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The Guppy Project



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Darwin thought that evolution by natural selection occurred very slowly, over hundreds if not thousands of years. Evolutionary biologists now know that evolutionary changes in species can happen very quickly, over a relatively few generations. To observe the procecess of adaptive evolution in nature, and to test evolutionary hypotheses, we are studying populations of guppies on the Caribbean island of Trinidad.

The National Science Foundation (NSF), through its Integrative Biological Research (FIBR) program, is funding a 5-year study by 13 biologists from colleges, universities, and research institutions throughout the United States and Canada, to study the relationship of adaptive evolution and environmental circumstances.

The Trinidadian guppy (Poecilia reticulata) is an excellent species for these purposes because:

  • It matures rapidly (one generation = 3-4 months)

  • It inhabits different ecological environments that can be easily manipulated

On Trinidad, guppies live in streams, or portions of streams, that can differ in the species of predators that the guppies have to contend with. Some streams are high-predation environments, others  low-predation. Different predation environments are often right next to one another, separated by a waterfall (which neither guppies nor predators can cross). 

Guppies from high-predation environments experience much higher mortality rates than do guppies in low-predation environments. High mortality is associated with the following characteristics, all of which have a genetic basis:

  • Earlier maturity

  • Greater investment of resources in reproduction

  • More and smaller offspring.

We have found that mortality rates can be manipulated by:

  • Transplanting guppies from high-predation localities into sites from which they and their predators had previously been excluded by natural waterfalls, thus lowering mortality rates;

  • Introducing predators into low-predation sites, thus increasing mortality rates. 

Such experiments have shown that species evolve as predicted by theory. We have also found that evolution by natural selection can be remarkably fast, on the order of four to seven orders of magnitude faster than had been inferred from the fossil record.


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University of California, Riverside
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Riverside, CA 92521
Tel: (951) 827-1012

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Project Information

Foundations in Integrative Biological Research (FIBR)
Funded by: National Science Foundation

Email: gupy@ucr.edu

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