Butterflies originated in North America after splitting from moths, new study suggests
Akito Kawahara remembers being eight years old when he went on a special tour of the insect collection at the American Museum of Natural History in New York City. He marveled at the vast array of pinned bugs before stopping in front of a large picture of the butterfly family tree.
A number of spots on that tree, he saw, were curiously blank.
"Just looking at it, realizing that scientists at these museums still don't know these basic things — I'll never forget that day," Kawahara says.
That moment sparked a lifelong passion in Kawahara to fill in those blanks and determine where these charismatic insects originated. Now, he's gotten a little closer to an answer. His latest research shows that butterflies probably first flapped their wings in present-day western North America or Central America.
"We were surprised," says Kawahara, now the curator of butterflies and moths at the University of Florida. Before this, "people had thought that butterflies originated somewhere in Asia."
This shift probably took place some 100 million years ago when a rogue lineage of moths moved dayward. The findings, published in the journal Nature Ecology & Evolution, shed light on the origins of this remarkable group of insects that now populate the globe with 19,000 different species.
Butterflies first evolved from moths when they began feeding on the nectar of new species of flowering plants usually available during the day. That shift allowed these insects to shed their earth tones in favor of the riot of colors they're known for today, which often act to attract mates or warn predators that they're poisonous.
Origins of a butterfly scientist
The new discovery about these insects' beginnings is as much an origin story of the world's butterflies as it is of Kawahara.
"And this unusual brown butterfly lands near the road," recalls Kawahara. "My dad said, 'Oh, it's a snout butterfly.' I was like, 'Oh my gosh. I've read about these things, but I've never caught one.' So my hands were trembling. I had my butterfly net in my hand. I ran up to it and I caught it."
That was the beginning of Kawahara's butterfly collection. "I still have that specimen," he says. "And the handwriting from when I was eight years old is on the label. It's a very important specimen for me."
Kawahara split his childhood between Tokyo and New York where, later that same year, his father took him on that fateful trip to the American Museum of Natural History.
"I remember walking through those amazing collections," he says, "and seeing all these butterflies and moths in these drawers."
That family tree he spotted on the office door revealed the gaps in scientists' knowledge that even a wealth of gossamer-winged specimens had yet to fill.
He credits his dad for shaping his life and for inspiring him to turn his passion for these insects into a profession. In the intervening years, those questions of where butterflies first emerged, how they evolved, and how they spread across the world only grew in importance to him.
"There's a lot of butterflies right now that are threatened," Kawahara explains. "And understanding how these butterflies are related to each other, it serves as a framework to help us conserve them."
It's also important for conserving the flowers and plants that rely on butterfly pollination, and the species of birds that depend on butterflies for food.
"When we lose our butterflies, we lose our birds," says Adriana Briscoe, an evolutionary biologist at the University of California, Irvine who wasn't involved in the study.
A worldwide research effort
To piece together that butterfly family tree, Kawahara worked with close to 90 colleagues from six continents to collect DNA from all kinds of butterflies.
"I felt like I was a kid all over again," he says.
He traveled to the Amazon rainforest, the dry savannahs of Mozambique, and back to Tokyo. He climbed the Andes to look for rare species. He even nabbed a yellow sulfur butterfly the size of a silver dollar right outside his office in Gainesville, Florida.
All he and his team needed for the DNA analysis was a tiny portion of one of each butterfly's six legs. "It's not harmful," says Kawahara. "And oftentimes, we can release the butterfly and this butterfly's still okay."
The bulk of the butterflies the research team studied were pinned specimens in museum collections. The oldest one was from 1946, a brown butterfly fringed in white captured in South Africa.
They used four supercomputers to run the genetic analysis of the DNA they'd gathered from 92% of all butterfly groups. And after nearly a decade of work, Kawahara had the family tree that he had been longing for since he was a boy.
This result — combined with knowing where butterflies are found today, plus the age and location of a few rare butterfly fossils — helped him and his colleagues zero in on where butterflies began some hundred million years ago.
"We were able to tell that where the butterflies originated was likely North or Central America," he says. "Conclusively, it's not Asia, it's not Africa, it's not Europe."
When butterflies first evolved, they fed on legumes. They likely then fluttered their way to South America, dispersing in waves across Asia, Australia, India, Africa and finally, 30 million years ago, Europe. This radiation resulted in the kaleidoscope of butterfly species we know today.
"It's an extremely rich view of the movement of butterflies — some of the most beautiful organisms on the planet," says Briscoe. She adds that it'll be worth analyzing the few remaining groups of butterflies that didn't make it into this analysis. "These missing groups," she says, "might help pinpoint where exactly in the Americas butterflies originated."
Briscoe says she has another reason for being excited about these findings.
"More than any other place in the world, butterflies were sacred to the ancient people of Mesoamerica," she says. "They were thought to be the souls of ancestors."
For Kawahara, the ancestor who's front of mind is his father, of course. He told his dad about this project right as it was beginning in 2014. "He told me, 'That's wonderful,'" recalls Kawahara, "and he wished me luck."
That was the last time the two men spoke. His dad died two days later.
Kawahara says that one way he remembers him is through his personal butterfly collection, which now has 20,000 specimens. "It's kind of like your diary," he says. "It's really touching."
Each butterfly is a memory for Kawahara — a moment in time where he can stand beside his dad once again.
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