  We present the results of medium-resolution spectroscopy of 28 globular
clusters (GCs) in six nearby galaxies of different luminosities and
morphological types, situated in: M33 (15 objects), M31 (3), IC10 (4), UGCA86
(4), HolmbergIX (1), and DDO71 (1) obtained at the Special Astrophysical
Observatory 6-meter telescope. Measurements of Lick absorption-line indices and
comparison with SSP models enabled us to obtain their spectroscopic ages,
metallicities and alpha-element to Fe abundance ratios. We found that all old
and intermediate-age GCs in our sample have low metallicities [Z/H] < -0.8 dex.
Metal-rich clusters are young and are preferentially found in galaxies more
massive than ~10^9 M_sun. The least massive dwarfs of our sample, DDO71 and
HolmbergIX, host one massive intermediate-age and one massive young metal-poor
GC, respectively. [a/Fe] abundance ratios tend to be enhanced but closer to
solar values for dwarf galaxies compared to GCs in more massive galaxies. We
analyse the age-metallicity relation for GCs in our galaxy sample and others
from the literature, and find, that 1) there is a general trend for GCs in low
surface brightness dwarf galaxies to be more metal-poor at a given age than GCs
in more massive galaxies; 2) the GC metallicity spread is wider for more
massive galaxies; 3) intermediate-age GCs in early-type dwarf galaxies are more
metal-rich at any given age than those in irregular galaxies of similar
luminosity.
