Bees use invisible heat patterns to choose flowers

beeIn the hidden world of flower-pollinator interactions, heat can act not only as life-sustaining warmth, but can also be part of the rich variety of sensory signposts that flowers use to provide advertisement and information for their insect pollinators.

The majority of flowers examined, including many common in gardens, such as poppies and daisies, had complex patterns of heat across their petals, echoing the colourful patterns that we see with our own eyes.

On average these patterns were 4–5°C warmer than the rest of the flower, although the patterns could be as much as 11°C warmer.

We made artificial flowers that copied these heat patterns, but did not include the corresponding colour patterns.

While these artificial flowers look identical to human eyes, and we are not able to tell them apart, it is a different case for foraging bumblebees.

Bumblebees, who visit a wide range of different flowers, were found to be able to use these patterns to distinguish between different flowers and the rewards that they provide.

The study’s lead author, Dr Heather Whitney, from the University of Bristol’s School of Biological Sciences, said: “The presence of multiple cues on flowers is known to enhance the ability of bees to forage efficiently, so maximising the amount of food they can take back to sustain the rest of their colony.

“Climate change might have additional previously unexpected impacts on bee-flower interactions by disrupting these hidden heat patterns.”

The lead author of this publication, Mike Harrap, is a NERC-funded PhD student based at the University of Bristol. Heather Whitney was funded by the European Research Council.

(edited version of University of Bristol press release)

FURTHER READING

Harrap MJM, Rands SA, Hempel de Ibarra N & Whitney HM (2017). The diversity of floral temperature patterns, and their use by pollinators. eLife 6: e31262 | full text (open access) | dryad dataset | accompanying insight article by Bing & Kessler

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arom’in around the flowers: how bees cope with a smelly environment

beeguest blog by David Lawson

Sensory overload happens to us all. Whether you’re in the centre of town or waiting for a train at a station, sometimes you’re bombarded by a cacophony of noises, images and even smells. Your mind can only do so much to sort out what’s relevant to you or what’s worth ignoring. People talking, music booming, buses passing, announcements blaring out into the air. You hear a phone ring and assume it’s someone else’s, but then you notice the vibrating of the phone in your pocket and know it’s yours. By matching up the ringing of the phone with the vibration, you’re certain that this information is relevant to you.

The environment of a foraging bee can be equally noisy, but not just with sound. These complex floral marketplaces are filled with the smells and colours of various flowers, some of which are more rewarding than others, but just like us and our phones, bees have a similar techniques to find the relevant flowers. In our recent publication in Royal Society Open Science, we have looked into the ways in which bumblebees find flowers while looking for nectar. Using artificial flowers, we recorded how quickly the bees can learn the difference between scented flowers when exposed to environments filled with different scents. We discovered that bees could differentiate between the flowers much faster when the flowers had visual aspects along with their scents.

These findings suggest that the visual aspects of flowers could be used as a backup for the scent of flowers when scent is compromised, ensuring that bees can find the most rewarding flowers in uncertain environments. This helps us understand how bees, and the pollination services they provide, might be affected in a rapidly changing world.

Further reading

Lawson DA, Whitney HM & Rands SA (2017). Colour as a backup for scent in the presence of olfactory noise: testing the efficacy backup hypothesis using bumblebees (Bombus terrestris). Royal Society Open Science 4: 170996 | full text (freely readable open access) | pdf

Bumblebees can tell each other apart using scent marks

We have discovered that bumblebees have the ability to use ‘smelly footprints’ to make the distinction between their own scent, the scent of a relative and the scent of a stranger.

beeBumblebees have the ability to use ‘smelly footprints’ to make the distinction between their own scent, the scent of a relative and the scent of a stranger. By using this ability, bees can improve their success at finding good sources of food and avoid flowers that have already been visited and mined of nutrients by recognising who has been there previously. A study conducted as part of Richard Pearce‘s PhD that shows this has been published in Scientific Reports today.

Bumblebees secrete a substance whenever they touch their feet to a surface, much like us leaving fingerprints on whatever we touch. Marks of this invisible substance can be detected by themselves and other bumblebees, and are referred to as scent marks.

We performed three separate experiments with bumblebees, where they were repeatedly exposed to rewarding and unrewarding flowers simultaneously that had footprints from different bees attached to them.

Each flower type either carried scent-marks from bumblebees of differing relatedness (either their own marks, sisters from their nest, or strangers from another nest), or were unmarked.

We discovered that bees were able to distinguish between these four different flower types, showing that not only can bees tell the marks of their own nest mates from strangers, but also that they can discriminate between the smell of their own footprints and those of their nest mate sisters.

This is the first time it has been shown that bumblebees can tell the difference between their scent and the scent of their family members. This ability could help them to remember which flowers they have visited recently.

Bumblebees are flexible learners and, as we have discovered, can detect whether or not it is they or a different bumblebee that has visited a flower recently. These impressive abilities allows them to be more clever in their search for food, which will help them to be more successful.

This work, published today in Scientific Reports, was funded by the EPSRC, through the Bristol Centre for Complexity Science. This blog posting is an edited version of the University of Bristol press release.

further reading

Pearce RF, Giuggioli L & Rands SA (2017). Bumblebees can discriminate between scent-marks deposited by conspecifics. Scientific Reports 7: 43872 | full text