Interspecific hybridization of the Korean native bumblebee, Bombus ignitus, and the introduced bumblebee, B. terrestris

The large bumblebee, Bombus terrestris, indigenous to Europe and used extensively for high-value crop pollination, has been artificially introduced in several parts of the world. Here we show the interspecific hybridization between bumblebee species, B. terrestris and B. ignitus, under laboratory conditions. The mating and oviposition percentages of the interspecific hybridization of a B. terrestris queen with a B. ignitus male were higher than those of the intraspecific mating of B. ignitus. Furthermore, the competitive copulation experiment indicated that the mating of B. ignitus males with B. terrestris queens was 1.8-fold more frequent than with B. ignitus queens. The interspecific hybridization of a B. ignitus queen with a B. terrestris male produced either B. ignitus workers or the B. ignitus male phenotype, and the hybridization of a B. terrestris queen with a B. ignitus male produced B. terrestris males. Genetic tests using a portion of the mitochondrial COI gene for the parent and hybrid phenotypes indicated that mitochondrial DNA in the interspecific hybridization was maternally inherited. Our results indicated that interspecific hybridization occurred between B. ignitus and B. terrestris, which suggests that the hybridization will have a negative impact of competition and genetic pollution of native bumblebees.