Scientists have discovered that fish indirectly help spread pollen among flowers near the water. That's because they eat dragonfly larva, which live in freshwater ponds and other water bodies. Adult dragonflies are major predators of bees, butterflies and other insect pollinators. The result is a simple but unexpected cascade: The more fish, the fewer dragonflies, the more bees and butterflies, the more plant pollination, reproduction and seeds.

A paper about the discovery, co-authored by scientists at the University of Florida and Washington University in St. Louis, will appear Thursday in Nature.

"Much of the science of ecology is elucidating the surprising and counterintuitive connections among species," said Robert Holt, a UF professor of zoology and one of five authors. "What we've done here is elucidate a heretofore unsuspected connection of that sort."

The research is significant in part because it shows how organisms from one ecosystem can change the lives of those in a seemingly separate one with the help of something, in this case the dragonfly, tying them together.

But it's also notable because it highlights an unusual example of how humans can potentially shape nature. For example, it's well known that habitat destruction and overfishing of salmon have ecological consequences from limiting food for grizzlies and other predators to reducing mountain stream nutrient levels. The fish-flower research shows the same potential for human impacts at a far more local and everyday level. People may never notice, but when they create, fill or drain a pond, or stock it, the ecological ripples lap onto shore.

"The presence or absence of fish can have an influence, we showed, on terrestrial plant reproduction," Holt said. "What often determines the presence or
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Contact: Robert Holt
rdholt@zoo.ufl.edu
352-392-6917
University of Florida
5-Oct-2005