Evolution of the luminosity gap from z = 0 to z = 1 for fossil, control, and random groups. The filled blue circles, open green triangles, and open red squares show the mean ΔM_1,2 as a function of redshift for fossil, control, and random groups, respectively, within SI (top panel), SII (middle panel), and SIII (bottom panel). The significant formation of magnitude gap occurs at redshifts 0 <z< 0.5.