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Title: Wound-induced chemical changes in plants and their effects on the behaviour of insect herbivores
Author: Barker, Alison Margaret
ISNI:       0000 0001 3444 9031
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 1992
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The importance of insect-plant interactions in insect behavioural ecology is increasingly being recognised. One class of such interactions involves dynamic chemical changes in the plant induced directly by insect feeding damage. This study set out to investigate the ecological significance of these wound-induced changes using a model predicting that, if their growth is affected by the induced chemicals, mobile, free-living insect herbivores should adapt their behaviour to minimise their intake of affected foliage, finding such foliage less palatable and foraging widely to find unaffected areas. Two plant-herbivore systems were used to investigate wound-induced changes. In one, Orthosia gothica and O.stabilis on birch (Betula pendula and B.pubescens), the herbivores' growth was unaffected by damage to plant foliage, and O.gothica's foraging behaviour was scarcely affected by such damage. It was concluded that wound-induced changes in birch are unimportant in the behavioural and population ecology of these species of herbivore, and any benefits to the plant must lie elsewhere. However, in the second system, Spodoptera littoralis on tomato, damage to the plant affected the herbivore in much the way predicted by the model. S.littoralis larvae suffer reduced growth on damaged foliage. They find such foliage reduced in palatability and tend to take smaller meals on it, producing patterns of many small holes rather than the fewer large ones seen on unaffected foliage. In choice situations they will tend to feed on the unaffected foliage in preference to foliage from damaged plants. The evidence therefore suggests that S.littoralis larvae benefit from avoiding areas of foliage affected by wound-induced changes. The significance of such effects for the plant has been much debated. This study found some evidence to support the idea that the principal benefit of wound-induced chemical changes for the plant lies in redirecting herbivore feeding damage away from the most valuable parts of the plant (Edwards and Wratten 1987, Edwards, Wratten and Parker 1992). Wound-induced changes in tomato seems to be greatest at the plant's growing tip; preventing this from being grazed may ensure that the plants do not lose disproportionately in competition for light.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Ecology