
- Full Text:
- Authors: Ndlovu, Mpilonhle S , Coetzee, Julie A , Nxumalo, Menzi M , Lalla, Reshnee , Shabalala, Ntombifuthi , Martin, Grant D
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149788 , vital:38884 , https://doi.org/10.3390/w12051472
- Description: Sagittaria platyphylla Engelm. (Alismataceae) is a freshwater aquatic macrophyte that has become an important invasive weed in freshwater systems in South Africa, New Zealand, Australia, and recently China. In South Africa, due to its rapid increase in distribution and ineffective control options, it is recognised as one of the country’s worst invasive aquatic alien plants. In this paper, we investigate the spread of the plant since its first detection in 2008, and the management strategies currently carried out against it. Despite early detection and rapid response programmes, which included chemical and mechanical control measures, the plant was able to spread both within and between sites, increasing from just one site in 2008 to 72 by 2019. Once introduced into a lotic system, the plant was able to spread rapidly, in some cases up to 120 km within 6 years, with an average of 10 km per year. The plant was successfully extirpated at some sites, however, due to the failure of chemical and mechanical control, biological control is currently being considered as a potential control option.
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Biological control of Salvinia molesta in South Africa revisited
- Martin, Grant D, Coetzee, Julie A, Weyl, Philip S R, Parkinson, Matthew C, Hill, Martin P
- Authors: Martin, Grant D , Coetzee, Julie A , Weyl, Philip S R , Parkinson, Matthew C , Hill, Martin P
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103878 , vital:32318 , https://doi.org/10.1016/j.biocontrol.2018.06.011
- Description: The aquatic weed Salvinia molesta D.S. Mitch. (Salviniaceae) was first recorded in South Africa in the early 1900s, and by the 1960s was regarded as one of South Africa’s worst aquatic weeds. Following the release of the weevil, Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) in 1985, the weed is now considered under successful biological control. However, the post-release evaluation of this biological control programme has been ad hoc, therefore, to assess the efficacy of the agent, annual quantitative surveys of South African freshwater systems have been undertaken since 2008. Over the last ten years, of the 57 S. molesta sites visited annually in South Africa, the weevil has established at all of them. Eighteen sites are under successful biological control, where the weed no longer poses a threat to the system and 19 are under substantial biological control, where biological control has reduced the impact of the weed. Since 2008, the average percentage weed cover at sites has declined significantly from 51–100% cover to 0–5% cover in 2017 (R2 = 0.78; P < 0.05). Observations of site-specific characteristics suggest that biological control is most effective at small sites and more difficult at larger and shaded sites. Our findings show that S. molesta remains under good biological control in South Africa, however, some sites require intermittent strategic management, such as augmentative releases of C. salviniae.
- Full Text:
- Authors: Martin, Grant D , Coetzee, Julie A , Weyl, Philip S R , Parkinson, Matthew C , Hill, Martin P
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103878 , vital:32318 , https://doi.org/10.1016/j.biocontrol.2018.06.011
- Description: The aquatic weed Salvinia molesta D.S. Mitch. (Salviniaceae) was first recorded in South Africa in the early 1900s, and by the 1960s was regarded as one of South Africa’s worst aquatic weeds. Following the release of the weevil, Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) in 1985, the weed is now considered under successful biological control. However, the post-release evaluation of this biological control programme has been ad hoc, therefore, to assess the efficacy of the agent, annual quantitative surveys of South African freshwater systems have been undertaken since 2008. Over the last ten years, of the 57 S. molesta sites visited annually in South Africa, the weevil has established at all of them. Eighteen sites are under successful biological control, where the weed no longer poses a threat to the system and 19 are under substantial biological control, where biological control has reduced the impact of the weed. Since 2008, the average percentage weed cover at sites has declined significantly from 51–100% cover to 0–5% cover in 2017 (R2 = 0.78; P < 0.05). Observations of site-specific characteristics suggest that biological control is most effective at small sites and more difficult at larger and shaded sites. Our findings show that S. molesta remains under good biological control in South Africa, however, some sites require intermittent strategic management, such as augmentative releases of C. salviniae.
