Public Release: 

Scarcity Of Illinois Prairie Chickens Tied To Lack Of Genetic Diversity

University of Illinois at Urbana-Champaign

CHAMPAIGN, Ill. - An endangered grasslands bird species that the state of Illinois is attempting to save - the greater prairie chicken - once was part of the stronger populations in other Midwest states but has been weakened by a loss of genetic diversity, researchers have concluded.

The findings, presented Aug. 14 during the annual meeting of the Ecological Society of America in Providence, R.I., provide hope for success for the state1s efforts under way to introduce birds from populations in Kansas, Minnesota and Nebraska into nests in two Southern Illinois counties, said Ken Paige, a professor of ecology, ethology and evolution at the University of Illinois.

A genetic analysis led by Paige and U. of I. doctoral student Juan Bouzat of Argentina indicates that the birds now isolated in Illinois had been part of the larger population. In his presentation to the ESA, Bouzat said that all of the alleles - alternative genes that provide the codes for particular characteristics - in Illinois birds were present in the birds in the other states.

The Midwest birds also contain other alleles, which provide for greater fitness, or heterozygosity. As part of the research, Bouzat analyzed seven Illinois museum specimens from the 1930s, finding two alleles that existed then in Illinois and now in the other Midwest populations but not in today1s Illinois birds.

"Our analysis strongly suggests that all populations were originally part of an ancestral population with higher levels of genetic variability, with the Illinois population losing considerable diversity as a result of a demographic bottleneck," Bouzat said. "As the population became smaller, some of the individuals who had had some of the original alleles died, and the alleles were lost."

The loss of alleles likely has resulted in a decrease in the fitness of the Illinois birds, and likely has occurred randomly over time, Paige said. "This study shows what has been lost genetically, especially in the change that has occurred since 1930," he said.

In the 1860s, millions of prairie chickens lived in 92 Illinois counties, but their numbers declined rapidly as the human population grew and their nests were destroyed or isolated from one another by human activity. Between 1933 and 1993, the number of greater prairie chickens in the state dropped from 25,000 to 50. The remaining populations live in Jasper and Marion counties. Hatchability rates for successful births were estimated at 56 percent in 1990, compared with 93 percent in 1933.

"This study has implications for the management and conservation of natural populations of animals facing extinction," Bouzat said. "This suggests that when populations become small, genetics count. This shows a lack of genetic diversity correlating with a lack of fitness. In the end, the question is: Do we want to see greater prairie chickens in Midwestern natural prairies, or do we want to see them in Midwestern museums with tags indicating they are extinct?"

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