Female mating frequencies in Bombus spp. from Central Europe

The mating frequency of females in social insects is particularly interesting, because polyandry reduces colony relatedness and increases within-colony genetic variance. It thereby affects a complex balance of benefits and costs that determine the degree of reproductive skew, sex allocation to offspring, or the opportunities for nepotism and policing strategies. Few systematic surveys of female mating frequencies exist and many are based on unreliable behavioural. observation or sperm counts. Here, we report the results of a survey of mating frequencies in eight European Bombus spp. by means of highly polymorphic microsatellite loci. Only B. hypnorum was found to be multiply mated, while the pattern found in B, terrestris, B. lucorum, B, pratorum, B. lapidarius, B. sicheli, B. hortorum, and B. pascuorum was compatible with single mating. The findings are compatible with recent claims that, with some exceptions, mating frequencies of social insect females are generally low.