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稳步增加到367ppm。碳循环模型预测，到2100年，二氧化碳浓度将达到百万分之540至970。由于农业径流和工业污染，自然生态系统中的氮可用性也在继续增加。本研究的重点是这两个环境变量如何改变昆虫对草本植物的食草性。pi将在开放式顶室实验中研究二氧化碳浓度升高和土壤氮含量增加对五种黄草属植物的昆虫食草性的影响。黄草属植物具有一系列的光合作用生理途径，为研究环境变化对植物及其昆虫食草动物的影响提供了一个非常合适的系统。据预测，黄草属植物对CO2和氮的有效性表现出一系列的生理反应，这可以根据它们的光合作用途径来清楚地解释。本研究将确定植物叶片特征对增加的CO2和氮的响应与这些叶片特征差异对昆虫取食的影响程度之间的关系。在二氧化碳浓度升高的环境中生长的植物，其叶片的含水量、抵御食草昆虫的化学物质浓度和氮含量都会发生变化。因此，植物化学的差异可能会改变昆虫的取食偏好，从而导致自然植物栖息地和群落的多样性和组成的变化。

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.