Ecology of galaxy stellar populations from optical spectroscopic surveys
  The age and chemical composition of the stars in present-day galaxies carry
important clues about their star formation processes. The latest generation of
population synthesis models have allowed to derive age and stellar metallicity
estimates for large samples of low-redshift galaxies. After reviewing the main
results about the distribution in ages and metallicities as a function of
galaxy mass, I will concentrate on recent analysis that aims at disentangling
the dependences of stellar populations properties on environment and on galaxy
stellar mass. Finally, new models that predict the response of the full
spectrum to variations in [alpha/Fe] will allow us to derive accurate estimates
of element abundance ratios and gain deeper insight into the timescales of star
formation cessation.
