Ecological maintenance of food-mixing in the woolly bear caterpillar Grammia geneura (Strecker) (Lepidoptera: Arctiidae)

Persistent Link:
http://hdl.handle.net/10150/289114
Title:
Ecological maintenance of food-mixing in the woolly bear caterpillar Grammia geneura (Strecker) (Lepidoptera: Arctiidae)
Author:
Singer, Michael Stuart
Issue Date:
2000
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Two major conceptual approaches for understanding the evolutionary ecology of insect-plant interactions, the plant-insect paradigm and the tri-trophic paradigm, have focused primarily upon dietary specialists and their host-plants. Here, I attempted to evaluate the utility of both paradigms for explaining the maintenance of food-mixing by the individually polyphagous caterpillars of Grammia geneura (Strecker) (Lepidoptera: Arctiidae). First, I conducted three experiments testing the hypothesis that individual G. geneura caterpillars perform better on mixed-plant diets than on single-plant diets due to improved physiological efficiency of food utilization. However, caterpillar performance was not always superior on mixed-plant diets. In the one case in which food-mixing improved performance, the host-plant species included in the mixture were individually of low suitability. Behavioral observations of individual caterpillars both in the above experiments, in nature, and in two further laboratory experiments with chemically-manipulated, synthetic diets supported the idea that such dietary benefits resulted from dilution of plant secondary metabolites, achieved behaviorally via the physiological mechanisms of neophilia and post-ingestive feedbacks on feeding. I also investigated the possibility that food-mixing was maintained by the unpredictable availability of high-quality host-plant species. A field survey of caterpillar feeding preference, frequency of parasitism, and host-plant availability suggested that this variation in food availability combined with the increased risk of parasitism incurred by individuals experiencing prolonged development (e.g. by searching excessively for a rare, preferred host-plant species) should favor polyphagy, and reinforce opportunistic food-mixing. However, because individual caterpillars showed a tendency to leave nutritionally superior host species for nutritionally inferior ones, I tested the idea that individuals ate some host-plant species for defense against parasitoids. Two experiments showed that diet modified the survival of parasitized caterpillars, and that at least one pair of host-plant species revealed a trade-off between their nutritive and defensive value to caterpillars. Taken together, the experiments in this study underscore the importance of the tri-trophic approach toward understanding the pattern and process of foraging in generalist as well as specialist herbivores.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Biology, Ecology.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Insect Science
Degree Grantor:
University of Arizona
Advisor:
Bernays, Elizabeth A.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleEcological maintenance of food-mixing in the woolly bear caterpillar Grammia geneura (Strecker) (Lepidoptera: Arctiidae)en_US
dc.creatorSinger, Michael Stuarten_US
dc.contributor.authorSinger, Michael Stuarten_US
dc.date.issued2000en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractTwo major conceptual approaches for understanding the evolutionary ecology of insect-plant interactions, the plant-insect paradigm and the tri-trophic paradigm, have focused primarily upon dietary specialists and their host-plants. Here, I attempted to evaluate the utility of both paradigms for explaining the maintenance of food-mixing by the individually polyphagous caterpillars of Grammia geneura (Strecker) (Lepidoptera: Arctiidae). First, I conducted three experiments testing the hypothesis that individual G. geneura caterpillars perform better on mixed-plant diets than on single-plant diets due to improved physiological efficiency of food utilization. However, caterpillar performance was not always superior on mixed-plant diets. In the one case in which food-mixing improved performance, the host-plant species included in the mixture were individually of low suitability. Behavioral observations of individual caterpillars both in the above experiments, in nature, and in two further laboratory experiments with chemically-manipulated, synthetic diets supported the idea that such dietary benefits resulted from dilution of plant secondary metabolites, achieved behaviorally via the physiological mechanisms of neophilia and post-ingestive feedbacks on feeding. I also investigated the possibility that food-mixing was maintained by the unpredictable availability of high-quality host-plant species. A field survey of caterpillar feeding preference, frequency of parasitism, and host-plant availability suggested that this variation in food availability combined with the increased risk of parasitism incurred by individuals experiencing prolonged development (e.g. by searching excessively for a rare, preferred host-plant species) should favor polyphagy, and reinforce opportunistic food-mixing. However, because individual caterpillars showed a tendency to leave nutritionally superior host species for nutritionally inferior ones, I tested the idea that individuals ate some host-plant species for defense against parasitoids. Two experiments showed that diet modified the survival of parasitized caterpillars, and that at least one pair of host-plant species revealed a trade-off between their nutritive and defensive value to caterpillars. Taken together, the experiments in this study underscore the importance of the tri-trophic approach toward understanding the pattern and process of foraging in generalist as well as specialist herbivores.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectBiology, Ecology.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineInsect Scienceen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorBernays, Elizabeth A.en_US
dc.identifier.proquest9965907en_US
dc.identifier.bibrecord.b40482200en_US
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