Butterfly tree of life reveals an origin in North America

About 100 million years ago, a group of moths with legume-eating caterpillars started flying during the day rather than at night. That chance event led to the evolution of all butterflies.
 
Before reaching these conclusions, researchers from dozens of countries assembled the world’s largest butterfly tree of life using DNA from more than 2,000 species representing all butterfly families and 92% of genera. Using this framework, they traced the movements and feeding habits of butterflies through time in a four-dimensional puzzle that led back to North and Central America. According to their results, published in the journal "Nature Ecology and Evolution," this is where the first butterflies took flight.

For senior author David Lohman, associate professor of biology at The City College of New York, the project was a long time coming.

“We live in the age of ‘big data,’ and this revolution has impacted biodiversity science profoundly,” said Lohman. "The problem is that comprehensive, global datasets only exist for vertebrates and a few plant groups. Insects are about half of all species, but there were virtually no ‘big data’ for bugs.”

There are over 19,000 butterfly species, and piecing together their evolutionary history required information about their modern distributions and associated host plants.

To kick-start the massive task of assembling data needed for a global analysis, Lohman assembled a core team of researchers from Georgetown, Harvard, Yale, and the University of Florida. From there, they recruited colleagues from all over the globe to form a network of butterfly biologists called “ButterflyNet.” With the collective expertise of these 80+ scientists from 28 countries, they set about amassing the biological data and samples into central repositories.

The team concluded that butterflies first appeared somewhere in western North America. 

Once they became established around the globe, butterflies quickly diversified alongside their host plants. 

The ButterflyNet team extracted records of caterpillar diets from their database to explore the relationship between plants, insects, and evolution.

“Among other conclusions, we were able to support a longstanding hypothesis that legumes (the pea and bean family) were eaten by the ancestor of all butterflies.”

In summary, Lohman said, “This study demonstrates the power of international teamwork and cooperation. Not only have we learned much about the evolution of a large and charismatic insect group, but we now have datasets and an evolutionary framework for butterflies that will stimulate  additional global studies on their biology and conservation.”

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Jay Mwamba
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e: jmwamba@ccny.cuny.edu