The effects of the Last Glacial Maxima on the current genetic diversity of the European wild boar (Sus scrofa)

In many terrestrial species, the geographic distribution of DNA lineages was heavily affected by the climatic fluctuations that occurred during the Quaternary, although the impact of human populations in more recent times, especially on harvested species, might have confounded the pattern. The wild boar (Sus scrofa) is one the most widely distributed terrestrial animals, naturally occurring from Western Europe to Japan. Previous studies suggested that Iberia, Balkans and Italy played a major role as European refugia during the Last Glacial Maximum (LGM), and these three areas were the responsible for the recolonization of the continent. We tested this hypothesis using 770 mtDNA sequences (HVR) from 75 sites covering the entire European continent. Northern populations show lower genetic diversity when compared to southern populations. Surprisingly, Iberian and some Balkans populations share haplotypes that were only found in these two areas, while Italian populations are more similar to central European region (France and Germany). To predict the distribution of the wild boar during the LGM and its relationship with the current distribution of genetic diversity, a maximum entropy method based on 11 climatic variables was used. The model predicts that Iberia, Balkans and Italy had great habitat suitability during the LGM. Italy and Iberia shows greater suitability when compared to other regions of Europe, which can indicate that these two areas may have retained large population size even during cold periods. The suitability map and the current distribution of the genetic diversity show parallel geographic patterns, also within the non-homogeneous Iberian refugium. This result suggests that the climatic conditions in Europe during the LGM affected the current geographic pattern of genetic variation. The genetic similarity between some Western (Iberia) and some Eastern (Balkans) populations suggests that these areas were not isolated during the LGM, but this hypothesis requires additional testing.