Climate Change is Strangely Shrinking Bumblee Tongues

The scientists believe the bees are evolving quickly in order to adapt to the changing flowers on which they feed, with the deeper flowers and longer tongues being replaced by shorter flowers whose nectar is more efficiently exploited by short-tongued bees. “That’s a good thing – they’re responding to these changes in selective pressure”, says Nicole Miller-Struttmann, an evolutionary ecologist at SUNY College at Old Westbury and a co-author on the paper, which was published Friday in the journal Science. Using what was no doubt a painstaking process, the researchers measured the tongue length of 170 bees.

In one of these species, the tongue had been half the size of the bee’s body – the equivalent of a human tongue going down to the waist. A comparison of the corolla depth of flowers collected between 1960 and 1982 showed different changes in corolla depth for different species but the ones that did get shorter actually received fewer visits in the past and there was also no increase in flowers with shallow corollas. A variety of so-called long-tubed flowers, including penstemon, Indian paintbrush, clover, wild indigo, monkshood, bluebell, snapdragon, larkspur, and foxglove, require long-tongued bumblebees for pollination.

“Our analyses suggest that reduced flower density [of blooms with longer corollas]…is driving this shift in tongue length”, the researchers say. And that these changes occurred in just 40 years-or about 40 generations for bees, “is a really significant finding”, Kerr adds. If the bees start to disappear, it could lead to a sharp decline in flowers as well.

Science finds connection between Bee’s tongue length and climate change. “But if you’re a generalist, short-tongued bee, you’re more likely to run into your resource”. This has many researchers concerned, as the shift could cause a large problem across flower and bee species alike. On Pennsylvania Mountain, home of one of the research sites, flower production has declined by 60% since the 1970s.

So the tongue-shrinking seems to be an adaptation that allows the bees to better cope with dwindling food supplies. There were also indications that in some species, long tongues were shrinking.

While biologists have tracked how global warming has altered the developmental, migration, timing and other behavior in plants and animals, what makes this study unusual is the physical changes in the bees, said study co-author Candace Galen at the University of Missouri. “And it takes less energy to get to them because you don’t have to search them out as much”. The economic value of bee pollination services ranges from $10 billion to $15 billion.

But globally, long-tongued bumblebees are declining, says Cameron, as are many bees, in part because of climate change, pesticide use, and habitat loss. But for now, it’s still unclear how the flowers will be affected. The bees studied were located in the Rocky Mountains. Miller-Struttman agrees but says that is something she plans to look at next.