  Considering a quadratic parametrization of the dark energy density, we
explore signatures of evolution using data from gas mass fraction in clusters,
type Ia supernova, BAO and CMB. We find -- excluding CMB data -- a preference
for a evolution of $\rho_{de}(z)$ towards smaller values as redshift increases,
a result consistent with a recent study using the BAO DR11 data by Delubac et
al. (2015).
