Collaborative Research: Hybrid Plants and Zones as 'Sinks' for Herbivores: A Model System for Integrating Ecology, Genetics and Physiology of a Plant Herbivore Interaction

植物杂交带是常见的，通常代表自然实验，其中植物的遗传防御已经混合，是检查植物和食草动物的生态和进化相互作用以及抗性机制的理想选择。本研究将研究天疱疮（Pemphigus betae）如何选择寄主并对窄叶棉杨（Populus angustifolia）和与白杨的天然杂交品种白杨（P. fremontii）做出反应。将提出两组相互关联的问题。第一个关于这种相互作用的生态学，进化和生物地理学将解决：a.在许多复制的河流排水系统中，杂交植物和区域是食草动物的“水槽”，这样一些易感植物支持了大多数害虫种群？b.如果一棵无性繁殖的树（即一棵树及其无性繁殖的后代）易受蚜虫的感染，它是否也易受其他食草动物（如麋鹿和伐木甲虫）的感染？c.是极度易感的无性系的存在阻止了食草动物成功地攻击具有抗性的无性系，还是易感植物只是充当了它们攻击其他种群的宿主？第二个问题是，为了解决抗性和易感性的机制，a.在成功开发了该系统的分子遗传技术（RFLPs）之后，是否可以标记抗性和/或易感性的基因，并在纯区和杂交种区筛选抗性树？ b.由于单个克隆可以是遗传镶嵌(即，同一棵树的不同部分在基因上是不同的)杂交和纯宿主克隆之间的嵌合模式是什么？它们与紧张的生长条件有什么关系？c.因为单个克隆也可以是抗性的发育嵌合体（即，同一棵树的不同分支或同一克隆的树干的抗性随年龄的变化而变化），那么杂交种和纯寄主的发育抗性是如何变化的？d.由于生理库源关系影响单个无性系的抗性性状，它们在影响单个无性系的发育抗性模式方面是否也很重要？

Plant hybrid zones are common and often represent natural experiments in which the genetically based defenses of plants have been mixed and are ideal for examining the ecological and evolutionary interactions of plants and herbivores as well as the mechanisms of resistance. This study will examine how the gall aphid, Pemphigus betae, selects hosts and responds to narrowleaf cottonwood, Populus angustifolia, and natural hybrids with Fremont cottonwood, P. fremontii. Two interrelated sets of questions will be asked. The first concerning the ecology, evolution and biogeography of this interaction will address: a. over many replicate river drainage systems are hybrid plants and zones "sinks" for herbivores such that a few susceptible plants support most of the pest population?, b. if a clone (i.e. a tree and its asexually derived progeny) is susceptible to aphids, will it also be susceptible to other kinds of herbivores such as elk and woodboring beetles?, and, c. does the presence of extremely susceptible clones prevent herbivores from successfully attacking resistant clones or do susceptible plants simply serve as reservoirs from which they attack the rest of the population? The second question, to address the mechanisms of resistance and susceptibility asks , a. having sucessfully developed molecular genetic techniques (RFLPs) for this system, can the genes for resistance and/or susceptibility be marked and trees screened for resistance in the pure and hybrid zones, b. since individual clones can be genetic mosaics (i.e., different parts of the same tree are genetically different) what are the patterns of mosaicism between hybrid and pure host clones and how are they related to stressful growing conditions?, c. because individual clones can also be developmental mosaics of resistance (i.e., different branches of the same tree or trunks of the same clone vary in resistance as a function of age), how do hybrids and pure hosts vary in their developmental resistance?, and d. because physiological sink-source relationships affect the resistance traits of individual clones, are they also important in affecting patterns of developmental resistance within individual clones.