(iv) Last, we used a SNP-based approach. The two first principal components were used to perform the genome scan for selection using Pcadapt V.2.2 (Additional file 2: Figure S6a). The Mahalanobis statistic distance fitted a normal distribution (Additional file 2: Figure S6b). The histogram of p-values showed an excess of small p-values, indicating the presence of outliers (Fig. 2d). Using a 5% threshold, we identified 2502 SNPs in 1602 candidate contigs with extremely low p-values. A total of 238 contigs that showed at least two SNPs putatively under selection were retained as candidates.