Rapid ecological replacement of a native bumble bee by invasive species

Despite rising global concerns over the potential impacts of non-native bumble bee (Bombus spp) introductions on native species, large-scale and long-term assessments of the consequences of such introductions are lacking. Bombus ruderatus and Bombus terrestris were sequentially introduced into Chile and later entered Argentina's Patagonian region. A large-scale survey in Patagonia reveals that, in 5 years post-arrival, the highly invasive B terrestris has become the most abundant and widespread Bombus species, and its southward spread is concurrent with the geographic retraction of the only native species, Bombus dahlbomii. Furthermore, a 20-year survey of pollinators of the endemic herb Alstroemeria aurea in northern Patagonia indicates that B ruderatus and B terrestris have replaced B dahlbomii, formerly the most abundant pollinator. Although the decline's underlying mechanisms remain unknown, the potential roles of exploitative competition and pathogen co-introduction cannot be ruled out. Given that invasive bumble bees can rapidly extirpate native congeners, further introductions should be discouraged.