Molecular identification of Azolla invasions in Africa: The Azolla specialist, Stenopelmus rufinasus proves to be an excellent taxonomist
- Madeira, P T, Dray, F Allen, Coetzee, Julie A, Paterson, Iain D, Tipping, Philip W
- Authors: Madeira, P T , Dray, F Allen , Coetzee, Julie A , Paterson, Iain D , Tipping, Philip W
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424765 , vital:72182 , xlink:href="https://doi.org/10.1016/j.sajb.2016.03.007"
- Description: Biological control of Azolla filiculoides in South Africa with the Azolla specialist Stenopelmus rufinasus has been highly successful. However, field surveys showed that the agent utilized another Azolla species, thought to be the native Azolla pinnata subsp. africana, which contradicted host specificity trials. It is notoriously difficult to determine Azolla species based on morphology so genetic analyses were required to confirm the identity of the Azolla used by the agent. Extensive sampling was conducted and samples were sequenced at the trnL-trnF and trnG-trnR chloroplastic regions and the nuclear ITS1 region. Current literature reported A. filiculoides as the only Section Azolla species in southern Africa but 24 samples were identified as Azolla cristata, an introduced species within Section Azolla that was not used during host specificity trials. A. pinnata subsp. africana was only located at one site in southern Africa, while the alien A. pinnata subsp. asiatica was located at three. What was thought to be A. pinnata subsp. africana was in fact A. cristata, a closer relative of A. filiculoides and a suitable host according to specificity trials. This study confirms that S. rufinasus is a proficient Azolla taxonomist but also supports the use of molecular techniques for resolving taxonomic conundrums.
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- Authors: Madeira, P T , Dray, F Allen , Coetzee, Julie A , Paterson, Iain D , Tipping, Philip W
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424765 , vital:72182 , xlink:href="https://doi.org/10.1016/j.sajb.2016.03.007"
- Description: Biological control of Azolla filiculoides in South Africa with the Azolla specialist Stenopelmus rufinasus has been highly successful. However, field surveys showed that the agent utilized another Azolla species, thought to be the native Azolla pinnata subsp. africana, which contradicted host specificity trials. It is notoriously difficult to determine Azolla species based on morphology so genetic analyses were required to confirm the identity of the Azolla used by the agent. Extensive sampling was conducted and samples were sequenced at the trnL-trnF and trnG-trnR chloroplastic regions and the nuclear ITS1 region. Current literature reported A. filiculoides as the only Section Azolla species in southern Africa but 24 samples were identified as Azolla cristata, an introduced species within Section Azolla that was not used during host specificity trials. A. pinnata subsp. africana was only located at one site in southern Africa, while the alien A. pinnata subsp. asiatica was located at three. What was thought to be A. pinnata subsp. africana was in fact A. cristata, a closer relative of A. filiculoides and a suitable host according to specificity trials. This study confirms that S. rufinasus is a proficient Azolla taxonomist but also supports the use of molecular techniques for resolving taxonomic conundrums.
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Morphological variations in southern African populations of Myriophyllum spicatum: Phenotypic plasticity or local adaptation?
- Weyl, Philip S R, Coetzee, Julie A
- Authors: Weyl, Philip S R , Coetzee, Julie A
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424789 , vital:72184 , xlink:href="https://doi.org/10.1016/j.sajb.2015.07.01"
- Description: Variability in aquatic plant morphology is usually driven by phenotypic plasticity and local adaptations to environmental conditions experienced. This study aimed to elucidate which of these drivers is responsible for the morphological variation exhibited by three populations of Myriophyllum spicatum L. (Haloragaceae), a submerged aquatic plant whose status as native or exotic within southern Africa is uncertain. Individuals from three populations on the Vaal River (Northern Cape), Klipplaat River (Eastern Cape) and Lake Sibaya (KwaZulu-Natal) were grown under two nutrient treatments (high: 30 mg N/kg sediment and low: sediment only), while all other variables were kept the same. Morphological characteristics were measured at the start of the experiment to obtain a baseline morphology, and again eight weeks later. By the end of the experiment, the individuals from each population had responded to the different growing conditions. In most cases, the individuals from each population were significantly larger under the high nutrient treatment (Stem diameter: F(5,86) = 18.435, P is less than 0.001, Internode length: F(5,86) = 5.0747, P is less than 0.001, Leaf length: F(5,86) = 19.692, P is less than 0.001). Despite these differences in nutrient treatments, the growth pattern of each population remained true to the original starting point indicated by the lack of overlap between populations in the PCA groupings. This suggests that local adaptations are responsible for the differences in morphology between populations of M. spicatum, but shows that phenotypic plasticity does play a role as evidenced by individual responses to the different nutrient conditions. The development of these local adaptations within southern Africa suggests that the populations have had a long evolutionary history in the region and are relatively isolated with little reproductive mixing.
