Comparison between the BaSTI (thick lines) and PARSEC (thin lines, upper panel), STAREVOL (thin lines, lower panel) predictions for the [C/N] _FDU−t relation at selected metallicities. BaSTI results for [M/H] = 0.06 (solid line) and [M/H] = −0.66 (dash-dotted line) are displayed together with PARSEC results for [M/H] = −0.02 (solid line) and [M/H] = −0.58 (dash-dotted line), and STAREVOL results for [M/H] = 0.0 (solid line) and [M/H] = −0.56 (dash-dotted line). STAREVOL models with rotation for the same metallicities are also displayed (with the same line styles). In the upper panel squares denote BaSTI calculations for [M/H] = 0.04 and the Caffau et al. (2011) solar heavy element distribution (see text for details).