  A literature compilation of nuclear star cluster (NSC) masses is used to
study the correlation between global and nuclear properties. A comparison of
observational data to the predictions of semi-analytical galaxy formation
models places constraints on the co-evolution of NSCs, massive black holes
(MBHs) and host galaxies. Both data and theoretical predictions show an
increased scatter in the NSC scaling correlations at high galaxy masses, and we
show that this is due to the progressively more efficient ejection of stars
from NSCs caused by MBH binaries in more massive stellar spheroids. Our results
provide a natural explanation of why in nucleated galaxies hosting a MBH, the
ratio (M_NSC+M_MBH)/M_bulge (with M_bulge the host spheroid's mass) shows
significantly less scatter than M_NSC/M_bulge, and suggest that the formation
of MBHs and NSCs are not mutually exclusive, as also supported by observations
of co-existing systems. Both MBHs and NSCs represent generic products of galaxy
formation, with NSCs being destroyed or modified by the merger evolution of
their companion MBHs.
