During the project I established numerous collaborations, across two continents (Africa and Europe), that made it possible to acquire samples and that are now contributing to the analysis and interpretation of data. The presence of genomic regions under selection for ASF was initially investigated with a Genome Wide Association Study (GWAS) which showed no difference between healthy and infected individuals, concordantly with the variability in immune-related genes. However, we are now performing an additional analysis based on haplotypes, instead of single loci to further address this topic.
Hybridization was studied using about 300 samples of domestic pigs, from 23 breeds, and a similar number of wild boars, from 24 European and 3 Near Eastern countries. Our results showed variable levels of hybridization though Europe. Overall the two populations are well differentiated, but in a few geographic areas hybridization can reach 100% in frequency. These areas usually are characterised by the presence of outdoor farming. We thus suggest to improve the fencing around these farms, to prevent both hybridization and disease spread.
These results were presented at international conferences and within a Cost action aiming at dealing with ASF and a scientific publication is now being prepared. At the conferences our audience included people from all over European and Africa, with different expertise such as veterinarians, wild boar experts, forestry managers, virologist, policy makers and managers. Additionally, thanks to TV coverage, the main points of some of the conferences were made available to the broad public. However, details on the project are also open to the public through my webpage.
Additionally, some of the research lines have been published in scientific journals. The preparation study on of the genome of an isolated, although managed, island population was published in Heredity in 2016. This paper on the Sardinian wild boar highlighted low levels of hybridization but high differentiation from other wild boar populations. We observed that the closer population is the Italian wild boar, in accordance with other molecular markers, and the most differentiated is the domestic pig. Additionally, despite introgression from both domestic and continental wild boar, the Sardinian population still shows signatures of evolutionary differentiation.
A study on hybridization levels focusing on two autosomal genes, the MC1R and the NR6A1, that underwent strong human selection during domestication processes was also published in 2016 in Mammalian Biology. MC1R codes for fur colour, while NR6A1 is involved in the development of the number of vertebrae. Both genes present different variants between the domestic pig and the wild boar, that usually have a single fixed allele (wild type). We sampled wild boar throughout Europe and observed that most of the analysed wild boars carried only the wild type allele, however, in 6% cases animals showed signs of introgression from the domestic counterpart with each marker. Considered together the two genes identified 11% of hybrids in the overall sample.
Finally, at the beginning of 2017 we published in Behavioural Processes a study on the behaviour of and towards hybrids in the wild. With this aim we considered movies captured by camera traps in Tuscany and analysed the behaviour of animals belonging to the same social unit. This is particularly important for a species, like the wild boar, where social bonds and cooperation are paramount. In this case we classified as hybrids individuals that had, partly or completely, the aspect of a domestic pig. What we observed is that animals that look like pigs were the last ones in their social unit and were often harassed by their fellows (while no aggression was recorded among animals that looked like wild boars). Our hypothesis is that the lack of camouflage might put the whole group at risk of predation.
