Many fundamental questions regarding population dynamics and microevolution of microbiome communities remain to be established. Because microbes evolve so quickly, microevolution and ecological pressures both impact host-associated microbial communities. Environmental factors, species interactions, and evolutionary dynamics all play a role in shaping communities. However, the relative contributions of each of these factors in driving microbial community composition remain unclear. Mammalian gut microbiomes are complex with thousands of species and strains, making it challenging to answer fundamental questions about microbiome dynamics. Moreover, in most hosts, it is virtually impossible to rule out confounding variables. Therefore, less complex and more tractable model systems are needed. To this aim, our lab uses the honeybee, an important agricultural and environmental pollinator, as a model system to study the evolution and dynamics of host-associated microbial communities. In particular, we are interested in understanding what factors shape the structure of host-associated microbial communities and how chemical and environmental perturbations impact microbial communities and host health. In addition, a major focus of our research involves investigating how microbial community imbalance and within-host evolution influences pathogen susceptibility, what role resident microbes play in protecting their host, and how and when opportunistic pathogens become virulent. In this seminar I will present our current and ongoing projects and our recent findings.