Robert Pore's Ag Blog

LINCOLN, Neb. -- A guppy in Trinidad may provide some answers about how changes in ecosystems and evolution interact.

University of Nebraska-Lincoln stream ecologist Steve Thomas is studying how evolution plays out in real time. Thomas is studying a fast-evolving guppy in Trinidad to track the effects of ecosystem changes on a species and the subsequent effects of its evolution on the local ecosystem.

Thomas's research, which also will look at human effects on the environment and subsequent changes in evolution, is part of a project involving several universities. It's funded by a five-year, $5 million National Science Foundation grant.

Popular notions that evolution operates too slowly to produce changes in human time, and certainly not in less than a decade, are not always correct, said Thomas, of UNL's School of Natural Resources.

"This system provides a unique opportunity to study evolution in real time, over the time an NSF grant can cover and over which ecological studies typically occur," he said. "What we've observed in the past is that these evolutionary changes occur after predation risk has been altered."

Streams in Trinidad are well suited for these experiments because they are separated by waterfalls creating stream sections with different kinds of guppy predators. David Rznick of the University of California, Riverside, who leads the overall project, has demonstrated that predation risk for guppies can influence size of offspring, age and size at maturity and aspects of growth and aging, Thomas said.

The study begins in January and involves a 12-person team with expertise in molecular biology, population ecology, ecosystem science, biogeochemistry and applied mathematics.

Administered through the NSF's Frontiers in Integrative Biology program, these grants support interdisciplinary work on the planet's most challenging scientific questions.
In a $1.7 million part of the overall study, with $307,000 directed to UNL, Thomas will work with Alex Flecker of Cornell University and Catherine Pringle of the University of Georgia on the ecological feedbacks between food web structure and evolutionary changes.

"For example, if we observe shifts in diet, do we get changes in algal composition, abundance and productivity?" Thomas asks. Algae feed invertebrates, which in turn are eaten by the fish.

Thomas, Flecker and Pringle form the ecosystem team, Thomas said. They will examine stream "metabolic" activity, an investigation Thomas will lead. They will use oxygen measurements to estimate the sum of all photosynthetic and respiration activity in an entire reach of the stream.

In addition, Thomas will lead experiments that use a stable isotope of nitrogen as a tracer to track nitrogen flow through the ecosystem and food web.
"If these evolutionary changes alter diet, we should see that in the way nitrogen flows through the system," he says.

He and colleagues also will manipulate light conditions in two stream reaches to examine how changes in the base of a food web influence the evolution of guppy populations. These changes will approximate the human effects of deforestation or other thinning effects on the canopy.

Flecker and Pringle will examine more direct interactions between guppy feeding and prey items and interactions between fish presence and algal growth and composition.
Thomas's portion of the grant will employ several UNL graduate and undergraduate students and help support post-doctoral researchers at Cornell and Georgia.