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Plant–herbivore–parasitoid interactions in an experimental freshwater tritrophic system: higher trophic levels modify competitive interactions between invasive macrophytes
- Martin, Grant D, Coetzee, Julie A, Compton, Stephen G
- Authors: Martin, Grant D , Coetzee, Julie A , Compton, Stephen G
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125686 , vital:35808 , https://doi.org/10.1007/s10750-017-341
- Description: Natural enemies are known to modify competitive hierarchies among terrestrial plants. Here we examine whether the same applies to freshwatersystems. Lagarosiphon major (Hydrocharitaceae) is a submerged aquatic macrophyte, indigenous to South Africa. Outside its native range, it outcompetes with indigenous submerged species and degrades aquatic habitats. Hydrellia lagarosiphon (Diptera: Ephydridae) is the most abundant and ubiquitous herbivore associated with L. major in South Africa and is a potential biological control agent elsewhere. Chaenusa anervata (Hymenoptera: Braconidae: Alysiinae) is its main parasitoid. We generated an experimental system involving one, two or three trophic levels to monitor variation in the competitive ability of L. major relative to that of Myriophyllum spicatum (Haloragaceae), a second submerged macrophyte that can also be invasive. Using inverse linear models to monitor competition, we found that herbivory by H. lagarosiphon greatly reduced the competitive ability of L. major. Addition of the wasp at typical field densities halved the impact of herbivory and reestablished the competitive advantage of L. major. Our results demonstrate how multitrophic interactions modify relative competitive abilities among aquatic plants, emphasize the significance of higher tropic levels in these systems and illustrate how parasitoids can reduce the effectiveness of insects released as biocontrol agents.
- Full Text:
- Authors: Martin, Grant D , Coetzee, Julie A , Compton, Stephen G
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/125686 , vital:35808 , https://doi.org/10.1007/s10750-017-341
- Description: Natural enemies are known to modify competitive hierarchies among terrestrial plants. Here we examine whether the same applies to freshwatersystems. Lagarosiphon major (Hydrocharitaceae) is a submerged aquatic macrophyte, indigenous to South Africa. Outside its native range, it outcompetes with indigenous submerged species and degrades aquatic habitats. Hydrellia lagarosiphon (Diptera: Ephydridae) is the most abundant and ubiquitous herbivore associated with L. major in South Africa and is a potential biological control agent elsewhere. Chaenusa anervata (Hymenoptera: Braconidae: Alysiinae) is its main parasitoid. We generated an experimental system involving one, two or three trophic levels to monitor variation in the competitive ability of L. major relative to that of Myriophyllum spicatum (Haloragaceae), a second submerged macrophyte that can also be invasive. Using inverse linear models to monitor competition, we found that herbivory by H. lagarosiphon greatly reduced the competitive ability of L. major. Addition of the wasp at typical field densities halved the impact of herbivory and reestablished the competitive advantage of L. major. Our results demonstrate how multitrophic interactions modify relative competitive abilities among aquatic plants, emphasize the significance of higher tropic levels in these systems and illustrate how parasitoids can reduce the effectiveness of insects released as biocontrol agents.
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Synergies between research organisations and the wider community in enhancing weed biological control in South Africa
- Martin, Grant D, Hill, Martin P, Coetzee, Julie A, Weaver, Kim N, Hill, Jaclyn M
- Authors: Martin, Grant D , Hill, Martin P , Coetzee, Julie A , Weaver, Kim N , Hill, Jaclyn M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68452 , vital:29258 , https://doi.org/10.1007/s10526-017-9846-4
- Description: Biological control offers a cost effective and ecologically sustainable tool for the management of invasive alien plants. Its implementation, however, has historically been slow and poorly co-ordinated. In South Africa, as in many other countries, most aspects of biological control programmes were done by researchers, but from 1995 onwards, with the advent of the Working for Water Programme, a more inclusive approach to biological control has been adopted. In this paper, we report on the development of community-based biological control implementation programmes in South Africa, after 1995, and highlight a number of initiatives, including employing persons with disabilities at mass-rearing facilities and in particular, we outline a suite of educational and outreach programmes for the general public and for schools, which have increased capacity, education and employment in the field of weed biological control.
- Full Text:
- Authors: Martin, Grant D , Hill, Martin P , Coetzee, Julie A , Weaver, Kim N , Hill, Jaclyn M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68452 , vital:29258 , https://doi.org/10.1007/s10526-017-9846-4
- Description: Biological control offers a cost effective and ecologically sustainable tool for the management of invasive alien plants. Its implementation, however, has historically been slow and poorly co-ordinated. In South Africa, as in many other countries, most aspects of biological control programmes were done by researchers, but from 1995 onwards, with the advent of the Working for Water Programme, a more inclusive approach to biological control has been adopted. In this paper, we report on the development of community-based biological control implementation programmes in South Africa, after 1995, and highlight a number of initiatives, including employing persons with disabilities at mass-rearing facilities and in particular, we outline a suite of educational and outreach programmes for the general public and for schools, which have increased capacity, education and employment in the field of weed biological control.
