Queen mating and paternity variation in the ant Lasius niger

We have electrophoretically analysed the variation in queen mating and work er paternity across and within seven populations of the ant Lasius niger in northwestern Europe. Populations were panmictic and not genetically differ entiated (F-ST = 0.003 +/- 0.004; range c. 1000 km). Queens (n = 535) were shown to mostly mate with a single male, but double mating occurred in all populations and triple mating was found in one case (the total number of wo rker offspring analysed for paternity was 4825). The genetically effective queen mating frequency was 1.16 on average across populations (range 1..04- 1.42). Double sampling of six out of the seven populations showed that most of the variation in queen mating occurred among populations and not within populations among years. Also, paternity skew in colonies with double-mate d queens was relatively constant per site but varied across populations. pa ternity skew was high in populations with low frequencies of double queen-m ating, low in populations with intermediate frequencies of double queen mat ing and ambiguous in a single population where more than half of the queens mated multiply. Double-mated queens were only collected halfway through a nuptial night, suggesting that double mating is time consuming and that the mating swarm sex ratio may affect the likelihood of multiple mating toward s the end of a flight. No difference in fresh weight between single- and do uble-mated queens from the same population was found.