MADISON - How the elephant got its trunk, the deer its antlers and the rattlesnake its rattles may seem like disparate questions of developmental biology, but the origins of these novelties, according to the genes of butterflies, may have much in common.
Writing in this week's edition (Jan. 22) of the journal Science, scientists from the Howard Hughes Medical Institute at the University of Wisconsin-Madison describe a genetic trick that helps explain the staggering diversity of patterning and color exhibited on butterfly wings. The same trick, the scientists suggest, is widely used among animals and may be one of the underlying mechanisms that helps explain how new morphological characteristics -- from teeth and tortoise shells to fur and feathers -- arise through the course of evolution.
"The origin of new morphological characters is a long-standing problem in evolutionary biology," write molecular biologists David N. Keys, David L. Lewis and Sean B. Carroll in a paper that may help explain how unique bits of body architecture are added long after an animal's basic body has evolved.
The new insight into how animals acquire "novelties" was derived from comparisons of the wing-making genes of fruit flies and two very different species of butterflies, one from North America and one from East Africa. By tracing the genetic circuits that govern the development of wing shape and coloration, the Wisconsin scientists discovered that butterflies, instead of inventing new genes for color, simply reuse a part of the wing-building genetic circuit to turn on enzymes that produce the pigments responsible for wing decoration.
In the big scheme of animal evolution, according to Keys, a graduate student in
Carroll's lab, the decoration of a butterfly's wing is a much more recent
invention than the building of the wing itself: "Evolution, somewhere along the
line, took this system and came up with a way to reuse it in an entirely new
context while maintaining it
Contact: Sean B. Carroll
University of Wisconsin-Madison