The blue xerces butterfly ( Glaucopsyche xerces) was last seen in San Francisco in the early 1940s and is considered a prime example of an insect species that has become extinct as a result of urban development. However, until now doubts persisted as to whether this butterfly was a species by itself, or was a subpopulation of another widespread species that inhabits the entire west coast of the North American continent.
Now, a study published in the journal Biology Letters confirms that, indeed, the blue xerces butterfly is extinct and that, in addition, we must begin to take the conservation of insects more seriously. The authors of the work analyzed the DNA of a 93-year-old specimen that was in a museum collection and concluded that its genetic material is unique enough to consider G. xerces a species on its own.
“It’s interesting to reaffirm that what people have been thinking for almost a century is true, that this was a species driven to extinction by human activities,” says Felix Grewe, co-director of the Grainger Center for Bioinformatics at Field and lead author of the job.
A job of great precision
The task of extracting the DNA from the specimen kept in the museum was a challenge, since the material was scarce and no sample could be wasted. “Taking the first steps and tearing out part of the butterfly’s abdomen with tweezers was very stressful, because I wanted to protect the material as much as possible,” explains Corrie Moreau, director of the Cornell University Insect Collections. “However, it was also refreshing to know that we could address a question that has been unanswered for almost a hundred years and cannot be answered by any other method.
Once the piece of the butterfly’s body was recovered, the sample went to the Pritzker DNA Laboratory at the Field Museum, where the tissues were treated with chemicals to isolate the remaining DNA. ” DNA is a very stable molecule, it can last a long time after the cells in which it is stored have died, ” says Grewe.
Although DNA is a stable molecule, over the years it also degrades. However, there is DNA in every cell, and by comparing multiple strands of DNA code, scientists can piece together what the original version looked like. “It’s like you made a bunch of identical structures with Legos and then dropped them. The individual structures would break apart, but if you look at them all together, you could figure out the shape of the original structure,” Moreau explains.
Grewe, Moreau and their colleagues compared the genetic sequence of the blue xerces butterfly with the DNA of the more widespread silver blue butterfly, and found that the DNA of the blue xerces was different, meaning it was a separate species.
The importance of conserving our insects
“The blue xerces butterfly is the most iconic insect for conservation because it is the first insect in North America that we know has become extinct due to human factors. There is even an insect conservation society named after it,” Moreau says.
The authors point to the urgent need to protect insects. “We are in the middle of what is called the insect apocalypse: massive declines in these animals are being detected around the world, ” Moreau recalls. “And while not all insects are as charismatic as the blue xerces butterfly, they have huge implications for the functioning of ecosystems. They aerate the soil, allowing plants to grow, and feed herbivores, which in turn feed carnivores. Each loss of an insect has a massive domino effect on ecosystems, ”they warn.