- Full Text:
- Authors: Weyl, Philip S R , Coetzee, Julie A
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424789 , vital:72184 , xlink:href="https://doi.org/10.1016/j.sajb.2015.07.01"
- Description: Variability in aquatic plant morphology is usually driven by phenotypic plasticity and local adaptations to environmental conditions experienced. This study aimed to elucidate which of these drivers is responsible for the morphological variation exhibited by three populations of Myriophyllum spicatum L. (Haloragaceae), a submerged aquatic plant whose status as native or exotic within southern Africa is uncertain. Individuals from three populations on the Vaal River (Northern Cape), Klipplaat River (Eastern Cape) and Lake Sibaya (KwaZulu-Natal) were grown under two nutrient treatments (high: 30 mg N/kg sediment and low: sediment only), while all other variables were kept the same. Morphological characteristics were measured at the start of the experiment to obtain a baseline morphology, and again eight weeks later. By the end of the experiment, the individuals from each population had responded to the different growing conditions. In most cases, the individuals from each population were significantly larger under the high nutrient treatment (Stem diameter: F(5,86) = 18.435, P is less than 0.001, Internode length: F(5,86) = 5.0747, P is less than 0.001, Leaf length: F(5,86) = 19.692, P is less than 0.001). Despite these differences in nutrient treatments, the growth pattern of each population remained true to the original starting point indicated by the lack of overlap between populations in the PCA groupings. This suggests that local adaptations are responsible for the differences in morphology between populations of M. spicatum, but shows that phenotypic plasticity does play a role as evidenced by individual responses to the different nutrient conditions. The development of these local adaptations within southern Africa suggests that the populations have had a long evolutionary history in the region and are relatively isolated with little reproductive mixing.
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Partial cold treatment of citrus fruit for export risk mitigation for Thaumatotibia leucotreta (Lepidoptera: Tortricidae) as part of a systems approach
- Moore, Sean D, Kirkman, Wayne, Albertyn, Sonnica, Love, C N, Coetzee, Julie A, Hattingh, Vaughan
- Authors: Moore, Sean D , Kirkman, Wayne , Albertyn, Sonnica , Love, C N , Coetzee, Julie A , Hattingh, Vaughan
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423796 , vital:72094 , xlink:href="https://doi.org/10.1093/jee/tow138"
- Description: Some of South Africa’s citrus export markets require mandatory postharvest cold treatment of citrus fruit as a phytosanitary risk mitigation treatment for Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae). An alternative to this may be partial cold treatment as one of the final steps in a systems approach to mitigate phytosanitary risk. Consequently, the efficacy of such partial cold treatments was evaluated. It was first determined that a 2C cold treatment was significantly more effective against fourth and fifth instars (the most cold-tolerant instars) than treatments at 3C and 4C for a duration of 18 d. Secondly, it was determined that 2C for 18 d and 1C for 16 d were similarly effective, but both treatments were significantly more effective than 1C for 14 d. Mean mortality of fourth and fifth instars treated with 2C for 18 d in seven replicates from four trials was 99.94%. Finally, it was determined that the inability of the majority of surviving larvae to develop to adulthood would further increase the efficacy of a 2C for 18 d treatment to 99.96%. Inclusion of reproductive nonviability of survivors increased mortality to 99.99%.
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- Authors: Moore, Sean D , Kirkman, Wayne , Albertyn, Sonnica , Love, C N , Coetzee, Julie A , Hattingh, Vaughan
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423796 , vital:72094 , xlink:href="https://doi.org/10.1093/jee/tow138"
- Description: Some of South Africa’s citrus export markets require mandatory postharvest cold treatment of citrus fruit as a phytosanitary risk mitigation treatment for Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae). An alternative to this may be partial cold treatment as one of the final steps in a systems approach to mitigate phytosanitary risk. Consequently, the efficacy of such partial cold treatments was evaluated. It was first determined that a 2C cold treatment was significantly more effective against fourth and fifth instars (the most cold-tolerant instars) than treatments at 3C and 4C for a duration of 18 d. Secondly, it was determined that 2C for 18 d and 1C for 16 d were similarly effective, but both treatments were significantly more effective than 1C for 14 d. Mean mortality of fourth and fifth instars treated with 2C for 18 d in seven replicates from four trials was 99.94%. Finally, it was determined that the inability of the majority of surviving larvae to develop to adulthood would further increase the efficacy of a 2C for 18 d treatment to 99.96%. Inclusion of reproductive nonviability of survivors increased mortality to 99.99%.
