Bumblebee tongues getting shorter because of climate change: Study


Global warming and climate change impact vegetation and wildlife and one such region where the effect is prominently visible is alpine habitats where there has been a noticeable decline in flowering among indigenous plants and this in turn has led to decline in population of several bumblebee species prevalent in those regions.

However, nature takes its course with adaptation and evolution and according to a new study by researchers at the University of Missouri, two alpine bumblebee species have responded to climate-induced decline in flowering by evolving shorter tongues.

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.

Researchers have long known that there is a direct relationship between length of tongues of bumblebees and the flowering plants of the region. Those with longer tongues are classified as “specialists” bees as they can feed on deep, long tubes, while those with short tongues are known as “generalists” and tend to play the role of pollinators.

The best way to analyse if there has been a change in tongue sizes over the course of years is to compare measurements taken a few decades earlier with current ones. To achieve that Galen and her colleagues measured the tongue lengths of alpine bumblebee species collected between 1966 and 1980 at three alpine sites of the central Rocky Mountains and archived at the University of Colorado and other museums.

To get the latest measurements, the team resurveyed the same bumblebee species in the alpine locations between 2012 and 2014.

The findings were surprising as they noticed that in just 40 years, the length of tongues of two bumblebee species had decreased by nearly 25 per cent.

Galen explains that a change of 25 per cent over a short period of 4 decades and over just 40 generations is startling because most evolutionary changes occur over a course of few hundred years or even thousands or millions of years.

When they investigated the flowers which bumblebees frequented, they found that there has been no change in the structure of the flowers, but they had become less prolific. Overall, they found that the total food resources available to alpine bumblebees had fallen by 60 per cent since the 1970s.

The research doesn’t say that the climate change isn’t having a negative impact on bumblebees, but it does provide “a glimmer of hope” for bumblebees. Researchers say that if we can manage human-induced negative aspects such as pesticides, and habitat destruction, we can help bumblebees by providing them with enough time to evolve and adapt to the climate change.

“We are not saying climate change isn’t a problem for bumblebees–it is a major problem,” said Galen. “However, these findings indicate that some bumblebees may be able to adapt if provided adequate habitat, and are largely shielded from environmental pollutants, such as pesticides.”