How does an introduced bumble bee affect native bumble bees?

Invasive species often compete strongly with native species, especially when they are closely related. In southwest British Columbia and northwest Washington, introduced eastern bumble bees (Bombus impatiens) are spreading rapidly. How does their presence affect our native Bombus species? This talk will present data from surveys done in BC across a gradient of B. impatiens invasion. We built plant-pollinator interaction networks based on floral visitation and used the networks to assess whether B. impatiens affects how native Bombus species forage.

We found that the mean number of plant species used by native Bombus species increased with B. impatiens abundance. This change in foraging behavior has the potential to affect both the nutritional quality of native Bombus diets and the effort expended on foraging. Additional research by a cross-border team is investigating the spread of B. impatiens, and will continue to explore how the invasion affects native Bombus assemblages. 

Susan Waters is Senior Ecologist at Quamash EcoResearch in Olympia, WA. Her recent research focuses…