Equivalent width of Li 670.8 nm absorption as a function of R − I (corrected for the extinction E(B − V) = 0.06 derived by Claria 1982) for stars with >80 per cent probability of belonging to population A (empty diamonds) or population B (red circles). The black dashed lines are isochrones of Li depletion calculated from the Baraffe et al. (1998) models at 10, 32, and 200 Myr, and the horizontal dotted blue line indicates the threshold used to select the pre-main sequence stars. The x-axis on the top of the panel reports a scale of effective temperature derived from R − I using the Pecaut & Mamajek (2013) colour-temperature transformations.