Microsatellite analysis in museum samples reveals inbreeding before the regression of Bombus veteranus

The worldwide decline of pollinators is an emerging threat and is a matter both for ecological and economic concerns. Population genetics can be used to correlate bumblebee decline with genetic parameters. In order to do so, historical data are needed. We used eight microsatellite loci to genotype pinned museum specimens of the declining bumblebee Bombus veteranus. Bumblebee samples were collected spanning a period of three decades (1895-1923). We detected low genetic diversity and inbreeding in the samples collected during the respective time periods. Inbreeding was also confirmed by the occurrence of sterile diploid males. Based on the data obtained, we speculate that low genetic diversity and inbreeding did not directly result in the collapse of B. veteranus in Belgium. However, inbreeding might still play an indirect role in the decline of bumblebee populations because of the appearance of diploid males and because a low H (E) might reduce the capacity to react to the drivers of bumblebee decline.