SREL Reprint #2101

Temporal changes in allele frequencies and a population's history of severe bottleneck

Christine Richards and Paul L. Leberg

Department of Biology, University of Southwestern Louisiana, Lafayette, LA 70504, USA

Abstract: Monitoring temporal changes in genetic variation has been suggested as means of determining if a population has experienced a demographic bottleneck. Simulations have show that the variance in allele frequencies over time (F) can provide reasonable estimates of effective population size (Ne). This relationship between F and Ne suggests that changes in allele frequencies may provide a way to determine the severity of recent demographic bottlenecks experienced by population. We examined allozyme variation in experimental populations of the eastern mosquitofish (Gambusia holbrooki) to evaluate the relationship between the severity demographic bottlenecks and temporal variation in allele frequencies. Estimates of F from both the fish populations and computer simulations were compared to expected rates of drift. We found that different methods for estimating F had little effect on the analysis. The variance in estimates of F was large among both experimental and simulated populations experiencing similar demographic bottlenecks. Temporal changes in allele frequencies suggested that the experimental populations had experienced bottlenecks, but there was no relationship between observed and expected values of F. Furthermore, genetic drift was likely to be underestimated in populations experiencing the most severe bottlenecks. The weak relationship between F and bottleneck severity is probably due to both sampling error associated with the number of polymorphic loci examined and the loss of alleles during the bottlenecks. For populations that may have experienced severe bottlenecks, caution should be used in making evolutionary interpretations or management recommendations based on temporal changes in allele frequencies.

SREL Reprint #2101

Richards, C. and P.L. Leberg 1996. Temporal changes in allele frequencies and a population's history of severe bottleneck. Conservation Biology 10:832-839.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).