Genetic diversity of the free-living population of Przewalski's horses in the Chernobyl Exclusion Zone

The present study is aimed at evaluating the genetic diversity, genetic status and the extent of hybridization with the domestic horse for the Przhevalski’s horse (Equus ferus przewalskii Poliakov 1881) population free-ranging in the territory of the Chernobyl Exclusion Zone (CEZ) in Belarus and Ukraine. The sample size included 12 individuals (10 sampled in the Belarusian part of the CEZ and 2 from the Ukrainian part of the CEZ). Ten microsatellites recommended by the International Society for Animal Genetics (ISAG) for horse genetic status and pedigree determination were used as markers in this study. The fragment analysis data obtained utilising this microsatellite panel determined that two individuals from Belarus possess no allelic variants typical for Przhevalski’s horse. Most of the other individuals presented diagnostically valuable allelic variants. Demographic history analysis for the population did not indicate any drastic population shrinkage events in the population’s recent history. The studied population is characterised by heterogeneous population structure with signs of inbreeding (0.21 %), intermediate level of genetic diversity (He = 0.63) and allelic richness (5.15), possesses 16 unique alleles among 2 microsatellite loci and valuable alleles for loci HMS3 and HMS7 (46.4 and 67.9 % specific alleles for Przhevalski’s horse, respectively). Genetic structure evaluation for the population was performed via Bayesian population structure analysis and factorial correspondence analysis (FCA), which indicated the presence of intrapopulation genetic subdivision. Taking into account the obtained indicators of genetic diversity, we may conclude on the relatively favourable status of Przewalski’s horse in the exclusion zone with good potential for the long-term existence of the species population in the wild. In order to minimise inbreeding effects and the risk of a decline in genetic diversity in the population of Przewalski’s horse of the exclusion zone, as well as to increase the value of this free-living group to preserve the gene pool of the species as a whole, it is necessary to provide detailed genetic monitoring of the livestock’s state, as well as develop a regional population management plan, including measures aimed to minimise the possibility of further hybridisation of wild horses with domestic ones