Isolated butterfly revealed as new species

Hidden in the wind-swept grasslands of nearby Waterton Lakes National Park, a tiny butterfly has been keeping a big secret.

Long believed to be just another population of the widespread half-moon hairstreak, this delicate insect—confined entirely to the Blakiston Fan—has now been recognized as its own species: the curiously isolated hairstreak (Satyrium curiosolus). Far more than a taxonomic update, this discovery reveals a lineage shaped by 40,000 years of evolutionary solitude—an ancient survivor tucked away in one of Canada’s most iconic and ecologically rich landscapes.

“With its official recognition as a distinct species, the curiously isolated hairstreak is a powerful example of how long-term isolation shapes biodiversity,” said Dr. James Glasier, Conservation Population Ecologist at the Wilder Institute. “But its rarity and extreme specialization also make it incredibly vulnerable—there’s no fallback population to sustain its survival.”

This reclassification is the result of groundbreaking genomic and ecological research—a collaborative effort between the Wilder Institute, Parks Canada and researchers from the University of Alberta, University of Kentucky and University of California, Los Angeles. Recently published in ZooKeys, the research confirms that the butterfly has been genetically and ecologically isolated from its closest relatives for approximately 40,000 years.

Despite surviving repeated glacial cycles, it has remained a distinct evolutionary lineage—both genetically unique and ecologically specialized. The only known population of the curiously isolated hairstreak (Satyrium curiosolus) exists on the Blakiston Fan—an alluvial grassland at the edge of the mountains in Waterton Lakes National Park—over 450 kilometers from any other half-moon hairstreak populations in British Columbia or Montana.

Unlike its relatives, which thrive in sagebrush steppe, this butterfly depends on a different host plant—silvery lupine (Lupinus argenteus)—and has a mutualistic relationship with a specific ant species (Lasius ponderosae), a pairing not seen in other hairstreak populations.

While adult numbers fluctuate seasonally—ranging from 2,200 to 13,000 individuals—genomic analyses reveal critically low genetic diversity and an effective population size of only about 500. This “genomic flatlining” poses a major conservation concern, as it limits the species’ capacity to adapt to environmental change, particularly as the climate shifts across its narrow range.

Conservation options are constrained. Because this species is so genetically distinct, interventions like wild-to-wild translocations from other populations are not viable. Tailored, site-specific strategies will be essential for its survival.

Long-term monitoring by the Wilder Institute, Parks Canada, and other partners is already underway to assess how the butterfly responds to shifting climatic and ecological conditions. Targeted efforts will also be required to mitigate habitat threats such as the spread of invasive plants like spotted knapweed (Centaurea stoebe).

The discovery and designation of the curiously isolated hairstreak (Satyrium curiosolus) adds to a growing list of species revealed through the power of genomics. It highlights the importance of collaboration between researchers, conservationists, and land managers in uncovering hidden biodiversity—and ensuring it endures in special places like Waterton Lakes National Park.

Read the full study: Genomic and ecological divergence support recognition of a new species of endangered Satyrium butterfly (Lepidoptera, Lycaenidae) – A study co-authored by Zachary G. MacDonald, Julian R. Dupuis, James R. N. Glasier, and others, now available in ZooKeys.

Visit WilderInstitute.org to learn more.

Images courtesy the Wilder Institute

Wilder Institute

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