It's been about 80 years since the last sighting of the Xerces blue butterfly flitting about on pastel wings across coastal California sand dunes. However, scientists are still learning more about insects.
According to new DNA research from a nearly century-old museum specimen, the butterfly was a distinct species. The Xerces blue butterfly (Glaucopsyche xerces) is the first U.S. insect species known to have gone extinct as a result of humans, according to a study published July 21 in Biology Letters. Scientists have strong suspicions that humans were responsible for the extinction of some insects, such as the Rocky Mountain locust (Melanoplus spretus). But there was no doubt in this butterfly's mind at the time.
The butterfly was once restricted to the San Francisco Peninsula. The gossamer-winged butterfly, however, had vanished by the early 1940s, less than a century after its formal scientific description in the 1850s. Its rapid extinction is attributed to the loss of habitat and native plant food as a result of urban development, as well as a possible influx of invasive ants spread via goods shipment.
According to Corrie Moreau, an entomologist at Cornell University, it has long been unclear whether the Xerces blue butterfly was its own species or simply an isolated population of another, more widespread species of a blue butterfly.
Moreau and colleagues used a 93-year-old Xerces specimen housed at Chicago's Field Museum to find out, extracting DNA from a tiny piece of the insect's tissue. Despite the DNA being degraded due to age, the researchers were able to compare certain Xerces genes to those of other closely related blue butterflies. The researchers also compared the genomes, or genetic instruction books, of the insects' mitochondria — cellular structures that produce energy and have their own set of DNA.
|Scientists determined that the extinct insect was a distinct species by analyzing DNA from a specimen in the Field Museum's collection of Xerces blue butterflies (shown). The Field Museum
The researchers created an evolutionary tree using the genes and "mitogenomes," showing how all of the butterfly species are related to one another. The team discovered that the extinct Xerces blue butterfly was genetically distinct enough to be classified as a species.
"When this species was driven to extinction, we lost a piece of the biodiversity puzzle that made up the tapestry of the San Francisco Bay area," Moreau says.
Akito Kawahara, a lepidopterist at the Florida Museum of Natural History in Gainesville who was not involved in the study, believes the findings are "fairly convincing" that the Xerces blue butterfly is a distinct species.
According to Moreau, the butterfly is a candidate for resurrection, which involves resurrecting extinct species through cloning or other genetic manipulations (SN: 102017). However, she advises against it. "Perhaps we should spend that time, energy, and money ensuring that we protect the blues that are already endangered that we are aware of," she suggests.
The endangered El Segundo blue (Euphilotes battoides allyni), which is native to the Los Angeles area, is one of these insects. Climate change, land-use changes, and pesticide use are among the many threats facing it and other butterfly populations (SN: 81716).
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The new discovery, according to Felix Grewe, an evolutionary biologist at the Field Museum, demonstrates why long-term museum collections are so important: The true utility of specimens may not be clear for many years. After all, the genetic techniques used in the study to reveal the true identity of the Xerces blue butterfly did not exist when the insect went extinct.
"You don't know what technology will be available in 100 years," Grewe says.
Museum genomics reveals the Xerces blue butterfly (Glaucopsyche xerces) was a distinct species driven to extinction, according to F. Grewe et al. Biology Letters. doi:10.1098/rsbl.2021.0123, online July 21, 2021.