  We present results for a galaxy formation model that includes a simple
treatment for the disruption of dwarf galaxies by gravitational forces and
galaxy encounters within galaxy clusters. This is implemented a posteriori in a
semi-analytic model by considering the stability of cluster dark matter
sub-haloes at z=0. We assume that a galaxy whose dark matter substructure has
been disrupted will itself disperse, while its stars become part of the
population of intracluster stars responsible for the observed intracluster
light. Despite the simplicity of this assumption, our results show a
substantial improvement over previous models and indicate that the inclusion of
galaxy disruption is indeed a necessary ingredient of galaxy formation models.
We find that galaxy disruption suppresses the number density of dwarf galaxies
by about a factor of two. This makes the slope of the faint end of the galaxy
luminosity function shallower, in agreement with observations. In particular,
the abundance of faint, red galaxies is strongly suppressed. As a result, the
luminosity function of red galaxies and the distinction between the red and the
blue galaxy populations in colour-magnitude relationships are correctly
predicted. Finally, we estimate a fraction of intracluster light comparable to
that found in clusters of galaxies.
