Dr. Marx will discuss two types of interactions: epistasis that emerges between beneficial mutations within a genome over the course of adaptation, and the interactions that occur between organisms as they evolve in a community. The former is characterized by a general trend of gentle diminishing returns for mutations that occur along an adaptive trajectory, which contributes to the deceleration of adaptation. When mutations are combined across independent adaptive trajectories, however, they do not necessarily interact so well. For the latter interactions between species, we have developed synthetic two- and three-species communities that we have evolved in spatially-structured environments. This type of environment has allowed costly cooperation to emerge due to the local feedbacks of metabolic exchange.