Developmental and reproductive performance of a specialist herbivore depend on seasonality of, and light conditions experienced by, the host plant
- Zachariades, Uyi O O,, Heshula, L U P, Hill, Martin P
- Authors: Zachariades, Uyi O O, , Heshula, L U P , Hill, Martin P
- Date: 2018
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59845 , vital:27667 , https://doi.org/10.1371/journal.pone.0190700
- Description: Host plant phenology (as influenced by seasonality) and light-mediated changes in the phenotypic and phytochemical properties of leaves have been hypothesised to equivocally influence insect herbivore performance. Here, we examined the effects of seasonality, through host plant phenology (late growth-season = autumn vs flowering-season = winter) and light environment (shade vs full-sun habitat) on the leaf characteristics of the invasive alien plant, Chromolaena odorata. In addition, the performance of a specialist folivore, Pareuchaetes insulata, feeding on leaves obtained from both shaded and full-sun habitats during autumn and winter, was evaluated over two generations. Foliar nitrogen and magnesium contents were generally higher in shaded plants with much higher levels during winter. Leaf water content was higher in shaded and in autumn plants. Total non-structural carbohydrate (TNC) and phosphorus contents did not differ as a function of season, but were higher in shaded foliage compared to full-sun leaves. Leaf toughness was noticeably higher on plants growing in full-sun during winter. With the exception of shaded leaves in autumn that supported the best performance [fastest development, heaviest pupal mass, and highest growth rate and Host Suitability Index (HSI) score], full-sun foliage in autumn surprisingly also supported an improved performance of the moth compared to shaded or full-sun leaves in winter. Our findings suggest that shaded and autumn foliage are nutritionally more suitable for the growth and reproduction of P. insulata. However, the heavier pupal mass, increased number of eggs and higher HSI score in individuals that fed on full-sun foliage in autumn compared to their counterparts that fed on shaded or full-sun foliage in winter suggest that full-sun foliage during autumn is also a suitable food source for larvae of the moth. In sum, our study demonstrates that seasonal and light-modulated changes in leaf characteristics can affect insect folivore performance in ways that are not linear.
- Full Text:
- Date Issued: 2018
- Authors: Zachariades, Uyi O O, , Heshula, L U P , Hill, Martin P
- Date: 2018
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59845 , vital:27667 , https://doi.org/10.1371/journal.pone.0190700
- Description: Host plant phenology (as influenced by seasonality) and light-mediated changes in the phenotypic and phytochemical properties of leaves have been hypothesised to equivocally influence insect herbivore performance. Here, we examined the effects of seasonality, through host plant phenology (late growth-season = autumn vs flowering-season = winter) and light environment (shade vs full-sun habitat) on the leaf characteristics of the invasive alien plant, Chromolaena odorata. In addition, the performance of a specialist folivore, Pareuchaetes insulata, feeding on leaves obtained from both shaded and full-sun habitats during autumn and winter, was evaluated over two generations. Foliar nitrogen and magnesium contents were generally higher in shaded plants with much higher levels during winter. Leaf water content was higher in shaded and in autumn plants. Total non-structural carbohydrate (TNC) and phosphorus contents did not differ as a function of season, but were higher in shaded foliage compared to full-sun leaves. Leaf toughness was noticeably higher on plants growing in full-sun during winter. With the exception of shaded leaves in autumn that supported the best performance [fastest development, heaviest pupal mass, and highest growth rate and Host Suitability Index (HSI) score], full-sun foliage in autumn surprisingly also supported an improved performance of the moth compared to shaded or full-sun leaves in winter. Our findings suggest that shaded and autumn foliage are nutritionally more suitable for the growth and reproduction of P. insulata. However, the heavier pupal mass, increased number of eggs and higher HSI score in individuals that fed on full-sun foliage in autumn compared to their counterparts that fed on shaded or full-sun foliage in winter suggest that full-sun foliage during autumn is also a suitable food source for larvae of the moth. In sum, our study demonstrates that seasonal and light-modulated changes in leaf characteristics can affect insect folivore performance in ways that are not linear.
