Bottom and middle panels show the distribution of the anisotropy parameter α_β for the FP and SP subpopulations of GCs in the sample (gray circles) as a function of N_h. The top panel shows the differential trend ${\alpha }_{\beta }^{\mathrm{S}\mathrm{P}}-{\alpha }_{\beta }^{\mathrm{F}\mathrm{P}}$. The dashed lines represent the mean of the observed α_β values derived for the dynamically young (N_h < 8) and old (N_h > 8) GCs. The star symbols are the result of the analysis on the two stacked samples and their sizes correspond to the errorbars.