BEE: Spatio-temporal factors shaping symbiotic networks: a case study with cyanolichens

共生相互作用，包括寄生、共生和互惠，形成了自然界常见的复杂网络。最终，只有通过研究所有共生相互作用的生物体，才能更全面地了解生命。本研究旨在了解使用蓝藻形成这些网络的过程，蓝藻是主要由互利真菌和蓝藻组成的标志性共生。该项目将解决的问题包括：自然界中各种自由生活的蓝藻的丰度是否决定了形成地衣群落的主要地衣伴侣对（一种真菌，一种蓝藻）？是否广泛分布的蓝藻与许多真菌物种（通才）相关联，这样做主要与密切相关的真菌物种？哪些生物分子决定了哪些蓝藻与哪些真菌伙伴相互作用？与其他共生系统相比，地衣伴侣的关联规则有何不同？该项目包括研究生和本科生的培训和教育内容，传播共生系统创新研究的新方法，推广活动，以及开发新的咨询模式，以帮助对科学和工程感兴趣的代表性不足的学生实现他们的学术目标。本研究的主要重点是确定在不同空间尺度上，进化和环境梯度是如何塑造共生网络的。为了达到这一目标，将实施一种将进化生物学和生态学完全结合起来的方法。最近对地衣模式属Peltigera及其Nostoc共生体的研究表明：(1)Peltigera种主要特化于一般的Nostoc系统群；(2)真菌的相互作用和高度特化在系统发育上是保守的；(3)在生物群系内尺度上，生物气候因素对解释Peltigera种地理分布的限制比蓝藻的可用性更大。本研究将利用艾伯塔省生物多样性监测研究所（ABMI）的大规模、系统、多分类的监测项目。该项目提供了一个独特的机会来测试共生网络组装的三个重要驱动因素：(1)空间尺度和梯度——环境生物和非生物特性是否可以很好地预测相互作用，以及/或随机分散导致的空间重叠？(2)系统发育史- Nostoc共生体在选择Peltigera伴侣时是否表现出系统发育保守性，正如Peltigera对其Nostoc伴侣所显示的那样？(3)特异性识别分子——Nostoc基因在地衣菌体和自由生活状态下是否有差异表达，它们是否解释了自然界中共生伙伴之间观察到的特异性？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。

Symbiotic interactions, including parasitism, commensalism and mutualism, form complex networks that are common in nature. Ultimately, a more complete understanding of life can be accomplished only through the study of all symbiotically interacting organisms. This study aims to understand the processes that shape those networks using cyanolichens, which are iconic symbioses consisting mainly of mutually beneficial fungi and cyanobacteria. Questions that will be addressed by this project include: Does the abundance of various free-living cyanobacteria in nature dictate the main lichen partner pairs (one fungus, one cyanobacterium) who shape lichen communities? Do broadly distributed cyanobacteria who associate with many fungal species (generalists) do so mostly with closely related fungal species? What are the biomolecules that determine which cyanobacteria interact with which fungal partners? How do the rules of association for lichen partners differ when compared to other symbiotic systems? This project includes training and educational components for graduate and undergraduate students, the dissemination of new methods for innovative research on symbiotic systems, outreach activities, and the development of a new advising model to help underrepresented students interested in science and engineering reach their academic goals. The main focus of this study is to determine how mutualistic networks are shaped by evolution and environmental gradients at different spatial scales. To reach this goal, a fully integrated approach combining evolutionary biology and ecology will be implemented. Recent studies of the lichen model genus Peltigera and its Nostoc symbionts have revealed: (i) that Peltigera species are mostly specialized on generalist Nostoc phylogroups, (ii) that the interactions and the high level of specialization by the fungus are phylogenetically conserved, and (iii) that bioclimatic factors, at an intra-biome scale, are more limiting than cyanobiont availability for explaining geographic distributions of Peltigera species. This study will capitalize on the large-scale, systematic, and multi-taxon, monitoring program of the Alberta Biodiversity Monitoring Institute (ABMI). This project represents a unique opportunity to test three important drivers of symbiotic network assembly: (1) Spatial scales and gradients - Are interactions well predicted by environmental biotic and abiotic properties, and/or spatial overlap due to stochastic dispersal? (2) Phylogenetic history - Do Nostoc symbionts show phylogenetic conservatism in their selection of Peltigera partners, as shown by Peltigera towards their Nostoc partners? (3) Specific recognition molecules - Are Nostoc genes differentially expressed in lichen thalli vs a free-living state, and do they explain the observed specificity between symbiotic partners in nature?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.