Scientists Identify Genetic Mechanism for Rapid Adaptation to Normally Lethal Levels of Toxic Pollution in Wild Atlantic Killfish

A new report identifies the genetic mechanism responsible for evolutionary adaptation to toxic pollution observed in wild Atlantic killifish populations. The Atlantic killifish is renowned for its ability to tolerate large fluctuations in temperature, salinity, and oxygen levels. However, its rapid adaptation to the normally lethal levels of toxic pollution found in some urban estuaries in the United States is unusual, even for such a hardy species. A report, published in the December 9, 2016 issue of Science. journal Science by a collaborative team of research institutions including the University of Birmingham, found that some populations of killifish are up to 8,000 times more resistant than others to highly toxic industrial pollutants such as dioxins, heavy metals, and hydrocarbons. The article is titled “The Genomic Landscape of Rapid Repeated Evolutionary Adaptation to Toxic Pollution in Wild Fish.” The team analyzed the genomes of four wild populations of pollution-tolerant killifish compared with four non-tolerant populations, to identify the mechanism behind this adaptation. The scientists found that the genes responsible for the trait were those involved in the aryl hydrocarbon receptor (AHR) signling pathway, which, combined with observations of desensitization of this pathway in tolerant populations, led them to conclude that the AHR pathway is a key target of natural selection. The team also showed that the potentially negative effects of desensitization of the AHR pathway were ameliorated through compensatory adaptations in terms of cell cycle regulation and immune system function. This, combined with the diversity of pollutants present in estuaries, results in a relatively complex adaptive genotype in wild populations compared to that of laboratory models.
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