Wright-Fisher sampling: allele frequency p(t+1) ~ Binomial(2N, p)/2N
The Wright-Fisher model samples 2N alleles each generation via binomial draws — random genetic drift. Small populations lose diversity rapidly (expected heterozygosity H_t = H_0(1−1/2N)^t). Bottlenecks dramatically accelerate allele loss: even one generation at N_b founders can eliminate most diversity.