Left panels: the white histograms show the photometric MDFs of all the stars within 3 mag below the TRGB, for Sculptor, Sextans, Carina, Fornax, and Leo II, while the shaded histograms show the same but only for the common stars. Middle panels: the white histograms show the Ca T-based MDFs on the CG97 metallicity scale for the full available spectroscopic sample, as described on the text, while the shaded histograms show the same but only for the stars in common. Right panels: the white histograms show the Ca T-based MDFs on the isoscale (discussed in Sect. 3.3), while the shaded histograms show the same but only for the common stars. In all panels, the vertical black dashed line corresponds to the median metallicity of the full sample, while the grey dashed line corresponds to the one of the common stars. The vertical dotted-dashed line in all panels corresponds to the isoschrone’s metal-poor limit of roughly  −2.5 dex. Note that for Sextans on the isoscale MDF (right panel), the total number of the common stars is three (shaded histogram), while the one for the full sample is twelve (white histogram).