DIMENSIONS: COLLABORATIVE RESEARCH: Biodiversity Gradients in Obligate Symbiotic Organisms: A Case Study in Lichens in a Global Diversity Hotspot

专性共生是两个或多个物种之间的关系，它们完全依赖于彼此的生长和生存。这种共生关系是地球上一些最常见和生态上最重要的关系的特征，从人类肠道细菌和疾病到珊瑚和专门的植物-传粉者关系。然而，这些专性共生体中的许多都受到前所未有的环境变化和生物多样性永久丧失的威胁。与鸟类、开花植物或哺乳动物等生命之树上的单一分支相比，人们对促进或限制自然界中大量存在的专性共生体分布的因素知之甚少。此外，对生物多样性分布的研究主要集中在非生物因素上（例如，温度、降水、海拔）而不是生物因素（即，与其他生物的相互作用），影响地理分布。本计画将以专性共生地衣为模式系统，探讨影响其多样性与分布的因素。 地理重点是美国东南部的阿巴拉契亚山脉南部-全球地衣多样性热点和独特的自然实验室。此外，该项目还将通过学生培训、合作以及与资源管理人员和公众的联系来发展美国地衣学的人力资本和基础设施。 它将建立一个公开的，高质量的数据集，并改善物理和数字资源，促进地衣保护的全球生物多样性热点。尽管几代人的研究，并提出理论的因素，产生和维持生物多样性，缺乏共识。长期以来，生物因素一直被认为是驱动因素，但由于难以评估众多可能的相互作用，很少对其进行研究。由于专性共生体之间固有的生物相互作用，地衣提供了一个独特的机会，探索生物多样性的生物和非生物驱动因素在多个维度。该项目将利用全球生物多样性热点地区地衣的实地和基因组库存。该研究将生成和综合来自单一信息源的多个共生生物多样性维度的数据：一个独特的博物馆凭证。在当地，区域和景观尺度，该项目将记录特定地点的系统发育（包括分类）和功能多样性的指标，以及特定地点的指标，主要是未开发的遗传层面，多样性的潜力，量化兼容共生繁殖体在环境中的可用性。根据生物和非生物变量对这些指标进行分析，可以评估影响生物多样性的因素。这些分析还将有助于理解维度之间的相互作用，例如，是否所有维度都是正相关的，并由相同的变量集预测，或者在什么情况下存在其他类型的相关性。该项目旨在产生生态学和进化生物学的两个主要概念进展。首先，它将揭示共生生物中生物多样性梯度的新的、涌现的特性。第二，解构对共生个体的约束，量化它们之间的反馈，将使全面分析包括生物约束在内的影响共生有机体多样性和分布的因素成为可能。

Obligate symbioses are relationships between two or more species that depend entirely on each other for growth and survival. Such symbioses characterize some of the most common and ecologically important relationships on Earth, ranging from human gut bacteria and diseases to corals and specialized plant-pollinator relationships. Yet, many of these obligate symbioses are imperiled by unprecedented rates of environmental change and permanent biodiversity losses. Compared to single branches on the tree of life such as birds, flowering plants, or mammals, much less is known about the factors that facilitate or limit the distributions of the obligate symbioses that abound in nature. Moreover, research on biodiversity distributions has focused largely on abiotic factors (e.g., temperature, precipitation, elevation) rather than on biotic factors (i.e., interactions with other organisms) that influence geographical distributions. This project will uncover the factors that impact diversity and distributions of obligate symbiotic lichens as a model system. The geographic focus is the southern Appalachian Mountains of the southeastern U.S. -- a global lichen diversity hotspot and unique natural laboratory. In addition, this project will develop human capital and infrastructure in U.S. lichenology through student training, collaborations, and outreach to resource managers and the public. It will establish a publicly available, high quality dataset and improve physical and digital resources that advance lichen conservation for a global biodiversity hotspot.Despite generations of research on, and proposed theories for factors that generate and maintain biodiversity, consensus is lacking. Biotic factors have long been proposed as drivers, but they are rarely studied due to the difficulty of assessing the multitude of possible interactions. Because of the inherent biotic interaction between obligate symbionts, lichens offer a unique opportunity to explore both biotic and abiotic drivers of biodiversity across multiple dimensions. This project will utilize both field and genomic inventories of lichens in a global biodiversity hotspot. The research will generate and synthesize data from multiple symbiotic biodiversity dimensions initiated from a single information source: a unique museum voucher. Across local, regional, and landscape scales, the project will record site-specific metrics for phylogenetic (including taxonomic) and functional diversity together with site-specific metrics for a mostly unexplored genetic dimension, potential of diversity, that quantifies the availability of compatible symbiont propagules in the environment. Analysis of these metrics in light of biotic and abiotic variables enables assessment of factors that impact the dimensions of biodiversity. These analyses will also permit understanding of interactions among dimensions, for example, whether all are positively correlated and predicted by the same sets of variables, or in what contexts other types of correlations exist. This project is designed to yield two major conceptual advances in ecology and evolutionary biology. First, it will reveal new, emergent properties of biodiversity gradients in symbiotic organisms. Second, deconstructing constraints on individual partners of the symbiosis and quantifying feedbacks between and among them will make possible a full analysis, including biotic constraints, of the factors that impact diversity and distribution of the symbiotic organism as a whole.