Distortion of allele frequency distributions provides a test for recent population bottlenecks

Abstract

We use population genetics theory and computer simulations to demonstrate that population bottlenecks cause a characteristic mode-shift distortion in the distribution of allele frequencies at selectively neutral loci. Bottlenecks cause alleles at low frequency (< 0.1) to become less abundant than alleles in one or more intermediate allele frequency class (e.g., 0.1-0.2). This distortion is transient and likely to be detectable for only a few dozen generations. Consequently only recent bottlenecks are likely to be detected by tests for distortions in distributions of allele frequencies. We illustrate and evaluate a qualitative graphical method for detecting a bottleneck-induced distortion of allele frequency distributions. The simple novel method requires no information on historical population sizes or levels of genetic variation; it requires only samples of 5 to 20 polymorphic loci and approximately 30 individuals. The graphical method often differentiates between empirical datasets from bottlenecked and nonbottlenecked natural populations. Computer simulations show that the graphical method is likely (P > .80) to detect an allele frequency distortion after a bottleneck of < or = 20 breeding individuals when 8 to 10 polymorphic microsatellite loci are analyzed.

Population genetic structure of the predatory, social wasp Vespula pensylvanica in its native and invasive range

“…1998). We found significant excesses of heterozygosity in Maui ( P  =   0.034) and New Mexico ( P  <   0.001).…”

“…The overall drop in expected heterozygosity is quite small compared to the drop in allelic richness, which is a characteristic of a brief population bottleneck (Luikart et al. 1998). In this case, some rare alleles are lost, although observed heterozygosity, which is more strongly influenced by common alleles, is not severely reduced (Luikart et al.…”

“…In this case, some rare alleles are lost, although observed heterozygosity, which is more strongly influenced by common alleles, is not severely reduced (Luikart et al. 1998). …”

“…In addition, we expect that some introduced populations may show evidence of population bottlenecks, which occur if populations undergo reductions in size during the founding process (Cornuet and Luikart 1996; Luikart et al. 1998). …”

European wildcat populations are subdivided into five main biogeographic groups: consequences of Pleistocene climate changes or recent anthropogenic fragmentation?

“…1998) in Bottleneck 1.2.02 (Cornuet and Luikart 1997), assuming a microsatellite “two‐phase mutational model” with 95% one‐step mutations. Two‐tailed Wilcoxon signed rank test was used for determining the significance of the observed deviations.…”