MULTI-DIMENSIONAL SCALING ANALYSIS OF GENOME-WIDE SNP DATA ON ITALIAN SHEEP BREEDS REVEALS A STRONG PHYLOGEOGRAPHIC GRADIENT

In Italy several local sheep breeds and populations are reared, though most of them are endangered or in very critical conditions and, therefore, in need of conservation actions. This paper aims to outline the genetic relationship among nineteen Italian local and country-wide sheep breeds by the means of a multidimensional scaling analysis conducted over the allele sharing distance estimated from the genotypic data at the Illumina OvineSNP50 BeadChip. The analysis highlighted the presence of a strong geographical gradient in the distribution of the genetic variability of the considered breeds, with a North to South main gradient, along which almost all the breeds were positioned, followed by a minor East to West gradient, discriminating insular breeds from continental breeds. The results suggest that historical events of admixture and gene flow among contiguous areas played a significant role in determining the current pattern of genetic diversity among the Italian breeds, consistently with traditional sheep management practices (extensive rearing and transhumance) characterizing the history of sheep breeding in the Italian peninsula