  Globular clusters which exhibit chemical and dynamical complexity have been
suggested to be the stripped nuclei of dwarf galaxies (e.g., M54, $\omega$
Cen). We use $N$-body simulations of nuclear star clusters forming via the
mergers of star clusters to explore the persistence of substructure in the
phase space. We find that the observed level of differentiation is difficult to
reconcile with the observed if nuclear clusters form wholly out of the mergers
of star clusters. Only the star clusters that merged most recently retain
sufficiently distinct kinematics to be distinguishable from the rest of the
nuclear cluster though the critical factor is the number of merger events not
the elapsed time. In situ star formation must therefore be included to explain
the observed properties of nuclear star clusters, in good agreement with
previous results.
