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Butterfly tree of life reveals an origin in North America [ufl.edu]:

About 100 million years ago, a group of trendsetting moths started flying during the day rather than at night, taking advantage of nectar-rich flowers that had co-evolved with bees. This single event led to the evolution of all butterflies.

Scientists have known the precise timing of this event since 2019, when a large-scale analysis of DNA [pnas.org] discounted the reigning hypothesis that pressure from bats prompted the evolution of butterflies after 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, published today in the journal Nature Ecology and Evolution [nature.com], this is where the first butterflies took flight.

[...] 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.

[...] 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 the Isthmus of Panama, but butterflies had little difficulty crossing the strait between them.

[...] Once butterflies had become established, they quickly diversified alongside their plant hosts. By the time dinosaurs were snuffed out 66 million years ago, nearly all modern butterfly families had arrived on the scene, and each one seems to have had a special affinity for a specific group of plants.

"We looked at this association over an evolutionary timescale, and in pretty much every family of butterflies, bean plants came out to be the ancestral hosts," Kawahara said. "This was true in the ancestor of all butterflies as well."

Journal Reference:
Kawahara, A.Y., Storer, C., Carvalho, A.P.S. et al. A global phylogeny of butterflies reveals their evolutionary history, ancestral hosts and biogeographic origins [open]. Nat Ecol Evol 7, 903–913 (2023). https://doi.org/10.1038/s41559-023-02041-9 [doi.org]

Original Submission