It’s been about 80 years since the Blue Heron butterfly was last seen on pastel wings across California’s coastal sand dunes. But scientists continue to learn about the insect.
New research into the DNA of a museum specimen nearly a century old shows that the butterfly was a distinct species. What’s more, that discovery means that the Blue Butterfly Herons (Glaucopsyche herons) is the first insect species in the United States to become extinct because of humans, researchers report July 21 in Biology Letters.
The butterfly lived only on the San Francisco Peninsula. But in the early 1940s, less than a century after its formal scientific description in the 1850s, the gossamer-winged butterfly had disappeared. Its rapid disappearance is attributed to the loss of native plant habitat and food as a result of urban development and possibly the influx of invasive ants that had probably spread through the shipment of goods.
But it has long been unclear whether the Xerces blue butterfly was its own species or simply a population isolated from another more widespread blue butterfly species, says Corrie Moreau, an entomologist at Cornell University.
To find out, Moreau and his colleagues went to a 93-year-old Xerces specimen housed in the Chicago Field Museum, extracting DNA from a small piece of insect tissue. Although DNA was degraded from age, the team could compare selected sherry genes with those of other closely related blue butterflies. The researchers also compared the genomes, or genetic instruction books, of insect mitochondria: cellular structures involved in energy production that have their own set of DNA.
Using genes and “mitogenomes,” the researchers developed an evolutionary tree, showing how all species of butterflies are related to each other. The team found that the extinct blue heron butterfly was genetically distinct, so it justified its classification as a species.
“We lost a piece of the biodiversity puzzle that made up the carpet in the San Francisco Bay Area when this species was led to extinction,” Moreau says.
Akito Kawahara, a lepidopteran at the Florida Museum of Natural History in Gainesville who did not participate in the study, thinks the results are "quite convincing" that the blue sherry butterfly was its own species.
The butterfly is considered a candidate for resurrection, according to Moreau, where extinct species are brought back through cloning or other genetic manipulations (SN: 20/10/17). But she warns against it. “Maybe we should spend that time, energy and money on making sure we protect the blues we’re already in danger of knowing,” he says.
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One of these insects is the endangered blue elephant (Euphilotes battoides allyni), 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 pesticide use (SN: 17/08/16).
For Felix Grewe, an evolutionary biologist at the Field Museum, the new discovery illustrates why long-term museum collections are so important: the true usefulness of specimens may not be clear for many years. After all, the genetic techniques used in the study to illuminate the true identity of the Blue Butterfly Xerxes did not exist when the insect became extinct.
“You don’t know what technology (will be) in 100 years,” Grewe says.