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The Strathprints institutional repository is a digital archive of University of Strathclyde's Open Access research outputs. Strathprints provides access to thousands of Open Access research papers by University of Strathclyde researchers, including by researchers from the Department of Computer & Information Sciences involved in mathematically structured programming, similarity and metric search, computer security, software systems, combinatronics and digital health.

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Large-amplitude cycles of Daphnia and its algal prey in enriched environments

McCauley, E. and Nisbet, R.M. and Murdoch, W.W. and de Roos, A.M. and Gurney, William (1999) Large-amplitude cycles of Daphnia and its algal prey in enriched environments. Nature, 402 (9). pp. 653-657. ISSN 0028-0836

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Abstract

Ecological theory predicts that stable populations should yield to large-amplitude cycles in richer environments1±3. This does not occur in nature. The zooplankton Daphnia and its algal prey in lakes throughout the world illustrate the problem4±6. Experiments show that this system its the theory's assumptions7±9, yet it is not destabilized by enrichment 6. We have tested and rejected four of ive proposed explanations 10. Here, we investigate the fifth mechanism: inedible algae in nutrient-rich lakes suppress cycles by reducing nutrients available to edible algae. We found three novel results in nutrient-rich microcosms from which inedible algae were excluded. First, as predicted by theory, some Daphniaedible algal systems now display large-amplitude predator-prey cycles. Second, in the same environment, other populations are stable, showing only small-amplitude demographic cycles. Stability is induced when Daphnia diverts energy from the immediate production of young. Third, the system exhibits coexisting attractors -a stable equilibrium and large-amplitude cycle. We describe a mechanism that flips the system between these two states.