When we mention global warming victims, most of us would first picture polar bears struggling on melting ice. But to some biologists, insects such as coastal butterflies also belong to the league of conservation icons.
“If you want to know how organisms react to climate change, it is important to find out how insects react to climate change,” said Dr. Jessica Hellmann, conservation biologist at the University of Notre Dame, explaining that most of the multicellular living organisms in our world are insects.
Despite the usual pest control we humans love to implement on bugs, some of them also have a good side. Insects are food sources to species in higher trophic levels and have an economic impact on crops and timber by helping flowers pollinate, which nearly 80 percent of the world’s crop plants need.
Yet, currently these invertebrates have become the hidden sufferers of global warming. As cold blooded organisms, insects cannot regulate their own body temperatures, making them particularly sensitive to climate change.
In order to test insects’ reaction to warming climate and likelihood of moving north, Dr. Shannon Pelini, Hellmann’s then doctorate student, designed a laboratory experiment to test Pacific Coast butterflies’ reaction to temperature change.
In growth chambers, the caterpillars of two butterfly species—Erynnis propertius and Papilio zelicaon—were exposed to the replicated climates and plants that occur across the butterflies’ usual living range from southwestern Oregon to Vancouver Island of Canada.
They started the experiment with caterpillars because “you have to look at them over their life stage,” said Hellmann.
The researchers concluded that the local adaption to winter environment counteracts the benefits of warming during summer.
As for both populations of P. zelicaon, they showed behaviors of decreasing growth and survival in warmer temperatures. In addition, there is a lack of host plants available for this species in the north.
“This assumption that species are going to move north actually encounters problems, such as needing food resources and being sensitive to heat,” said Hellmann.
“Butterflies don’t move very well—they are not like birds. E. propertius has no food further to the north. They eat oak trees. People can actually help them move north, but then they will also need to move oak trees north. It’s just oak trees and butterflies, and we get very nervous.
“Humans don’t have a very good history of moving things. There are a lot of species out there, moving all of them is probably impossible ... So we need to think about what these species are telling us about the whole climate change. The experiment we did is like a window to what kind of [things] we are trying to figure out now.”
Aside from managed relocation, other ways potentially exist to save these species, said Hellmann.
“Managed relocation is one idea; it’s not necessarily a great idea. We haven’t really come up with a new idea yet. So the conservation community is really working on how we can change how we do things now,” she said.
In order to figure out a way to prevent these endangered butterflies’ from becoming extinct, Hellmann is now following up on Pelini’s research by surveying genes in the two butterfly species to recognize genes that are turned off or on by climate change. The study is designed to reveal the genetic bases for the insect species’ level of tolerance to climate change.
For Pelini’s research paper, please visit http://www.pnas.org/content/106/27/11160
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