DNA extracted from a preserved 93-year-old Xerces blue butterfly confirms it is first known insect to go extinct from urbanization in the US.
The butterfly, with stunning, iridescent periwinkle wings, was last seen in San Francisco in the early 1940s, but urban development wiped out the plant the Xerces caterpillar would eat, leading to the butterfly’s demise.
Scientists had long wondered if Xerces was an extinct species or part of a subspecies of butterflies called slivery blue.
Using the same DNA analysis, a team of scientists led by Field’s Grainger Bioinformatics Center compared the genetic sequence of the Xerces blue butterfly with the DNA of the more widespread silvery blue butterfly, and found that the Xerces blue’s DNA was different – confirming it was its own species.
The butterfly with stunning, iridescent periwinkle wings was last seen in San Francisco in the early 1940s, but urban development wiped out the plant the Xerces caterpillar used that led to the butterfly’s demise
Felix Grewe, co-director of the Field’s Grainger Bioinformatics Center and the lead author of the Biology Letters paper on the project, said in a statement: ‘It’s interesting to reaffirm that what people have been thinking for nearly 100 years is true, that this was a species driven to extinction by human activities.’
The Field’s Grainger Bioinformatics Center is home to hundreds of preserved Xerces blue butterflies, which allowed scientists from Cornell University Insect Collections to conduct a DNA analysis.
Corrie Moreau, director of the Cornell University Insect Collections, who began work on the study as a researcher at Chicago’s Field Museum, said: ‘There was a long standing question as to whether the Xerces blue butterfly was truly a distinct species or just a population of a very widespread species called the silvery blue that’s found across the entire west coast of North America.’
Using forceps, Moreau and her colleagues pinched off a tiny piece of the abdomen of a butterfly collected in 1928.
The Field’s Grainger Bioinformatics Center is home to hundreds of preserved Xerces blue butterflies, which allowed scientists from Cornell University Insect Collections to conducted a DNA analysis
‘It was nerve-wracking, because you want to protect as much of it as you can,’ Moreau recalled.
‘Taking the first steps and pulling off part of the abdomen was very stressful, but it was also kind of exhilarating to know that we might be able to address a question that has been unanswered for almost 100 years that can’t be answered any other way.’
The sample was then sent to the Field Museum’s Pritzker DNA Laboratory, where the tissues were treated with chemicals to isolate the remaining DNA, allowing scientists to compare it with the DNA from a silvery butterfly.
The study’s findings have broad-reaching implications.
‘The Xerces blue butterfly is the most iconic insect for conservation because it’s the first insect in North America we know of that humans drove to extinction. There’s an insect conservation society named after it,’ said Moreau.
Using the same DNA analysis, a team of scientists led by Field’s Grainger Bioinformatics Center compared the genetic sequence of the Xerces blue butterfly with the DNA of the more widespread silvery blue butterfly, and found that the Xerces blue’s DNA was different – confirming it was its own species
‘It’s really terrible that we drove something to extinction, but at the same time what we’re saying is, okay, everything we thought does in fact align with the DNA evidence.
‘If we’d found that the Xerces blue wasn’t really an extinct species, it could potentially undermine conservation efforts.’
Moreau also touched on the urgency to protect insects.
‘We’re in the middle of what’s being called the insect apocalypse— massive insect declines are being detected all over the world,’ she said.
‘And while not all insects are as charismatic as the Xerces blue butterfly, they have huge implications for how ecosystems function.
‘Many insects are really at the base of what keeps many of these ecosystems healthy.
‘They aerate the soil, which allows the plants to grow, and which then feeds the herbivores, which then feed the carnivores. Every loss of an insect has a massive ripple effect across ecosystems.’