- Full Text:
Community entomology: insects, science and society
- Weaver, Kim N, Hill, Jaclyn M, Martin, Grant D, Paterson, Iain D, Coetzee, Julie A, Hill, Martin P
- Authors: Weaver, Kim N , Hill, Jaclyn M , Martin, Grant D , Paterson, Iain D , Coetzee, Julie A , Hill, Martin P
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123343 , vital:35429 , https://hdl.handle.net/10520/EJC-c859bebd5
- Description: Educative outreach programmes have been found to be effective ways in which to raise awareness around basic scientific concepts. The Biological Control Research Group (BCRG) in the Department of Zoology and Entomology at Rhodes University, South Africa, is involved in community engaged initiatives that aim to be interactive and informative around entomology, and more specifically, the use of biological control against invasive alien plants. As a higher education institution, Rhodes University has a civic responsibility to engage with local communities and work with them around local challenges. Three groups of activities undertaken by the BCRG in partnership with local schools and other community partners are described and assessed in this paper as a way of assessing them and exploring future research areas around the aims and outcomes of these programmes.
- Full Text:
- Authors: Weaver, Kim N , Hill, Jaclyn M , Martin, Grant D , Paterson, Iain D , Coetzee, Julie A , Hill, Martin P
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123343 , vital:35429 , https://hdl.handle.net/10520/EJC-c859bebd5
- Description: Educative outreach programmes have been found to be effective ways in which to raise awareness around basic scientific concepts. The Biological Control Research Group (BCRG) in the Department of Zoology and Entomology at Rhodes University, South Africa, is involved in community engaged initiatives that aim to be interactive and informative around entomology, and more specifically, the use of biological control against invasive alien plants. As a higher education institution, Rhodes University has a civic responsibility to engage with local communities and work with them around local challenges. Three groups of activities undertaken by the BCRG in partnership with local schools and other community partners are described and assessed in this paper as a way of assessing them and exploring future research areas around the aims and outcomes of these programmes.
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Genetic analysis of native and introduced populations of the aquatic weed Sagittaria platyphylla – implications for biological control in Australia and South Africa
- Kwong, Raelene M, Broadhurst, Linda M, Keener, Brian R, Coetzee, Julie A, Knerr, Nunzio, Martin, Grant D
- Authors: Kwong, Raelene M , Broadhurst, Linda M , Keener, Brian R , Coetzee, Julie A , Knerr, Nunzio , Martin, Grant D
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76991 , vital:30653 , https://doi.org/10.1016/j.biocontrol.2017.06.002
- Description: Sagittaria platyphylla (Engelm.) J.G. Sm. (Alismataceae) is an emergent aquatic plant native to southern USA. Imported into Australia and South Africa as an ornamental and aquarium plant, the species is now a serious invader of shallow freshwater wetlands, slow-flowing rivers, irrigation channels, drains and along the margins of lakes and reservoirs. As a first step towards initiating a classical biological control program, a population genetic study was conducted to determine the prospects of finding compatible biological control agents and to refine the search for natural enemies to source populations with closest genetic match to Australian and South African genotypes. Using AFLP markers we surveyed genetic diversity and population genetic structure in 26 populations from the USA, 19 from Australia and 7 from South Africa. Interestingly, we have established that populations introduced into South Africa and to a lesser extent Australia have maintained substantial molecular genetic diversity comparable with that in the native range. Results from principal coordinates analysis, population graph theory and Bayesian-based clustering analysis all support the notion that introduced populations in Australia and South Africa were founded by multiple sources from the USA. Furthermore, the divergence of some Australian populations from the USA suggests that intraspecific hybridization between genetically distinct lineages from the native range may have occurred. The implications of these findings in relation to biological control are discussed.
- Full Text:
- Authors: Kwong, Raelene M , Broadhurst, Linda M , Keener, Brian R , Coetzee, Julie A , Knerr, Nunzio , Martin, Grant D
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76991 , vital:30653 , https://doi.org/10.1016/j.biocontrol.2017.06.002
- Description: Sagittaria platyphylla (Engelm.) J.G. Sm. (Alismataceae) is an emergent aquatic plant native to southern USA. Imported into Australia and South Africa as an ornamental and aquarium plant, the species is now a serious invader of shallow freshwater wetlands, slow-flowing rivers, irrigation channels, drains and along the margins of lakes and reservoirs. As a first step towards initiating a classical biological control program, a population genetic study was conducted to determine the prospects of finding compatible biological control agents and to refine the search for natural enemies to source populations with closest genetic match to Australian and South African genotypes. Using AFLP markers we surveyed genetic diversity and population genetic structure in 26 populations from the USA, 19 from Australia and 7 from South Africa. Interestingly, we have established that populations introduced into South Africa and to a lesser extent Australia have maintained substantial molecular genetic diversity comparable with that in the native range. Results from principal coordinates analysis, population graph theory and Bayesian-based clustering analysis all support the notion that introduced populations in Australia and South Africa were founded by multiple sources from the USA. Furthermore, the divergence of some Australian populations from the USA suggests that intraspecific hybridization between genetically distinct lineages from the native range may have occurred. The implications of these findings in relation to biological control are discussed.
