If you were getting tired of the peppered-moth-in-industrialized-Britain example of evolution in action, here’s a new twist: bee tongues evolving in response to global warming! This example isn’t likely to convince skeptics of evolution or global warming, but maybe it’s efficient to have all your enemies arrayed against you at once?
In the midst of a widespread decline in bees, particularly in the United States, a few bumblebees are finding a way to cope: shorter tongues. In just 40 years, the tongues of two bumblebee species living high up in Colorado’s Rocky Mountains have shrunk by almost 25% in their average length, according to a new study. A warming world has spurred these changes, researchers conclude, because the total number of flowers has declined in this region—and the shorter tongue enables the bees to suck nectar from more kinds of flowers.
“It’s one of the best examples of the effect of climate that I’ve seen,” says Sydney Cameron, an entomologist at the University of Illinois, Urbana-Champaign, who was not involved with the work. But the bees’ successful adaptation may be the silver lining of a very dark cloud. 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. “The reality is that long-tube flowers will disappear,” Cameron warns. And then, “you are losing biodiversity on a major scale.”
Many of the bumblebees that first arose sport tongues about half the length of their bodies, having evolved special relationships with particular long-tubed flowers. Matching tongue length to flower depth makes foraging and pollination more efficient, and many such matches have evolved through time.
But globally, long-tongued bumblebees are declining, says Cameron, as are many bees, in part because of climate change, pesticide use, and habitat loss. There were also indications that in some species, long tongues were shrinking.