Worker self-restraint and policing maintain the queen’s reproductive monopoly in a pseudomyrmecine ant


Division of reproductive labor in insect societies is often based on worker self-restraint and both queen and worker policing. Workers of many hitherto studied wasps, bees and ants do not lay eggs in the presence of a queen. However, it is presently unclear how far these observations in a few select clades can be generalized. We investigated if and how queens maintain a reproductive monopoly in colonies of the elongate twig ant, Pseudomyrmex gracilis, a member of the previously unstudied ant subfamily Pseudomyrmecinae. Colonies are usually headed by a single, singly mated queen (monogyny, monandry). Workers therefore would be more closely related to males produced by other workers (r = 0.375) than to the sons of queens (r = 0.25). Nevertheless, workers appear to refrain from laying male-destined eggs in the presence of the queen. In queenless conditions, workers form dominance hierarchies by antennal boxing, and only one or a few high-ranking individuals readily begin to lay eggs. When returned into a queenright colony, egg-laying workers are immediately bitten, stung and expelled or killed by other workers. While the composition of cuticular hydrocarbons clearly differed between castes, it less clearly reflected worker ovarian development. An association with worker ovarian development that would allow workers to monitor the reproductive status of nestmates could only be tentatively postulated for certain substances. Our study broadens our knowledge about reproductive conflict in social Hymenoptera and shows that worker sterility in the presence of a queen is more common in monogynous, monandrous ants than expected from relatedness alone.

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The study would not have been possible without the great logistic support of Dr. Josefina Steiner, Universidade Federal de Santa Catarina, who also provided the opportunity to conduct the investigations in the framework of a project on the interaction among bromeliads and the associated fauna. We also thank Phil Ward for ant identification. The study was authorized by IBAMA, permit 12826, in 2008 and material transfer agreement 003/2005/DZUP between Dr. M.A. Navarro da Silva, Departamento de Zoologia da Universidade Federal do Parana, and University of Regensburg. V.S.S. was supported by scholarships of Universität Bayern e.V. and DAAD. M.K. gratefully acknowledges financial support from the Volkswagen Foundation and the Max Planck Society.

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The authors declare that they have no conflict of interest.

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Correspondence to Volker S. Schmid.

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Communicated by L. Sundström

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Video file showing two instances of antennal boxing (indicated by yellow arrows) (MPG 13792 kb)

Video file showing one instance of antennal boxing (indicated by a yellow arrow) (MPG 7860 kb)

Video file showing one instance of antennal boxing (indicated by a yellow arrow) (MPG 3416 kb)

Online Resource 1

Video file showing two instances of antennal boxing (indicated by yellow arrows) (MPG 13792 kb)

Online Resource 2

Video file showing one instance of antennal boxing (indicated by a yellow arrow) (MPG 7860 kb)

Online Resource 3

Video file showing one instance of antennal boxing (indicated by a yellow arrow) (MPG 3416 kb)

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PDF file containing Tables S1–S4 and Fig. S1 (PDF 156 kb)

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Schmid, V.S., Kaltenpoth, M., Strohm, E. et al. Worker self-restraint and policing maintain the queen’s reproductive monopoly in a pseudomyrmecine ant. Behav Ecol Sociobiol 67, 571–581 (2013).

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  • Cuticular hydrocarbons
  • Dominance
  • Policing
  • Pseudomyrmex gracilis
  • Reproductive conflict
  • Worker reproduction