Gulf Killifish survived polluted waters with genes from another fish
NIEHS grantees found that Gulf Killifish in the Houston Ship Channel rapidly evolved to adapt to lethal levels of aromatic hydrocarbon pollutants. The findings suggest that the Gulf Killifish acquired the resistance genes from breeding with the closely related Atlantic Killifish.
The researchers sampled fish from 12 sites spanning the pollution gradient, spawned them separately in the laboratory, and exposed their embryos to a range of concentrations of pollutants. They found that fish from the most polluted sites were the most resistant to harmful effects, and that resistance was retained through at least two generations in a clean environment. To understand the genetic basis of this resistance, they sequenced the genomes of hundreds of Gulf Killifish from very polluted, moderately polluted, and clean water. Fish with higher resistance had lower activation of the aryl hydrocarbon receptor (AHR), a protein that is involved in cardiac toxicity by aromatic hydrocarbons.
The scientists were surprised to find that the adaptive DNA regulating AHR signaling came from an Atlantic Coast species of killifish, which has been known to rapidly evolve resistance to high levels of pollution. The authors suggest that their transport to the Gulf was likely an accident initiated by humans. Non-native species can put populations at risk for negative ecological consequences, but according to the authors, this study shows that in some rare cases, interbreeding between distinct genetic populations can provide variation necessary for adaptation following extreme environmental change.
Citation: Oziolor EM, Reid NM, Yair S, Lee KM, VerPloeg SG, Bruns PC, Shaw JR, Whitehead A, Matson CW. 2019. Adaptive introgression enables evolutionary rescue from extreme environmental pollution. Science 364(6439):455-457.