... a model system for the ecological and evolutionary effects of small populations
In collaboration with individuals from the Illinois Natural History Survey, the Illinois Department of Natural Resources and the University of Illinois, we recently completed a 35-year study of a remnant population of the greater prairie chicken located in south-eastern Illinois. During the course of this study, population size was shown to decrease from 2000 individuals in 1962 to fewer than 50 by 1994. Concurrently, both fitness, as measured by fertility and hatching rates of eggs, and genetic diversity declined significantly. Conservation measures initiated in 1992 with translocation of birds from large, genetically diverse populations restored egg viability. Thus, sufficient genetic resources appear to be critical for maintaining populations of greater prairie chickens.
In particular, my lab conducted the genetic work. Using microsatellite markers we showed that the Illinois population had the lowest estimate of mean heterozygosity per locus and approximately two-thirds the allelic diversity, sharing 95-100% of all their alleles with each of the other populations studied in Kansas, Nebraska, and Minnesota. These three large populations had no known history of bottlenecks or associated declines in fitness.
We also provided the first clear case history where both prebottleneck and postbottleneck measures of genetic diversity have been collected from a natural system. Analysis of DNA from museum specimens of the greater prairie chicken collected from the same Illinois population in the 1930's and 1960's revealed loss of specific alleles (known to have been present earlier in this century) following the demographic contraction. Lost alleles included common ones present in all other populations sampled and others unique to the Illinois population.