Bee Tongues Shrink as Climate Warms

Bumblebees' tongues are getting shorter as the climate warms and their preferred flowers become more scarce. CHRISTINE CARSON

Global warming may be leading to the shortening of bumblebee tongues, potentially imperiling some of the flower species that they normally pollinate, new research shows.

When bumblebees visit certain flowers, they have to dip their tongues into tube-like petals to reach nectar, and in the process they spread pollen from one bloom to another, leading to fertilization and the eventual creation of seeds. One species of alpine bee, Bombus sylvicola, specializes in flowers in the central Rocky Mountains with deep tubes, for which it has evolved a long tongue, all the better to slurp nectar with. But populations of these flowers are declining with increased temperatures and less rain, and at the same time, bumblebee tongues are shrinking. Since the 1970s, the tongues of this species have shortened by nearly 25 percent, according to a study published September 24 in the journal Science.

Researchers think they know why. Previous research has shown that when a desired flower becomes scarce, bees switch from specializing in one or several plants to broadening their foraging habits and becoming generalists. Most flowers do not have deep floral tubes, so shorter tongues are better for getting a taste of their nectar.

The researchers suggest that the decline of deep-tubed flowers, driven by climate change, is favoring bumblebees with short tongues and leading them to quickly evolve shorter tongues.

"It speaks to the magnitude of the change of the climate that it's affecting the evolution of the organisms," study co-author Candace Galen, a biology professor at the University of Missouri, tells the Associated Press. "It's a beautiful demonstration of adaptive evolution."

Of course, this presents a major problem for both flowers and bees, because the plants and the insects have co-evolved for eons, so a change or decline can drastically affect the other. The flowers might be in worse shape, however, as there are no other bees to pollinate them, while the bumblebee is able feed upon other flowering plants.