Signals of Pig Ancestry in Wild Boar, Sus scrofa, from Eastern Austria: Current Hybridisation or Incomplete Gene Pool Differentiation and Historical Introgressions?

In wild boar, Sus scrofa, from Europe, domestic pig-typical ancestry is traced at varying levels. We hypothesised wild boar with pig-typical gene pool characteristics, i.e., “introgression”, congregate more in peri-urban habitats, because of less shyness and better adaptation to anthropogenic stress. We used 16 microsatellites to study introgression levels of 375 wild boar from peri-urban Vienna, Austria, and rural regions in comparison to commercial slaughter pigs, Mangaliza, and Turopolje pigs. We also expected more introgression in locations of warmer climates and lower precipitation. Despite discrimination of wild boar and pigs with 99.73% and 97.87% probability, respectively, all wild boars exhibited pig-typical gene pool characteristics, mostly at a very low level. Recent hybridisation was suspected in only 0.53% of wild boar, corresponding to the current largely indoor pig breeding/rearing in the region, with no chance of natural gene exchange between pigs and wild boar. Rather, pig ancestry in wild boar stems from incomplete gene pool differentiation during domestication and/or historical introgressions, when free-ranging pig farming was common. Individual introgression levels were lower in wild boar from peri-urban habitats, possibly reflecting the largely historical absence of pig farms there. Moreover, a marginal precipitation effect, but no temperature effect on introgression was observed. The latter, however, needs to be explored further by a more comprehensive data set.