DNA from a 93-year-old specimen shows the Xerces blue was its own species, not just a subgroup
The extinct Xerces blue butterfly (shown) is the first U.S. insect species known to go extinct because of people, a study finds.
It’s been roughly 80 years since the Xerces blue butterfly was last spotted flitting about on pastel wings across coastal California sand dunes. But scientists are still learning about the insect.
New research on DNA from a nearly century-old museum specimen shows that the butterfly was a distinct species. That finding means that the Xerces blue butterfly (Glaucopsyche xerces) is the first U.S. insect species that scientists recognized went extinct because of humans, researchers report July 21 in Biology Letters. There are insects that went extinct earlier, like the Rocky Mountain locust (Melanoplus spretus), that scientists have strong suspicions that humans were to blame for the extinction. But for this butterfly, there was no question at the time.
The butterfly used to live only on the San Francisco Peninsula. But by the early 1940s, less than a century after its formal scientific description in the 1850s, the gossamer-winged butterfly had vanished. Its rapid disappearance is attributed to the loss of habitat and native plant food as a result of urban development and, possibly, an influx of invasive ants likely spread though the shipment of goods.
But it’s long been unclear if the Xerces blue butterfly was its own species, or simply an isolated population of another, more widespread 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 at Chicago’s Field Museum, extracting DNA from a tiny bit of the insect’s tissue. Despite the DNA being degraded from age, the team could compare selected Xerces genes with those of other closely related blue butterflies. The researchers also compared the genomes, or genetic instruction books, of the insects’ mitochondria — cellular structures involved in energy production that have their own set of DNA.