The ongoing loss of global biodiversity is endangering ecosystem functioning and human food security.While environmental pollutants are well known to reduce fertility, the potential effects of commonneonicotinoid insecticides on insect fertility remain poorly understood. Here, we show thatfield-realisticneonicotinoid exposure can drastically impact male insect fertility. In the laboratory, male and femalesolitary beesOsmia cornutawere exposed to four concentrations of the neonicotinoid thiamethoxam tomeasure survival, food consumption, and sperm traits. Despite males being exposed to higher dosages ofthiamethoxam, females revealed an overall increased hazard rate for survival; suggesting sex-specificdifferences in toxicological sensitivity. All tested sublethal concentrations (i.e., 1.5, 4.5 and 10 ng g1)reduced sperm quantity by 57% and viability by 42% on average, with the lowest tested concentrationleading to a reduction in total living sperm by 90%. As the tested sublethal concentrations match esti-mates of global neonicotinoid pollution, this reveals a plausible mechanism for population declines,thereby reflecting a realistic concern. An immediate reduction in environmental pollutants is required todecelerate the ongoing loss of biodiversity.
