Acknowledgements

We are grateful to all collaborators who provided specimens for this study. We would also like to thank Silas Bossert, Gideon Pisanty, Robert Paxton, Daniel Frei and Beatrice Frey for there valuable repective contribution in regards to bioinformatic, laboratory and statictical aspects of this study. This work was mainly funded by the Swiss Federal Office for Agriculture (FOAG); the sampling of bees was funded by the Swiss Federal Office for Environment (FOEN).