Thursday, January 21, 2010

Bugs: Victims of Climate Change

If it were up to Jessica Hellmann, insects such as butterflies and beetles would wield just as much conservation clout as traditional conservation icons, such as polar bears, tigers and dolphins.

"Animals such as polar bears, tigers and dolphins are tremendously important, but mostly because they help define how we think about our relationship with the natural world," says Hellmann. "But when it comes to the functioning of ecosystems, insects are where it's at."

Why are insects so ecologically important? "They carry diseases, they pollinate and they have economic impacts on crops and timber," says Hellmann, a biologist at the University of Notre Dame. In fact, almost 80 percent of the world's crop plants require pollination, and the annual value of insect-pollinated crops in the U.S. is about $20 billion. What's more, most of the multicellular living organisms on Earth are insects.

They are also particularly sensitive to climate change--as invertebrates, they can't regulate their own body temperatures--making them "great little thermometers," Hellmann adds.
On the road again
How will those "great little thermometers" respond when climate change makes their habitats too hot or too dry for them?
Research conducted by Hellmann and Shannon Pelini, one of Hellmann's doctoral students, indicates that global warming may affect a single insect species differently throughout its various life stages, and that global warming affects different insect species in different ways.

Most importantly, as climate change progresses, some insects may become trapped--like fish out of water--in habitats that can no longer support them. The insects may therefore go extinct or lose genetically important segments of their populations. But other species, and no one knows which ones yet, may be able to reach cooler climates by moving north on their own.

Will such mobile species be able to survive on the unfamiliar plants living in their new habitats? To help answer that question, Pelini conducted laboratory experiments that involve exposing caterpillars of two butterfly species to climates and plants that occur across their ranges, and then monitoring the growth and survival rates of these groups.

She will soon announce in the journal Proceedings of the National Academy of Sciences (PNAS) how populations of these two butterfly species that live at the edges of their ranges will be affected by climate change and the various factors that may limit or reduce their northward expansion.

Hellmann is currently following up on Pelini's research by surveying thousands of genes in the two butterfly species in order to identify the genes that are turned off or on by climate change. These studies are designed to reveal the genetic bases for the tolerance of some insect species to climate change and the intolerance of others.

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