Bumblebees make flowers grow bigger and smell sweeter
Gardeners have long known the importance of bees for pollination, but the insects can also help flowers grow bigger and smell more fragrant, scientists have discovered.
Swiss researchers found that plants evolve differently depending on the insect which is pollinating them.
Tests on a type of cabbage species called field mustard, a close relative of oilseed rape, showed that when pollinated by bumblebees, the plants grew three inches taller than with hover flies in just nine generations.
They also flowered a day earlier and had double the fragrance. And when placed on ultraviolet light, they had more colours which bees can see.
“The traditional assumption is that evolution is a slow process,” said Professor Florian Schiestl.
“But a change in the composition of pollinator insects in natural habitats can trigger a rapid evolutionary transformation in plants.”
The change happens because insects differ in their preference for plants. Bees like taller more fragrant plants so will seek out and pollinate those more often than shorter, un-fragranced varieties, causing the bigger, smellier plants to thrive.
Flies, alternatively are not so effective at pollination, and so plants will self-pollinate more often, which slows down the emergence of new traits.
Professor Schiestl said the rapid decline of bee populations in Britain could be leading to flowers that do not grow as abundantly or smell as fragrant. In the long term, it could also reduce the genetic diversity of plants leaving them more susceptible to disease.
Friends of the Earth (FOE) are currently encouraging gardeners to plant bee-friendly gardens ahead of the Great British Bee count in May and June.
Purple and blue flowering plants are best because they are easier for the bees to see, and different species prefer different shapes of flower, so a mix of snapdragons, lavender, heathers, sunflowers, wallflowers, yarrow, and verbena will attract all kinds. They are also drawn to shrubs, trees, fruit, and vegetables as well as spring and autumn flowering bulbs.
“Bees are brilliant pollinators – and this study underlines their importance,” said Friends of the Earth bee campaigner Paul de Zylva.
“Bees aren’t the only pollinator, but many plants will not thrive if they are only visited by other insects, as this new research shows.
“But Britain’s bees are under threat, and we can all do more to help them – such as by growing pollinator-friendly plants, avoiding pesticides and turning gardens and other spaces into bee-friendly habitats.
“And you can check out the bees in your garden, park or neighbourhood by taking part in the Great British Bee Count later this spring.”
Gardeners with lawns are also encouraged to leave dandelions and clover to flower for the bees, and a ‘messy corner’ of old wood and leaves will provide shelter. Chemical pesticides should also be avoided, especially those containing bee-harming neonicotinoid pesticides.
Bee expert Professor Simon Potts from the University of Reading said: “Everyone can help our under-threat bees this Spring. Research has already shown that our towns and cities can be great places for bees – if the right plants are grown in parks and green spaces.
“With a bit of bee-friendly gardening and a bit more tolerance of weeds, we can all help to make sure our streets and neighbourhoods are buzzing with these amazing insects.”