The Origin of Butterflies: 100 Million Year Evolution

Thursday - May 18 2023, 19:53 UTC - 1 year ago

Roughly 100 million years ago, the pioneer group of moths began foraging during the day instead of night, leading to the evolution of the entire butterfly species. Now, thanks to extensive DNA analysis, scientists have discovered where the first butterflies originated and which plants they relied on for food. It took a massive collaboration between researchers from over dozens of countries to trace the movements and feeding habits of butterflies over 100 million years, leading them to conclude that the first butterflies took flight in North and Central America.

Roughly 100 million years ago, a pioneering group of moths began to venture out during the day instead of night, seizing the opportunity presented by flowers abundant in nectar that had evolved alongside bees. This single event sparked the evolution of the entire butterfly species.

Since 2019, through extensive DNA analysis, scientists have known the precise timing of this evolutionary shift, debunking a previous theory that suggested the rise of butterflies was a result of pressure from bats following the extinction of dinosaurs.

Now, scientists have discovered where the first butterflies originated and which plants they relied on for food.

Before reaching these conclusions, researchers from dozens of countries had to create the world’s largest butterfly tree of life, assembled with DNA from more than 2,000 species representing all butterfly families and 92% of genera. Using this framework as a guide, 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, recently published in the journal Nature Ecology and Evolution, this is where the first butterflies took flight.

For lead author Akito Kawahara, curator of lepidoptera at the Florida Museum of Natural History, the project was a long time coming.

"This was a childhood dream of mine," he said. "It’s something I’ve wanted to do since visiting the American Museum of Natural History when I was a kid and seeing a picture of a butterfly phylogeny taped to a curator’s door. It’s also the most difficult study I’ve ever been a part of, and it took a massive effort from people all over the world to complete." .

There are some 19,000 butterfly species, and piecing together the 100 million-year history of the group required information about their modern distributions and host plants. Prior to this study, there was no single place that researchers could go to access that type of data.

"In many cases, the information we needed existed in field guides that hadn’t been digitized and were written in various languages," Kawahara said.

Undeterred, the authors decided to make their own, publicly available database, painstakingly translating and transferring the contents of books, museum collections and isolated web pages into a single digital repository.

Underlying all these data were 11 rare butterfly fossils, without which the analysis would not have been possible. With paper-thin wings and threadlike, gossamer hairs, butterflies are rarely preserved in the fossil record. The few that are can be used as calibration points on genetic trees, allowing researchers to record the timing of key evolutionary events.

The results tell a dynamic story — one rife with rapid diversifications, faltering advances, and improbable dispersals. Some groups traveled over impossibly vast distances while others seem to have stayed in one place, remaining stationary while continents, mountains, and rivers moved around them.

Butterflies first appeared somewhere in Central and western North America. At the time, North America was bisected by an expansive seaway that split the continent in two, while present-day Mexico was joined in a long arc with the United States, Canada, and Russia. North and South America hadn’t yet joined via th Panama land bridge, effectively cutting off the butterflies from their counterparts to the south.