Genes Save Killifish From Killer Pollutants in Texas

Student David Roberts (foreground) and UC Davis professor Andrew Whitehead catch Gulf killifish in a coastal Mississippi salt marsh. (Patrick Sullivan)

(CN) – The tiny Gulf killifish has adapted to killer toxins in the Houston Ship Channel in Texas, thanks to a genetic variation and a bit of luck, according to a new study.

“Our data show that some of the necessary variation was already present in the species’ gene pool. But that wasn’t enough for survival in the most severely polluted sites,” said study corresponding author Andrew Whitehead, a University of California, Davis, professor of environmental toxicology.

The study, published in the peer-reviewed journal Science Magazine, outlines how the minnow-sized killifish outlive other species in the highly polluted waters. A key lesson to take from the research, Whitehead said, is that it is important to keep migration corridors open.

“In order for these populations to be rescued from decline, they required new variation – and that came in the form of migrants from another species that came from a distant location,” he said.

Baylor University scientists, including associate professor Cole Matson and lead author Elias Oziolor, first noticed and questioned why the species was resistance to toxins. Researchers searching for the answer to that question sequenced genomes in Gulf killifish across a range of waters, from clean to super polluted.

They were surprised to discover DNA from an Atlantic species of killifish among the hardiest survivors. The Atlantic killifish were already known for being adaptive to pollution, but how did the non-natives travel more than 1,500 miles to mate with the Texans? For now, scientists can only surmise this was an accident linked to humans.

“They got very lucky by having some individuals of the Atlantic coast species, from over 2,500 kilometers away, dumped into their habitat at just the right time, sometime in the 1970s, give or take a decade, and bring them new genetic mutations that were key for extreme adaptation,” Whitehead said.

The introduction of the non-natives does not qualify as invasive, as is often the case when a strange species enters an ecosystem.

The Gulf killifish population was huge to begin with and teeming with genetic diversity long before the life-saving genetic mutation.

Whitehead cautioned against interpreting the findings the conclude that nature can solve human-caused environmental problems.

“A dangerous misinterpretation of our findings is that evolution can solve environmental problems that we are causing for many species,” he said. “It is also important to add that we likely can’t genetically engineer our way out of our environmental responsibilities.”

Study funding came from the C. Gus Glassock Endowed Research Fellowship, Exxon-Valdez Oil Spill Trustee Council, National Science Foundation, National Institutes of Environmental Health, and Baylor and Indiana Universities.

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