The Evolution of Butterflies

summarized by Bryan Pfeiffer

published in, May 26,2023

Clockwise from upper left: Atala (Eumaeus atala), Canadian Tiger Swallowtail (Papilio canadensis), Little Metalmark (Calephelis virginiensis), Leonard’s Skipper (Hesperia leonardus), Red Admiral (Vanessa atalanta) Sara Orangetip (Anthocharis sara) / All images @ Bryan Pfeiffer

Butterflies: Made in the Americas

Lepidopterists everywhere dropped our butterfly nets and read with glee a new scientific paper¹ tracing the origins and early diet of our most lovely and inspirational insects. I had planned to translate the paper’s science and conclusions, its phylogeny, for you. But among the abundant news coverage of this research, you’ll find a solid explanation from the University of Florida, the academic home of the paper’s lead researcher, Akito Kawahara. Even so, I’ll summarize the results (not the methods) in bullet points below, but not before giving you an angle I never saw in all the news about this research, which is this: 

Beyond its revelations about butterfly evolution, research like this is monumental because it helps write the most magisterial story ever told — the history of life on earth. Study by study, gene sequence by gene sequence, we’re reconstructing how living things came to exist, how they thrived and died millions of years ago, how they related to one another, and how everything that has ever lived also relates to us (even as we ourselves can’t seem to relate civilly and morally with one another).

The story of butterflies begins 300 million years ago, when moths first show up on earth. I’ll summarize what happened next for you in about two minutes of reading:

  • We’ve known for quite some time that butterflies are a lineage of day-flying moths. But what first drove those moths into the light? Bats were prime suspects. Moths that flew by day could visit flowers more safely. From that novel move toward the light, in an absence of bats, evolution gave us butterflies. Or did it?
  • A 2019 paper undermined the bat hypothesis. It found that butterflies split from their mothy ancestors about 100 million years ago. Bats didn’t arrive on the scene until about 50 million years later (after dinosaurs went extinct).
  • The new research, rather than explaining the move toward the light, reveals the location where butterflies first evolved: western North America or Central America — and probably nowhere else on Earth.
  • And like good human children, young butterflies at the time ate their peas. Well, okay, the larvae (caterpillars) of butterflies’ most recent common ancestors were eating peas, by which I mean plants in the family Fabaceae (legumes).
  • From the Americas butterflies spread around the world. Back then, however, the world wasn’t arranged as it is now. One hundred million years ago a supercontinent called Pangaea was in the late stages of breaking apart by way of plate tectonics. The Americas, like the rest of the continents, were going their separate ways. Butterflies did too. (By the way, Pangaea will be the name of my indie rock band if I ever form one; the name of my nascent heavy metal band will be revealed when I write for you about dragonfly sex.)
  • Butterflies spread from the Americas mostly by way of a land bridge at Beringia toward what we now consider east Asia; they also spread toward what we now call Australia, which was situated at the time much closer to what became South America.
  • Once they spread across the tropics, butterflies diversified into some of the most ornate and delightful animals that have ever lived — upwards of 20,000 species transporting joy around the world by way of gossamer wings. So thanks, evolution — we owe you big-time.

[I have no idea what a graphic like this tells us, other than there are a lot of different butterflies, and it makes me feel intelligent to present it as if I am somehow able to understand the governing order of life. Butterflies are very pretty and there are lots of them in The Jungle. SB SM]

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