A reassessment of the mating system characteristics of the army ant Eciton burchellii
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In a recent study, Denny et al. (2004a) showed that queens of the army ant, Eciton burchellii, mate with multiple males and presented estimates suggesting that they mate with more males than queens of any other ant species so far investigated. They also inferred that data were consistent with queens being inseminated repeatedly throughout their life, which would be exceptional among the social Hymenoptera and contradictory to predictions from kin selection theory. In the present study, we reanalyze these data using new software and supplement them with similar microsatellite data from other colonies of the same species. Mating frequencies in E. burchellii are indeed very high (mean observed and effective queen-mating frequencies of 12.9 each) but considerably lower than the previous estimates. We show that the number of patrilines represented in the first worker offspring of a young queen is lower than in older queens but suggest that this may be due to initial sperm clumping in the queen’s sperm storage organ, rather than to repeated inseminations. Moreover, we found no evidence for repeated mating by genotyping sequential worker generations produced by a single old queen, showing that she did not obtain new inseminations despite ample opportunities for mating.
This work was supported by grants from the Danish Research Training Council (DJCK), the Danish Natural Science Research Council, and the Danish National Research Foundation (JJB), the Leverhulme Trust (F/00 182/A1 to SMB, KJE and NRF), the Natural Environment Research Council (NER/S/A/2001/05997 to SP and NER/B/S/2002/00225 to AJD), and the Smithsonian Tropical Research Institute (SRA award to SMB and Predoctoral award to SP). We also thank the Smithsonian Tropical Research Institute for providing facilities and arranging for ANAM collection and export permits. All research reported in this paper complies with the present laws of Denmark and the UK.
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