Dissertation Research: Plant-Mediated Effects of Global Climate Change on Insect Herbivory

摘要自工业革命以来，大气中二氧化碳（CO2）的浓度从280 ppm稳步上升到367 ppm。 碳循环模型预测，到2100年，浓度将达到540至970 ppm。 由于农业径流和工业污染，自然生态系统中的氮供应也在继续增加。 本研究的重点是如何这两个环境变量改变昆虫植食性草本植物。 PI将在开顶室实验中研究CO2浓度升高和土壤氮含量增加如何影响昆虫对五种黄菊属物种的食草性。 黄菊属提供了一个非常合适的系统来研究环境变化对植物及其食草昆虫的影响，因为该属的物种具有一系列光合作用的生理途径。 预测黄菊属植物对CO2和氮素有效性表现出一系列的生理反应，这可以根据它们的光合途径清楚地解释。 这项研究将确定植物的叶片特性增加的CO2和氮的反应和昆虫取食的影响程度之间的关系在这些叶片特性的差异。 在二氧化碳水平升高的情况下生长的植物的叶子在其含水量、防御昆虫植食性的化学物质的浓度和氮含量方面发生变化。 因此，植物化学的差异可能会改变昆虫物种的取食偏好，导致自然植物生境和群落的多样性和组成发生变化。

ABSTRACTAtmospheric concentrations of carbon dioxide (CO2) have steadily increased from 280 ppm to 367 ppm since the industrial revolution. Carbon cycle models predict that concentrations will reach between 540 and 970 ppm by 2100. Nitrogen availability in natural ecosystems is also continuing to increase, due to agricultural run-off and industrial pollution. This research focuses on how these two environmental variables alter insect herbivory on herbaceous plants. The PIs will investigate how elevated CO2 and increased soil nitrogen affect insect herbivory on five Flaveria species in an open top chamber experiment. The genus Flaveria provides a highly suitable system with which to investigate effects of environmental change on plants and their insect herbivores because the species in this genus possess a range of physiological pathways for photosynthesis. Flaveria species are predicted to show a range of physiological responses to CO2 and nitrogen availability, which can be clearly explained based on their photosynthetic pathways. This research will determine the relationship between the responses of a plant's leaf characteristics to increased CO2 and nitrogen and the degree to which insect feeding is influenced by differences in these leaf characteristics. The leaves of plants grown at elevated CO2 levels undergo changes in their water content, in the concentrations of chemicals that defend against insect herbivory, and nitrogen content. Differences in plant chemistry may therefore alter the feeding preferences of insect species, leading to changes in the diversity and composition of natural plant habitats and communities.