We present spectroscopic observations of ultra compact dwarf ( UCD ) galaxies in the Fornax and Virgo Clusters made to measure and compare their stellar populations .
The spectra were obtained on the Gemini-North ( Virgo ) and Gemini-South ( Fornax ) Telescopes using the respective Gemini Multi-Object Spectrographs .

We estimated the ages , metallicities and abundances of the objects from measurements of Lick line-strength indices in the spectra ; we also estimated the ages and metallicities independently using a direct spectral fitting technique .
Both methods revealed that the UCDs are old ( mean age 10.8 \pm 0.7 Gyr ) and ( generally ) metal-rich ( mean [ Fe/H ] = -0.8 \pm 0.1 ) .
The alpha-element abundances of the objects measured from the Lick indices are super-Solar .

We used these measurements to test the hypothesis that UCDs are formed by the tidal disruption of present-day nucleated dwarf elliptical galaxies .
The data are not consistent with this hypothesis because both the ages and abundances are significantly higher than those of observed dwarf galaxy nuclei ( this does not exclude disruption of an earlier generation of dwarf galaxies ) .
They are more consistent with the properties of globular star clusters , although at higher mean metallicity .
The UCDs display a very wide range of metallicity ( -1.7 < [ Fe/H ] < 0.0 ) , spanning the full range of both globular clusters and dwarf galaxy nuclei .

We confirm previous reports that most UCDs have high metalliticities for their luminosities , lying significantly above the canonical metallicitiy-luminosity relation followed by early-type galaxies .
In contrast to previous work we find that there is no significant difference in either the mean ages or the mean metallicities of the Virgo and Fornax UCD populations .