Introductory remarks: Positive vs. negative interactions in the function of ecological communities

Ecologists have long been fascinated by death, by the predator consuming the prey, by the competitive stranglehold of one plant smothering another. Indeed, negative interactions like predation, parasitism, and competition have been the foundation of ecological and evolutionary theory since the conception of the Lotka-Volterra equations. Recently, however, ecologists have found that positive interactions including mutualism and facilitation are surprisingly widespread and have strong impacts on the ecology and evolution of species interactions, though to-date there has been little progress made toward understanding the relative effects of positive vs. negative interactions in ecological and evolutionary processes. Here, I briefly describe the history of negative vs. positive interactions in ecological research, then I present an outline of the topics covered by each speaker and how they relate to the goal of the symposium: understanding how positive and negative interactions work individually and in combination to structure entire communities.