G/D as a function of metallicity for the 2 values of X_CO: X_CO,MW (left) and X_CO,Z (right) with the three chemical evolution model considered in Sect. 4. The symbols are the same as for Fig. 4. The model ranges from Galliano et al. (2008) are delineated by the dark grey stripe. The models from Asano et al. (2013a) are shown with the red, blue and purple lines and the light grey tolerance zone. The models from Zhukovska (2014) are shown with the orange, green brown solid lines and cyan dash-3 dots line. The black dashed line represents the reference scaling of the G/D with metallicity (not fit to the data).