Daphnia as keystone predators: effects on phytoplankton diversity and grazing resistance
Year of Publication
Journal of Plankton Research
4m3, mesocosm, freshwater, California, USA
Theory predicts that a predator can promote coexistence among competing prey, and so enhance prey diversity (the keystone predation effect), by fostering dominance of slow-growing, consumption-resistant prey. In contrast, if the predator promotes dominance by fast-growing vulnerable prey, theory predicts that the predator is unlikely to promote prey diversity. Theory is silent about keystone predation effects when the predator does not cause a net change in the vulnerability of the prey assemblage. I present experimental evidence that Daphnia can act as a keystone predator without causing a net change in the grazing resistance of the phytoplankton assemblage. No change in resistance was observed, despite strong Daphnia effects on the species composition of the phytoplankton.
Date of Published
December 1, 2005
Type of Article