Reproductive interference by alien hornet Vespa velutina threatens the native populations of Vespa simillima in Japan

Abstract

The yellow-legged hornet Vespa velutina has become one of the major alien species in European and East Asian countries. As in its homeland, the invading V. velutina is reported as the major predator of honeybees and is becoming a threat to beekeeping in Europe. However, it remains unknown how V. velutina might affect native hornets when it invades Asia, where a large number of Vespa species are distributed. Thus, by analyzing the mitochondrial cytochrome c oxidase subunit I gene, we investigated whether interspecific mating occurs between V. velutina and Japanese native Vespa spp. Our results showed that the alien V. velutina causes reproductive interference in Japanese native hornet Vespa simillima. Forty-three percent of native V. simillima queens had the sperm of V. velutina males, and among the all V. simillima queens analyzed, 28% only had V. velutina sperm. We did not find evidence of V. velutina queens having the sperm of V. simillima males. These findings suggest that reproductive interference by V. velutina males poses a threat to the native V. simillima populations. A decline of V. simillima may also negatively affect other insects that interact with V. simillima.

Appendix

Fig. 1

Detection of possibly interspecifically mated samples. a Double peaks in the chromatograph and the base sequences of V. simillima and V. velutina above them. b Electrophoretic gel image of PCR products using the common primer for V. simillima and V. velutina, showing the water (negative control) 1, the DNA marker M, the DNA samples from the leg 2, and the spermatheca 3 of V. simillima queen, and those of V. velutina queen 4, 5. c Electrophoretic gel image of PCR products using the specific primer for V. simillima, showing the water (negative control) 1, the DNA marker M, the DNA samples of V. simillima queens (from the leg 2, the spermatheca that is inseminated by conspecific male 3, the spermatheca that is inseminated by both of conspecific and allospecific males 4, and the spermatheca that is inseminated by allospecific V. velutina male 5), and those of V. velutina queen (from the spermatheca that is inseminated by conspecific male 6, and the leg 7). d Electrophoretic gel image of PCR products using the specific primer for V. velutina, showing the water (negative control) 1, the DNA marker M, the DNA samples of V. simillima queens (from the leg 2, the spermatheca that is inseminated by conspecific male 3, the spermatheca that is inseminated by allospecific V. velutina male 4, and the spermatheca that is inseminated by both of conspecific and allospecific males 5), and those of V. velutina queen (from the leg 6, and the spermatheca that is inseminated by conspecific male 7)