Dissertation Research: Resistance to Herbicide and Susceptibility to Herbivores: Testing the Mechanistic Basis of a Trade-off and its Population-level Consequences

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AbstractFutuyma 0206448The researchers will test the mechanisms by which herbivorous insects affect the cost of resistance to the herbicide triazine in pigweed Amaranthus hybridus (Amaranthaceae). The triazine-resistance mutation imposes a cost by slowing photosynthesis. Mutant plants are preferentially eaten by herbivores, are less tolerant of feeding damage, and suffer an increased fitness cost when exposed to herbivores. This work will address how the availability of light and nutrients affects a mutant plant's allocation to carbon-based defenses and its susceptibility to herbivores. The potential for herbivores to impose frequency-dependent selection will be tested. Additionally, the researchers will test if a mutant plant's increased allocation to carbon acquisition (i.e. leaves) at the expense of nutrient and water acquisition (i.e. roots) causes its reduced tolerance. This research will provide an independent test of how photosynthetic rate shapes patterns of defense and tolerance, and it will contribute to future strategies for managing resistance to herbicide.The researchers will test the mechanisms by which herbivorous insects affect the cost of resistance to the herbicide triazine in pigweed Amaranthus hybridus (Amaranthaceae). The triazine-resistance mutation imposes a cost by slowing photosynthesis. Mutant plants are preferentially eaten by herbivores, are less tolerant of feeding damage, and suffer an increased fitness cost when exposed to herbivores. This work will address how the availability of light and nutrients affects a mutant plant's allocation to carbon-based defenses and its susceptibility to herbivores. The potential for herbivores to impose frequency-dependent selection will be tested. Additionally, the researchers will test if a mutant plant's increased allocation to carbon acquisition (i.e. leaves) at the expense of nutrient and water acquisition (i.e. roots) causes its reduced tolerance. This research will provide an independent test of how photosynthetic rate shapes patterns of defense and tolerance, and it will contribute to future strategies for managing resistance to herbicide.