Abstract
In Greece, a number of local sheep breeds are raised in a wide range of ecological niches across the country. These breeds can be used for the identification of genetic variants that contribute to local adaptation. To this end, 50k genotypes of 90 local sheep from mainland Greece (Epirus, n = 35 and Peloponnesus, n = 55) were used, as well as 147 genotypes of sheep from insular Greece (Skyros, n = 21), Lemnos, n = 36 and Lesvos, n = 90). Principal components and phylogenetic analysis along with admixture and spatial point patterns analyses suggested genetic differentiation of ‘mainland-island’ populations. Genome scans for signatures of selection and genome-wide association analysis (GWAS) pointed to one highly differentiating marker on OAR4 (FST = 0.39, FLK = 21.93, FDR p-value = 0.10) that also displayed genome wide significance (FDR p-value = 0.002) during GWAS. A total number of 6 positional candidate genes (LOC106990429, ZNF804B, TEX47, STEAP4, SRI and ADAM22) were identified within 500 kb flanking regions around the significant marker. In addition, two QTLs related to fat tail deposition are reported in genomic regions 800 kb downstream the significant marker. Based on gene ontology analysis and literature evidence, the identified candidate genes possess biological functions relevant to local adaptation that worth further investigation.
Highlights
Post domestication sheep (Ovis aries) have spread and distributed over a wider geographic range around the globe and adapted to a variety of diverse, often harsh, environments
First we examined whether mainland-island present genetically different entities and conducted genome scans and genome-wide association analysis in attempts to address two questions with regard to local adaptation (LA)
Principal Component Analyses (PCA) revealed the formation of four clusters: one with Lemnos and Lesvos samples, a second with genotypes from Skyros island in the center of the plot, a third with genotypes from Peloponnesus and the Oreino breed (Epirus, blue color) and a fourth cluster with genotypes from Katsika breed (Epirus, blue color, upper right)
Summary
Post domestication sheep (Ovis aries) have spread and distributed over a wider geographic range around the globe and adapted to a variety of diverse, often harsh, environments. A number of indigenous sheep breeds are found in Greece, in a range of ecological and environmental conditions [1]. Two local breeds (Katsika and Oreino) are traditionally kept on the alpine climate zone of the Pindos mountain chain under a vertical transhumance system with livestock displacement from lowlands to highlands in summer and vice versa, in wintertime. Genetic differentiation of mainland-island sheep of Greece
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