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Double jeopardy: Endangered butterfly depends on endangered plants
They are picky eaters and breeders, and without certain plants to eat and lay their eggs on, Fender's blue butterflies may soon be extinct, scientists say.
The nectar plants and larval food plants needed by this rare butterfly are in short supply. The native prairies where the plants once flourished have vanished with the onset of residential and commercial development. Less than 1 percent of the indigenous prairies remain in Oregon's Willamette Valley, where the butterfly lives.
Cheryl Schultz, a post-doctorate fellow at the National Center for Ecological Analysis and Synthesis at the University of California at Santa Barbara, has studied the effect of landscape on butterfly restoration for several years. She presented her findings at the recent annual meeting for the Society for Conservation Biology in Missoula, Montana.
Found only in isolated populations in Oregon's Willamette Valley, the Fender's blue was presumed to be extinct in the 1930s. It was not until 1989 that small numbers of the radiant butterfly were rediscovered. In January, the species was listed for the first time under the Endangered Species Act.
To estimate the minimum amount of nectar and larval food plants necessary to restore Fender's blue habitat, Schultz studied the relationship between butterfly population density and the amount of available nectar sources and larval host plants at four sites.
She found that Kincaid's lupine, a threatened plant species in the Pacific Northwest, is the only available host plant for Fender's blue eggs in the southern part of their range. Moreover, she discovered the butterflies are only attracted to native plant species as their nectar source.
"There was a significant correlation between the amount of nectar available from native wildflowers and the number of butterflies," Schultz said. "This was not that unusual. A very common reason for butterflies to become endangered is that their habitat disappears due to development."
"This is one of the first studies to link the quantitative resource needs of an endangered species to methods to re-establish key habitat components," said Schultz. "What makes my work unique is the direct connection between resources quantified in an intact population and efforts to reestablish those resources in restored habitats."
Schultz added that restoration is usually assessed based on comparisons of reference sites. "Comparing restored sites to reference sites does not give us a very specific idea of how good the restored site is in terms of habitat for a focal species," she said.
So far, solarization is the most promising way to restore Fender's blue habitat, Schultz explained. Developed as an agricultural technique, the method involves laying large sheets of clear plastic over the soil during the summer months.
By baking the soil, weed seeds are killed. When native seeds are planted in the fall, they face less competition from weeds and therefore have higher rates of establishment.
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