“…Although home range and toxicology studies are lacking for F. grandis, we infer that F. grandis is also relatively sensitive to pollutants and exhibits high site fidelity, such that the biology of this species is likely affected primarily by the local environment, given the recent shared ancestry of F. grandis with F. heteroclitus (8) and similar physiology, life history, and habitat (9-13). We sampled from populations resident in Gulf of Mexico-exposed marshes before oil landfall (May 1-9, 2010), during the peak of oil landfall (June [28][29][30]2010), and after much of the surface oil was no longer apparent 2 mo later (August 30-September 1, 2010) at six field sites from Barataria Bay, Louisiana, east to Mobile Bay, Alabama ( Fig. 1 and Dataset S1).…”