'Curiously isolated' butterfly species discovered in Waterton Lakes National Park

Tucked away in Waterton Lakes National Park, little greyish brown butterflies — long thought to be just another population of the half-moon hairstreak butterflies — are now being recognized as their own species known as Satyrium curiosolus, or the curiously isolated hairstreak.

The pollinator lives exclusively across approximately 300 hectares of the prairie-grassland landscape of the Blakiston Fan, the park's largest alluvial fan — flat areas where flowing mountain streams have deposited sediment.

And its territory is located more than 450 kilometres away from any of its relative populations in British Columbia or Montana, according to the Wilder Institute/Calgary Zoo, a partner in the study.

Zachary MacDonald, co-first author alongside Julian Dupuis of a new study published in the biodiversity research journal ZooKeys, said the new species is an exciting discovery, but what comes next is even more so.

"This is just the tip of the iceberg," said MacDonald, La Kretz and NSERC postdoctoral fellow at the University of California. "I think what's most interesting to us is what do we do about the conservation of this highly endangered species now?"

Using genomic tools, the researchers assembled the entire DNA sequence of the individual insects collected from Blakiston Fan.

The resulting sets of genomes — along with ecological evidence — were used to determine the curiously isolated hairstreak was both genetically and ecologically removed from its closest relatives up to 40,000 years ago.

James Glasier, a conservation population ecologist and co-author of the study, said that when the Wilder Institute and Parks Canada began looking at this butterfly population, they didn't go into it expecting to discover a new species.

"When we kind of went through those five years doing all the research, we found out that it has a lot more unique traits than we thought," he said. "And so it's great. It makes it an endemic, unique species to Alberta and Canada."

Named quite literally for its curiosity-provoking isolation in the Blakiston Fan, MacDonald said the curiously isolated hairstreak's genome indicates it has always been small with a wingspan of an inch to an inch and a half (2.5 to 4 centimetres).

While other hairstreak populations have gone up and down in size over time (due to factors like the last ice age), the newly recognized butterfly "basically flatlined through time, and so it's been very small and very isolated for tens of thousands of years," he explained.

On the outside, the new species looks much like its closest relative, the half-moon hairstreak. But unlike the half-moon hairstreak, which thrives in sagebrush steppe, the newly identified species relies on silvery lupine as its host plant to develop larvae and for caterpillars to feed on.

They also have an interesting mutual relationship with a particular species of ant (Lasius ponderosae). The curiously isolated hairstreak caterpillars excrete a sugary substance called honeydew for the ants to eat, while the ants protect the caterpillars from parasites and predators.

When disturbed or when the temperature is too hot, the caterpillars retreat into ant galleries, according to the study. Adult females have been seen laying their eggs near the entrances of ant colonies, right under the silvery lupine plant.

MacDonald said the study's use of genomics — the study of an organism's genome — allowed the researchers to answer questions they couldn't quite get at before.

With a small effective population of about 500 individuals, the insect's genomic analysis revealed extremely low genetic diversity and exceptionally high levels of historic inbreeding, according to the study.

"You would assume that inbreeding depression is going to drive this thing to extinction," MacDonald said. "But this population has been very small for a very long time, and slow inbreeding has basically allowed it to get rid of its bad genes."

Arthur Shapiro, an entomologist and professor emeritus of evolution and ecology at the University of California, who was not involved in the study, said the research is "one more case where the genetics tells the story more dramatically than the morphology." He said this bolsters scientists' conviction that "there is more going on out there than may be superficially evident."

"Decisions about species status used to be predicated almost entirely on morphology," he explained in an email. "Nowadays, genomics is of equal, if not overriding, importance."

Glasier said the population's low genetic diversity poses a major concern for conserving the endangered species as it limits the butterfly's capacity to adapt to environmental change — especially the consequences of a warming climate like increased wildfires.

He said the Wilder Institute, in partnership with Parks Canada, is already monitoring the population to see how it responds to changing conditions.

Another challenge they're trying to tackle is invasive spotted knapweed, which threatens the quality of the butterflies' habitat in the Blakiston Fan.

In the longer term, Glasier said the organizations are potentially looking at captive rearing. That means bringing some butterflies under human care and releasing them back into either their natural habitat or finding them another home within the park to start up a secondary population.

"We have found a few places where we expect them to potentially survive, and so we're looking at potentially, in the future, releasing them there to spread the population out and allow for them to kind of expand a bit so that there's backup populations in the future," he said.

Glasier said the challenge to conserve the curiously isolated hairstreaks is "definitely a puzzle" as they work on finding the best ways to protect the endangered species, but he feels optimistic about a "positive outcome."