A failed invasion? Commercially introduced pollinators in Southern France

The natural diversity of Bombus terrestris subspecies could be under threat from the commercialisation of bumblebees. Therefore, to determine whether commercially imported bumblebees are able to establish and spread, we carried out long-term observations of bumblebees in southern France. Our surveys occurred before, during, and after the importation (between 1989 and 1996) of thousands of colonies of the Sardinian subspecies B. t. sassaricus. Queens and males of B. t. sassaricus were observed foraging outside commercial greenhouses in 1991, 1993, and 1994 and feral workers were observed foraging on native vegetation nearly two years after the importation of B. t. sassaricus ceased. However, no B. t. sassaricus, or F1 hybrids were observed after 1998. We conclude that B. t. sassaricus remains inconspicuous in France and competition from the three native subspecies may have prevented it from becoming invasive. However, genetic interference through introgression cannot be ruled out.