"We know that some flowers had evolved spectral signatures to suit bee pollinators, but the story for bird-pollinated flowers was not clear," Adrian Dyer says. (Credit: Andrew Mercer/Flickr)


To attract pollinating birds, flowers go red

Flowers that once relied on insects for pollination have since changed their colors to be attractive to birds, biologists have discovered.

New research has shown that certain Australian native flowers have shifted away from using insects as pollinators and evolved their flower color to the red hues favored by birds.

In a study published in New Phytologist, biologists have shown for the first time that Australian native flowers exclusively pollinated by birds have evolved color spectral signatures that are best discriminated by those birds.

Biologist Adrian Dyer of Monash University and RMIT University says previous studies had shown that flower color evolved to attract bees as pollinators.

“We know that some flowers had evolved spectral signatures to suit bee pollinators, but the story for bird-pollinated flowers was not clear,” Dyer says.

Lead author and graduate student Mani Shrestha of the School of Biological Sciences collected spectral data from over 200 flowering plants and identified the pollinators as birds or insects. Then, with Associate Professor Martin Burd, Shrestha did phylogenetic analyses to identify how the flowers have evolved spectral signatures.

“We found that flowers exclusively pollinated by birds had initially evolved to suit insect vision, but more recently the spectral signature of bird-pollinated flowers had shifted towards longer wavelengths,” Shesthra says.

The research showed that rather than just having any type of red reflection, bird-pollinated flowers targeted the specific wavelengths that best match the long wavelength tetrachromatic (four color) vision of many Australian native birds.

“Bird-pollinated flowers may have evolved red signals to be inconspicuousness to some insects that are poor pollinators, whilst also enhancing the discrimination of bird pollinators,” Shresthra says.

Burd says the work has broad significance for understanding how flower colors have evolved to suit specific pollinators, and how color may continue to evolve in particular environments depending upon the availability of effective pollinators.

“The color cues in Australian flowers would be easily detected by honeyeaters, the most important family of nectar feeding birds in Australia. Hummingbirds in the Americas have similar visual systems to honeyeaters, so we expect to find similar color signals among American flowers,” Burd says.

“But in Asia and Africa, birds with a different type of color vision are the primary avian pollinators. If flower colors in these regions are tuned to the specific capacities of their own birds, we would have strong evidence that we’ve cracked the code that plants use to communicate with birds.”

Source: Monash University

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