Rapid growth in the field of microbial ecology in recent years has been possible primarily due to technical advances in high-throughput molecular methods, biocomputing, and vital connections among collaborative scientists. The number of talks at ESA’s annual meeting focusing on microbiomes has increased over the past few years, highlighting growing interest in this topic. The proposed session will explore our understanding of the factors that mediate phyllosphere (above-ground portions of the plant) microbiome assembly and function in agricultural and natural habitats, and consider the potential for identifying general principles. Talks will focus primarily on the leaf microbiome, which has received considerably less attention than below-ground plant microbiomes. This is so, despite the importance of plant leaves for photosynthesis and other essential plant functions, and the potential impact of the microbiome on these functions. Talks in our session will focus on key factors predicted to shape structure and function in agricultural and natural habitats, including vital interactions among microbes within a community. Group discussion will consider the potential for defining general principles in microbiome assembly and function across agricultural and natural systems. The session will also highlight the potential for collaborative and synthetic research across the interface between natural and agricultural systems, particularly through cross-systems analyses tapping into existing research platforms (LTAR, LTER, NEON), and for leveraging of national and international initiatives (RCNs, International working groups) to achieve cross-system syntheses. Participants will be encouraged to contribute to post-meeting preparation of a synthesis white paper highlighting rules of assembly and function for wild and agricultural microbiomes, as well as to engage in ongoing research and training activities through the National Science Foundation, Agricultural Microbiomes RCN. This session responds directly to the conference theme “Vital connections in ecology” by focusing on how key insights into microbiome ecology, including the importance of microbial interactions for determining microbiome composition and function, have been derived from collaborative research efforts.