Mating frequency and mating system of the polygynous ant, Leptothorax acervorum

Multiple mating by queens (polyandry) and the occurrence of multiple queens in the same colony (polygyny) alter patterns of relatedness within societi es of eusocial insects. This is predicted to influence kin-selected conflic ts over reproduction. We investigated the mating system of a facultatively polygynous UK population of the ant Leptothorax acervorum using up to six m icrosatellite loci. We estimated mating frequency by genotyping 79 dealate (colony) queens and the contents of their sperm receptacles and by detailed genetic analysis of 11 monogynous (single-queen) and nine polygynous colon ies. Results indicated that 95% of queens were singly mated and 5% of queen s were doubly mated. The corrected population mean mating frequency was 1.0 6. Parentage analysis of adults and brood in 17 colonies (10 monogynous, 7 polygynous) showed that female offspring attributable to each of 31 queens were full sisters, confirming that queens typically mate once. Inbreeding c oefficients, queen-mate relatedness of zero and the low incidence of diploi d males provided evidence that L. acervorum sexuals mate entirely or almost entirely at random. Males mated to queens in the same polygynous colony we re not related to one another. Our data also confirmed that polygynous colo nies contain queens that are related on average and that their workers had a mixed maternity. We conclude that the mating system of L. acervorum invol ves queens that mate near nests with unrelated males and then seek readopti on,by those nests, and queens that mate in mating aggregations away from ne sts, also with unrelated males.