Genetic drift is most effective in:
Genetic drift describes random fluctuations in allele frequencies due to sampling error in finite populations, especially impactful when effective population size is small, such as island populations or endangered species. It can fix or lose alleles irrespective of fitness, reduce heterozygosity by 1/2Ne per generation and cause loss of rare alleles. Unlike selection, drift is non-adaptive and non-directional. Therefore phenomenon Small populations captures stochastic evolutionary force important in conservation genetics. This concept integrates genetics, ecology and molecular evidence, freque
Ref: Hartl & Clark, Principles of Population Genetics, Chapter 7: Drift.