TALLAHASSEE, Fla.--In the natural stream communities of Trinidad, guppy populations live close together, but evolve differently. Upstream, fewer predators mean more guppies but less food for each; they grow slowly and larger, reproduce later and less, and die older. Downstream, where predators thrive, guppies eat more, grow rapidly, stay small, reproduce quickly and die younger.
While it is clear to ecologists that an ecosystem shapes the evolution of animals living in it, population biology experts such as Joseph Travis of The Florida State University believe the reverse can also be true, making the relationship between evolution and ecology a model of reciprocity.
Now, he can prove it.
The evidence comes from an experiment in evolution that Travis designed with David N. Reznick of the University of California-Riverside and their fellow members of an interdisciplinary research team. Findings from the study expand the body of knowledge about the interactions between evolution and ecology by demonstrating that evolutionary adaptations can also act as triggers for a cascade of in-tandem changes to both ecosystem and animal.
In the experiment, led by Ronald D. Bassar of UC-Riverside, the team used artificial streams filled with the same spring water and insect larvae found in Trinidad's natural habitats to examine whether genetically distinct guppies from upstream or downstream had different effects on ecosystem processes. They compared the two types of guppies because earlier work showed that the little freshwater fish could evolve rapidly from a downstream "type" to an upstream "type."
The team found dramatic differences between the effects of each type of guppy on the nutrient cycles and overall productivity of the stream ecosystems. Travis said the results, which emerged very rapidly during the experiment, predict that the team's larger experiment introducing downstream guppies to upstream habitats wil
|Contact: Joseph Travis|
Florida State University