Many plants rely on insect pollination to survive, but what can they do to ensure they are visited as frequently as possible?
Ingenious ways flowers attract bees
Honeybees visit flowers to fetch pollen and nectar, so you might think the best option for a flower would be to provide an ample supply of sugary nectar to attract as many bees as possible.
But for pollination to be effective, the flowers need to make sure the bees visit multiple flowers during each trip. This means they must balance the amount of nectar available in each visit. If a bee could fill up in a single visit, then the bee would return to the hive, and no pollination would occur. So volume isn’t the answer; flowers typically provide nectar in small amounts.
Bees are always looking to reduce the effort required to find nectar, so flowers must ensure the nectar is easy to find. But if the nectar is too easy to find, other animals may be tempted to help themselves or eat the whole flower as a sugary snack. And if they make the nectar too hard to find, the bees won’t bother and will go to other flower species; so to make nectar easier to find, some flowers have evolved ultra-violet patterns on their petals to guide the bees to the nectar. But other flowers have come up with more ingenious solutions.
Some flowers, like coffee and citrus, can produce caffeine as part of their defence mechanism. They use it to create a bitter taste, which deters animals from eating the flowers and leaves.
But at some point, the flowers also added caffeine to their nectar.
This seems odd, as why would flowers want to add a bitter taste to their nectar? But evidence suggests that the buzz from the caffeine boosts the bees’ cognitive functions and memory by up to 3 times. And memory is crucial in the pollination process.
The location of nectar is different in every flower species, so to successfully pollinate flowers, bees need to learn how to find the nectar in each flower. And once they have learnt a particular flower, they will typically stick with that species, as switching to a different species means learning a new path to the nectar.
So it’s been proven that the shot of caffeine makes the bees more likely to remember how to find the nectar. The caffeine buzz means the bees will keep visiting the caffeinated flowers for extended periods, which can significantly improve pollination.
The effect of pesticides on bees’ memories
While researching the cognitive functions of bees, scientists have also found that certain pesticides have the opposite effect of caffeine and can impair the bees’ ability to remember. When exposed to typical levels of pesticides used on many farms, as many as 30% of honeybees tested could not perform basic memory tests.
The bees also showed an alarming preference for sugar contaminated with pesticides, which could worsen the problem.
Impaired memory functions affect the bees’ ability to locate, evaluate and communicate information about food to their colleagues. This can quickly lead to colony collapse, as when the experienced foragers start to lose effectiveness, they are assisted by younger bees who try to make up the shortfall. But the younger bees are typically inexperienced and often lack the navigation skills required to return to the hive, and the problem can quickly escalate. This can lead to colony collapse disorder, where beekeepers find their hives mysteriously empty without apparent cause.
Some beekeepers estimate that pesticides contribute to as many as 25-50% of commercial pollinator deaths in a season. They point out that if 25-50% of livestock were lost in any other circumstances, there would be public uproar, but unfortunately, for some reason, people don’t have the same attitude towards bees.
