Atlantic Coast of the USA. Tolerant killifish populations (red) are from New Bedford Harbor (NBH) MA, USA; Bridgeport (BP) CT, USA; and Newark (NWK) NJ, USA. Reference killifish populations (blue) are from Block Island (BI) RI, USA; Flax Pond (Flax) NY, USA; and Sandy Hook (SH), NJ, USA. Precise locations (coordinates) can be found in Nacci et al. [5]. Symbols (circles, squares, triangles) unite geographically paired populations, whereas colour (red or blue) unite populations with similar pollution exposure histories.