Resistance and tolerance of aspen to mammalian herbivores: Costs, benefits and selection in ontogenetic context

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。食草哺乳动物和树木之间的相互作用在塑造北美森林生态系统中起着关键作用。这些相互作用的性质可能受植物防御特性的控制，如化学抗性、耐受性和逃逸。尽管这些综合防御综合征在食草昆虫中的作用已被广泛记录，但相对较少的可比工作涉及了食草哺乳动物的影响。昆虫和哺乳动物对各种防御性状的发育限制可能不同。最近对白杨（Populus tremuloides）的研究表明，在抗性方面存在很强的发育变异，并暗示哺乳动物在塑造这种基础树种的防御表达方面发挥了重要作用。本项目将调查白杨对食食哺乳动物的成本、收益、发育限制以及多变量防御系统（抗性、耐受性和逃逸）的生态和进化后果。这项工作将采用一组不同的白杨基因型，在普通花园研究中生长，并进行人工和自然浏览，以确定特定化合物对浏览哺乳动物的防御程度，评估多种环境下的抗性，耐受性和逃避的成本和收益，以及潜在的权衡，并评估浏览对实验群体中防御性状遗传结构的选择性影响。白杨是一种在北美分布广泛且具有重要经济价值的树种。这项工作应该为土地管理者和机构提供新的见解和工具，以便在整个西部山间地区的衰落环境中维持白杨。这项研究也将有助于培养本科生、研究生和博士后。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Interactions between browsing mammals and trees play key roles in shaping North American forest ecosystems. The nature of these interactions is likely governed by plant defense traits, such as chemical resistance, tolerance, and escape. Although the roles of these integrated defense syndromes have been extensively documented for herbivorous insects, relatively little comparable work has addressed impacts of browsing mammals. Developmental constraints on the efficacy of various defense traits likely differ between insects and mammals. Recent work with aspen (Populus tremuloides) has demonstrated strong developmental variation in resistance, and implicated mammals as instrumental in shaping the expression of defense in this foundation tree species. This project will investigate the costs, benefits, developmental constraints, and ecological and evolutionary consequences of multivariate defense systems (resistance, tolerance and escape) in aspen against browsing mammals. This work will employ a set of diverse aspen genotypes, grown in common garden studies and subjected to artificial and natural browsing, to determine the degree to which specific chemical compounds confer defense against browsing mammals, assess the costs and benefits of, and potential tradeoffs among, resistance, tolerance and escape in multiple environments, and evaluate the selective impact of browsing on the genetic structure of defense traits in an experimental population. Aspen is a widely distributed and economically important species in North America. This work should provide new insights and tools relevant to land managers and agencies working to maintain aspen in environments of decline throughout the Intermountain West. This research will also contribute to the training of undergraduate, graduate and postdoctoral students.