What’s the buzz? Pollinator diversity and distribution along the Chilkoot Trail

Rykken, Jessica

Insect pollinators, specifically bees (Hymenoptera: Anthophila) and flower flies (Diptera: Syrphidae), are critical to maintaining healthy plant communities and functioning ecosystems. Despite their ecological importance and potential vulnerability to environmental threats such as climate change, the diversity of these pollinators has remained largely unknown to park staff and visitors in Klondike Gold Rush National Historical Park and Chilkoot Trail National Historic Site. We conducted surveys of bees and flower flies along the length of the Chilkoot Trail to document the diversity and distribution of pollinators along an elevational gradient of more than 1000 m, passing through three distinct ecozones. Field work was conducted from July 9-14, 2019. Between two and four people used insect nets to collect bees and flower flies at 13 sites in three ecozones along flower-rich sections of the trail, beginning in coastal forest at Dyea, climbing steeply to alpine tundra at higher elevations, and descending gradually to boreal forest in the headwaters of the Yukon River at Lindeman and Bennett Lakes. Elevations ranged from a few meters above sea level at Dyea to 1,067 m at Chilkoot Pass. In all, we collected 348 bees and 19 flower flies, representing 16 bee species and 10 flower fly taxa. Bumble bees dominated the catch (94% of the total), but we also collected a few solitary bees in addition to flower flies. Among the three ecozones, tundra stood out as the least diverse, however it yielded several bumble bee species that were strongly associated with high elevation/Arctic habitats. Coastal and boreal forests were somewhat more similar in their sampled fauna, both yielded several flower flies and shared most of their bumble bee species, although relative abundances differed. Coastal forest had one strongly associated bumble bee Bombus sitkensis and was the only ecozone where we collected solitary bees. Boreal forest was distinct for having a very large number of male parasitic bumble bees, and the highest richness of sampled host plants. This survey provided a quick snapshot of pollinator diversity along the Chilkoot Trail, it was not intended to be a comprehensive survey. We recommend continued sampling to further explore patterns of pollinator diversity and distribution across these very pronounced ecological gradients. We also recommend establishing monitoring protocols for documenting long-term changes in pollinator populations, ranges, and phenology in the face of warming temperatures and other environmental changes.

What’s the buzz? Pollinator diversity and distribution along the Chilkoot Trail

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