Low mitochondrial DNA variation in the endangered bumble bee Bombus cryptarum florilegus

The distribution of the bumble bee Bombus cryptarum florilegus is very local: Nemuro Peninsula and Notsuke Peninsula in Japan and the southern part of Chishima (Kuril) Islands. It is listed as a near-threatened species in the Japan Red List. In this study, we sequenced 687 bp of the mitochondrial COI gene of Japanese B. c. florilegus to obtain information about its genetic structure. We found three base substitutions between samples from Nemuro Peninsula and those from Notsuke Peninsula, whereas sequences within each peninsula were identical. The results indicate that the population of Nemuro Peninsula and that of Notsuke Peninsula are fragmented, and both populations have lost genetic diversity. In addition, the sequence of Notsuke Peninsula is identical to that from Etorofu Island (Chishima (Kuril) Islands), suggesting that the population of Notsuke Peninsula is maintained by individuals immigrating from Chishima (Kuril) Islands. Previous studies suggested that a potential cause of B. c. florilegus decline is the expansion of feral populations of the alien commercial pollinator Bombus terrestris. To conserve B. c. florilegus, and to preserve the natural ecosystem, it is better to use native species as agricultural pollinators.