Scientists have today 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.
Study leader Dr Geraldine Wright, Reader in Neuroethology at Newcastle University, UK, explained 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.
"In turn, bees that have fed on caffeine-laced nectar are laden with coffee pollen and these bees search for other coffee plants to find more nectar, leading to better pollination.
"So, caffeine in nectar is likely to improve the bee's foraging prowess while providing the plant with a more faithful pollinator."
In the study, researchers found that the nectar of Citrus and Coffea 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.
Co-author Professor Phil Stevenson from the Royal Botanic Gardens, Kew and the University of Greenwich's Natural Resources Institute, UK, said: "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."
The effect of caffeine on the bees' long-term memory was profound with three times as many bees remembering the floral s
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