New research done by Joseph Travis and colleagues proves that not only does environment shape fish biology but those fish, in turn, shape the environment they live in. In a paper published in the Feb. 1, 2010 online edition of the journal PNAS (Proceedings of the National Academy of Sciences), researchers studied two distinct guppy populations in Trinidad, upstream fish and downstream fish. The upstream fish, who encounter fewer predators and a smaller food supply, grow more slowly, reproduce later, and live longer. Meanwhile, downstream fish, whose environment includes lots of predators and a larger food supply, reproduce earlier, but stay smaller and die younger.

Joseph Travis in his lab

“Evolution can be very fast,” Travis said. “Past work by David Reznick, our study’s principal investigator, showed that if you take downstream guppies and introduce them to pools upstream with no guppies, the descendants of those founders will evolve to look like upstream guppies in a few dozen generations.”

The researchers wondered whether the two very different guppy populations would affect the environment in different ways, so they put them in artificial streams that they’d built next to real streams and filled those streams with the same spring water and insect larvae found naturally. The results were dramatic. “Within just four weeks, the two types of guppies drove the parameters of the artificial streams in very different directions,” said Travis. “The combined effects of different grazing and different fertilization patterns served to change algal growth rates, detritus decay rates – because guppies can eat the little animals that eat decaying leaves – and the overall oxygen consumption rates in the ecosystem.”

Travis, dean of the College of Arts and Sciences, is Robert O. Lawton Distinguished Professor of Biological Science. Reznick is a professor at the University of California-Riverside. To read more about the study and its implications, go to http://www.fsu.edu/news/2010/02/04/ecology.evolution/