It’s able to alter the behavior of tiny marine organisms, change the circulation of the oceans and even prompt walruses to huddle en masse on the Alaskan shore. One possibility is that the bees are just getting smaller. When the summers get hotter, shorter-tongued bees that can drink from a variety of different flowers are thriving compared to bees that need flowers with deep tubes.
Decreased flower populations mean bees in the Rocky Mountains have to search harder for nectar, and can’t be picky when they come across a suitable plant. Certain types of flowers require long tongues for bees to reach the sweet nectar inside. This has many researchers concerned, as the shift could cause a large problem across flower and bee species alike.
“Long tongues are expensive”. To better understand why, a team of researchers studied two species of the bees in Colorado.
This tactic works best when food is abundant.
Those increasing temperatures – 2014 was the hottest year on record, and 2015 is on track to top it – are wreaking havoc on the flower populations, say the scientists.
Nicole Miller-Struttmann is a biology professor at SUNY College at Old Westbury in New York. Flower population declines are cited as the most likely cause of the tongue shortening issue – a sort of very rapid evolution in response to a changing environment.
“We found, on average, about a 24 per cent decrease in tongue length, which is pretty substantial”, says Miller-Struttmann.
In recent years the bumblebees have had to rely more and more on those shorter flowers. Colla, who was not involved in the research, called the news “depressing, as most of the stuff that comes my way is”.
The researchers had several ideas about what might be causing the tongues to shorten – the effects of climate change on floral density was one of their theories, but not the only one.
“They have adapted to diminished resource levels, a major impact of climate change”, writes senior author Candace Galen in an email to the Monitor. According to the researchers, minimum summer temperatures in the mountains they sampled have increased by about 2 degrees Celsius since 1960. It reduced the number of all flowers.
Overall, bee tongues have shrunk by almost 25 percent since the 1970’s. So that takes a lot of resources to grow a tongue that big. How do you measure a bee’s tongue?
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. The economic value of bee pollination services ranges from $10 billion to $15 billion. The results also highlight how climate change can decouple well-established mutualisms between bees and plants. But for now, it’s still unclear how the flowers will be affected.
No evidence of a shrinking body size or competition with invading species was found so these weren’t the reason.
And Richardson added that similar studies should be conducted in other locations to see if the trend holds up.
At first, the scientists figured the flowers were evolving with the bees, as often happens over long time periods in nature, but Miller-Struttmann said that’s not the case. But the bees’ successful adaptation may be the silver lining of a very dark cloud. “That’s true from both the plants’ and the bees’ perspective”.