cluster-member dEs vs. infall dEs should be derived for more clusters, but observations are unfortunately very time-expensive if possible at all.

In addition to classical dEs, ultra-compact DGs (UCDs) have been detected and classified as a new type of cluster dEs that differ by their intrinsic structure and brightness (see e.g. [@phi01; @gre09]). The origin of these peculiar DGs is mysterious and not yet understood but requests transformation if they are surviving nuclei of tidally stripped nucleated DGs [@goe08].

Morphological transitions
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As the transformation picture from late-type dwarfs into dEs is still not completely understood and only qualitative, in sect.\[dEs\] we tried to shed light on the expected witnesses of differences in system parameters which allow to distinguish between two different populations of dEs. That almost all DGs can be associated with morphological types and that only a few exceptions show morphological transformations, implies that the act of mutation seems to happen rapidly and thus to be observable with only low probability.

During the approach to galaxy clusters, ram pressure should act on dIrrs already at group conditions or in the outskirts of clusters [@mar03; @roe05]. When this process pushes the gas out of dIrrs, wouldn’t one expect to 