Swimming in polluted waters

Human activities alter ecosystems around the planet, often rendering environmental conditions unfavorable for plant and animal survival. In the salt marshes along North America's Atlantic coast, the influx of industrial waste has caused chemical pollutants to accumulate at lethal levels, causing the disappearance of many species from affected sites. Yet, multiple populations of the Atlantic killifish ( Fundulus heteroclitus ) have adapted to cope with levels of pollution orders of magnitude higher than those that members of the same species from unaffected habitats can tolerate. On page 1305 of this issue, Reid et al. ( 1 ) provide strong evidence that adaptation has occurred rapidly and through similar genetic changes in multiple populations of killifish that have independently colonized polluted habitats.