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Friday, 25 September 2015

Bees Are Growing Shorter Tongues To Combat Climate Change

We know the effects of climate change are strange and unpredictable, but the idea of global warming leading to shorter tongues...now that’s weird. However, that’s exactly what a new study discovered when it looked at two bumblebee species on the slopes of Colorado’s Rocky mountains.
In only 40 years, those honey-seeking tongues have shortened by almost a quarter. While forty years might seem like a short time for such a significant evolutionary change, it represents 40 generations for the bees.
A classic “good news/bad news” climate change story
This adaptation has allowed the two species, Bombus balteatus and B.
sylvicola, to cope with the challenges of global warming, but in the long term, it could be disastrous for the ecosystem as a whole.
Bee numbers are crashing everywhere, particularly in the United States . These Colorado bees have evolved the shorter tongues as the total number of flowers in the region falls, as a shorter tongue allows the bees to suck nectar from a wider range of flowers.
Nicole Miller-Struttmann, evolutionary ecologist, working with colleagues from the State University of New York at Old Westbury, made the discovery while studying bees in the alpine regions of the Rockies. As part of the study, they used measured tongue lengths of bees collected between 1966 and 1980 from three Colorado peaks and compared them to those measured between 2012 and 2014. The tongues had become 24 percent shorter.
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. Cameron was not involved with the work.
It’s a neat workaround for the bees, but according to the team behind the research, it could be the silver lining of a very dark cloud . “Long-tubed flowers”, like penstemon, Indian paintbrush, clover, wild indigo, monkshood, bluebell, snapdragon, larkspur, and foxglove need long-tongued bumblebees for pollination.
“The reality is that long-tube flowers will disappear. And then, you are losing biodiversity on a major scale,” warned Cameron.
Evolution in action
So how did the adaptation happen? When Miller-Struttmann and her colleagues compared other decades-old data about plants visited by the bees with more bee visit information, they believed they had the answer. The “modern” bees are taking nectar from many more kinds of flowers than their ancestors 40 years ago.
Since the 1970s, flower density on the mountain slopes has dropped more than 70 percent and, said Miller-Struttmann, climate change is to blame. Alpine flowers grow less well when summer minimum temperatures exceed 3.25°C, and the soil doesn’t cool off and dries up as a result. Nights were too warm in only 12 percent of the years between 1960 and 1985, but since then there have been “hot years” 48 percent of the time.
For bumblebees specializing in just a few species, this was bad news. There were simply too few flowers to go around. So bees with shorter tongues, which are better able to make use of the broader diversity of short-tubed flowers, did better and gradually came to dominate the peaks.
The speed with which the bees adapted over just 40 years “is a really significant finding,” said Kerr. If other bumblebees are adapting in similar ways, “there’s a prospect that bee populations facing climate change can evolve to some degree to not suffer the negative impacts.”
In the long run though, the long-tubed flowers may be the big losers and, said Cameron, “This is not trivial.”

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