A new study reveals how bumblebees in high altitude habitats are adapting to the pressures of climate change, and what we can do to help them.
Climate change means bad news for bees. As temperatures in alpine habitats rise across the globe, certain plants stop growing in certain areas. This leaves bees with nowhere to turn for food, and contributes to the massive declines we’ve seen in their numbers in recent years. According to a press release from Eurekalert, however, bees may have a trick up their sleeve to combat the changes in their habitats.
A study from researchers at the University of Missouri-Columbia reveals a fascinating moment in evolution in two species of alpine bumblebees. The study, published in the journal Science, shows that bees have evolved shorter tongues to respond to the decline in flowering plants due to rising temperatures. The research suggests that bumblebees may be more resilient than we initially thought.
According to Candace Galen, a professor of biological sciences at the University of Missouri-Columbia’s College of Arts and Sciences, climate change still poses a major threat to bumblebees. The findings show that it may be possible for bumblebees to adapt if they were given the right conditions – that is, if their habitats are not negatively impacted by environmental contaminants like pesticides.
Bumblebees rely heavily on the flowers and plants in their habitat for survival, as do the plants rely on the bees. Galen and her research team wanted to study how bumblebee populations were holding up in the high altitudes of the Rocky Mountains. They discovered that the length of the bees’ tongues is directly related to the types of flowers in their habitat. Bees with long tongues act as specialists, feeding on flowers with deep tubes that store their nectar. Bumblebees with short tongues, on the other hand, are less picky and will eat the nectar from nearly any flower than can reach.
Galen and her team measured the length of the tongues in alpine bumblebee species that were gathered between 1966 and 1980 in the Central Rocky Mountains that were stored at the University of Colorado and other museums. Between 2012 and 2014, they went back and collected present-day samples of both species and measured their tongue lengths as well.
The comparison revealed that the populations of both species of bumblebees on three specific mountains exhibited a 25 percent reduction in tongue length over the forty-year period.
“A change of 25 percent over this amount of time is dramatic, especially when we take into account that this change has occurred over just 40 generations,” Galen said. “Most evolutionary change occurs on a timescale of a few hundreds, thousands, or millions of years. Forty years is a timescale that happens in a human lifetime.”
The scientists examined the flowers on each of the mountains studied to try and figure out why the bees’ tongues had changed so quickly. They found that there were no changes to the morphology of the deep-tubed flowers that bees with long tongues preferred, but there were simply less of them in the area. These flowers likely enjoyed a cooler climate and were less likely to reproduce and create subsequent generations as the conditions changed.
The team found that despite there being fewer flowers, being a specialist had distinct advantages. When the total flower density in an area drops, the generalists have a much better chance of finding something to eat than the specialists.
Ricardo Holdo, an assistant professor of biological sciences at the University of Missouri, specialist populations only hold up if there is a sufficient food supply mixed in with the rest of the local flora. As resources become less available, the specialist bees are hit much harder than the generalists. “It shows that the change in the flower population is actually exerting a selective pressure on the pollinator,” he says.
With this information, bee management becomes a clearer task. Keeping habitat destruction and pesticide use to a minimum and planting companion plants that can keep floral communities diverse can have a significant impact on protecting bees that otherwise seem able to adapt to changes in their environment. Or as Galen puts it, “Giving bumblebees ‘running shoes’ in this race against climate change.”