A Variations in labial colouration of the ‘Europe’ (green range) and the ‘Greece’ (purple range) clades of Natrix tessellata across Europe, categorised into four distinct types. The question mark represents an uncertain geographic position of the locality; B Eight individuals representing the division of four labial colouration types with the geographic origin as follows (left/right): Type 1 – Zvolen, Slovakia*/Plitvica Lakes, Croatia*; Type 2 – Ckla, Montenegro*/Tlmače, Slovakia*; Type 3 – Histria, Romania*/Ioannina, Greece**; Type 4 – Shënepremte, Albania**/NP Divjakë-Karavasta, Albania**; * the ‘Europe’ and **the ‘Greece’ clade; C Correlation plot (corrplot) displaying Pearson’s residuals indicating the contribution to the results of the chi-square test. Red colour indicates negative and blue positive correlation.