PUBLIC RELEASE DATE:

8-Sep-2014

Contact: Layne Cameron Layne.Cameron@cabs.msu.edu 517-353-8819 Boston University http://www.twitter.com/BostonUNews

A well-known biologist once theorized that many roads led to Rome when it comes to two distantly related organisms evolving a similar trait. A new paper, published in Nature Communications, suggests that when it comes to evolving some traits especially simple ones there may be a shared gene, one road, that's the source.

Jason Gallant, MSU zoologist and the paper's first author, focused on butterflies to illustrate his metaphorical roadmap on evolutionary traits. Butterfly wings are important biological models. While some butterflies are poisonous and notify their predators via colorful wing markings, others are nontoxic but have evolved similar color patterns to avoid being eaten.

Many scientists, including the famed Ernst Mayr, favored the "many roads" theory. This was largely attributed to being unable to identify a shared gene for such traits. Gallant, Sean Mullen, co-author and Boston University biologist, and their collaborators, however, were able to pinpoint the single gene responsible for two different families of butterflies' flashy markings.

The North American and South American species last had a common ancestor more than 65 million years ago. So, rather than evolve these traits independently using two unique mechanisms, the genetic control of particular butterfly markings can be traced to a single gene present in their ancient ancestors, said Gallant, who also teamed with Arnaud Martin and Bob Reed from Cornell University, and Marcus Kronforst from the University of Chicago.

"This result represents the culmination of a decade's worth of effort, but we identified the mechanism for a single aspect of wing patterns in a lineage," Gallant said. "Is this the rule or the exception? For simple traits, it's beginning to look like it could be the rule. The jury is still out on complicated traits, but there may be fewer roads leading to Rome than we once thought."

The decade-long journey began as a butterfly mapping study and later involved the 30,000 genes that comprise white admiral butterflies and red-spotted purple butterflies in North America. They are the same species of butterflies, but to a common observer, they look completely unrelated.

In the southern United States, the red-spotted purples have dark-blue wings that mimic the poisonous pipevine swallowtail. The white admirals, with distinctive white bands on their wings, reside in northern climes where the swallowtail is not found. A hybrid of the two can be found in a region near Pennsylvania.

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A single evolutionary road may lead to Rome

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