In 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.”
(edited version of University of Bristol press release)
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