“Sensory drive, color, and color vision”

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Trevor D. Price

The classic example of sensory drive: Two cichlid fish species live at different depths in Lake Victoria, where their colors have evolved to match the prevailing light environments.
(Credit: Oliver Selz and Ole Seehausen)

Without a doubt, the diversity of natural colors greatly enriches our lives. Without a doubt too, exactly why a plant or animal is the color it is remains one of the more vexing and least understood questions in nature. Twenty-five years ago in an article in the American Naturalist, John Endler synthesized research up to that time to argue that both an animal’s color and how an animal sees color are affected by the environment it lives in. But at that time, theory also suggested colors might be present simply because they induce favorable reactions in other members of the species. Much has happened over the past quarter-century. For example, we can make a good case that primates such as ourselves have better color vision than other mammals (especially in the red-green part of the spectrum) because it helped an ancient primate to distinguish edible fruits from green leaves in the rainforest. And following on from that, primates are the most colorful of mammals because their improved color vision allows them to distinguish amongst potential mates or rivals. So one approach to further our understanding might be to ask how and why color vision varies among different related species, and how this is associated with their colors. That is the research program Trevor Price has reviewed in an address appearing in The American Naturalist. It is a challenging yet exciting area. Color vision itself is a remarkably complex trait, with perception of an object’s color changing as the spectrum of background light changes, but staying roughly constant even as the spectrum of the illuminating light varies. However, we are making progress by getting at the nuts and bolts: studying the genes and developmental mechanisms that affect color vision. Opsin proteins in cone cells of the eye affect which wavelengths of light are best absorbed. Across fish and bird species, opsin differences can be explained partly by the color of light the species experiences, and in a few cases, so can color. In another 25 years we may understand why a robin is red and a blue jay blue. Read the Article