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Study: Garden diversity key to preserving bumblebees

UK researchers track flower preferences

Bumblebee butt and thistle.

A bumblebee searches for pollen on a thistle bloom. bberwyn photo.

By Summit Voice

FRISCO — Diversity in urban gardens can play a key role in sustaining pressured bumblebee populations, ecologists in the UK said this week, explaining the results of a study that measured bumblebee preferences for both native and non-native plants.

The most common species of bumblebee is not picky about a plant’s origin when searching for nectar and pollen. But other species, including long-tongued bees, favor plants native to the UK and Europe.

“Urban gardens are increasingly recognized for their potential to maintain or even enhance biodiversity,” said Dr. Mick Hanley, an ecology lecturer at Plymouth University. The study showed the continued importance of promoting diversity and encouraging gardeners to cast their net wide when choosing what to cultivate, Hanley said. That diversity will help many pollinating insects that are dwindling as they face habitat loss.

“By growing a variety of plants from around the world, gardeners ensure that a range of food sources is available for many different pollinators. But until now we have had very little idea about how the origins of garden plants actually affect their use by our native pollinators,” he said.

The study, in the forthcoming April issue of the journal Annals of Botany (published by Oxford University Press), set out to examine whether bumblebees preferentially visited plants with which they share a common biogeographical heritage, with researchers conducting summer-long surveys along a typical residential street.

Rather than discriminating between Palaearctic (a range extending across Europe, north Africa and northern Asia) and non-Palaearctic garden plants, bees simply visited plants in proportion to flower availability. Indeed, of the six most commonly visited garden plants, only one – Foxglove – was a British native and only three of Palaearctic origin.

Among individual species, however, there were distinct preferences, with the long-tongued ‘garden bumblebee’ (Bombus hortorum) showing a strong preference for ‘native’ Palaearctic-origin garden plants, choosing them for 78 percent of its flower visits.

Meanwhile, the UK’s most common species – the ‘buff-tailed bumblebee’ (Bombus terrestris) – favoured non-Palaearctic garden plants over species with which it shares a common evolutionary heritage.

“As a general rule, bees will go wherever there are flowers available. However, if native plants were to disappear completely from our towns and cities, the long-term survival of some of our common pollinators like the garden bumblebee could be in jeopardy,” Hanley said.

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One Response

  1. I can often count 7 species all on the same bush in my yard in Northglenn, CO. I keep a huge row of ornamental sage, 2 large beds of lamb’s ear, and sunflowers that spring up volunteer everywhere. I estimate that at any given moment during the season there are thousands of bees in my yard. I use no pesticides or herbicides. I have yet to see the weed that can survive me and a shovel. As you might imagine, I have produce setting on throughout the entire summer season. Feeding the bees is a guarantee of being fed yourself!

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