  We find that the fraction of early-type galaxies in poor groups (containing
from 4 to 10 members) is a weakly increasing function of the number of the
group members and is about two times higher than in a sample of isolated
galaxies. We also find that the group velocity dispersion increases weakly with
the fraction of early-type galaxies. Early-type galaxies in poor groups are
brighter in the near-infrared with respect to isolated ones by 0.75 mags (in K)
and to a lesser degree (by 0.5 mags) also in the blue. We also find early-type
galaxies in groups to be redder than those in the field. These findings suggest
that the formation history for early-type galaxies in overdense regions is
different from that of in underdense regions, and that their formation in
groups is triggered by merging processes.
