GENETIC EVALUATION OF A DEMOGRAPHIC BOTTLENECK IN THE GREATER PRAIRIECHICKEN

Although the theoretical relationship between population size, fitness , and genetic variation is well established, only a few studies have p rovided direct evidence that ties a decline in both genetic variation and fitness to a demographic bottleneck for a natural system. We repor t on a genetic comparison of four populations of the Greater Prairie C hicken (Tympanuchus cupido) with different demographic histories. Spec ifically, we compared a population from Illinois that has suffered an extreme demographic contraction and an associated decline in populatio n fitness (measured in terms of hatchability rates) with populations f rom Kansas, Nebraska, and Minnesota with no known history of bottlenec ks or associated declines in fitness. Using the polymerase chain react ion, we amplified six microsatellite loci from which levels of heteroz ygosity, allelic diversity, and geographic differentiation (F-ST and R -ST) of the studied populations were estimated. Results of this analys is showed that the Illinois Prairie Chicken had the lowest estimate of mean heterozygosity per locus and approximately two-thirds the alleli c diversity, sharing 95-100% of all their alleles with each of the oth er populations. This finding suggests that the Illinois Prairie Chicke n originally had higher levels of genetic diversity that were subseque ntly lost through an extreme demographic contraction. To our knowledge this is the first example of loss of genetic diversity being associat ed with a decrease in population fitness as a result of a known demogr aphic bottleneck in a wild bird species.