A new study using bumblebees has found that the sweetest nectar is not necessarily the best: too much sugar slows down the bees. The results will inform breeding efforts to make crops more attractive to pollinators, boosting yields to feed our growing global population.
Bumblebees drink nectar from flowers, then offload it in their nest – by vomiting – for use by other bees in the colony. The sugar within nectar makes it appealing, and the more sugar within the nectar, the more energy it contains. But nectar also gets more thick and sticky as the sugar content rises, and this makes it more difficult for bees to drink and regurgitate – requiring more time and energy.
Published in the Journal of the Royal Society Interface, the study looked at the mechanics of both nectar drinking and regurgitation in one of the most common bumblebees in the UK, Bombus terrestris. It found that the best concentration of nectar for bumblebees in terms of overall energy gain is lower than might be expected. Nectar that is low in sugar is easy for bees to drink and very easy to vomit back up. As nectar gets more sugary, it gradually takes bees longer to drink, but swiftly becomes much more difficult to vomit.
“Bumblebees must strike a balance between choosing a nectar that is energy-rich, but isn’t too time-consuming to drink and offload. Nectar sugar concentration affects the speed of the bees’ foraging trips, so it influences their foraging decisions,” said Dr Jonathan Pattrick, first author of this study, formerly a PhD student based jointly in the University of Cambridge’s departments of Plant Sciences and Zoology and now a post-doctoral researcher in the University of Oxford’s Department of Zoology.
This new information will help scientists make better predictions about which types of nectar bumblebees and other pollinators should like best, and consequently the kinds of flowers and plants they are most likely to visit. This will inform crop breeders in producing the most appealing flowers for better crop pollination and higher yields.
Current crop breeding is focused on enhancing traits like yield and disease resistance, rather than considering pollinator preference. The new results improve predictions of the perfect nectar concentration for making the most efficient use of pollinating bumblebees.
Nectar is produced by flowers to attract pollinators, and a source of food for many species of insect, bird and mammal. The levels of the sugars sucrose, glucose and fructose within the nectar vary depending on the plant producing it.
“Studies have shown that numbers of some pollinators are going down, but there are more and more people in the world to feed. We need to make better use of the pollinators we have,” said Professor Beverley Glover in Cambridge’s Department of Plant Sciences and Director of Cambridge University Botanic Garden, who led the study. “This research will help us understand the types of flowers and plants the bees are most likely to visit, which will inform crop breeding to make the best use of the available pollinators.”
This research was funded by the Biotechnology and Biological Sciences Research Council (BBSRC).
Find out more on the University of Cambridge website.