- Full Text:
- Date Issued: 2018
Changes in chemical composition of essential oils from leaves of different Lantana camara L. (Verbenaceae) varieties after feeding by the introduced biological control agent, Falconia intermedia Distant (Hemiptera: Miridae)
- Ngxande-Koza, S W, Heshula, L U P, Hill, Martin P
- Authors: Ngxande-Koza, S W , Heshula, L U P , Hill, Martin P
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59834 , vital:27664 , https://doi.org/10.4001/003.025.0462
- Description: Lantana camara L. (Verbenaceae) is one of the most problematic plant invaders in South Africa and has been targeted for biological control for over 50 years. Essential oil constituents which often change in response to insect herbivory are reported to play a crucial role in plant-insect interactions. However, nothing is known about the chemical profiles of essential oils of L. camara varieties in South Africa and how this changes under herbivory. Therefore, essential oils were collected using hydrodistillation from undamaged and insect-damaged leaves of four L. camara varieties and analysed using gas chromatography-mass spectrometry to elucidate their chemical profiles. A total of 163 compounds were identified from the undamaged leaves of the various L. camara varieties. Feeding by the biocontrol agent Falconia intermedia Distant (Hemiptera: Miridae) resulted in changes in the quality and quantity of chemical constituents of the essential oils. Only 75 compounds were identified from the insect-damaged leaves of L. camara varieties. Terpenes were the major components across the varieties, while caryophyllene, hexane, naphthalene, copaene and a-caryophyllene were common in all the varieties tested from both undamaged and insect-damaged leaves. Results from this study indicated the chemical distinctiveness of the Whitney Farm variety from other varieties. The changes in chemical concentrations indicated that feeding by the mirid on L. camara varieties causes an induction by either reducing or increasing the chemical concentrations. These inductions following the feeding by F. intermedia could be having a negative impact on the success of biological control against L. camara varieties. However, the focus of this paper is to report on the chemical baseline of L. camara varieties. Hence, comparisons of chemical compound concentrations of L. camara essential oils tested and the feeding-induced changes with respect to their quality and quantity are discussed.
- Full Text:
- Date Issued: 2017
- Authors: Ngxande-Koza, S W , Heshula, L U P , Hill, Martin P
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59834 , vital:27664 , https://doi.org/10.4001/003.025.0462
- Description: Lantana camara L. (Verbenaceae) is one of the most problematic plant invaders in South Africa and has been targeted for biological control for over 50 years. Essential oil constituents which often change in response to insect herbivory are reported to play a crucial role in plant-insect interactions. However, nothing is known about the chemical profiles of essential oils of L. camara varieties in South Africa and how this changes under herbivory. Therefore, essential oils were collected using hydrodistillation from undamaged and insect-damaged leaves of four L. camara varieties and analysed using gas chromatography-mass spectrometry to elucidate their chemical profiles. A total of 163 compounds were identified from the undamaged leaves of the various L. camara varieties. Feeding by the biocontrol agent Falconia intermedia Distant (Hemiptera: Miridae) resulted in changes in the quality and quantity of chemical constituents of the essential oils. Only 75 compounds were identified from the insect-damaged leaves of L. camara varieties. Terpenes were the major components across the varieties, while caryophyllene, hexane, naphthalene, copaene and a-caryophyllene were common in all the varieties tested from both undamaged and insect-damaged leaves. Results from this study indicated the chemical distinctiveness of the Whitney Farm variety from other varieties. The changes in chemical concentrations indicated that feeding by the mirid on L. camara varieties causes an induction by either reducing or increasing the chemical concentrations. These inductions following the feeding by F. intermedia could be having a negative impact on the success of biological control against L. camara varieties. However, the focus of this paper is to report on the chemical baseline of L. camara varieties. Hence, comparisons of chemical compound concentrations of L. camara essential oils tested and the feeding-induced changes with respect to their quality and quantity are discussed.
- Full Text:
- Date Issued: 2017
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