Scientists, including a member of the university’s Natural Resources Institute, have shown that caffeine improves a honeybee’s memory and could help the plant recruit more bees to spread its pollen.
Publishing in Science, the researchers show that in tests honeybees feeding on a sugar solution containing caffeine, which occurs naturally in the nectar of coffee and citrus flowers, were three times more likely to remember a flower’s scent than those feeding on just sugar.
The Natural Resources Institute’s Professor of Plant Chemistry Phil Stevenson, who co-authored the paper, says: “Caffeine is a defence chemical in plants and tastes bitter to many insects including bees, so we were surprised to find it in the nectar. However, it occurs at a dose that’s too low for the bees to taste, but high enough to affect bee behaviour.”
Study leader Dr Geraldine Wright, Reader in Neuroethology at Newcastle University, explains that the effect of caffeine benefits both the honeybee and the plant. “Remembering floral traits is difficult for bees to perform at a fast pace as they fly from flower to flower and we have found that caffeine helps the bee remember where the flowers are,” he says.
In the study, researchers found that the nectar of Citrus and Coffee species often contained low doses of caffeine. They included ‘robusta’ coffee species, mainly used to produce freeze-dried coffee and ‘arabica’ used for espresso and filter coffee. Grapefruit, lemons, pomelo and oranges were also sampled and all contained caffeine.
The effect of caffeine on the bees’ long-term memory was profound, with three times as many bees remembering the floral scent 24 hours later and twice as many bees remembering the scent after three days.
Dr Wright adds: “This work helps us understand the basic mechanisms of how caffeine affects our brains. What we see in bees could explain why people prefer to drink coffee when studying.”
Dr Julie Mustard, a contributor to the study from Arizona State University, explains further. “Although human and honeybee brains obviously have lots of differences, when you look at the level of cells, proteins and genes, human and bee brains function very similarly, “ she says. “Thus, we can use the honeybee to investigate how caffeine affects our own brains and behaviours.”
This project was funded in part by the Insect Pollinators Initiative, which supports projects aimed at researching the causes and consequences of threats to insect pollinators and to inform the development of appropriate mitigation strategies.
Population declines among bees have serious consequences for natural ecosystems and agriculture, since bees are essential pollinators for many crops and wild flowering species. If declines are allowed to continue, there is a risk to natural biodiversity and crop production.
Professor Stevenson, who also works at the Royal Botanic Gardens, Kew, adds: “Understanding how bees choose to forage and return to some flowers over others will help inform how landscapes could be better managed. Understanding a honeybee’s habits and preferences could help find ways to reinvigorate the species to protect our farming industry and countryside.”
Caffeine in floral nectar enhances a pollinator’s memory of reward. G.A. Wright, D.D. Baker, M.J.Palmer, J.A. Mustard, E. F. Power, A. M Borland, P.C. Stevenson. Science.
BBSRC Insect Pollinators Initiative:
Bee food project at Royal Botanic Gardens, Kew:
Story by Public Relations