  Gas-phase abundances in galaxies are the products of those galaxies'
evolutionary histories. The star-formation history (SFH) of a region might
therefore be expected to influence that region's present day gaseous
abundances. Here, we employ data from the MaNGA survey to explore how local gas
metallicities relate to star-formation histories of galaxy regions. We combine
MaNGA emission line measurements with SFH classifications from absorption line
spectra, to compare gas-phase abundances in star-forming regions with those in
regions classified as starburst, post-starburst and green valley. We find that
starburst regions contain gas that is more pristine than in normal star-forming
regions, in terms of O/H and N/O; we further find that post-starburst regions
(which have experienced stochastic SFHs) behave very similarly to ordinary
star-forming regions (which have experienced far smoother SFHs) in O/H-N/O
space. We argue from this that gas is diluted significantly by pristine infall
but is then re-enriched rapidly after a starburst event, making gas-phase
abundances insensitive to the precise form of the SFH at late times. We also
find that green-valley regions possess slightly elevated N/O abundances at a
given O/H; this is potentially due to a reduced star-formation efficiency in
such regions, but it could also point to late-time rejuvenation of green valley
regions in our sample.
