Genetic diversity and structure of the Lesvos sheep breed

• We use microsatellite molecular markers.
• We examine the genetic diversity and structure of the Lesvos sheep breed.
• We found high observed heterozygosity and moderate mean number of alleles.
• The differentiation between flocks is low.
• High exchange of animals between neighboring and distant flocks.

We investigated, through the use of 11 microsatellite molecular markers, the genetic diversity and structure of 350 individuals from ten flocks of the Lesvos sheep breed population (Greece). The results revealed that although the breed shows particularly high levels of observed heterozygosity (Ho = 0.83), the mean number of alleles of 6.8 is somewhat lower than in other sheep breeds. FIS (−0.143 ± 0.065) was significantly negative over loci for the five out of the ten flocks and the observed heterozygosity was consistently higher than the expected for all flocks. The low value of FST (0.021 ± 0.003) implies that the quasi-totality of genetic variability is due to within-flock variability, suggesting a strong genetic cohesion of the total population. Furthermore, we revealed a breeding practice that comprises an important exchange of animals: the number of migrants between flocks ranged from 6.41 to 53.92. These exchanges happen both between neighboring and more distant farms as indicated by the correspondence analysis and the neighbor-joining dendrogram. This is also reflected in the clustering obtained by STRUCTURE analysis according to which all flocks had comparable proportions of membership to the five clusters detected. In conclusion, the implemented management practice confers high gene variability both at the flock level and in the total population which is very promising for the conservation of the breed as a genetic resource. However, in conjunction with the isolation of the breed on the island of Lesvos, the high gene flow among flocks may also be responsible for the rather low mean number of alleles as it decreases the overall effective size. Moreover, it is still unknown whether the present breeding practice meets adequately production objectives of the breeders, which is the other important facet of the breed management.