Walking together: artificial and natural selection in traditional husbandry of feral pigs

Abstract

The history of Homo sapiens is studded with many events promoting relationships with wild animals changing their evolutionary path or impacting their adaptation. Artificial selection is recognized as the product of planned actions aimed to annex useful species into the anthropic niche. However, the effect of humans on animal evolutionary trajectories is diversified and cannot be assigned to a single driver. We characterized the genomes of feral pigs managed by different traditional husbandry practices to infer about the combining effect of artificial and natural selection. Whole genome characterization showed a clear distinctiveness of Sardinian wild boars (Sus scrofa) from free-range pig and domestic pig (Sus domesticus) populations, while Eurasian wild boars and hybrids are closely related, also in agreement with allelic frequency. In the Southern Italy system, we found 7 SNPs putatively under selection, associated with genomic regions including genes mainly involved in body weight control and feeding behavior, muscle growth and development, and adipocyte proliferation. Considering Sardinian wild boar and free-range pigs, over 3000 SNPs were found putatively under selection, and the genomic regions in which these SNPs fall include genes linked mainly to litter size and number of teats. The screening of genomic variability was useful to characterize feral pigs and wild boars from Southern Italy and Sardinia and the relationships between them, highlighting the effect of a peculiar artificial selection that modulates its weightiness due to the concomitant natural selection. In particular, the traditional Sardinian pig husbandry seems to act pushing down gene flow towards wild boar while favoring adaptations to life in the wild, creating a unique genetic pattern in free-range pigs, different both from the domestic and the wild genetic makeup. Our contribution opens up a discussion on the current European policy for the management of free-range pigs, the effective conservation actions for diversity in Suidae forms and their consequent impacts on biodiversity.