Fig. 4

Outlier detection results from BAYESCAN [25, 26] analyses of European populations. N: number of samples; Black asterisks: non-outlier loci (log₁₀(PO) < 1.5); Blue triangle: outlier loci within form analysis (log₁₀(PO) ≥ 1.5); Red dot: outlier loci between pipiens and molestus (log₁₀(PO) ≥ 1.5 only for all populations outlier analysis). Note that logarithm of Posterior Odds to base 10 (log₁₀(PO)) is arbitrarily fixed to 4 when the posterior probability is 1 (should be infinity)