Researcher explores cautionary tale of landscape genetics

Western Science // Special to Western News

Over time, Biology professor Nusha Keyghobadi has developed an affinity for the beautiful Rocky Mountain Apollo butterflies who share size and flight behavior with the more common Cabbage White, but possess creamy coloring punctuated by distinctive red and black spots.

After a brief frenzy of summertime mating, the Rocky Mountain Apollo is well into winter hibernation in Kananaskis Region, Alberta. Fertilized eggs that will become next summer’s adult butterflies are quietly incubating in a connected constellation of pristine alpine meadows dotting the mountain range in at an elevation of 2,000 metres, just above the treeline. If it’s a good winter, they will hatch in June, metamorphose into winged adults, forage for food, and mate. By late August, they will die.

It’s a short life for the Apollo, but this very brevity makes the species a perfect bellweather for the ‘one-two punch’ of climate change and habitat loss that is threatening to wipe out all species – including humans.

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Winter 2002 started off warm in Kananaskis Region without much snow. Then the temperature dropped dramatically to minus-30 degrees. In spite of a normal breeding season, the alpine butterfly population was decimated. Researchers couldn’t find any adult butterflies in some meadows the next summer. Even populations that fared best still declined by almost 60 per cent.

Despite the massive and sudden decline, the butterfly population was back in full force without any loss of genetic diversity in just two years.

The big question was, why?

“Movement between patches saved the whole system,” said Biology professor Nusha Keyghobadi, who is currently leading the genetic component of a longitudinal study that spans almost 20 years.

She explained the connected spaces between meadows acted like a highway, allowing butterflies to move easily between patches, share their genes, and rapidly rebound. “Connectivity gave the whole system a degree of resilience, clearing the way for a genetic rescue effect.”

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It’s rare that a researcher gets the opportunity to return to her roots. Keyghobadi started researching the Rocky Mountain Apollo butterfly in Kananaskis Region, Alberta, for her PhD thesis.

Today, she is back on the project with a host of compelling questions still to answer. “It’s a great system to study because of its spatial structure of semi-connected populations,” she said. “How habitat affects genetics is what’s really driving me.”

Each summer, groups of five to 10 students swarm the butterfly’s habitat to conduct mark-recapture studies. They trek up the mountain daily to established patch locations, capture adults with a net as they wake with the warming sun, and write a three-letter code on their wings with a magic marker.

“It’s very low-tech,” Keyghobadi laughed. “But no butterflies are harmed.”

Various teams of student researchers from Western, the University of Alberta and the University of Cincinnati have monitored the adult butterfly patterns since 1995. The beauty of such a long study is the depth of the data and the opportunity to crunch it with new tools.

“Now we can take this long-term data on movement and population cycles, and apply new genetic tools,” Keyghobadi said. “We are getting a really expansive view of how changes in landscape affect the ongoing genetic diversity of a species.”

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Fast-forward 10 years, same butterfly species, same location. As average temperatures continue to rise due to climate change, graduate student Maryam Jangjoo is discovering the butterfly highway is rapidly disappearing, and the genetic rescue effect along with it.

Jangjoo is currently researching another population collapse in 2010, when the butterflies experienced similar conditions to 2002. Armed with almost 20 years of data on the Kananaskis Region Apollo, Jangjoo can see that climate change is having two distinct effects on this system. First, winter weather is becoming more variable, making the conditions that caused the 2002/2003 crash more common, and second, the tree line is moving uphill, cutting off easy access between meadows.

Without immigration and the critical gene flow that goes with it, the butterfly population simply isn’t recovering as easily as it did in 2003.

“During the first half of field camp this summer, there were large numbers of butterflies in most patches,” she explains. “But by the second half, the population had shrunk dramatically. During the last two days, I couldn’t even find a butterfly.”

As average temperatures go up, natural highways between meadows will eventually close altogether, impacting connectivity, genetic diversity, and the fate of the entire species.

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A cynic might say, oh well, who cares about a few less pretty butterflies?

But Keyghobadi is quick to point out that the processes affecting the butterflies are affecting us too.

“Our entire planet is facing more variable weather conditions and all species will experience more violent demographic ups and downs. At the same time, we are destroying and fragmenting habitats,” she said. “If you lose connectivity between populations, you lose genetic diversity.”

Keyghobadi says that creatures with short lifespans and connected habitats present the perfect storm for research into the combined effects of climate change and habitat loss.

“The time-and-spatial scale at which insects work allows us to see patterns faster than in polar bears, for example, even though they’re more visible,” Keyghobadi said. “It’s not just the independent actions of climate change or habitat loss, it’s the combination that is potentially devastating.

“We’re losing biodiversity.”

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Biodiversity loss has direct implications for all species. Keyghobadi explains that we are increasingly in danger of losing ecosystem services, those processes that occur in healthy, diverse environments and provide us with food, clean water, and clean air, essentially for free.

She cautions that we’re also in danger of creating ideal conditions where other, less beneficial species, can flourish. And once the system is out of balance it will take a very long time to stabilize, if ever.

What is happening now with the butterflies is a glimpse into our own future.

“We don’t have all the answers, we don’t have the timeline, but if human actions continue to warm up the earth, life on our planet is about to get a whole lot more precarious.”