Dissertation Research: Influence of Resource Limitation on Plant Responses to Herbivory: Responses of Silphium integrifolium to Gall Insect Attack

昆虫食草动物对植物的性能、生活史和人口统计学有很大的影响，并经常对植物种群施加强烈的自然选择。此外，植物经常同时受到生物(即食草、寄生)和非生物(即资源限制、热量)的胁迫。本项目将使用高草草原多年生整体叶绿僵菌(菊科)及其主要食草性动物之一--五倍子黄蜂(膜翅目：食草蜂科)作为模式系统，研究草食、营养胁迫和水分胁迫如何相互作用影响植物的生活史和生理反应。实验将解决两个具体问题。2.营养限制和水分胁迫如何影响植物对根瘤虫害的生理和生长反应？为了回答第一个问题，将在两年的时间里测量植物生理学(即光合作用、水势)、生长、生物量分配和繁殖，这些植物生长在自然田间种群中，经过实验检验没有虫害。第二个问题将在一个常见的园艺实验中解决，在该实验中，将采用析因设计来控制虫害频率和养分/水分的有效性，并将再次测量生理、生长和生殖输出。

Insect herbivores can have large effects on the performance, life histories, and demography of plants, and often exert strong natural selection on plant populations. In addition, plants are often exposed simultaneously to stresses from biotic (i.e. herbivory, parasitism) and abiotic (i.e. resource limitation, heat) sources. This project will use the tallgrass prairie perennial Silphium integrifolium (Asteraceae) and one of its major herbivores, the gall wasp Antistrophus silphii (Hymenoptera:Cynipidae), as a model system to examine how herbivory, nutrient stresses, and water stress interact to affect life history and physiological responses of plants. Experiments will address two specific questions. 1. How does gall infestation affect life-history traits and fitness components of Silphium intergrifolium? 2. How do nutrient limitation and water stress influence the physiological and growth responses of plants to gall insect attack? To answer the first question, plant physiology (i.e. photosynthesis, water potential), growth, biomass allocation, and reproduction will be measured over a two-year period in experimentally galled and gall-free plants growing in natural field populations. The second question will be addressed in a common garden experiment in which gall frequencies and nutrient/water availabilities will be manipulated in a factorial design, and physiology, growth, and reproductive output will again be measured.