In their research, Reznick and colleagues will contrast populations of guppies that live in low-predation sites (guppies and Hart's killifish) with those that live in high-predation sites (guppies, Hart's killifish and other predators). Low- and high-predation sites exist in the same stream in Trinidad. They are separated by natural, barrier waterfalls that exclude predators but not guppies and Hart's killifish.

Previous research by Reznick has shown that guppies in low predation sites are found at higher population densities than in high predation sites. They have lower levels of food availability, which causes them to have lower growth rates and a smaller body size. Reznick found, too, that guppies living in environments with a large number of predators have adapted to reproduce earlier in life than guppies from low-predation localities.

"These differences occur because guppy populations expand in the absence of predators," he said. "The converse is that guppy population density is lower and food availability is higher in the presence of predators. In our experiments, we will add guppies in sections of the stream that had none before to see if ecological interactions are independent of evolution and if these interactions impact all aspects of the ecosystem.

The research team chose Trinidad as the research site because of prior history of work done on guppies on the island and the simplified nature of island communities. Reznick, who specializes in the study of adaptation, has more than 25 years of experience working with guppies in Trinidad.

The researchers plan to genetically tag each guppy and follow its progress over time, including not only its grow
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Contact: Iqbal Pittalwala
iqbal@ucr.edu
951-827-6050
University of California - Riverside
6-Oct-2006