One Downside of Early Spring: a Drop in Rocky Mt. Butterflies

	A Mormon Fritillary butterfly feeding on an aspen fleabane daisy, a main nectar source. Credit: Carol Boggs Click on image for higher resolution

COLLEGE PARK, Md. - The early arrival of spring across the U.S. undoubtedly has warmed the hearts of many people, but for flowering plants and pollinating insects, the trend toward earlier springs brings complicated, and not always good, results. For example, a new study from the University of Maryland and Stanford University shows earlier snowmelts in the Colorado Rockies is causing a decline in the population of the Mormon Fritillary butterfly (Speyeria mormonia).

Early snowmelt caused by climate change in the Colorado Rocky Mountains negatively affects these butterflies in two different ways, say biologists David Inouye, of the University of Maryland and Carol Boggs, of Stanford University. Early springs in the Rockies result in a decrease in the number of flowers, which, in turn, decreases available nectar for the butterflies. Earlier springs can also result in young caterpillars coming out early, only to be killed during early-season frosts. Their results, published early online, are in the March 19 issue of Ecology Letters.

A frost-killed bud of aspen fleabane daisy; the frost damage means no nectar for butterflies. Credit: David Inouye, University of Maryland

"This study illustrates that fact that impacts of climate change, even on a single species, usually are mediated through more than one mechanism, says Inouye. "Thus capturing the full effects of climate change on a species requires understanding how that species interconnects with others in its community and how changes in the climate affect those interconnections."

The new findings by Boggs and Inouye are based on long-term data on date of snowmelt, butterfly population sizes and flower numbers collected at the Rocky Mountain Biological Laboratory (RMBL). However, the findings also build on decades of RMBL research by each scientist.

Inouye's work at the Rocky Mountain Biological Laboratory focuses on variation in the timing and abundance of wildflowers, and the consequences of climate change for the wildflowers and animals that interact with them. Previous work has shown that earlier spring thaws in the Rockies harm wildflowers rather than benefit them because flowers come out early, but are damaged by late frosts for which the timing has not changed. He has ongoing studies of the population biology of wildflowers and how that is changing with climate change, on ant-plant mutualisms, bumble bee ecology, and long-term studies of variation in insect populations.

Boggs' research addresses the effects of environmental variation on individuals, populations and interactions among species. Using butterflies as focal organisms, her current work includes tests of the effects of variation in climate and food availability on birth and death rates and population sizes.

Media Contacts:
David W. Inouye
Phone: 301-405-6946
Inouye@umd.edu

Carol L. Boggs
Phone: 650-723-5923
cboggs@stanford.edu

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