The last of the Xerces blue butterflies floated in the air in San Francisco in the early 1940s. Now they can only be seen in museum windows.
These pearly-winged periwinkle insects lived in the coastal sand dunes along San Francisco and were first characterized by scientists in 1852. When urban development swept through this part of California, the sandy soils were disrupted. . This caused a ripple effect, wiping out the species of the plant used by Xerces caterpillars. The habitat change was too great for the Xerces blue butterfly, and the species became extinct.
“The Xerces Blue Butterfly was the first insect in the United States that has been documented to be driven to extinction by human activities,” said Corrie Moreau, director of the Cornell University Insect Collection, Martha N. and John C Moser professor of arthropod biosystematics and biodiversity at Cornell, and author of a new study on the Xerces butterfly.
“Habitat conversion and urban development have caused the loss of this species. The Xerces Blue Butterfly has become an icon of insect conservation. In fact, the world’s largest insect conservation organization even bears the name of this species.”
But scientists have long wondered if Xerces was a separate species, or if it was a subspecies or just an isolated population of another type of butterfly, the silvery blue that lives in the western United States and Canada.
Moreau, who began working on it as a researcher at the Field Museum in Chicago, and her colleagues turned to museology to answer the question.
The new study published Tuesday in the journal Biology Letters.
“Museomics is the use of museum collections for genome sequencing and other analytical techniques that could not even be imagined when the majority of museum specimens were collected,” Moreau said. “What makes this so revolutionary is that we can answer questions that cannot be answered otherwise. This study is a great example of that because we can’t go after the Xerces Blue Butterfly and the only way to answer genetic questions about this species is by turning to museum collections. “
The Field Museum houses several specimens of the Xerces blue butterfly. Moreau and his colleagues therefore decided to extract the DNA of a 93-year-old butterfly specimen from the museum’s collection and see if it met the conditions for belonging to a single species.
How do you extract DNA from a pinned butterfly that is nearly a century old? Very carefully, using pliers. Moreau was able to recover the DNA after pinching a tiny part of the insect’s abdomen.
“It was scary, because you want to protect as much of it as possible,” Moreau said. “Taking the first steps and removing part of the abdomen was very stressful, but it was also a little exhilarating to know that we could maybe answer a question that has been unanswered for almost 100 years and that cannot be answered. answer otherwise way. “
The Field Museum also includes the Grainger Bioinformatics Center, which has the ability to sequence and analyze DNA.
“DNA is a very stable molecule, it can last a long time after the cells in which it is stored have died,” said Felix Grewe, lead author of the study and co-director of the Grainger Bioinformatics Center, in a statement.
The study team were able to recover enough strands of DNA to compare it to the DNA of the Silver Blue butterfly and determine that the Xerces Blue butterfly was a distinct species – and that humans indeed caused it to become extinct. .
“It’s interesting to reaffirm that what people have believed for almost 100 years is true, that this was a species brought to extinction by human activities,” Grewe said. “When this butterfly was collected 93 years ago, no one was thinking of sequencing its DNA. That’s why we have to keep collecting, for researchers 100 years into the future.”
Next, the researchers want to understand whether this species, which was considered genetically diverse, has experienced a decline in diversity as it neared extinction. This could be a contributing factor to its premature end.
The team was able to collect enough genetic information to prove that Xerces was a unique species, but it was not enough to resuscitate the butterflies, the researchers said. And there are many factors to consider before trying to bring a species back through de-extinction.
“While I know there are some people who are potentially interested in resuscitating this species, I think we have a long way to go before we can actually do that,” Moreau said. “It would not only take significant time and financial resources to recapitulate its genome, but also to establish the required host plants for the native symbiotic larvae and ants. In this time of global insect decline, I would prefer our resources to be devoted to saving these already endangered species or protecting their critical habitat.
Meanwhile, other butterflies are in decline, such as the El Segundo blue, due to the loss of its sand dune habitat, and the Karner blue due to the loss of the blue lupine flower that its caterpillars use. , according to Moreau.
“Before we start putting a lot of effort into the resurrection, let’s put that effort to protect what’s there and learn from our past mistakes,” Grewe said.
The researchers noted that we are in the midst of what many scientists are calling the insect apocalypse as species decline around the world – something humans have made a big contribution to.
“The current ‘insect apocalypse’ is truly a death by a thousand cuts,” Moreau said. “Pesticide use, land use modification and climate change are probably the main factors behind these global insect declines and all are due to human activities. I think he’s in. our interest in trying to mitigate as many of them as possible from every species on the planet is important. “
Insects are more essential to our lives than most people realize, the researchers said. While not all of them are as pretty or eye-catching as the Xerces Blue Butterfly, they aerate the soil and help with plant growth, which feeds everything else.
“As insects are essential for any ecosystem, the loss of a given species has ripple effects across the community,” said Moreau.
“As we can see in these examples above, the interconnection of species, from mutualists to food plants to habitat requirements, can have huge impacts on the survival of a species. honestly, without bugs our planet would become inhospitable to humans in a matter of months. We need bugs even though we don’t always realize them. “