No great surprise: We really don’t understand how plants and pollinators communicate with one another, but we’re learning. We do know that bees “see” flowers differently and use a number of perceptions to identify good nectar and pollen sources. In this UK study, the researchers specifically looked at iridescence—think of the iridescent sheen of a CD rom or Japanese beetle. They devised a way to test trained Bombus terrestris bumblebees (not shown in the photo) to “perfectly” iridescent flowers.
Turns out that perfection disrupted their ability to tell differences between flowers, especially when they used underlying flower colors very close to one another in the blue/purple ranges. Bees had an easier time identifying separate flowers when the underlying colors were opposite one another: Red compared to blue, for instance. The bees also had fewer problems telling flowers apart when the iridescent was imperfect.
The authors write that iridescence is used by plants to draw pollinators from afar, but it’s relatively rare and when it does appear, generally is confined to only certain parts of the flower. They speculated that it may be “used in conjunction with other flower features like floral surface structures that provide a secure grip for pollinators” and that there may be a trade-off between features that enhance a pollinator’s pollination experience “and those that enhance floral detectability.” Imperfect iridescence may be a balance to attract pollinators while not calling out too much attention for foragers seeking to eat the plant.
“On each foraging trip a bee will usually retain a single search image of a particular type of flower,” co-author Beverly Glover said in Science Direct, “so if they find a blue flower that is rich in nectar, they will then visit more blue flowers on that trip rather than hopping between different colors.
“If you watch a bee on a lavender plant, for example, you’ll see it visit lots of lavender flowers and then fly away – it won’t usually move from a lavender flower to a yellow or red flower.”
If you’ve ever watched bumblebees work an inflorescence on Agastache foeniculum, for instance, they move deliberately, in sequence, like it’s a job. The next time I’m observing a bumblebee work a plant, it’ll be with fresh eyes looking for faint gleams of light caused by imperfect iridescence and studying the petal texture to see how it may be structured to assist visiting pollinators.
Flowers tone down the iridescence of their petals and avoid confusing bees Executive Summary with author quotes in Science News. https://www.sciencedaily.com/releases/2016/02/160225135708.htm
Full paper: Flower Iridescence Increases Object Detection in the Insect Visual System without Compromising Object Identity, Open Access article in Current Biology.
NewTerrain March 16, 2016.