Positive association of queen number and queen-mating frequency in Myrmica ants: a challenge to the genetic-variability hypotheses

摘要

The mating frequency of queens in a polygynous population of the red ant Myrmica sulcinodis was studied. Genetic mother-offspring analysis showed that double mating occurred at a considerable frequency, but that the effective number of queen-mates remained close to one. After quantifying the effects of multiple maternity (polygyny) and multiple paternity (polyandry) on the genetic diversity of workers, it was concluded that multiple paternity in M. sulcinodis did not evolve as an adaptation to increase genetic variation within colonies. Contrary to the predictions from 'genetic variability' hypotheses, a positive correlation between colony-specific queen number and the average number of mates per queen was found. Such positive association of queennumber and frequency of multiple mating was also found after analysing comparative data across 6 species of Myrmica ants. These results suggest that restricted dispersal of young queens may be a common factor promoting both polygyny and polyandry at thesame time, and that moderate degrees of multiple mating may be an unselected consequence of (1) mating at low cost when mating occurs close to the nest and (2) mating in swarms with a highly male biased operational sex ratio. Future comparative tests ofgenetic-variability hypotheses should therefore not include species with such evolutionary derived mating system characteristics.