Potential negative impacts of commercial bumblebees on native conspecifics – genetic contamination and parasite spillover

Abstract: Bumblebees are traded across the world for crop pollination with known and potential negative impacts on native pollinators. Two of those impacts are 1) hybridization between commercial and native species, which can lead to introgression of maladaptive alleles and 2) spillover of parasites or pathogens from commercial to native bumblebees. In this study we used genome-wide single nucleotide polymorphisms markers to detect hybrids between the commercial lineages (likely from Bombus terrestris terrestris and B. t. dalmatinus) and native lineages (from B. t. lusitanicus), in two areas in the western Iberian Peninsula near and far from greenhouses where commercial lineages are used for pollination. We detected hybrids and also putative escaped commercial bumblebees, some of them potentially fertile males. The molecular screening with parasite specific PCR primers to assess parasite prevalence in the gut of commercial and native bumblebees, has revealed so far the presence of the parasites Apicystis bombi (Apicomplexa: Neogregarinorida) and Crithidia bombi (Kinetoplastea: Trypanosomatidae) in both commercial and native B. terrestris. Their prevalence in areas both near and far from greenhouses will be further assessed. These are the first steps to assess the risks of using commercial bumblebee stocks, in order to avoid their putative negative impacts on local bumblebee populations.