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Competition between two aquatic macrophytes, Lagarosiphon major (Ridley) Moss (Hydrocharitaceae) and Myriophyllum spicatum Linnaeus (Haloragaceae) as influenced by substrate sediment and nutrients
- Martin, Grant D, Coetzee, Julie A
- Authors: Martin, Grant D , Coetzee, Julie A
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76925 , vital:30641 , https://doi.org/10.1016/j.aquabot.2013.11.001
- Description: Competition between two globally economic and ecologically important submerged aquatic macrophytes, Lagarosiphon major (Rid.) Moss ex Wager and Myriophyllum spicatum L., was studied in response to growing in different substrate nutrient and sediment treatments. Addition series experiments were conducted with mixed plantings of L. major and M. spicatum grown under two soil nutrient concentrations (high vs. low) and two sediment treatments (sand vs. loam). Competitive ability of the plants was determined using an inverse linear model of the total dry weights as the yield variable. In high nutrient sediment treatments, L. major was the stronger competitor relative to M. spicatum, with one L. major plant being competitively equivalent to 2.5 M. spicatum plants in terms of their respective ability to reduce L. major biomass. In the loam sediment treatments, L. major was an even stronger competitor relative to M. spicatum with one L. major being equivalent to 10 M. spicatum plants. Additionally, L. major had a faster relative growth rate (RGR) than M. spicatum when grown in mixed cultures, a loam sediment type and at both high and low planting densities. The results indicated that L. major is a superior competitor to M. spicatum and that both nutrient and sediment conditions significantly affect the competitive ability of both species. The results contribute to the understanding of competition between submerged invasive macrophytes, and provide insight into the establishment and spread of invasive submerged macrophytes.
- Full Text:
- Authors: Martin, Grant D , Coetzee, Julie A
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76925 , vital:30641 , https://doi.org/10.1016/j.aquabot.2013.11.001
- Description: Competition between two globally economic and ecologically important submerged aquatic macrophytes, Lagarosiphon major (Rid.) Moss ex Wager and Myriophyllum spicatum L., was studied in response to growing in different substrate nutrient and sediment treatments. Addition series experiments were conducted with mixed plantings of L. major and M. spicatum grown under two soil nutrient concentrations (high vs. low) and two sediment treatments (sand vs. loam). Competitive ability of the plants was determined using an inverse linear model of the total dry weights as the yield variable. In high nutrient sediment treatments, L. major was the stronger competitor relative to M. spicatum, with one L. major plant being competitively equivalent to 2.5 M. spicatum plants in terms of their respective ability to reduce L. major biomass. In the loam sediment treatments, L. major was an even stronger competitor relative to M. spicatum with one L. major being equivalent to 10 M. spicatum plants. Additionally, L. major had a faster relative growth rate (RGR) than M. spicatum when grown in mixed cultures, a loam sediment type and at both high and low planting densities. The results indicated that L. major is a superior competitor to M. spicatum and that both nutrient and sediment conditions significantly affect the competitive ability of both species. The results contribute to the understanding of competition between submerged invasive macrophytes, and provide insight into the establishment and spread of invasive submerged macrophytes.
- Full Text:
Hydrellia lagarosiphon Deeming (Diptera: Ephydridae), a potential biological control agent for the submerged aquatic weed, Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae)
- Martin, Grant D, Coetzee, Julie A, Baars, Jan-Robert
- Authors: Martin, Grant D , Coetzee, Julie A , Baars, Jan-Robert
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103912 , vital:32322 , https://doi.org/10.4001/003.021.0118
- Description: The leaf-mining fly, Hydrellia lagarosiphon Deeming (Diptera: Ephydridae), was investigated in its native range in South Africa, to determine its potential as a biological control agent for Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae), an invasive submerged macrophyte that is weedy in many parts of the world. The fly was found throughout the indigenous range of the plant in South Africa. High larval abundance was recorded at field sites with nearly all L. major shoots sampled ontaining larvae, with densities of up to 10 larvae per shoot. Adults laid batches of up to 15 eggs, usually on the abaxial sides of L. major leaves. The larvae mined internally, leaving the epidermal tissues of the upper and lower leaves intact. The larvae underwent three instars which took an average of 24 days and pupated within the leaf tissue, from which the adults emerged. Impact studies in the laboratory showed that H. lagarosiphon larval feeding significantly restricted the formation of L. major side branches. Based on its biology and damage caused to the plant, Hydrellia lagarosiphon could be considered as a useful biological control candidate for L. major in countries where the plant is invasive.
