Collaborative Research: Division of Labor in Communal Groups

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Collaborative Proposals 0446415 and 0446342Title: Division of labor in communal groupsJennifer Fewell, Susan Bertram, Penny KukukProject Summary: Social groups from insects to humans divide their labor among individuals so that different group members specialize on different tasks. This division of labor has long been considered one of the key adaptations of sociality. Recent work suggests that its underlying mechanisms involve simple rules of individual behavior, which when combined with interactions among individuals generate complex group level properties (self-organization). Self-organization is thought to occur across all biological levels, but this has proven difficult to test experimentally. Social groups provide an important opportunity to test this assertion, because individuals can be observed and interactions between group members quantified. This research will examine how local interactions among the members of simple social groups could produce division of labor during early social evolution. The central hypothesis is that division of labor can self-organize if interactions among group members amplify differences in their probability of performing tasks. If so, division of labor could emerge even in the absence of selection, and thus could appear spontaneously at the origins of sociality. The alternate hypothesis will be tested, that division of labor is produced primarily via selection for increased differences in task performance after the formation of social groups.The research will use two different modeling approaches to explore how interactions among group members could potentially generate division of labor. The first assumes that individuals within any group vary naturally in their tendency to perform tasks, and that amplification of these differences generates division of labor. The second borrows from economics by treating group members as "companies" that compete for tasks; tasks become distributed among group members based not on initial variation, but on differences in individual success at performing them. To test these models and to examine how division of labor changes during early social evolution, the researchers will compare the behavior of groups made up of normally social individuals to those of solitary individuals that are forced to form social groups. Two taxa have been identified in which solitary and social populations can be compared. These are the ground nesting bee genus Lasioglossum, which contains both solitary and communal species, and the seed harvester ant species, Pogonomyrmex californicus, which has two populations of the same species that initiate nests alone versus in communal groups. Both of these taxa can be brought into the laboratory, allowing artificial social groups to be constructed and observed. This provides a unique opportunity to test how social structure and division of labor change during the transition from solitary to social living. Broader Impact: This work makes an important contribution to our understanding of the mechanisms underlying division of labor, an essential component of social organization within human cultural as well as biological systems. It also addresses the broad question of how properties emerge across levels of biocomplexity. The research actively engages undergraduate and graduate students in the process of science, from data collection to analysis, presentation, and publication. Students will have the opportunity to participate in both the theoretical and experimental components of the research. The PIs have exceptional records of undergraduate mentoring, including directing undergraduate research programs at their respective institutions.