To the ladies, the spots - waved frenetically by suitors in the fruit fly courtship ritual - connote sex appeal.
To a team of Wisconsin scientists, however, the origin of these decorative spots has proven to be a critical portal to unraveling a long-standing genetic mystery: What is it, exactly, that governs the development and evolution of form? Is it the genes themselves or the devices within DNA that control where genes are used in the making of the animal's body?
The answer, according to the team from the Howard Hughes Medical Research Institute (HHMI) at the University of Wisconsin-Madison, and published this week (Feb. 2) in the journal Nature, is that the heavy lifting of evolution is accomplished through changes in the genetic switches that direct how genes work.
"This is smoking gun evidence of how animal patterns evolve," says Sean B. Carroll, a UW-Madison professor of genetics and the senior author of the Nature paper.
While discovered in flies, it is almost certain that the same mechanisms are at play in all other animals, including humans, and help determine everything from the snout of an aardvark to the stripes of the zebra.
The discovery is important because it provides critical evidence of how animals evolve new features to improve their chances of reproductive success and survival. It is, says Carroll, convincing proof that evolution occurs as accidental mutations create features - a spot here or a stripe there - that confer advantages in attracting mates, hiding from or confusing predators, or gaining access to food. The mutations are preserved, according to the Nature r