Jessica Forrest, a PhD student in the Department of Ecology and Evolutionary Biology, examines the toll of changing temperatures on the interaction between bees and the plants they pollinate.
Her experiments began in 2006 in the Colorado mountains. “Working in the mountains provides a good elevation gradient, and different sites experience different season lengths, which is representative of the variation in climate change,” explains Forrest. The main research site is at a 3000 metre elevation, where air temperatures can drop down to -20 degrees Celsius in the winter. Summer conditions are similar to those experienced in Toronto, with temperatures reaching 25 degrees in the day, but cool off significantly to about five degrees at night.
To attract bees to her study site, Forrest placed trap-nests for leaf-cutter bees and their larvae at various elevations. “The bees find these trap-nests and then they [provision holes in wood with pollen and nectar for their larvae],” says Forrest. “[The trap-nests] were colonized last summer and this summer I went out and monitored these nests every three days or so to see how many bees had come out [in each time interval].” She has recorded which flowers bloom simultaneously with bee emergence to see whether the two organisms are controlled by the same environmental factors.
Many plants rely on certain pollinators being present when they’re in bloom. However, changing climate conditions have the potential to cause organisms to alter their biological timing. Increased temperatures could cause earlier snowmelts, which would trigger flowers to bloom earlier. If flowers are in bloom but lack the bees to pollinate them, it could have a serious impact on the plants’ population. Forrest wants to determine if, even in early snowmelt years, bees are available to pollinate alpine bluebells, which blossom soon after snowmelt.
Her preliminary data shows no significant decoupling between flowers that bloom and the number of bees that pollinate them. “The pollinators are actually responding to similar cues,” she says. “They are managing to stay in sync it seems, but I could be telling a different story next year.” Forrest stresses that while her findings are still in the preliminary stage, her research details a significant change.
Is there a link between the bee-bluebell interaction and climate change? As the study site climate varies year-to-year, plant pollinators might be relatively used to an alteration in temperature. If a separation between plants and pollinators is observed, it’s possible that the plants will be able to self-pollinate or attract other species. Forrest notes a possibility for evolutionary change. “If bees are emerging before there are any plants around, natural selection will act to change their timing of emergence.”
Forrest hopes to finish her study in the next two years. After its completion, she plans to examine the consequences for bees that emerge too early. She is also interested in investigating the basic biology of bees for signs of evolution, especially in their flexibility of food choice.
Despite the impact of climate change, for now it’s business as usual for the bees in Colorado. Forrest seems content with her work, saying, “It’s not a bad job. Working in a field of flowers and watching bees sure beats working at a desk all the time!”
