This summer’s heatwave could have been bad for British bumblebees, according to a new analysis that studied collections of long-dead bees held in museums.
Bumblebees have endured nearly a century of stress, possibly due to warmer, wetter conditions, the research shows, but new DNA techniques may help focus future conservation efforts.
Researchers from Imperial College London and the Natural History Museum joined four other Scottish and English museums to analyze their bumblebee collections and look for variations in body shape.
When bumblebees are stressed, it has an impact on their developing offspring. Their bodies, particularly the wings, become asymmetrical. By correlating the level of asymmetry in four bumblebee species with climate records from the last 120 years, the researchers found that stress appears to be related to climatic conditions.
“When conditions were warm and relatively humid, stress was higher,” says Dr Richard Gill of Imperial College London, who led the study.
Climate change was already known to be having an impact on the geographic distribution of some bumblebees, but this is the first study to show its potential impacts on insects that lived in the past.
“Museum specimens are almost like little time machines tracking that stress,” says Dr Gill.
The researchers found that for the species they studied, stress levels were lowest around 1925. Since then, there has been a general increase in stress levels, with higher levels found in years that were wetter and warmer than the average.
It’s not clear why things started to change around 1925, according to the research team. One possibility is that it is related to changes in agricultural practices and pesticide use that are known to have led to insect declines in the latter part of the 20th century.
That is pure speculation, Dr. Gill emphasizes. However, a parallel study also published today could help identify threats to bumblebees and broader insect declines by extracting DNA from museum specimens.
Borrowing techniques used to study ancient DNA from people like Neanderthals and woolly mammoths, Professor Ian Barnes of the Natural History Museum was able to recover genetic data from dry, dusty collections of bumblebees.
Taking just one leg from around 100 bee specimens, his team was able to reconstruct long-dead bee genomes, a highly valuable tool compared to the genetic code of bees living today.
“A genome constitutes a large amount of information about a past situation,” says Professor Barnes.
By comparing historical data on things like weather, pesticide use, and land-use changes with bee genetics at the time, researchers can see how bee populations responded or identify whether particular species were more vulnerable to change than others.
“We can look for changes in diversity or signs of adaptation,” says Dr. Gill. “It could reveal things we can’t see on the outside of a bee.”
Getting a picture of how bees dealt with stress in the past could help focus conservation efforts in the future, according to the researchers.
The work also highlights the importance of museums for prospective research.
“These museums have all the secrets, it’s just about unlocking them,” says Dr. Gill.