Herbivore behaviour, multitrophic interactions and a lack of wound-induced defence in a member of the cruciferae
Herbivore behaviour, multitrophic interactions and a lack of wound-induced defence in a member of the cruciferae
Insect-plant relationships were originally seen as a case of simple trophic relationships, but underlying this initial simplicity is a vast array of complex relationships. Plants may possess mechanisms to reduce herbivory, including defences that are dynamic and mobilised in response to insect attack. A key problem of many studies has been that they excluded the role of herbivore natural enemies.
The fundamental aim of this project was to test a model of wound-induced defence in herbaceous plants. This model predicts that a plant under insect attack will elevate production of "defensive" chemicals which will cause insects to move away from the site of damage, or suffer reduced growth. Wound-induced defence/resistance can be understood to have two aspects: firstly directly, whereby the elevated levels of defensive/resistant chemicals in the leaf cause behavioural and growth changes, and secondly indirect effects where elevated levels of foliar chemicals have no effect on herbivore performance, but may alter its physiology or behaviour with consequent impact on other features in the ecology of the insect.
These predictions were tested in the system Pieris brassicae feeding on Brassica oleracea (cabbage), with the parasitoid Cotesia glomerata. Prior herbivory had no effect on P. brassicae performance on cabbage, but did cause a trend to increased oviposition on wounded plants. Herbivory is known to be most attractive to foraging parasitoids, this work showed that herbivory at the top of the plant was most attractive. However, parasitism of the herbivore does not lead to a reduction in herbivory. These apparently paradoxical results lead to the conclusion that many models of plant defence are premature and over-simplistic, and perhaps the application of general models should be questioned.
University of Southampton
1996
Coleman, Ross Antony
(1996)
Herbivore behaviour, multitrophic interactions and a lack of wound-induced defence in a member of the cruciferae.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Insect-plant relationships were originally seen as a case of simple trophic relationships, but underlying this initial simplicity is a vast array of complex relationships. Plants may possess mechanisms to reduce herbivory, including defences that are dynamic and mobilised in response to insect attack. A key problem of many studies has been that they excluded the role of herbivore natural enemies.
The fundamental aim of this project was to test a model of wound-induced defence in herbaceous plants. This model predicts that a plant under insect attack will elevate production of "defensive" chemicals which will cause insects to move away from the site of damage, or suffer reduced growth. Wound-induced defence/resistance can be understood to have two aspects: firstly directly, whereby the elevated levels of defensive/resistant chemicals in the leaf cause behavioural and growth changes, and secondly indirect effects where elevated levels of foliar chemicals have no effect on herbivore performance, but may alter its physiology or behaviour with consequent impact on other features in the ecology of the insect.
These predictions were tested in the system Pieris brassicae feeding on Brassica oleracea (cabbage), with the parasitoid Cotesia glomerata. Prior herbivory had no effect on P. brassicae performance on cabbage, but did cause a trend to increased oviposition on wounded plants. Herbivory is known to be most attractive to foraging parasitoids, this work showed that herbivory at the top of the plant was most attractive. However, parasitism of the herbivore does not lead to a reduction in herbivory. These apparently paradoxical results lead to the conclusion that many models of plant defence are premature and over-simplistic, and perhaps the application of general models should be questioned.
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Published date: 1996
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Local EPrints ID: 459926
URI: http://eprints.soton.ac.uk/id/eprint/459926
PURE UUID: 9a03760c-9c18-4d05-a1a8-4b142d41df15
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Date deposited: 04 Jul 2022 17:27
Last modified: 04 Jul 2022 17:27
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Author:
Ross Antony Coleman
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