MULTIPLE MATING IN THE ANT ACROMYRMEX VERSICOLOR - A CASE OF FEMALE CONTROL

In eusocial insects, polyandrous mating has the potential to reduce ge netic relatedness of individuals within a colony, which may have a pro found effect on the stability and social structure of the colony. Here we present evidence that multiple mating is common in both males and females of the desert leaf-cutter ant Acromyrmex versicolor. Females s eem to have complete control over the number of matings, and mate on a verage with three males, even though the sperm transferred in a single copulation is sufficient to fill the spermatheca. To determine whethe r there is a bias in the representation of sperm from different mates in the spermatheca, females were mated to three or four males in contr olled mating experiments and were subsequently allowed to found coloni es in the laboratory. Paternity analysis of the offspring by random am plified polymorphic DNA analysis showed that all males that have been mated to a female successfully contributed sperm to the production of her offspring. No significant asymmetry id sperm use was detected, sug gesting complete sperm mixing. Different hypotheses to explain polyand rous mating are discussed, and it is argued that the best hypothesis t o explain polyandrous mating and complete sperm mixing in A. versicolo r is that utilizing genetically diverse sperm confers a selective adva ntage on females.