The plant microbiome consists of microorganisms both above and belowground, and understanding their interactions within plants represents a vital next step in community ecology. Furthermore, these microbiome interactions may be influenced by components of global change which may be critical in predicting future microbial diversity as well as host plant success. Using a long-term field study (2010-2019) in Great Lakes sand dunes, we analyzed how root endophytes responded to the aboveground systemic endophyte, Epichloe amarillans, associated with a dominant native dune-building grass species, Ammophila breviligulata (American beachgrass). We also compared root endophyte diversity under ambient and fertilized treatments which mimicked enhanced atmospheric nitrogen-deposition, an important aspect of global change. We used fungal culturing procedures as well as molecular techniques to quantify root endophyte diversity across treatments.
Results/Conclusions
We isolated approximately 50 different root endophyte morphotypes using culturing methods. The presence of Epichloe in plants increased root endophyte richness by 41% across all fertilizer treatments, though did not influence overall community composition. The addition of nitrogen also increased root endophyte diversity by 64% and altered community composition within plants. These results suggest that Epichloe may reduce defenses of host plants, subsequently allowing a higher diversity of belowground endophytic colonization within roots. Increased atmospheric nitrogen deposition associated with urbanization and agriculture may also increase belowground microbial diversity within plants. Future work in this system will explore whether changes to root endophyte communities have any fitness consequences for host plants. Our study demonstrates the importance of examining the entire microbiome when addressing plant responses to future global change.