  In addition to their low stellar densities, ultra-diffuse galaxies (UDGs)
have a broad variety of dynamical mass-to-light ratios, ranging from dark
matter (DM) dominated systems to objects nearly devoid of DM. To investigate
the origin of this diversity, we develop a simple, semi-empirical model that
predicts the structural evolution of galaxies, driven by feedback from massive
star clusters, as a function of their departure from the mean SMHM relation.
The model predicts that a galaxy located $\gtrsim 0.5$ dex above the mean
relation at $M_{\rm halo}=10^{10}M_{\odot}$ will host a factor of $\sim 10-100$
larger globular cluster (GC) populations, and that feedback from these GCs
drives a significant expansion of the stellar component and loss of DM compared
to galaxies on the SMHM relation. This effect is stronger in haloes that
collapse earlier and have enhanced star formation rates at $z\gtrsim2$, which
leads to increased gas pressures, stellar clustering, and mean cluster masses,
and significantly enhances the energy loading of galactic winds and its impact
on the DM and stellar orbits. The impact on galaxy size and DM content can be
large enough to explain observed galaxies that contain nearly the universal
baryon fraction, as well as NGC1052-DF2 and DF4 and other isolated UDGs that
contain almost no DM. The trend of increasing galaxy size with GC specific
frequency observed in galaxy clusters also emerges naturally in the model. Our
predictions can be tested with large and deep surveys of the stellar and GC
populations in dwarfs and UDGs. Because stellar clustering drives the
efficiency of galactic winds, it may be a dominant factor in the structural
evolution of galaxies and should be included as an essential ingredient in
galaxy formation models.
