After weeding those variables out, the researchers reported that the climate change was most likely the cause of the bees’ tongue length evolution. You’re probably not thinking of a bumblebee, flitting about an alpine meadow with a shorter-than-average tongue.
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Since the bumblebees feed on the wildflowers that have been dwindled because of climate, the bumblebees do not need their long tongues any more.
A team led by Nicole Miller-Struttmann of the University of Missouri in Columbia studied several high-altitude sites in Colorado where two species of long-tongue alpine bumble bee – Bombus balteatus and B. sylvicola – are the main flower-feeding insects.
More broadly, the authors said these bees could help shed light on how climate change disrupts the mutually beneficial relationship between insects – as well as long-tongued critters like bats and hummingbirds – and their hosts. They found that tongue length, between both species, has declined by 24.4 percent in all, or about 0.61 percent each year. The scientists performed their research by measuring the bee’s tongues from different times: bees gathered around 50 years ago, taken from various museum selections, and bees collected in the recent years.
As the climate warms, their homes near the peaks of the Rocky Mountains have fewer flowers than before. Other bee species who may have migrated to the region do not compete with the long-tongued bees for access to the deep-tubed flowers. So, the bumblebees had to go to other flowers in search of food. Researchers assume bumblebees could have pollinized flowers with longer tongues, as well, but that wouldn’t have been energy efficient for them. “If there had not been that historical record, we would have completely missed that these bees might have been evolving”, notes Jeremy Kerr, an ecologist at the University of Ottawa in Canada, who was not involved with the work. Since 1985, fully half of the summers are too hot for abundant flowering.
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The heat itself is certainly not a factor in diminishing the size of their tongues, but evolution is. Furthermore, as the planet continues to warm, bee tongues will continue to shrink, 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. “It suggests that these bees may have an especially low effective population size and that they could have been through an evolutionary bottleneck, allowing very rapid change in these traits”. The bodies of bumblebees in the United States are quickly adapting to the changing climate. Bumblebees with long tongues are often referred to as “specialists” because they specialize on a certain species of flower with a deep corolla while shorter tongued bees are generalists because they can visit a wide range of flowers.
