Lower panel: the velocity–distance distribution for all sample clusters. The green lines mark the boundaries defined by Equation (2). The blue, red, and green dots are cluster members in the low-mass bin (﹩8.5\lt \mathrm{log}({M}_{* }/{M}_{\odot })\lt 9.5﹩), medium-mass bin (﹩9.5\lt \mathrm{log}({M}_{* }/{M}_{\odot })\lt 10.5﹩), and high-mass bin (﹩10.5\lt \mathrm{log}({M}_{* }/{M}_{\odot })﹩). The black dots are the targets close to the clusters, yet not bound by the cluster. Upper panel: galaxy number histogram of the cluster member galaxies with spec-z for each mass bin. The number of galaxies in a virialized system should decrease steadily within R/R₂₀₀. The flat distribution of the low-mass bin is caused by the incompleteness of the spec-z dwarf sample.