Comparison of the Fan et al. (2010) lines and the theoretical models by Merlin et al. (2012; green filled squares) with the observational data of Burstein et al. (1997) from GCs (small red squares), to DGs (small blue triangles), and GCGs (light blue filled circles) plus the ETGs of Bernardi et al. (2010; red dots). The short-dashed blue line is the Fan et al. (2010) relation for z = 0. The thin solid lines of different colours are the same relation but for z = 1, z = 5, z = 10, z = 15, and z = 20 from top to bottom in the order. The long-dashed, thick blue line is the best-fit of the ETGs of Bernardi et al. (2010) extended to GCs and GCGs.