Left: luminosity-metallicity (L−Z) relation of the galaxies in the CALIFA survey with detected WR stars. In grey those galaxies showing some signs of undergoing or recent interaction (M), and in blue those galaxies classified as isolated (I). L−Z relations for various galaxy samples from the literature are also drawn: UV-selected galaxies (solid orange; Contini et al. 2002), SDSS star-forming galaxies (solid blue; Tremonti et al. 2004), a large magnitude-limited sample (dotted pink; Lamareille et al.2004), irregular and spiral galaxies (dashed red; Kobulnicky et al. 1999), emission-line galaxies at z ~ 0.8 from the Deep Extragalactic Evolutionary Probe 2 survey (dot-dashed; Zahid et al. 2011) and star-forming BCGs (three dot-dashed green; Shi et al. (2005). The large error bars in the absolute magnitudes refer to the uncertainties in the galaxy distance moduli, taken from NED. Right: number density of WRs vs. their projected galactocentric distance. The colours of the regions denote if they belong to a merging (M) or an isolated (I) galaxy. Regions circled in red are those whose host galaxy does not follow the luminosity-metallicity relation and have a metallicity 12 + log (O/H) < 8.4 simultaneously.