No reversion to single mating in a socially parasitic ant

Area of Science:

• Evolutionary biology
• Behavioral ecology
• Social insects

Background:

• Social Hymenoptera provide insights into the evolution of multiple mating (polyandry) due to varying lifestyles and mating strategies in sister species.
• Workerless social parasites are predicted to exhibit single mating, as the primary advantage of polyandry—increased genetic diversity in offspring—is absent.

Purpose of the Study:

• To investigate queen mating frequency in the ant Plagiolepis pygmaea and its social parasite P. xene.
• To test the hypothesis that workerless social parasites revert to single mating.

Main Methods:

• Comparative study of mating frequencies between a host ant species (P. pygmaea) and its social parasite (P. xene).
• Pedigree analysis of mother-offspring combinations to determine queen mating frequency in P. xene.

Main Results:

• Queens of the host species, P. pygmaea, are obligately polyandrous.
• Over 50% of P. xene queens engaged in multiple mating, with 2-4 males, indicating no reversion to single mating.
• The genetic diversity benefit of polyandry for worker offspring is not applicable to workerless parasites.

Conclusions:

• Reversal from multiple to single mating may not be favored in polyandrous, workerless social insect parasites.
• The persistence of polyandry in workerless parasites could be due to multiple mating being virtually cost-free.