Indiscriminate egg cannibalism and reproductive skew in a multiple-queen ant

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Abstract
Societies of ants with several egg-laying queens (polygyny) permit the study of the evolution of a stable allocation of reproduction (reproductive skew). One factor that could influence the stable skew in the polygynous ant Leptothorax acervorum is cannibalism by queens of other queens' eggs. To test for discrimination during egg-eating, isolated queens were offered a choice between their own eggs and eggs laid by either a nestmate queen or a queen from another colony. The eggs had been made distinguishable by exposing queens to dye. In a total of 45 trials, queens preferentially ate non-nestmate eggs but did not show a significant preference for a nestmate's over their own eggs. This suggests that mutual egg-eating within colonies does not affect the stable reproductive skew. Once established, indiscriminate egg-eating could be evolutionarily stable because queens that give up egg-eating suffer the costs of having their eggs eaten but lose the nutritional benefits.