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，但影响这种多样性的因素仍然知之甚少。这项研究将阐述遗传多样性如何受到树木生长和抵御虫害的能力的影响，以及来自邻近树木对资源的竞争。此外，还将根据遗传多样性来探讨森林生产力。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，然后遭受了食叶毛虫的爆发。这项工作将促进关于如何最好地管理森林以最大限度提高产量，同时将虫害降至最低的科学知识。这项研究的结果将特别适用于杨树种群普遍下降的地区。该项目将培训生物科学方面的本科生和研究生，并促进对高中生和大学生的指导，这些学生来自目前在科学中代表性不足的群体。这项研究将探索基础植物物种中环境调节的生长-防御权衡如何影响种内(基因类型)变异，进而基因类型变异如何塑造林分水平的生产力和对虫害的抵抗力。杨树在生理、生长和化学防御方面表现出显著的基因变异，生长和防御之间存在很强的负基因相关。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。本研究利用16种不同类型的种内竞争强度(CI)或低或高种内竞争强度(CI)的杨树实验林，对以下假说进行检验：1)低CI与高CI条件下叶片生理、化学性状的表型表达；2)竞争选择对杨树林分生长与防御性状选择的影响；3)基因差异对林分抗毛虫落叶能力的影响。假设检验将包括地上生长、光合作用和叶片化学防御的测量，以及对帐篷毛虫造成的林分水平落叶的评估。这项研究将促进对影响森林生态系统的分布、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.