- Full Text:
- Authors: Martin, Grant D , Coetzee, Julie A , Baars, Jan-Robert
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103912 , vital:32322 , https://doi.org/10.4001/003.021.0118
- Description: The leaf-mining fly, Hydrellia lagarosiphon Deeming (Diptera: Ephydridae), was investigated in its native range in South Africa, to determine its potential as a biological control agent for Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae), an invasive submerged macrophyte that is weedy in many parts of the world. The fly was found throughout the indigenous range of the plant in South Africa. High larval abundance was recorded at field sites with nearly all L. major shoots sampled ontaining larvae, with densities of up to 10 larvae per shoot. Adults laid batches of up to 15 eggs, usually on the abaxial sides of L. major leaves. The larvae mined internally, leaving the epidermal tissues of the upper and lower leaves intact. The larvae underwent three instars which took an average of 24 days and pupated within the leaf tissue, from which the adults emerged. Impact studies in the laboratory showed that H. lagarosiphon larval feeding significantly restricted the formation of L. major side branches. Based on its biology and damage caused to the plant, Hydrellia lagarosiphon could be considered as a useful biological control candidate for L. major in countries where the plant is invasive.
- Full Text:
Natural enemies from South Africa for biological control of Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae) in Europe
- Baars, Jan-Robert, Coetzee, Julie A, Martin, Grant D, Hill, Martin P, Caffrey, J M
- Authors: Baars, Jan-Robert , Coetzee, Julie A , Martin, Grant D , Hill, Martin P , Caffrey, J M
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76914 , vital:30637 , https://doi.org/10.1007/s10750-010-0427-0
- Description: The non-native invasive plant, Lagarosiphon major (Hydrocharitaceae) is a submersed aquatic macrophyte that poses a significant threat to water bodies in Europe. Dense infestations prove difficult to manage using traditional methods. In order to initiate a biocontrol programme, a survey for natural enemies of Lagarosiphon was conducted in South Africa. Several phytophagous species were recorded for the first time, with at least three showing notable promise as candidate agents. Amongst these, a leaf-mining fly, Hydrellia sp. (Ephydridae) that occurred over a wide distribution causes significant leaf damage despite high levels of parasitism by braconid wasps. Another yet unidentified fly was recorded mining the stem of L. major. Two leaf-feeding and shoot boring weevils, cf. Bagous sp. (Curculionidae) were recorded damaging the shoot tips and stunting the growth of the stem. Several leaf-feeding lepidopteran species (Nymphulinae) were frequently recorded, but are expected to feed on a wide range of plant species and are not considered for importation before other candidates are assessed. The discovery of several natural enemies in the country of origin improves the biological control prospects of L. major in Europe.
- Full Text:
- Authors: Baars, Jan-Robert , Coetzee, Julie A , Martin, Grant D , Hill, Martin P , Caffrey, J M
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76914 , vital:30637 , https://doi.org/10.1007/s10750-010-0427-0
- Description: The non-native invasive plant, Lagarosiphon major (Hydrocharitaceae) is a submersed aquatic macrophyte that poses a significant threat to water bodies in Europe. Dense infestations prove difficult to manage using traditional methods. In order to initiate a biocontrol programme, a survey for natural enemies of Lagarosiphon was conducted in South Africa. Several phytophagous species were recorded for the first time, with at least three showing notable promise as candidate agents. Amongst these, a leaf-mining fly, Hydrellia sp. (Ephydridae) that occurred over a wide distribution causes significant leaf damage despite high levels of parasitism by braconid wasps. Another yet unidentified fly was recorded mining the stem of L. major. Two leaf-feeding and shoot boring weevils, cf. Bagous sp. (Curculionidae) were recorded damaging the shoot tips and stunting the growth of the stem. Several leaf-feeding lepidopteran species (Nymphulinae) were frequently recorded, but are expected to feed on a wide range of plant species and are not considered for importation before other candidates are assessed. The discovery of several natural enemies in the country of origin improves the biological control prospects of L. major in Europe.
- Full Text:
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