Famous Blue Butterfly: Still Extinct, But More Distinctive

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More than a century ago, a bluish butterfly flew between the sand dunes of San Francisco’s Sunset District and laid its eggs on a plant known as stagweed. As the city’s development grazed the dunes and deer, the butterflies disappeared. The last Xerces blue butterfly was collected by an entomologist from Lobos Creek in 1941 and would later lament that it had killed one of the last living members of the species.

But was this butterfly really a unique species?

Scientists can agree that the dire fate of the Xerces blue, the first butterfly known to become extinct in North America due to human activities, is a loss to biodiversity. But they were divided over whether Xerces had a distinctive species, a subspecies of the common silvery-blue butterfly Glaucopsyche lygdamus, or even just an isolated population of silvery-blues.

This may sound like a scientific pun, but technically it wouldn’t really be extinct if the Xerces blue weren’t actually a genetically distinct lineage.

Now, researchers have sequenced a nearly complete mitochondrial genome of a 93-year-old museum specimen; This suggests that Xerces blue is a different species, which they say could be correctly called Glaucopsyche xerces, according to an article published Wednesday. Biology Letters.

“This shows how critical it is not only to collect specimens but to preserve them,” said Corrie Moreau, director and curator of the Cornell University insect collection and author of the paper. “We can’t even imagine how it will be used 100 years from now.”

Durrell Kapan, a senior research fellow at the California Academy of Sciences who was not involved in the research, said he found the new findings “important and very exciting”, but added that there may be limits to this type of research. Two organisms, different species, cannot always be directly addressed with genetic information.”

Dr. a closing separate genomic project On Xerces blue butterflies and their close relatives with Revive & Restore, a nonprofit initiative to restore extinct and endangered species through genetic engineering and biotechnology.

Researchers began working on the project a few years ago by Dr. It started when Moreau was at the Field Museum in Chicago. He and Felix Grewe, now director of the phylogenomics initiative of the Grainger Center for Bioinformatics at the museum, scoured the museum archives of Xerces blue butterflies to find the least damaged specimens that would theoretically produce the best preserved DNA.

Dr. “You’re grinding off a piece of an extinct butterfly,” Moreau said. “You only have one chance.”

Dr. Moreau removed and sequenced the one-third of the butterfly’s abdomen, a body part filled with muscle, fat, and other tissues. This ancient DNA breaks down into short pieces. Historically, researchers sequenced long, uninterrupted DNA sequences by breaking them apart and putting them back together. But the new sequencing technology allows researchers to work with already chopped, fragmented DNA. Dr. “We’re skipping this step,” Grewe said.

After recovering their sequence, the researchers analyzed publicly available data from other related butterfly specimens.

Mitochondrial DNA sequences did not look similar. They suggested that the Xerces blue is a separate species and that two other butterflies traditionally believed to be subspecies of the silvery blue butterfly – australis and pseudoxerces clades – may be different species and the closest living relatives of the Xerces blue.

These results are surprising because these two butterflies are located in Southern California, a long way from the Xerces blue’s original home on the San Francisco Peninsula.

The sequencing of the new paper focused on the CO1 bar-encoding mitochondrial gene. Mitochondrial DNA is an excellent option for older museum specimens because a single cell contains many more copies of the mitochondrial genome than the nuclear genome, the researchers said. Mitochondrial DNA is inherited from the mother and nuclear DNA from both parents.

However, saying that the CO1 gene represents “a very small sample of the genome”, Dr. Kapan added that he thinks the new article does not definitively resolve the genre debate.

Dr. Lam, a genomics researcher at the California Academy of Sciences, Athena Lam, Dr. Kapan and others said they want to shed light on where Xerces falls on the evolutionary scale.

Dr. Such genomic studies could reveal where populations of surviving species in the genus Glaucopsyche may be found, Kapan said, making it well-suited for potential re-entry into the sand dunes of San Francisco. Good candidates to investigate might be australis or pseudoxerces, which have wings reminiscent of Xerces’ bright blue hue, according to the new paper.

Dr. Moreau said he hopes the new study will shed light on currently endangered blue butterflies, such as the El Segundo blue, which lives in coastal dunes in Southern California, and the Karner blue, which is most commonly found in Wisconsin. wild lupine grows.

And while the Xerces blue is long gone, the deer grass it once needed has been recently replanted in the sand dunes at the Presidio, and a somewhat familiar future butterfly awaits.

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