Figure 1 from: Nijman V, Vonk R, Roselaar K, van Brandwijk H, Beentjes K (2013) DNA barcoding of Dutch birds. ZooKeys 365: 25-48. https://doi.org/10.3897/zookeys.365.6287

Figure 1 - Comparisons of K2P-pairwise distances based on the COI gene of 141 species of birds from the Netherlands, showing a clear barcoding gap. Interspecific distances are indicated with light grey bars and intraspecific distances with dark grey bars. Left Y-axis: numbers of intraspecific comparisons; Right Y-axis: numbers of interspecific comparisons.