Submitted to: Proceedings of the National Academy of Sciences(PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/1997
Publication Date: N/A
Interpretive Summary: The Greater Prairie Chicken in Illinois underwent a severe decline in population size. As a result, the extent of genetic or germplasm diversity was greatly reduced. In this study, the use of genetic markers to evaluate the amount of genetic diversity was demonstrated. Specifically, Greater Prairie Chickens from Illinois have only a small subset of the genetic diversity present in other populations that have not undergone a decline i population fitness. Researchers involved in germplasm preservation and the evaluation of wildlife fitness can benefit from the methods used in this study.
Technical Abstract: Although the theoretical relationship between population size, fitness, and genetic variation is well established, no direct evidence exists that ties both a decline in genetic variation and fitness to a demographic bottleneck for any natural system. This lack of direct evidence typically arises from not having the foresight or the opportunity to sample genetic variability and reproductive success from pre-bottleneck populations. We present an alternative approach that compares conspecific populations which have undergone different ecological histories. Here, we report on a genetic comparison (based on six microsatellite loci) of four populations of the Greater Prairie Chicken. Specifically, we compare a population from Illinois that has suffered an extreme demographic contraction and an associated decline in population fitness with three others from Kansas, Nebraska, and Minnesota, with no bottleneck history or associated declines in fitness. Results of this analysis showed that the Illinois population had the lowest estimate of mean heterozygosity per locus and approximately half the allelic diversity, sharing 95-100% of all its alleles with each of the other populations. The fact that the Illinois population shares the majority of alleles with the other populations suggests that it was part of a larger ancestral population with higher levels of genetic diversity that were consequently lost through an extreme demographic contraction. To our knowledge, this is the first example that associates loss of genetic diversity with a decrease in population fitness as a result of a demographic bottleneck in a wild bird species.