PARENT SESSION
Oral Session #77: Aquatic Ecology: Food webs, invertebrates. Presiding: R.A. Washington-Allen.
Friday, August 10, 2001. 8:00 AM to 12:00 PM. Hall of Ideas H.
The Stabilizing Role of Prey Defense in a Pelagic Food Web.
BOEING, WIEBKE1, WISSEL, BJOERN1, RAMCHARAN, CHARLES1, 1
ABSTRACT- Prey defenses not only protect the individual but can also benefit the predator by preventing overexploitation of the prey. Moreover, the cost of prey defense may actually benefit the prey in the long-term by suppressing population growth rates below overexploitation (boom and bust cycles). Although the population growth rate of the prey may be reduced in the short-term by the costs of defense, overexploitation may be prevented in the long-term. Prey defenses may thus enhance both energy flow through the food web and productivity of both prey and predator populations. To test those hypotheses we conducted two sets of enclosure experiments (1-m diameter; 7-m deep) with planktivorous fish and Chaoborus as predators. As prey we used a Daphnia clone with strong (S) and another with no (N) defense mechanisms (vertical migration) to the predator. Controls had no predators and predation treatments exposed the clones to either fish or Chaoborus. We found that the predation treatments with the less vulnerable clone (S) had the most stable population densities, highest energy flow rates through the food web, and the highest sustained predator biomass.
KEY WORDS: Population Stability, Antipredator Defense, Daphnia Vulnerability, Energy Flow