BUMBLEBEE POLLINATION RELATIONSHIPS ON THE BEARTOOTH PLATEAU TUNDRA OF SOUTHERN MONTANA

Area of Science:

• Ecology
• Pollination Biology
• Alpine Entomology

Background:

• Alpine tundra ecosystems host dynamic coevolutionary relationships between plants and their pollinators.
• Bumblebees (Bombus spp.) are key pollinators in many environments, including high-altitude regions.

Purpose of the Study:

• To investigate the coadaptive relationship between bumblebee pollinators and alpine floral communities.
• To identify patterns of resource use and plant reliance on bumblebee pollination.

Main Methods:

• Field observations of bumblebee foraging on various alpine plant species.
• Analysis of corbicular pollen loads to determine foraging specialization (monolectic vs. polylectic).
• Spectrophotometry and UV photography to assess floral reflectance properties.

Main Results:

• Ten Bombus species were observed foraging on seven plant species, with 1–9 Bombus species per plant.
• Foragers were nearly equally divided between monolectic (53.5%) and polylectic (46.5%) specialists.
• No clear resource partitioning was indicated by floral tube length, pollinator tongue length, or plant stature.
• Most plant species, except Delphinium bicolor and Penstemon procerus, showed high reliance on bumblebee pollination.

Conclusions:

• Bumblebee foraging in alpine tundra is diverse, with a near balance of specialist and generalist pollinators.
• Floral traits and phenology did not reveal specific resource partitioning mechanisms.
• The majority of studied alpine plants are significantly dependent on bumblebee pollination for reproductive success.