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Pupfish evolution on fast-forward

UC DAVIS (US) — A pupfish that survives by biting the scales off its underwater neighbors is evolving up to 130 times faster than other pupfish species.

The approximately 50 different species of pupfish found from Massachusetts to Venezuela are all pretty much the same. “They look the same and they act the same,” eating detritus and algae off rocks, says Chris Martin, a graduate student working with Peter Wainwright, professor of evolution and ecology at the University of California, Davis.

Except for two. One, that lives in shallow, salty lakes on San Salvador Island in the Bahamas and is the only pupfish known to eat scales and another that eats small snails and clam shrimp. Changes to the fish’s jaws to match their specialized diet allowed researchers to construct an evolutionary map.

The research is published in the journal Evolution.

If the evolution of all pupfish is like a steadily expanding cloud, Martin says the San Salvador Island and Yucatan pupfish are like bursts of fireworks within it, showing explosive rates of evolution.

Among pupfish originally from the Yucatan area, one eats other fish and another feeds on plankton, but those species are extinct in the wild and only found in labs and aquaria.

It’s not clear why the pupfish in the two locations are evolving so fast. In both places, the lake water is hot and salty—but that’s true in other places where pupfish live. And mosquito fish, found in the same two lakes, show no signs of rapid change.

As a next step, Martin is taking lab-bred fish, including hybrids, back to the lakes to see whether they thrive. He hopes to see which fish succeed out of a spectrum of hybrids.

The study was funded by the National Science Foundation.

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