Introduction to Symposium: The Developmental and Proximate Mechanisms Causing Individual Variation in Cooperative Behavior

Nearly all animals interact with members of their own species at some point during their lives. These behavioral interactions range from courtship, mating, and parental care to the complex cooperative behavior among related or unrelated individuals in group-living species. A number of theoretical models have attempted to explain how cooperation can evolve through natural selection. Although tremendously influential in animal behavior research, these traditional models have largely ignored individual variation in cooperative behavior and its underlying developmental and proximate mechanisms. However, a set of emerging models suggest that the evolution of cooperation can be heavily influenced by the degree of individual variation in cooperative behavior, as well as the complexity of the underlying mechanisms. Yet, while theoreticians argue the importance of studying individual variation in cooperation and the mechanisms underlying it, empiricists have not focused upon these aspects. The main objectives of our symposium at the 2017 meeting of the Society for Integrative and Comparative Biology is to establish new research avenues to study variation in cooperative behavior using both proximate and ultimate explanations and to produce a road map to study the developmental and proximate mechanisms in generating individual variation in cooperative behavior. This symposium brought together empiricists and theoreticians investigating cooperative behavior in diverse taxa and across multiple levels of analysis. Here we briefly describe the rationale for this symposium and why we thought it was needed as well as provide a brief overview of the contributions.