It’s cold. There’s extreme weather.
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As flower populations shrink, bumble bees are forced to broaden their diet and, at the same time, compete with shorter-tongued bees that are have started encroaching on their turf. But if the trend holds true, it represents an instance of surprisingly rapid evolution in the bees.
Entomologists and botanists get teased about traveling the world, meeting interesting insects and plants, and then killing them. “So if there isn’t any major benefit to having that long tongue, then it’d behoove the colony to have bees with shorter tongues that can visit the greater diversity of things that are out there”. The length of the corolla tubes of the majority of flowers that bees feed on has shortened in response to the higher temperatures produced byclimate change.
The warmer summers have reduced the number of the deep flowers. On one of the mountains in the study, between 1960 to 1985 only 12 percent of the years were hot enough to reduce flowering. There were simply too few flowers to go around.
Decline in indigenous flowering plants is evident in alpine regions and to check how this decline could have impacted bumblebees, Candace Galen, a professor of biological sciences in the MU College of Arts and Science, and her colleagues were motivated to study how the bumblebee species of Rocky Mountains were coping. What did that mean for bees?
Authors Jessica Kettenbach and Elizabeth Hedrick monitoring plant density on Niwot Ridge Long Term Ecological Research Site, Colorado.
Over 95 percent of bees in the study regions between 1966 and 1980 were just two species of “long-tongued” bees.
But long tongues come with a cost: they take extra energy to grow and can be cumbersome for feeding on shorter flowers. She and her colleagues believe the bees’ tongues are shrinking to allow them to be more generalized when it comes to the flowers they visit, giving them a wider range of food sources to choose from.
Mutualism is an evolutionary concept that shows that two species can evolve simultaneously to produce advantages to each species.
Bees collected from 2012 to 2014 were different, though.
Why are bee populations declining?
Hunting down the reason for the dramatic change in a body part of the bees, the scientists have honed on the warming summers. The entire community of bumble bees changed. “Thus, even with gains of a few thousand flowers on the summit, total food resources for alpine bumble bees on Pennsylvania Mountain have fallen by 60% since the 1970s”, researchers say. How do you measure a bee’s tongue?
“We found, on average, about a 24 per cent decrease in tongue length, which is pretty substantial”, says Miller-Struttmann.
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Galen first thought bee tongues were getting shorter because the insects were getting smaller.
