The Xerces Blue butterfly (Glaucopsyche xerces) is native to the coastal dunes of San Francisco, in the United States. As the city grew, much of the butterfly’s habitat was destroyed and its population moved to Golden Gate National Park. Its wings are a deep iridescent blue, with characteristic white spots on the ventral side.
The last living specimens of the species were found in 1941, by entomologist W. Harry Lange. It is considered the first type of insect to become extinct in historical times. Its disappearance made it a global icon of anthropogenic extinction, to the extent that it was given its name by a famous American conservation association, the Xerces Society.
A previous study in 2022 recovered mitochondrial DNA from a specimen of the Xerces Blue butterfly and compared it to the Silvery Blue butterfly (Glaucopsyche lygdamus), its closest living relative, concluding that they are indeed separate species. and not just different populations.
The research was led by Carles Lalueza-Fox, director of the MCNB and researcher of the IBE (CSIC-UPF), and Roger Vila, researcher of the IBE (CSIC-UPF), with the participation of Tomàs Marquès-Bonet, researcher of the ICREA of the Department of Medicine and Sciences of Life (MELIS) at Pompeu Fabra University and the IBE and Professor at the same university.
Their work, published in eLife, successfully sequenced the genomes of four Xerces Blue butterflies and seven Silvery Blue butterflies between 80 and 100 years old from the Smithsonian Institution in Washington. The researchers concluded that the two species diverged between one and two million years ago and that they represent two distinct evolutionary lines.
A comparison of the genomes of the two species reveals that the DNA of the Xerces Blue butterfly shows a high incidence of inbreeding, a sign of population decline that can be used to identify other insect species that are threatened by the activity. in humans and whose patterns of extinction, unlike those of vertebrates, are currently poorly known. It could also pave the way towards the extinction of this famous butterfly, a project that has interested the scientific community for years.
The Xerces Blue genome reveals the story of its extinction
The results of the research show that the Xerces Blue butterfly has experienced a significant population decline for tens of thousands of years, which may have been caused by climate change that did not affect the Silvery Blue. The destruction of its habitat by humans, however, led to its extinction.
This is the conclusion of the study after finding characteristics of its genome typical of small populations, including low genetic diversity, high chromosomal fragments without genetic variation and high frequency of deleterious alleles, which impair viability. of individuals and made it. what we now call a vulnerable species.
Genomic clues could save other endangered insects
The Xerces Blue butterfly is an icon of insect extinction worldwide. Now its genome can help prevent the extinction of other endangered insects whose rapid population declines are not immediately apparent.
“The identification of endangered mammalian species is easier, because in many cases it is possible to count individuals,” explained Roger Vila, the researcher of the IBE (CSIC-UPF) who accompanied the research.
“However, there are many endangered insects whose status goes unnoticed because it is very difficult to census their populations, which usually seem to us to be very large. However, they can be very sensitive to climate differences and human action, for example, of pesticides. Therefore, we believe that the genomic characteristics that mark the decline of the population of the Xerces butterfly can serve as a warning, and help us to identify vulnerable insects in the future studies.”
Knowing the whole genome is the first step towards extinction
The extinction of insects, especially pollinators, is a serious global ecological problem. The extinction of species such as the Xerces Blue butterfly, using genetic engineering techniques based on CRISPR, is of great interest to the scientific community.
“The Xerces Blue butterfly is an excellent candidate for de-extinction because it is an insect that disappeared very recently, so the ecological impact of its return is reduced, and there is no risk of pests or excess increase due to the limited time of appearance. of adults (between March and April) and their ecological specialization. So we hope that having its complete genome will help in future de-extinction initiatives, “said Carles Lalueza-Fox, a researcher at the IBE (CSIC-UPF) and director of the Natural Sciences Museum in Barcelona,
Toni de-Dios et al, Whole-genomes from the extinct Xerces Blue butterfly help identify a declining insect species, eLife (2023). DOI: 10.7554/eLife.87928.1
Provided by the Spanish National Research Council
Citation: An icon of anthropogenic extinction: Xerces Blue butterfly genome sequenced (2023, July 13) retrieved 13 July 2023 from https://phys.org/news/2023-07-icon-anthropogenic-extinction-xerces-blue. html
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