• bottleneck;
  • effective population size;
  • genetic monitoring;
  • inbreeding;
  • multilocus heterozygosity;
  • temporal groups

The aim of this study was to assess potential post-bottleneck temporal genetic differentiation following the reintroduction of the species into the Białowieża Forest. Variability of 12 polymorphic microsatellite markers was analysed for 178 individuals born between 1955 and 2005, divided by birth year into five temporal groups. Low overall allelic richness (AR) per locus (AR = 2.0) and a low overall expected heterozygosity (HE = 0.28) were observed. The overall FIS was not significantly different from zero. The mean FIS values were, however, significantly different from zero for individuals born between 1955 and 1965 (FIS = 0.19). A Bayesian computation was used to estimate effective population size (Ne) for each temporal group. We observed relatively small values of Ne ranging from 7.9 to 28.4. The low Ne values confirm that, despite a rapid growth of the bison population following the founder event, Ne increased only slowly. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 801–809.