DISSERTATION RESEARCH: The functional consequences of antagonism in fungal communities

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Understanding how the Earth's climate will change over the next century is of enormous scientific, social, and economic importance. In order to make these projections of future climate, scientists will need to understand how the world's smallest organisms, fungi and bacteria, respond to changing environmental conditions. These microbes play a critical role in the Earth's carbon cycle. They decompose dead plant material, releasing carbon dioxide back into the atmosphere. Current climate models assume that the rate of this release is determined by environmental conditions, such as temperature, moisture, or soil pH. Changes in these conditions are expected to "turn the dial" on microbial activity. If it gets warmer, microbes will release more carbon dioxide; if it gets colder, microbes will release less carbon dioxide. Yet this assumption ignores a key aspect of most microbes: they are highly skilled warriors. Fungi and bacteria release an astonishing number of chemicals and compounds intended to kill their fellow microbes and colonize their territory. This warfare, however, comes at a considerable cost. A microbe must choose between using its energy for combat or using its energy for growth. In the proposed work, the researchers will quantify how microbial combat affects decomposition rates across environmental conditions, helping to understand where and when microbially-driven carbon dioxide releases will respond unpredictably to changing environmental conditions. The investigators will also train a high school student and develop outreach activities with a natural history museum. Building on previous diversity-function studies, the researchers will develop a generalizable model to disentangle the relative importance of antagonistic competition versus environmental conditions as drivers of microbial-mediated decomposition rates. Using baseline trait data collected on 44 wood-decay fungi, 100 unique communities will be selected with varying levels of combative ability, average stress-tolerance ability, and species richness (from 3 to 12 unique species). The communities will be assembled in realistic microcosms and incubated under both optimal conditions (warm and wet) and stressful conditions (cold and dry). Total wood decomposition will be measured after 12 weeks. This study will allow the researchers to address three main questions: (1) Does community-level decomposition differ from what is predicted using the microbes' individual decomposition rates? (2) Do these differences depend on whether the individuals are combative fungi or stress-tolerant fungi? and (3) Does the relative importance of antagonistic interactions differ between stressful and optimal environmental conditions? The answers to these questions will ultimately help restructure existing climate models and better project how global carbon dioxide fluxes will change over time.