Inference of hidden population substructure of the Iberian pig breed using multilocus microsatellite data

The census and structure of Iberian pig breed have experienced important changes along the last decades. Bayesian methods based on multilocus genotypes have been applied for ascertaining the actual breed structure and for identifying genetically distinctive populations. DNA samples from 170 Iberian pigs previously assigned to the strains or varieties Torbiscal, Guadyerbas, Retinto, Entrepelado and Lampiño and 64 Duroc pigs were genotyped for 36 microsatellites. A best partition of only five clusters was estimated in the clustering analysis at group level, when the previous assignation to populations was taken into account. But the individual-based assessment of population structure, ignoring the previous assignation of animals to populations, showed a more complex partition of ten clusters. Results of admixture analyses for artitioning individuals into the inferred clusters showed an important proportion of admixed individuals pre-assigned to the Retinto, Entrepelado and Lampiño varieties. The frequencies of private alleles of the MC1R gene also evidenced an important genetic flow between these varieties. The future definition of conservation units in the Iberian breed should consider these results.