SG: Growth-defense tradeoffs, context dependency and genetic variation in aspen: implications for plant-insect interactions

遗传多样性对森林生态系统的健康很重要，但对影响这种多样性的因素仍然知之甚少。这项研究将解决遗传多样性如何受到树木生长和抵御昆虫攻击的能力以及邻近树木对资源的竞争的影响。 此外，还将根据遗传多样性探讨森林生产力。这项研究将在白杨的实验林中进行，在那里，树木以不同的密度生长了几年，然后遭受食叶毛虫的爆发。这项工作将推进关于如何最好地管理森林以最大限度地提高产量，同时最大限度地减少虫害的科学知识。这项研究的结果将与白杨种群普遍减少的地区特别相关。该项目将培养生物科学的本科生和研究生，并促进指导高中和大学生的群体，目前在科学中代表性不足。这项研究将探讨环境介导的生长-防御权衡在基础植物物种如何影响种内（基因型）变异，反过来，基因型变异如何塑造林分水平的生产力和抗虫性。白杨在生理、生长和化学防御等方面表现出显著的基因型差异，生长与化学防御之间存在较强的负相关。这种权衡如何影响选择以塑造植物种群的遗传结构在很大程度上是未知的。一系列实验白杨林分，每一个都包含16个基因型，并受到低或高的种内竞争强度（CI），将被用来检验关于以下方面的假设：1）低CI与高CI下叶片生理和化学性状的表型表达，2）白杨林分的基因型组成的变化是生长与防御性状竞争介导选择的结果，3）基因型差异对林分抗森林帐篷毛虫落叶能力的影响。假设检验将包括地上生长，光合作用和叶面化学防御措施，以及帐篷毛虫的立场水平落叶评估。这项研究将促进对影响森林生态系统分布、遗传组成和功能的生态和进化因素的理解。

Genetic diversity is important to the health of forest ecosystems, but the factors that influence such diversity remain poorly understood. This research will address how genetic diversity is affected by trees' ability to grow and defend themselves against insect attack, and by competition from neighboring trees for resources. Also, forest productivity will be explored in light of genetic diversity. The research will take place in experimental stands of aspen, where trees have been grown for several years at different densities and then subjected to an outbreak of leaf-eating caterpillars. This work will advance scientific knowledge of how best to manage forests to maximize production, while also minimizing insect damage. Results from this research will be particularly relevant to regions where aspen populations are in widespread decline. The project will train undergraduate and graduate students in biological science and promote mentoring of high school and college students from groups that are currently under-represented in science.This research will explore how environmentally mediated growth-defense tradeoffs in a foundation plant species influence intraspecific (genotypic) variation and, in turn, how genotypic variation shapes stand-level productivity and resistance to insect attack. Aspen exhibits striking genotypic variation in physiology, growth and chemical defense, and strong negative genotypic correlations between growth and defense. How such tradeoffs influence selection to shape the genetic architecture of plant populations is largely unknown. An array of experimental aspen stands, each containing 16 genotypes and subjected to low or high intraspecific competition intensity (CI), will be used to test hypotheses concerning: 1) phenotypic expression of leaf physiological and chemical traits under low vs. high CI, 2) shifts in the genotypic composition of aspen stands as a consequence of competition-mediated selection for growth vs. defense traits, and 3) effects of genotypic divergence on stand resistance to defoliation by forest tent caterpillars. Hypothesis testing will incorporate measures of aboveground growth, photosynthesis and foliar chemical defenses, as well as assessments of stand-level defoliation by tent caterpillars. This research will advance understanding of the ecological and evolutionary factors that influence the distribution, genetic composition, and function of forest ecosystems.