Rapid ecological replacement of a native bumble bee by invasive species

Abstract

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.