Mountain ecosystems and their butterflies
Posted on 16 October 2018
Montana State research ties butterfly population to mountain systems ecology
By Denise Hoepfner
BOZEMAN – Mountain ecosystems have a big impact on butterfly populations, researchers in Bozeman say.
Diane Debinski, head of the Department of Ecology in MSU’s College of Letters and Science, has been studying Parnassius clodius butterflies for 30 years, dating back to when she was an MSU graduate student in the late ‘80s.
“What we’re doing is looking at how environmental variations like snowpack and the timing of snowmelt are affecting Parnassius clodius populations in Wyoming and Montana,” Debinski said.
She explained that mountain meadows have high levels of plant diversity and plant productivity that are important to elk, deer and other herbivores, and butterflies and other pollinators also use these meadows, particularly if there are a lot of flowers.
“So, the question is: If the world gets warmer and drier, how are these mountain meadows going to change and how will those changes affect the pollinators?” Debinski said.
Debinski and her collaborators hope to answer that question through their seasonal count of Parnassius clodius, a white, medium-sized butterfly found primarily in high-elevation meadows in North America and Europe, and also in Asia. The research was recently published in the Journal of Insect Conservation and awarded a $50,000 grant from the Disney Conservation Fund.
Debinski explained that insects are good indicators of environmental change because they are numerous and respond quickly to environmental variation — meaning population numbers will fluctuate each year in connection with environmental conditions, such as winter temperature.
“The reason for using butterflies is that they are easily surveyed for population numbers and they are also a good choice of insect with which to tell a conservation story,” she said. “People are interested in butterflies and usually not afraid of them. Because butterflies don’t sting or bite and they are beautiful, they are an effective taxonomic group with which to engage the public.”
Changes in the populations of Parnassius butterflies can serve as an indicator of potential changes in the many other insects which are much less easy to survey or identify, Debinski said. Because insects serve important ecosystem roles as pollinators and food for species higher in the food chain, changes in insect populations could presage changes in other animal and plant populations within the ecosystem.
Each year, Debinski and her research team travel to a roughly 2-mile-wide alpine meadow during the time the butterflies fly — mid-June to mid-July, depending on the weather that year. Their goal is to capture and mark each butterfly so they can estimate the total population.
After a butterfly is netted, the researchers carefully use a permanent marker to number it on its wings then release it unharmed. They do this each day the butterflies are flying.
Debinski said a “good” number can range from 400 to 800 Parnassius butterflies marked in a season, although there have been years the number has been as low as 200. This year, the research team marked 664 individual butterflies.
“If the snow melts early and the caterpillars emerge and then it gets really cold again, that’s when we expect to have a poor population size because we know the caterpillars will die if temperatures get particularly cold — minus 13 degrees Fahrenheit or below,” Debinski said. “This year, the snow stayed around a long time and it was deep snow, so we had a good population size.”
Overall, she said, the Parnassius clodius population in the Tetons is “probably stable,” which makes it a good example of how a population can naturally vary over time. This information is important to conservation efforts to save the genus in other parts of the world, where sister species are threatened due to habitat loss, change in habitat or climate change.
Debinski said they are working to link their findings to what is happening to populations in Canada and Europe. In Europe, she said, the sister species of Parnassiusis listed as “vulnerable” on the International Union for Conservation of Nature’s Red List of Threatened Species.
“In Poland, Parnassius apollo is sort of a mascot of Pieniny National Park and they’re very proud of it,” she said. “This species occurs in Spain, Hungary and Finland and is not doing quite so badly in some of these places, but in many cases there’s an issue of habitat loss and climate change, and people are concerned about the population. So, we’re studying the Tetons primarily because it has a good population size, is easy to get to, and we can go back every year and count how many butterflies there are when they fly.”
One reason for the declining population in other countries, such as Finland and Poland, is agricultural and tree-line encroachment on the butterflies’ habitat, something that doesn’t threaten the Tetons population, Debinski said.
Debinski’s research began in 1987 at MSU under the late Peter Brussard, her former adviser and department head of what was then the Department of Biology. During that time, her work concentrated on Glacier National Park, where she surveyed biodiversity patterns of birds and butterflies. She then began to focus on the hundreds of species of butterflies in the Mountain West, including the 120 or so species that live in the Greater Yellowstone Ecosystem, on which she authored a book.
She returned to MSU in 2017 as department head, in the same office where Brussard once worked, where her research focuses on understanding and predicting species distribution and abundance patterns across the landscape at local and regional scales. Trends in these patterns can become bioindicators of environmental change.
“I’m a conservation biologist, so I study what makes a species rare, and how we can recover those species. I am also interested in whether rarity is influenced by habitat loss, habitat modification, or climate change,” Debinski said. “As a scientist, those are some of the questions I ask.”
Nicol Rae, dean of MSU’s College of Letters and Science, said Debinski’s work has important downstream effects regarding other insect, animal and plant species.
“Professor Debinski’s research on conservation of the butterflies as pollinators in the Greater Yellowstone Ecosystem is especially critical since butterflies can be a significant bellwether for ecosystem changes,” Rae said.