Abstract An increasing number of pollinator species are being reared by humans to ensure crop pollination. The release of reared pollinators can lead to genetic admixture with wild conspecifics, potentially disrupting local adaptations. While such admixture has been reported in bumblebees, respective data for solitary bees are lacking. We investigated whether the release of locally reared solitary bees ( Osmia spp.) influences genetic diversity and population structure of wild conspecifics. Osmia bicornis and Osmia cornuta females were sampled from two commercial breeders as well as from high, mid and low Osmia spp. management intensity areas in Switzerland. Museum specimens of O. bicornis sampled from the same areas before commercial rearing were used to control for the effect of management. Genetic diversity, population structure and admixture between managed and wild bee populations were investigated across sampling areas and time periods using mitochondrial and nuclear DNA markers. In the contemporary period, both species showed no differences in genetic diversity and low genetic differentiation between sampling areas and breeder stocks, indicating high gene flow despite Osmia spp. being considered philopatric and relatively short‐distance flyers. Similar levels of gene flow were found in O. bicornis before and after management. Genetic diversity of O. bicornis declined over time, which is probably independent of management. Synthesis and application . The data suggest that the release of locally reared Osmia spp. is unlikely to interfere with the genetic structure of wild conspecifics. This contrasts with bumblebees, where the use of non‐local colonies has led to significant genetic introgression with local conspecific populations. Our results emphasize the importance of using locally reared pollinator populations in order to minimize the risks associated with genetic pollution. Further investigation into the population genetics of pollinators is essential to identify the main drivers of genetic erosion.
Piovesan et al. (Sun,) studied this question.