Collaborative Research: Metabolic Bet-Hedging as a mechanism for the maintenance of functional diversity in tree-ectomycorrhizal mutualisms

这个项目将测试树木和土壤真菌之间的相互作用如何帮助树木适应不断变化的环境。在温带森林中，树木依靠与地下真菌的伙伴关系或共生关系来帮助它们获得生长所需的营养。这些共生体的多样性令人难以置信。例如，道格拉斯冷杉是一种具有商业价值的树木，它的根系上可以同时有几十种不同的真菌。这个项目测试了道格拉斯冷杉树保持真菌多样性作为适应环境变化的一种方式。换句话说，就像人类投资者可能会持有股票投资组合一样，冷杉树可能会持有真菌投资组合，以“对冲”其环境中不可预测的变化。同时拥有许多真菌伴侣可能会保证至少其中一些真菌能够在环境不利的情况下为树木提供营养。为了验证这一假设，该项目使用了温室实验、数学模型和真菌多样性的实地调查。除了提高对物种之间有益的相互作用如何影响自然生物多样性的认识外，该项目还将提供有关道格拉斯冷杉的宝贵数据，道格拉斯冷杉是美国西部一种重要的商业和生态树木。研究结果将帮助科学家预测道格拉斯冷杉及其真菌伙伴将如何应对未来更温暖、更干燥的气候条件。该项目还为下一代美国科学家提供培训，包括为当地高中生提供实地考察经验。道格拉斯-冷杉外生菌根共生符合下注对冲假说的假设：(1)长寿伴侣必须容忍变化的环境；(2)互惠伴侣之间的性状差异；(3)伴侣质量差异的证据。该项目通过结合温室实验（测量树木对不同质量真菌伙伴的投资）、基于环境变化预测组合多样性的数学模型以及在不同环境条件梯度下量化真菌多样性的实地调查，推进了互惠共生的生态进化理论。总的来说，这些方法将使研究人员能够(1)在暂时波动的环境中量化最佳的树木投资策略，(2)测试沿海道格拉斯冷杉分布的下注对冲证据，以及(3)将真菌多样性与宿主树木的表现联系起来。该项目支持三名终身教职前的教师，为博士后、技术人员和学生研究人员提供培训机会，并为大学转校生和青少年志愿者提供基于课程的研究经验和科学培训。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will test how interactions between trees and soil fungi help trees to adapt to changing environments. In temperate forests, trees rely on partnerships, or symbioses, with belowground fungi that help them to obtain the nutrients they need for growth. These symbioses can be incredibly diverse. For example, Douglas-fir is a commercially valuable tree that can have dozens of different fungal species on its root system at the same time. This project tests the idea that Douglas-fir trees maintain this fungal diversity as a way of adapting to variation in the environment. In other words, much like human investors might maintain a portfolio of stocks, fir trees might maintain a portfolio of fungi to “bet-hedge” against unpredictable changes in their environment. Having many fungal partners at the same time might guarantee that at least some of them are able to provide nutrients to the trees even when the environment is unfavorable. To test this hypothesis, the project uses experiments in greenhouses, mathematical models, and field surveys of fungal diversity. In addition to improving knowledge of how beneficial interactions between species affect natural biodiversity, this project will also provide valuable data on Douglas-fir, a commercially and ecologically important tree in the western United States. The results will help scientists to predict how Douglas-fir and its fungal partners will respond to warmer, drier future climate conditions. The project also provides training to the next generation of American scientists, including fieldwork experiences for local high school students.The Douglas-fir ectomycorrhizal symbiosis meets the bet-hedging hypothesis’s assumptions of (1) long-lived partners that must tolerate variable environments, (2) trait variation across mutualist partners, and (3) evidence of variation in partner quality. This project advances eco-evolutionary theory for mutualisms by combining greenhouse experiments that measure tree investments in fungal partners of different quality, mathematical models that predict portfolio diversity based on environmental variation, and fieldwork to quantify fungal diversity across a gradient of environmental conditions. Collectively, these approaches will allow researchers to (1) quantify optimal tree investment strategies in temporally fluctuating environments, (2) test for evidence of bet-hedging across the distribution of coastal Douglas-fir, and (3) link fungal diversity to host tree performance. The project supports three pre-tenure faculty members, provides training opportunities for postdocs, technicians, and student researchers, and supports course-based research experiences and scientific training for college transfer students and teenage volunteers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.