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Nat Commun. 2014 May 12;5:3873. doi: 10.1038/ncomms4873.

Parallel evolution of cox genes in H2S-tolerant fish as key adaptation to a toxic environment.

Author information

Molecular Ecology Group, Biodiversity and Climate Research Centre by Senckenberg Naturforschende Gesellschaft and Goethe-Universit├Ąt, 60325 Frankfurt, Germany.
Department of Ecology and Evolution, Institute for Ecology, Evolution and Diversity, J.W. Goethe-Universit├Ąt, 60438 Frankfurt, Germany.
Department of Zoology, Oklahoma State University, Stillwater, Oklahoma 74078, USA.
Department of Genetics, Stanford University, Stanford, California 94305, USA.


Populations that repeatedly adapt to the same environmental stressor offer a unique opportunity to study adaptation, especially if there are a priori predictions about the genetic basis underlying phenotypic evolution. Hydrogen sulphide (H2S) blocks the cytochrome-c oxidase complex (COX), predicting the evolution of decreased H2S susceptibility of the COX in three populations in the Poecilia mexicana complex that have colonized H2S-containing springs. Here, we demonstrate that decreased H2S susceptibility of COX evolved in parallel in two sulphide lineages, as evidenced by shared amino acid substitutions in cox1 and cox3 genes. One of the shared substitutions likely triggers conformational changes in COX1 blocking the access of H2S. In a third sulphide population, we detect no decreased H2S susceptibility of COX, suggesting that H2S resistance is achieved through another mechanism. Our study thus demonstrates that even closely related lineages follow both parallel and disparate molecular evolutionary paths to adaptation in response to the same selection pressure.

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