How the lion got its mane, and the peacock its magnificent tail

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Washington, August 22 : A team of Wisconsin scientists have explained the mechanics of how the male lion got his mane, how the bull moose acquired such an impressive set of antlers, and, how the peacock got its magnificent tail.

The work is an extension of a research about the molecular details of how a simple genetic switch controls decorative traits in male fruit flies and how that switch evolved.

A team led by University of Wisconsin-Madison molecular biologist Sean Carroll described the regulation and evolution of a genetic circuit in fruit flies that permits the male to decorate its abdomen.

The work also shows how the regulation of the same genetic circuit in females represses such ornamentation.

"This study is about the how, not the why," said Carroll, a Howard Hughes Medical Institute investigator. "How can this trait be made in one gender and not the other?" he added.

According to Thomas Williams, a UW-Madison postdoctoral fellow who helped lead the study, the question of the origins of secondary sexual characteristics - traits other than reproductive organs that are peculiar to one gender or another - is one that dominates modern evolutionary biology.

"Males and females basically have the same set of genes, so how do you specifically modify the activity of a male's genes but not a female's genes?" asked Williams.

The answer, according to the new Cell report, resides in the genetic repression of a protein in the male fruit fly that permits it to color the tail end of its abdomen.

"The flies did not need new genes to make a new pattern," said Carroll. "They just changed how males and females use a common set of genes," he added.

The genetic switch that governs expression of the protein is ancient and originally evolved for an entirely different purpose, but over time mutations accumulated, perhaps in response to sexual selection, that drove the evolution of male flies with more colorful derrieres.

"The switch existed for tens of millions of years because it had a different job. But it got remodeled," said Carroll.

"With this particular trait, it evolved by exploiting (genetic) information that was already there to make male bodies different from female bodies," he added.

The same process, Carroll and Williams argue, is at play in animals from humans and elephant seals to fish and beetles.

"These are the most rapidly evolving traits in evolution," said Carroll. "If female tastes change, these traits go away. There is no reinforcement," he added.

ANI

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