Collaborative Proposal: MRA: Macroecology of microorganisms: Scaling fungal biodiversity from soil cores to the North American continent

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Soil fungi are mostly invisible to the naked eye, but they provide a wide range of ecosystem functions: as decomposers, they break down complex organic materials, and as plant symbiotic partners, they help plants scavenge for scarce nutrients that improve growth. Because both these roles involve a transfer of critical elements, such as carbon, nitrogen, and phosphorus, these fungi play an essential part in global nutrient budgets. Soil fungi can also regulate ecosystems by acting as pathogens of plants and animals. In some cases, pathogenic fungi can have detrimental impacts such as crop disease outbreaks, but more commonly, they promote biodiversity on a global scale by preventing any single species from dominating the ecosystem. Despite their role in regulating these critical ecosystem functions, little is known about what determines the structure of fungal communities across the North American continent, and what consequences future changes in fungal community structure may have. One of the main barriers to this research goal is the lack of a large-scale, systematic effort to sample and identify soil fungi. This research project will overcome this barrier by quantifying patterns of soil fungal diversity using two new, next-generation DNA sequencing datasets that characterize soil fungal communities across the North American continent: the National Ecological Observatory Network (NEON) and the Dimensions of Biodiversity project on North American soil fungi (DoB-FUN). By leveraging state-of-the-art modeling techniques to consider not only how soil fungi change with the environment, but how those changes may depend on their neighboring plant communities, this project will transform our understanding of soil microbial diversity.By integrating two of the most extensive datasets on soil fungal communities with nearly identical sampling design, molecular methods, and spatial range, the investigators will have an unprecedented opportunity to answer two key questions about the fundamental factors that structure microbial geographic ranges and biodiversity. (1) What are the key environmental variables, and (2) how are they influenced by the interactions and associations between fungi and plants? The researchers will leverage this information with a novel three-pronged approach to modeling biodiversity at the community-level: top-down, bottom-up, and integrated methods. This approach overcomes a significant limitation in previous studies, which fail to account for the importance of species interactions in controlling microbial distributions. The novel data and models will help solve critical challenges in scaling predictions from microorganisms to macrosystems. In the context of rapid environmental change, this project can make some of the first robust predictions of change and uncertainty in microbial diversity at the continental scale. While preliminary results have already highlighted the possibility for substantial future changes in fungal community composition and geographic distribution, the synthesis of top-down, bottom-up, and integrated modeling approaches will lead to significant advances in our understanding of fungal biogeography and the ability to forecast the response of fungi to future environmental stressors.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.