G. Luikart et al., USEFULNESS OF MOLECULAR MARKERS FOR DETECTING POPULATION BOTTLENECKS VIA MONITORING GENETIC CHANGE, Molecular ecology, 7(8), 1998, pp. 963-974
It is important to detect population bottlenecks in threatened and man
aged species because bottlenecks can increase the risk of population e
xtinction. Early detection is critical and can be facilitated by stati
stically powerful monitoring programs for detecting bottleneck-induced
genetic change. We used Monte Carlo computer simulations to evaluate
the power of the following tests for detecting genetic changes caused
by a severe reduction in a population's effective size (N-e): a test f
or loss of heterozygosity, two tests for loss of alleles, two tests fo
r change in the distribution of allele frequencies, and a test for sma
ll N-e based on variance in allele frequencies (the 'variance test').
The variance test was most powerful; it provided an 85% probability of
detecting a bottleneck of size N-e = 10 when monitoring five microsat
ellite loci and sampling 30 individuals both before and one generation
after the bottleneck. The variance test was almost 10-times more powe
rful than a commonly used test for loss of heterozygosity, and it allo
wed for detection of bottlenecks before 5% of a population's heterozyg
osity had been lost. The second most powerful tests were generally the
tests for loss of alleles. However, these tests had reduced power for
detecting genetic bottlenecks caused by skewed sex ratios. We provide
guidelines for the number of loci and individuals needed to achieve h
igh-power tests when monitoring via the variance test. We also illustr
ate how the variance test performs when monitoring loci that have wide
ly different allele frequency distributions as observed in five wild p
opulations of mountain sheep (Ovis canadensis).