Cross-mating between the alien bumblebee Bombus terrestris and two native Japanese bumblebees, B. hypocrita sapporensis and B. cryptarum florilegus, in the Nemuro Peninsula, Japan

Abstract

The rapid naturalization of Bombus terrestris across the Nemuro Peninsula has led to a decline in two closely related native Japanese species, namely Bombus hypocrita sapporensis and Bombus cryptarum florilegus, both belonging to the common subgenus Bombus. Although it is widely believed that cross-mating of native and non-native species is influenced by the common male sex pheromone in this region, no study has been conducted to substantiate this claim. Thus, we investigated the cross-activities of male sex pheromones between native and non-native bumblebees, as well as the frequencies of cross-mating, using chemical and DNA assays. Our gas chromatography–electroantennographic detector analyses and behavioral tests revealed the presence of sex pheromonal cross-activities between B. terrestris and the two Japanese bumblebees species. Furthermore, DNA analyses revealed the occurrence of cross-mating between native and non-native species in the Nemuro Peninsula. Overall, these results indicate the immediate need for conservation measures to safeguard Japanese bumblebee populations in the Nemuro Peninsula.

Niche analyses and the potential distribution of four invasive bumblebees worldwide

“…These factors may affect behavior, physiology, reproduction, and species distribution, impacting the foraging areas and the ecosystem, which are important variables affecting these species (Gérard et al., 2022 ). However, the adaptations in some species of Bombus , such as the physiological mechanisms of thermoregulation and other key factors (Dafni et al., 2010 ; Wynants et al., 2021 ), together with the commercialization events in different countries and the poor management in the culture greenhouses, have potentiated the invasion processes in different regions of the world (Acosta, 2015 ; Sutherland et al., 2017 ), promoting potential mating with wild bees (Kubo et al., 2023 ; Miller et al., 2023 ; Naeem et al., 2018 ) and competition for resources with native species, to the degree of putting them at risk of extinction (Dafni et al., 2010 ; Esterio et al., 2013 ; Hallmen, 2017 ; Madjidian et al., 2008 ; Morales et al., 2013 ; Naeem et al., 2018 ; Pérez & Macías‐Hernández, 2012 ; Sachman‐Ruiz et al., 2015 ).…”

“…mating with wild bees (Kubo et al, 2023;Miller et al, 2023;Naeem et al, 2018) and competition for resources with native species, to the degree of putting them at risk of extinction (Dafni et al, 2010;Esterio et al, 2013;Hallmen, 2017;Madjidian et al, 2008;Morales et al, 2013;Naeem et al, 2018;Pérez & Macías-Hernández, 2012;Sachman-Ruiz et al, 2015).…”