LB 19-171 - Land-use changes influence the assembly of endophytic fungal symbiont communities

Land-use change, including the conversion of prairies to agricultural fields, is one of the major factors threatening biodiversity and functioning of ecosystems. Despite the importance of microbial symbionts communities (the “microbiome”) in mitigating effects of changing environment on their host, we lack a clear understanding on the impact of land-use changes on the fundamental processes by which these communities assemble within the host. Here, we compared endophytic fungal communities of the iconic prairie grass, little bluestem (Schizachyrium scoparium) and those of the cultivated crop, corn (Zea mays) to evaluate the impacts of agriculture on microbial symbiont community diversity and assembly. We used Illumina community sequencing of the fungal barcode rDNA to characterize root and foliar communities from adjacent prairie and agricultural fields at five locations across a gradient in mean annual precipitation (MAP) spanning over 450 km. We compared the richness, composition and the phylogenetic structure of these endophytic fungal communities to make inferences regarding the role of differing processes in community assembly. Our results show that root endophytic fungi constitute a diverse community, with an average of 87 taxa per plant and 603 taxa per site. Overall, across each sampled location, we found that little bluestem and corn differed in both the root and leaf endophytic fungal communities, suggesting that biotic interactions with the host play an important role in shaping these communities. We also found that in both plant hosts, the composition of endophytic fungal communities significantly shifts across the MAP gradient, suggesting that the differing precipitation environments may act as factors affecting the distribution of fungal taxa. Interestingly, within site, endophytic fungal communities associated with corn were more homogenous compared to those associated with little bluestem regardless of the tissues evaluated, suggesting that agricultural practices create more homogeneous environments for fungal symbionts. Further, increased nutrient inputs in agriculture fields may intensify competitive interactions among cooccurring fungi as we found lower richness in root fungal communities of corn compared to those of little bluestem. Together, our results to date suggest that agricultural practices affect microbial symbiont assembly processes and imply that anthropogenic changes will likely disrupt the stability of plant microbiomes.