By Carl Zimmer
The Channel Islands, off the coast of Southern California, are a natural laboratory for a particularly adorable experiment in evolution.
A unique species called the island fox has lived there for several thousand years, their bodies shrinking over the generations until now each is smaller than a house cat. Adult island foxes weigh as little as 2.35 pounds.
Now a team of scientists has discovered another way in which island foxes are extraordinary: Genetically, they are nearly identical to one another. In fact, a fox community on one island has set a record for the least genetic variation in a sexually reproducing species.
Oliver A. Ryder, the director of genetics at the San Diego Zoo Institute for Conservation Research, said the new research posed a biological puzzle.
It’s an axiom of evolutionary biology that low levels of genetic variation put species at risk of extinction. Yet the delicate island foxes are still racing across meadows and bounding up trees.
“How can the island foxes get away with it?” Dr. Ryder said.
The new study, published on Thursday in Current Biology, was led by Robert K. Wayne, a geneticist at the University of California, Los Angeles. Dr. Wayne has been studying the DNA of island foxes since the early 1990s, hoping to understand their remarkable makeup.
“They’re like dodos,” Dr. Wayne said in an interview. “They have no notion of human fear. You can just put them in your lap.”
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