Long-term study of female multiple mating indicates direct benefits in Tribolium castaneum

Polyandry or female mating with several different partners in a single fertile period is a widespread phenomenon possibly involving both costs and benefits. This study tested whether remating after weeks of initial copulation (periodic multiple mating) has fitness consequences for females of red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), a cosmopolitan storage pest. We hypothesize that females benefit from higher mating frequency and more mates through sperm replenishment and/or compatible sperm. Thus, offspring production and survivorship were examined of females that were mated to multiple males or the same male repeatedly at variable intervals (every 2 weeks, 1, 3, and 5 months). Our results suggest that remating, after months of initial copulation, confers direct benefits to females, likely by providing additional sperm or through an alternative mechanism such as better ability of fresh sperm to fertilize eggs, stimulation of oviposition from copulation itself, and/or hydration benefit of the ejaculate. We did not detect any additional benefit of female multiple mating.