RIVERSIDE, Calif. The direct effect predators have on their prey is to kill them. The evolutionary changes that can result from this direct effect include prey that are younger at maturity and that produce more offspring.
But killing prey also has indirect effects rarely characterized or measured such as a decline in the number of surviving prey, resulting, in turn, in more food available to survivors.
In a new study characterizing the complex ecological interactions that shape how organisms evolve, UC Riverside biologists Matthew Walsh and David Reznick present a novel way of quantifying these indirect effects by showing that prey adapt to food availability as well as the presence of predators.
Our study can serve as a model for how humans alter ecosystems when they remove key predators like wolves and bears from land or tuna and billfish from seas, said Reznick, a professor of biology.
He and Walsh compared life history traits between Trinidadian fish communities impacted by the presence of predators. They settled on Trinidadian waterfalls as study sites because the waterfalls serve as barriers to the upstream distribution of predator and prey fish, thereby creating distinct ecological communities in similar habitats only a few hundred meters from each other like test-tubes in nature.
First, they used killifish from killifish-only localities, above waterfalls, where killifish are the only fish present; and killifish from high predation localities, below these waterfalls, where the killifish coexist with a diversity of predators. Second, they reared the grandchildren of these killifish in a lab at UCR to ensure that any differences observed between populations are likely to be genetic, and not environmental, in origin.
To quantify the direct and indirect effects of predation, Walsh and Reznick reared the killifish under m
|Contact: Iqbal Pittalwala|
University of California - Riverside