LTREB: Collaborative Research: Host-microbe symbiosis through the lens of stochastic demography

几乎所有的植物和动物都含有微生物，如生活在它们身上或体内的细菌。了解这些微生物对其宿主物种的影响可能会提高我们解决农业，野生动物疾病和人类健康问题的能力。在完全实现这些应用之前，生物学家首先需要更好地了解微生物何时以及如何影响宿主的适应性。该项目将测试一个假设，即微生物对宿主的影响每年都在波动，在压力大的年份（宿主需要帮助时）是有益的，但在有利的年份是中性的或昂贵的。因此，与没有微生物的宿主相比，具有微生物的宿主可能经历适应性的逐年波动减少，这可能是窝藏微生物的重要益处。这一假设将通过扩展对含有真菌微生物的草物种的长期田间实验的数据收集，收集该实验中草遗传学的新数据，以及应用统计建模方法来进行测试。生活在植物内部的真菌微生物在草中广泛存在，包括对牲畜很重要的牧草，这项研究可能具有重要的农业应用。此外，该项目还将为高中生、本科生和研究生提供研究培训。共生宿主中人口统计学差异减少的假设导致了两个新的预测，该项目旨在测试。首先，通过缓冲主机对恶劣的条件，共生体可以限制遗传漂变，促进宿主种群的遗传多样性。第二，主机与共生体和无共生体可能会表现出不同的模式的时间波动，在他们的人口率，从而促进存储效果，一种机制，可以稳定竞争共存的共生和共生体免费主机，并可能解释混合物的主机类型，广泛观察到的植物和动物共生的多样性。科学小组将使用德克萨斯州和印第安纳州的长期实地实验来测试这些预测，在这些实验中，建立了有或没有真菌内生菌的草种群。基于九年的人口统计数据，并利用分层贝叶斯分析框架，该团队将量化和比较共生对宿主适应性的影响，通过减少方差与对平均性能的影响，并测试存储效应对有和没有共生体的主机共存的贡献。该奖项反映了NSF的法定使命，并通过使用基金会的学术价值和更广泛的影响审查标准。

Nearly all plants and animals harbor microbes such as bacteria that live on or in them. Understanding the influence of these microscopic organisms on their host species may advance our ability to solve problems in agriculture, wildlife disease, and human health. Before these applications can be fully realized, biologists first require a better understanding of when and how microbes influence the fitness of their host. This project will test the hypothesis that the effects of microbes on their hosts fluctuate from year to year, being beneficial in stressful years (when hosts need assistance) but neutral or costly in favorable years. As a consequence, hosts with microbes may experience reduced year-to-year fluctuation in fitness compared to hosts without microbes, which may be an important benefit of harboring microbes. This hypothesis will be tested by extending data collection of a long-term field experiment with grass species that harbor fungal microbes, collecting new data on the genetics of the grasses in that experiment, an applying a statistical modeling approach. Fungal microbes that live inside plants are a widespread in grasses, including forage grasses that are important to livestock, and this research could have important agricultural applications. Additionally, this project will provide research training for students at the high school, undergraduate, and graduate levels.The hypothesis of reduced demographic variance in symbiotic hosts leads to two novel predictions that this project is designed to test. First, by buffering hosts against harsh conditions, symbionts may limit genetic drift and promote higher genetic diversity in host populations. Second, hosts with and without symbionts may exhibit different patterns of temporal fluctuation in their demographic rates, thus promoting the storage effect, a mechanism that can stabilize competitive coexistence of symbiotic and symbiont-free hosts, and potentially explain the mixtures of host types that are widely observed in a diversity of plant and animal symbioses. The scientific team will test these predictions using a long-term field experiment with sites in Texas and Indiana, in which grass populations were established with or without fungal endophytes. Building on nine years of demographic data and leveraging a hierarchical Bayesian analytical framework, the team will quantify and compare the effects of symbiosis on host fitness via reductions in variance versus effects on mean performance, and test the contributions of the storage effect to the coexistence of hosts with and without symbionts.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.