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Friday, July 6, 2012

Flower color is shaped by bees

Australia has been geographically isolated from the other continents for over 34 million years. And yet, the flowering plants of Australia display similar colors and reflectance as their North American counterparts. According to Adrian Dyer and his colleagues from RMIT University, Monash University and the Swedish Museum of Natural History, it may be the discriminating eyes of bees that have driven that example of parallel evolution.

Bees (order hymenoptera) have trichromatic vision, meaning that their eyes contain three types of photoreceptors (cone cells) just as ours do. Unlike humans, who have blue, green and red cones, bees have blue, green and ultraviolet photoreceptors. This means that the vision of bees is shifted toward the ultraviolet compared to ours. Bees can best discriminate colors with wavelengths of about 400 and 500 nm.


Silverweed (Potentilla anserine)
Left: human vision; Right: bee vision.
Credit: Norwegian scientist-cameraman Bjorn Roslett

As you may have surmised, the majority of both North American and Australia flowers have colors that peak at either 400 or 500 nm. This makes perfect sense if you consider that it’s in the plants best interest to be as attractive as possible to its chief pollinators. Although flowers evolved around 125-130 million years ago, well before Australia went its lonely way, for much of that time flowers were not brightly colored as they are today. By the time flowers began to evolve colors, the Australian flora was no longer in contact with plants from other regions. They were in constant contact with insects, however.

You can compare human vision to bee vision in the video below.