Semimajor axis and surface temperature evolution for the 1500 planetesimals in the nominal HL Tau simulation, produced in a similar manner as in Fig. 2 (same data as in Fig. 8). Planetesimals formed at the gap edge of the innermost planet is shown in the upper panel. For the middle and outermost planet, these are shown in the middle and bottom panels, respectively. Since the planetary masses are set to equal the pebble isolation mass, and the pebble isolation mass increases with semimajor axis, the planetesimals formed at the gap edge of the outermost planet experience stronger scatterings and diffuse faster than those formed at the innermost planet’s gap edge.