Competition and cooperation: bumblebee spatial organization and division of labor may affect worker reproduction late in life
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Within-group conflict may influence the degree to which individuals within a group cooperate. For example, the most dominant individuals within a group often gain access to the best resources and may be less inclined to perform risky tasks. We monitored space use and division of labor among all workers in three colonies of bumblebees, Bombus impatiens, during the ergonomic and queenless phases of their colony cycle. We then measured the two largest oocytes in each worker to estimate each individual's reproductive potential at the end of the colony cycle. We show that workers that remained farther from the queen while inside the nest and avoided risky or more energy-expensive tasks during the ergonomic phase developed larger oocytes by the end of the colony cycle. These individuals also tended to be the largest, oldest workers. After the queen died, these workers were more likely than their nestmates to increase brood incubation. Our results suggest that inactive bumblebees may be storing fat reserves to later develop reproductive organs and that the spatial organization of workers inside the nest, particularly the distance workers maintain from the queen, may predict which individuals will later have the greatest reproductive potential in the colony.
KeywordsDivision of labor Ovary Reproductive potential Spatial organization Worker competition
We thank Nicolas Skye Robbins, Eden Huang, Amanda Barth, and Wendy Isner for their help in data collection, bumblebee dissections, and assistance with bumblebee maintenance. Margaret Couvillon, Scott Powell, and Aimee Dunlap provided feedback on the manuscript and statistical analyses. We also thank Laurent Keller and two anonymous reviewers for their detailed comments and suggestions. Research supported through the College of Science, Department of Ecology & Evolutionary Biology, University of Arizona, and NSF grant to AD (grant no. IOS 0841756).
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