The cost of promiscuity: sexual transmission of Nosema microsporidian parasites in polyandrous honey bees

doi: 10.1038/srep10982

Abstract

Multiple mating (and insemination) by females with different males, polyandry, is widespread across animals, due to material and/or genetic benefits for females. It reaches particularly high levels in some social insects, in which queens can produce significantly fitter colonies by being polyandrous. It is therefore a paradox that two thirds of eusocial hymenopteran insects appear to be exclusively monandrous, in spite of the fitness benefits that polyandry could provide. One possible cost of polyandry could be sexually transmitted parasites, but evidence for these in social insects is extremely limited. Here we show that two different species of Nosemamicrosporidian parasites can transmit sexually in the honey bee Apis mellifera. Honey bee males that are infected by the parasite have Nosemaspores in their semen, and queens artificially inseminated with either Nosemaspores or the semen of Nosema-infected males became infected by the parasite. The emergent and more virulent N. ceranaeachieved much higher rates of infection following insemination than did N. apis. The results provide the first quantitative evidence of a sexually transmitted disease (STD) in social insects, indicating that STDs may represent a potential cost of polyandry in social insects.

Keywords

Multiple mating, Sperm competition, Female choice, Genetic diversity, Social evolution, Kin selection, Review.