93-Year-Old Butterfly Is The First US Insect To Go Extinct Because Of Humans

Did humans cause the extinction of the Xerces blue? It seems so – we deserve those butterflies in our tummies. Image credit: Field Museum

Last seen around 80 years ago, the Xerces blue butterfly has been presumed extinct ever since. Its extinction has been considered the first in an American insect species to have been directly caused by humans. But questions have always persisted as to whether it was ever actually its own species to begin with and whether it did in fact go extinct all those years ago. Now, new research has confirmed the species and its extinction, giving credence to the first human-led insect extinction theory.

Published in the journal Biology Letters, the study analyzed the DNA of a 93-year-old Xerces blue butterfly (Glaucopsyche xerces), which had been part of a collection at the Field Museum in Chicago. Enough unique DNA was found to define it as its own, unique species and silence any doubters still questioning this as the first US insect extinction at the hands of humans. "It's interesting to reaffirm that what people have been thinking for nearly 100 years is true, that this was a species driven to extinction by human activities," said Felix Grewe, lead author and co-director of the Field's Grainger Bioinformatics Center, in a statement.

Field Museum butterflies
The collection of Xerces blue at Chicago's Field Museum. Image credit: Field Museum

The Xerces blue, aptly named for its iridescent blue wings, was native to the San Francisco Peninsula and was last seen in the early 1940s, less than a century after it was initially identified and described in 1852. It is believed that growing urban development caused considerable disturbance and habitat loss, ultimately wiping out the butterflies for good.

The confusion surrounding the species and its extinction stems from its similarities to another, very widespread species, known as silvery blue. According to study author and entomologist at Cornell University, Corrie Moreau, the two species share many traits, which had led some to believe that Xerces blue was an isolated population of this broader species.

Fortunately, Moreau had the Field Museum’s extensive collection of Xerces blue at her disposal to help her prove the skeptics wrong. After the “nerve-wracking” process of collecting a sample from the abdomen of a butterfly that was collected in 1928, DNA was extracted and analyzed. Whilst DNA is a notoriously stable molecule, it does still degrade over time. The team, therefore, had to compare DNA fragments from multiple cells to piece the genome together – sort of like a really complicated, micro-scale jigsaw. Or, as Moreau put it: "It's like if you made a bunch of identical structures out of Legos, and then dropped them. The individual structures would be broken, but if you looked at all of them together, you could figure out the shape of the original structure."

Once the genetic sequence had been patchworked together, it was compared against that of the silvery blue butterfly. The two were different enough to finally prove that they are separate species and that, therefore, the Xerces blue had been made extinct. "The Xerces blue butterfly is the most iconic insect for conservation because it's the first insect in North America we know of that humans drove to extinction," said Moreau.

The team’s focus now is on conservation efforts, as opposed to a Jurassic Park-esque resurrection – “let's put that effort into protecting what's there and learn from our past mistakes," said Grewe.

We are currently in the midst of an “insect apocalypse”, meaning it is more vital than ever that we protect other insects from meeting the same fate as the Xerces blue. Not only for their own populations, but for maintaining biodiversity and healthy ecosystems. As Moreau said, insects “aerate the soil, which allows the plants to grow, and which then feeds the herbivores, which then feed the carnivores. Every loss of an insect has a massive ripple effect across ecosystems." Or a butterfly effect, if you will.


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