Introduced Bumblebee Species Becomes Invasive in South America

A European bumble bee species introduced in Chile in the 1990s to supplement the pollination efforts of native honeybees has grown into a certifiably invasive species, out-competing native pollinators not just in Chile, but across the South American continent.

In 1998, the help of the buff-tailed bumblebee (Bombus terrestris) was enlisted by a handful of greenhouses to provide supplemental pollination. The move was backed by state authorities, who did not expect the bees to go on to overtake the entire continent.

Ecologist Paul Schmid-Hempel has spent the last decade monitoring the spread of the buff-tailed bumblebee.

"This is one of the most spectacular examples of the invasion of an entire continent by a foreign species introduced by man," he said.

Schmid-Hempel and his colleagues published the results of their bumblebee analysis in the Journal of Animal Ecology.

Their research shows that the European buff-tailed bumblebee moved southward through Chile along the Andes Mountains at the rate of about 200 kilometers per year, a rate faster than the ecologists expected.

It only took the bees a few years before they crossed the mountain chain and were present on the Atlantic coast of Argentina as early as 2011. By 2012, Schmid-Hempel and his team found the bees in the Patagonia region in the far south area of the continent.

"Given that colonies and not individual insects have to become established, this migration speed is astonishingly fast," Schmid-Hempel said, adding that it's only a matter of time before the bees will be found in the national parks on the southern tip of the continent.

The spread of the buff-tailed bumblebee is troubling for the five native bumblebee species known in South America, as they are handily out-competed by the non-native species. One native species, Bombus dahlbomii, has been documented disappearing rapidly upon the appearance of the European buff-tailed bumblebees.

The ecologists hypothesize that one reason why the native bumblebee populations cannot live alongside the invasive species is because the European bees carry Crithidia bombi, an intestinal parasite that affects the native populations by altering their behavior and and increasing their mortality, which hinders the native bees from establishing new colonies.

"The European bumblebee could disrupt the ecological balance of southern South America to a major degree," Schmid-Hempel said, adding that he does not see much that can be done to stop the bees from continuing to spread across the continent.