The overarching goal of our research is to understand how symbiotic associations evolve and influence host (e.g., plant) and guest (e.g., fungal) communities. We study mainly plant-microbial interactions, including highly co-evolved legume-rhizobia mutualisms and the poorly understood fungal endophytes living inside plant leaves. We are particularly interested in evolutionary patterns and mechanisms (e.g., evolution of host-specificity, natural selection for symbiotic traits, neutral vs. niche-selection mechanisms).