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Two in one: cryptic species discovered in biological control agent populations using molecular data and crossbreeding experiments
- Paterson, Iain D, Mangan, Rose, Downie, Douglas A, Coetzee, Julie A, Hill, Martin P, Burke, Ashley M, Downey, Paul O, Henry, Thomas J, Compton, Stephen G
- Authors: Paterson, Iain D , Mangan, Rose , Downie, Douglas A , Coetzee, Julie A , Hill, Martin P , Burke, Ashley M , Downey, Paul O , Henry, Thomas J , Compton, Stephen G
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424877 , vital:72191 , xlink:href="https://doi.org/10.1002/ece3.2297"
- Description: There are many examples of cryptic species that have been identified through DNA-barcoding or other genetic techniques. There are, however, very few confirmations of cryptic species being reproductively isolated. This study presents one of the few cases of cryptic species that has been confirmed to be reproductively isolated and therefore true species according to the biological species concept. The cryptic species are of special interest because they were discovered within biological control agent populations. Two geographically isolated populations of Eccritotarsus catarinensis (Carvalho) [Hemiptera: Miridae], a biological control agent for the invasive aquatic macrophyte, water hyacinth, Eichhornia crassipes (Mart.) Solms [Pontederiaceae], in South Africa, were sampled from the native range of the species in South America. Morphological characteristics indicated that both populations were the same species according to the current taxonomy, but subsequent DNA analysis and breeding experiments revealed that the two populations are reproductively isolated. Crossbreeding experiments resulted in very few hybrid offspring when individuals were forced to interbreed with individuals of the other population, and no hybrid offspring were recorded when a choice of mate from either population was offered. The data indicate that the two populations are cryptic species that are reproductively incompatible. Subtle but reliable diagnostic characteristics were then identified to distinguish between the two species which would have been considered intraspecific variation without the data from the genetics and interbreeding experiments. These findings suggest that all consignments of biological control agents from allopatric populations should be screened for cryptic species using genetic techniques and that the importation of multiple consignments of the same species for biological control should be conducted with caution.
- Full Text:
- Authors: Paterson, Iain D , Mangan, Rose , Downie, Douglas A , Coetzee, Julie A , Hill, Martin P , Burke, Ashley M , Downey, Paul O , Henry, Thomas J , Compton, Stephen G
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424877 , vital:72191 , xlink:href="https://doi.org/10.1002/ece3.2297"
- Description: There are many examples of cryptic species that have been identified through DNA-barcoding or other genetic techniques. There are, however, very few confirmations of cryptic species being reproductively isolated. This study presents one of the few cases of cryptic species that has been confirmed to be reproductively isolated and therefore true species according to the biological species concept. The cryptic species are of special interest because they were discovered within biological control agent populations. Two geographically isolated populations of Eccritotarsus catarinensis (Carvalho) [Hemiptera: Miridae], a biological control agent for the invasive aquatic macrophyte, water hyacinth, Eichhornia crassipes (Mart.) Solms [Pontederiaceae], in South Africa, were sampled from the native range of the species in South America. Morphological characteristics indicated that both populations were the same species according to the current taxonomy, but subsequent DNA analysis and breeding experiments revealed that the two populations are reproductively isolated. Crossbreeding experiments resulted in very few hybrid offspring when individuals were forced to interbreed with individuals of the other population, and no hybrid offspring were recorded when a choice of mate from either population was offered. The data indicate that the two populations are cryptic species that are reproductively incompatible. Subtle but reliable diagnostic characteristics were then identified to distinguish between the two species which would have been considered intraspecific variation without the data from the genetics and interbreeding experiments. These findings suggest that all consignments of biological control agents from allopatric populations should be screened for cryptic species using genetic techniques and that the importation of multiple consignments of the same species for biological control should be conducted with caution.
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Was Myriophyllum spicatum L.(Haloragaceae) recently introduced to South Africa from Eurasia?
- Weyl, Philip S R, Thum, R A, Moody, M L, Newman, R M, Coetzee, Julie A
- Authors: Weyl, Philip S R , Thum, R A , Moody, M L , Newman, R M , Coetzee, Julie A
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/425463 , vital:72242 , xlink:href="https://doi.org/10.1016/j.aquabot.2015.09.003"
- Description: There is debate over the native or exotic status of Myriophyllum spicatum L. (Haloragaceae) in South Africa, which has important implications for developing and implementing management strategies. The aim of this study was to determine if M. spicatum was recently introduced from Eurasia by reconstructing the genetic relationships between South African and Eurasian M. spicatum using both a nuclear ribosomal (ITS1-5.8S-ITS2-26S) and a chloroplast intron (trnQ-rps16) sequence from 40 populations. For both these DNA markers, the South African populations were distinct from Eurasian populations, but always stemmed from a European origin. The data suggest that South African and European M. spicatum share a common ancestor, however the divergence of both markers are characteristic of a long period of isolation rather than a recent introduction from Europe. The genetic data from this study suggest that M. spicatum has not been introduced recently, but is most likely a native component of the South African flora.
- Full Text:
- Authors: Weyl, Philip S R , Thum, R A , Moody, M L , Newman, R M , Coetzee, Julie A
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/425463 , vital:72242 , xlink:href="https://doi.org/10.1016/j.aquabot.2015.09.003"
- Description: There is debate over the native or exotic status of Myriophyllum spicatum L. (Haloragaceae) in South Africa, which has important implications for developing and implementing management strategies. The aim of this study was to determine if M. spicatum was recently introduced from Eurasia by reconstructing the genetic relationships between South African and Eurasian M. spicatum using both a nuclear ribosomal (ITS1-5.8S-ITS2-26S) and a chloroplast intron (trnQ-rps16) sequence from 40 populations. For both these DNA markers, the South African populations were distinct from Eurasian populations, but always stemmed from a European origin. The data suggest that South African and European M. spicatum share a common ancestor, however the divergence of both markers are characteristic of a long period of isolation rather than a recent introduction from Europe. The genetic data from this study suggest that M. spicatum has not been introduced recently, but is most likely a native component of the South African flora.
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