Evolution of Social Behavior
Our research group has a long-standing interest in how interactions between conspecifics affect the evolutionary process. This work includes the development of indirect genetic effect (IGE) and social selection theory, as well as empirical explorations of these topics.
Currently, we are exploring the evolution of social network structure and the impact of social network position on fitness in natural populations of the forked fungus beetle (Bolitotherus cornutus). This work is a multi-year field study of natural populations at Mountain Lake Biological Station (MLBS) in collaboration with Vince Formica (Swarthmore). Every year, we are lucky to have a spectacular group of undergraduate research assistants and REU students on the Beetle Crew that make the sampling of field observations of social behavior possible (Figure 1).
Through direct observation and genetic markers, we are able to collect fitness data roughly 500 adult beetles spread between 10-15 populations each season. Each of the beetles in our study area is individually marked with a unique three-letter code. Forked fungus beetles conduct all of their mating and reproductive behaviors on the surfaces of three species of bracket fungi that infect logs and snags in the forest (Figure 2). This structure creates subpopulations with a limited exchange of individuals, so we can estimate the structure of social networks on individual logs (Figure 3).
Future work on this system is aimed at trying to understand the factors, genetic and environmental, that influence the structure of social networks. We know that some measures of social network position are consistently expressed by individual beetles in the laboratory. We do not yet know whether there are direct or indirect genetic effects on variation in social network position or group structure that would be required for these social phenotypes to be evolvable characters.