Mating frequency and fitness in a monogynous ant

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While males can increase their reproductive success by additional matings, female fitness is typically more limited by the number of eggs they can produce than by the number of their mates. Nevertheless, female multiple mating (polyandry) is a common phenomenon in animals. While hypotheses on the adaptive value of polyandry abound, testing them has often been difficult. In particular in social insects, studies on the association between mating frequency and female fitness frequently remain correlative as sexuals rarely mate in the laboratory. Workers of the ant Cardiocondyla elegans carry young queens from nest to nest to promote repeated outbreeding with locally mating, wingless males in other colonies. We will interrupt queen carrying at different periods of the mating period to obtain queens that mated only with one or a few related males, a few, or many additional unrelated males. We will allow these mated queens to start new colonies in the laboratory. We will monitor colony growth rate, offspring quality, and disease resistance, and later correlate these traits with genetically determined queen mating frequencies and inbreeding coefficients. By additionally combining field observations, microsatellite genotyping, controlled mating and experimental manipulations in the lab we will explicitly test the following hypotheses:Worker-induced multiple mating increases the fitness of queens. Workers choose particular colonies for the export of female sexuals, i.e., intersexual selection (female choice) is shifted from female sexuals to sterile workers.The transfer of female sexuals widens male competition to a population-wide scale and increases post-copulatory sperm competition among males. Our study will contribute to a fundamental question in behavioral ecology and at the same time will shed light on the evolutionary meaning of a bizarre and hitherto unstudied behavior, royal matchmaking in Cardiocondyla ants.