This butterfly marks the primary human-caused U.S. insect extinction


It’s been roughly 80 years since the blue Xerces butterfly was last spotted on pastel-colored wings through the California sand dunes. But scientists are still learning about the insect.

New research on the DNA of an almost 100-year-old museum specimen shows that the butterfly was a species of its own. In addition, this find means the blue xerces butterfly (Glaucopsyche xerces) is the first U.S. species of insect known to be extinct by humans, researchers report July 21 in Biology Letters.

The butterfly previously only lived on the San Francisco peninsula. But by the early 1940s, less than a century after its formal scientific description in the 1850s, the paper-thin butterfly was gone. Its rapid disappearance is attributed to habitat and native plant food loss as a result of urban development and possibly an influx of invasive ants, likely to spread through shipping of goods.

But it has long been unclear whether the blue Xerces butterfly was its own species or simply an isolated population of another, more common species of blue butterfly, says Corrie Moreau, an entomologist at Cornell University.

To find out, Moreau and colleagues turned to a 93-year-old Xerces specimen housed in the Field Museum in Chicago, which extracted DNA from a tiny portion of the insect’s tissue. Although the DNA was degraded with age, the team was able to compare selected Xerces genes with those of other closely related blue butterflies. The researchers also compared the genomes, or genetic textbooks, of the insect’s mitochondria – cell structures that are involved in energy production and have their own DNA.

Scientists analyzed DNA from a specimen in the collection of Xerce’s blue butterflies (pictured) at the Field Museum in Chicago to show that the extinct insect was a species of its own. Field Museum

Using the genes and the “mitogenomes”, the researchers created an evolutionary tree that shows how all butterfly species are related to one another. The extinct blue Xerces butterfly was genetically different, which warranted classification as a species, the team found.

“We lost a piece of the biodiversity puzzle that made up the tapestry of San Francisco Bay when this species was critically endangered,” says Moreau.

Akito Kawahara, a lepidopterist at the Florida Museum of Natural History in Gainesville who was not involved in the study, thinks the results are “fairly convincing” that the blue Xerces butterfly was a species in its own right.

The butterfly is considered a candidate for resurrection, says Moreau, where extinct species are brought back through cloning or other genetic manipulation (SN: 10/20/17). But she warns against it. “Maybe we should spend this time, energy, and money making sure we protect the already endangered blues that we know about,” she says.

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One such insect is the critically endangered blue El Segundo (Euphilotes battoides allyni), which is native to the Los Angeles area. He and other butterfly populations are increasingly endangered by numerous threats such as climate change, land use changes and the use of pesticides (SN: 08/17/2016).

For Felix Grewe, evolutionary biologist at the Field Museum, the new insight shows why long-term museum collections are so important: the real usefulness of specimens may only be clear after many years. After all, the genetic techniques used in the study to shed light on the true identity of the blue Xerces butterfly did not exist when the insect became extinct.

“You don’t know what technology is there [will be] In 100 years, ”says Grewe.