Dissertation Research: Symbiont-mediated niche expansion and partitioning in a native grass-fungal endophyte symbiosis

生态学家感兴趣的一个关键领域是为什么一个物种出现在一个特定的环境范围，通常被称为物种生态位。研究人员通常会研究生物体的非生物限制（例如热耐受性）以及负面的物种相互作用（例如竞争和捕食）如何影响生物体成功生存的地方。虽然这项工作被证明是无价的，但同样重要和广泛的积极物种相互作用对物种生态位的影响实际上被忽视了。pi的研究调查了这样一个问题：参与互惠共生（一种所有合作伙伴都受益的积极互动）如何影响生物体的生态位？他们在内生真菌（生活在植物内部的真菌）和一种本土草——支努克雀麦（Bromus laevipes）之间的关系中研究了这个问题。基于大约100个草种群的内生菌发生数据和气候数据的模型强烈表明，内生菌扩大了草的生态位（即草可以在没有共生伙伴的栖息地中生存）。在国家科学基金会的资助下，pi将通过在加州各地种植实验花园来测试这一结果。在每个花园内，他们将种植来自12个种群的奇努克雀花，有或没有内生菌，并测量植物性能（如茎/叶/种子产量），物候（如开花/休眠时间）和食草动物的损害。这项研究不仅将通过将积极的相互作用纳入生态位理论来阐明生态学中的概念问题（如物种分布和多样性、群落聚集和物种形成），而且还将为应用领域（如农业和保护活动）提供信息。虽然真菌内生菌存在于所有被研究的植物物种中，但在大多数情况下，我们对它们的生态学或进化知之甚少。鉴于在不同的环境中，内生菌对植物的成功有很大的影响，从本研究中获得的有关内生菌的信息可以帮助制定保护、恢复、农业或发展决策。

A key area of interest to ecologists is why a species occur in a particular range of environments, often called the species niche. Researcher have typically investigated how abiotic limitation of an organism (e.g. thermal tolerance) as well as negative species interactions (e.g. competition and predation) impact where organisms can successfully persist. While this work has proved invaluable, the effect of equally important and widespread positive species interactions on species niches has been virtually ignored. The PIs' research investigates the question: How participation in mutualism (a positive interaction in which all partners benefit) affects the niche of an organism? They examine this question in the association between endophytic fungi (fungi that lives inside plants) and a native grass, Chinook brome (Bromus laevipes). Models based on their endophyte occurrence data from ~100 populations of the grass and climate data strongly suggest that endophytes expand the niche of the grass (i.e. the grass can persist in habitats that would be untenable in the absence of the mutualistic partner). With NSF funding, the PIs will test this result by planting experimental gardens throughout California. Within each garden, they will plant Chinook brome with and without endophyte from 12 populations and measure plant performance (e.g. stem/leaf/seed production), phenology (e.g. flowering/dormancy timing), and herbivore damage. This research will not only elucidate conceptual questions in ecology (e.g. species distributions and diversity, community assembly, and speciation) by incorporating positive interactions into niche theory, but it will also inform applied fields (e.g. agricultural and conservation activities). Although fungal endophytes live inside all plant species examined, we know little about their ecology or evolution in most cases. Given the large impact of endophytes on plant success in different environments, the information about endophytes garnered from this research can help make conservation, restoration, agriculture, or development decisions.