Study probes ecosystem of ...( most common factors that affect commun...)

most common factors that affect communities, but few studies look at all these factors together" Kneitel said. "Not surprisingly, predators, resources, and disturbances all had really strong effects, but the interesting finding was how these various factors interacted. Community composition was altered by all treatments, depending on which treatments were present. Certain species were associated with each of the treatments those in predator treatments were those tolerant of predators, those in disturbance treatments were tolerant of disturbances, and so on." Kneitel studied between 20 and 25 protozoan species and four rotifers; protozoans are single-celled organisms, rotifers, multi-celled, yet some protozoans are bigger than rotifers and will prey upon them. Mosquito larvae browse and filter-feed and will attack either of the groups of species.

'It's war inside a tree hole," Kneitel said. "We found that predation has the strongest effect when there are no disturbances. Disturbance has the strongest effect when there is little predation. When there is no disturbance or predation, competition is the primary source of extinction. A disturbance a dry tree hole pretty much kills everything but certain protozoans that can go dormant and survive the cycle."

The results will be published in a forthcoming issue of Ecology. The work was supported by NSF. Kneitel said most studies of this sort look at two factors, compared with the three he and Chase studied.

"Our results show that if you change any one of the three factors, you alter the face of the community," Kneitel said. "We found that we had a group of species that were good competitors, another that is good at tolerating predators, and yet another that can survive and tolerate disturbances.

"These traits (niche) differences allow many species to coexist with one another at different spatial scales. This is true for this community, but also many other co
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Contact: Tony Fitzpatrick
tony_fitzpatrick@wustl.edu
314-935-5272
Washington University in St. Louis
15-Jun-2004

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