The impacts of variation across the community- and population- scales on interactions in the rhizosphere are understudied and are responsible for changes in plant and bacterial fitness and ecosystem dynamics. Streptomyces has interactions that alter microbial community composition and influence plant health traits that are mediated by natural products encoded by a highly variable accessory genome. However, the population structure and dynamics of this variability are poorly defined. Long-term nitrogen addition drives changes in community composition and rhizosphere interactions, including rhizobial symbiosis. Long-term nitrogen addition sites provide a context in which to observe microbial evolution in the rhizosphere across scales, and in response to nitrogen addition at levels comparable to agricultural fertilization. GEMS trainee Isabelle Lakis will investigate the population structure and dynamics of environmental Streptomyces isolates across scales in long-term nitrogen addition and control plots. She hypothesizes that nitrogen addition will have eco-evolutionary impacts that diverge the accessory genomes and alter both population structure and interaction traits of Streptomyces associated with the legume rhizosphere.