Response thresholds alone cannot explain empirical patterns of division of labor in social insects |
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| Authors: | Yuko Ulrich Mari Kawakatsu Christopher K. Tokita Jonathan Saragosti Vikram Chandra Corina E. Tarnita Daniel J. C. Kronauer |
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| Affiliation: | 1. Laboratory of Social Evolution and Behavior, The Rockefeller University, New York, New York, United States of America;2. Institute of Integrative Biology, ETH Zurich, Zurich, Switzerland;3. Program in Applied and Computational Mathematics, Princeton University, Princeton, New Jersey, United States of America;4. Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America;Queen Mary University of London, UNITED KINGDOM |
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| Abstract: | The effects of heterogeneity in group composition remain a major hurdle to our understanding of collective behavior across disciplines. In social insects, division of labor (DOL) is an emergent, colony-level trait thought to depend on colony composition. Theoretically, behavioral response threshold models have most commonly been employed to investigate the impact of heterogeneity on DOL. However, empirical studies that systematically test their predictions are lacking because they require control over colony composition and the ability to monitor individual behavior in groups, both of which are challenging. Here, we employ automated behavioral tracking in 120 colonies of the clonal raider ant with unparalleled control over genetic, morphological, and demographic composition. We find that each of these sources of variation in colony composition generates a distinct pattern of behavioral organization, ranging from the amplification to the dampening of inherent behavioral differences in heterogeneous colonies. Furthermore, larvae modulate interactions between adults, exacerbating the apparent complexity. Models based on threshold variation alone only partially recapitulate these empirical patterns. However, by incorporating the potential for variability in task efficiency among adults and task demand among larvae, we account for all the observed phenomena. Our findings highlight the significance of previously overlooked parameters pertaining to both larvae and workers, allow the formulation of theoretical predictions for increasing colony complexity, and suggest new avenues of empirical study.This study uses automated tracking of clonal raider ants and mathematical modeling to reveal how previously overlooked traits of larvae and workers might shape social organization in heterogeneous ant colonies. By incorporating the potential for variability in task efficiency among adults and task demand among larvae, the authors were able to account for all empirically observed phenomena. |
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