More than a century ago, a blue butterfly flew among the sand dunes of the Sunset District in San Francisco and laid its eggs on a plant called deerweed. As the growth of the city overtook the mounds and deer, the butterflies also disappeared. The last Xerces blue butterfly was collected from Lobos Creek in 1941 by an entomologist who would later lament that it had killed one of the last surviving members of the species.
But was this butterfly really a unique species?
Scientists can all agree the dire fate of Xerces Blue – the first butterfly to go extinct in North America due to human activities – was a loss to biodiversity. But they were divided over whether Xerces had its own distinct species, a subspecies of the widespread silver blue butterfly Glaucopsis ligdamus, or even a separate population of silver blues.
This may sound like a scientific quibble, but if the Xerces blue had not actually been a genetically distinct lineage, it would not technically have actually been extinct.
Now, researchers have sequenced the nearly complete mitochondrial genome of a 93-year-old museum specimen, which suggests that Xerces blue was a separate species, which they say can be properly named Glucosyceae xerces, according to a report published Wednesday. According to the paper. biology paper.
“This shows how important it is to not only collect specimens, but to protect them,” said Cory Morrow, director and curator of Cornell University Insect Collections and an author on the paper. “We can’t imagine how they’ll 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 “suggesting and very exciting”, but added that such research may have limitations because “what makes Two organisms that are different species are not always directly addressed with genetic information.”
dr. kapan is working on a separate genomic project With Revive and Restore on Xerces Blue butterflies and close relatives, a non-profit initiative to restore extinct and endangered species through genetic engineering and biotechnology.
Researchers began working on the project several years ago, when Dr. Morrow was at the Field Museum in Chicago. He and Felix Grave, who is now director of the Grainger Bioinformatics Center’s phylogenomics initiative at the museum, sifted through the museum archives of Xerxes blue butterflies to find the least damaged specimen, which would theoretically yield the best-preserved DNA .
“You’re grinding up a piece of an extinct butterfly,” said Dr. Morrow. “You only get one chance.”
Dr. Morrow removed a third of the butterfly’s abdomen, the body part filled with muscle, fat and other tissue, and sequestered it. This old DNA breaks down into smaller pieces. Historically, researchers would sequence by cutting long, unbroken stretches of DNA and gluing them back together. But new sequencing technology allows researchers to work with previously harvested, fragmented DNA. “We just skipped that step,” Dr. Gravey said.
After recovering their sequences, the researchers examined publicly available data from other related butterfly specimens.
Their mitochondrial DNA sequences did not appear to be identical. He suggested that Xerces blue was a separate species and that two other butterflies traditionally considered subspecies of the silver blue butterfly – the Australis and Pseudoxers clades – may also be separate species, and Xerces blue’s closest living relatives. can.
These results are surprising, as those two butterflies are found in Southern California, a far cry from Xerxes Blue’s original home on the San Francisco Peninsula.
The sequencing of the new paper focused on the CO1 barcoding mitochondrial gene. The researchers said mitochondrial DNA is an excellent alternative to older museum samples because a single cell contains many more copies of the mitochondrial genome than the nuclear genome. Mitochondrial DNA is inherited from the mother, whereas nuclear DNA is inherited from both parents.
But the CO1 gene represents a “very small sample of the genome,” Dr. Kapan said, adding that he doesn’t think the new paper has definitively settled the species debate.
At the California Academy of Sciences, Athena Lamm, a genomics researcher, Dr. Kapan and others want to shed light on where Xerces falls on the evolutionary scale, Dr. Lam said.
This type of genomic study, Dr. This, Kapan said, could reveal where populations of living species in the Glaucopsis genus could be found that could be suitable for a possible re-introduction of San Francisco’s sand dunes. According to the new paper, good candidates to investigate would be Australis or Pseudoxar, the latter of which has wings that recall the brilliant blue color of Xerces.
Dr Moro said he hopes the new study sheds light on blue butterflies that are currently endangered, such as the El Segundo blue, which lives in coastal sand dunes in Southern California, and the Kerner blue, which is commonly found in Wisconsin. Found where wild lupine grows.
And though the Xerces blue is long gone, the deer once in need of it have recently been replicated in the sand dunes at the Presidio, something familiar awaits the future butterfly.