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Manipulation of plant defenses by belowground herbivory
Titre du projet
Manipulation of plant defenses by belowground herbivory
Description
Plants attacked by herbivorous insects deploy a wide variety of defense mechanisms, including physical and chemical barriers that deter or reduce the fitness of the herbivore. Physical or chemical defenses deter herbivores directly, whereas, plant-emitted volatile organic compounds, which can serve as olfactory cues to attract predators and parasites of the herbivore, reduce herbivore attack indirectly. Moreover, plant defense strategies can be constitutive (always present) or induced (activated upon attack). Direct and indirect defenses are variably constitutive or inducible depending on the species, genotype, or plant part (e.g., shoots versus roots). All the defense strategies of a plant, both above- and belowground, act as a suite of traits which are shaped by the evolutionary history of both plants and the plant’s herbivore community. I aim to explore the vast domain of plant-insect interactions by taking comparative and experimental approaches. The comparative approach is appropriate for asking questions about common patterns of macroevolutionary changes, whereas taking an experimental approach and focusing on species-specific interactions is a suitable complement to the previous, in that it allows one to mechanistically investigate functionality or adaptability of a particular trait.
The wide and diverse group of American milkweeds (genus Asclepias) share many characteristics, including the production of latex and cardenolides, both potent defensive chemicals. Moreover, some of these species are associated with specialist herbivores, such as the longhorn beetles of the genus Tetraopes, whose adults feed on leaves and flowers and whose larvae feed on roots. The Asclepias-Tetraopes system offers an ideal opportunity to study macroevolutionary patterns of coevolution between plants and insects as well as the evolution of belowground plant defenses. Agricultural systems such as corn (Zea mays) or oilseed rape (Brassica napus) are also suitable and important species for the study of plant defenses because of their applied relevance and use as model systems with a wealth of background data available. Thus, the present research proposal will exploit both natural and agricultural systems to study plant defenses against belowground herbivores. Specifically, through a comparative and phylogentic study, I will test whether belowground chemical defenses in Asclepias, and habitat (soil type) can explain the patterns of association with the specialist herbivores of the genus Tetraopes. I will test whether risk of attack by herbivores influences production of constitutive vs. induced defenses belowground within closely related species of Asclepias that differ in their degree of association with the specialist root herbivore T. tetraophthalmus. I will further test the relative production (and potential trade-off) of direct vs. indirect defenses belowground by investigating both a natural (Asclepias) and an agricultural (Zea mais) system. Finally, I will study allocation patterns of direct and indirect defenses above- and belowground in oilseed rape plants by allowing simultaneous feeding by shoot and root herbivores. This research program will enable me to test predictions about the effect of belowground herbivory on allocation to direct vs. indirect, and constitutive vs. induced defenses above- and belowground. Coupled with comparative analyses, the experimental data set will facilitate generalizations about plant-insect interaction and coevolution and will prepare me to return to Switzerland for a career in science.
The wide and diverse group of American milkweeds (genus Asclepias) share many characteristics, including the production of latex and cardenolides, both potent defensive chemicals. Moreover, some of these species are associated with specialist herbivores, such as the longhorn beetles of the genus Tetraopes, whose adults feed on leaves and flowers and whose larvae feed on roots. The Asclepias-Tetraopes system offers an ideal opportunity to study macroevolutionary patterns of coevolution between plants and insects as well as the evolution of belowground plant defenses. Agricultural systems such as corn (Zea mays) or oilseed rape (Brassica napus) are also suitable and important species for the study of plant defenses because of their applied relevance and use as model systems with a wealth of background data available. Thus, the present research proposal will exploit both natural and agricultural systems to study plant defenses against belowground herbivores. Specifically, through a comparative and phylogentic study, I will test whether belowground chemical defenses in Asclepias, and habitat (soil type) can explain the patterns of association with the specialist herbivores of the genus Tetraopes. I will test whether risk of attack by herbivores influences production of constitutive vs. induced defenses belowground within closely related species of Asclepias that differ in their degree of association with the specialist root herbivore T. tetraophthalmus. I will further test the relative production (and potential trade-off) of direct vs. indirect defenses belowground by investigating both a natural (Asclepias) and an agricultural (Zea mais) system. Finally, I will study allocation patterns of direct and indirect defenses above- and belowground in oilseed rape plants by allowing simultaneous feeding by shoot and root herbivores. This research program will enable me to test predictions about the effect of belowground herbivory on allocation to direct vs. indirect, and constitutive vs. induced defenses above- and belowground. Coupled with comparative analyses, the experimental data set will facilitate generalizations about plant-insect interaction and coevolution and will prepare me to return to Switzerland for a career in science.
Chercheur principal
Statut
Completed
Date de début
1 Septembre 2008
Date de fin
28 Février 2011
Organisations
Identifiant interne
28777
identifiant