Aggregation and the Population Dynamics of Parasitoids and Predators

Aggregation by parasitoids and predators has long been considered an important factor helping to stabilize host-parasitoid and predator-prey interactions. This consensus has recently been challenged by W. W. Murdoch and A. Stewart-Oaten, who conclude, from an analysis of a model formulated in a novel way, that aggregation independent of host density has no effect on stability, whereas aggregation to host or prey patches of high density is normally destabilizing. It is argued here that part of the discrepancy in conclusions results from the use of different concepts of aggregation: behavioral versus statistical. It is also argued that the conclusions of the Murdoch and Stewart-Oaten model should be treated with caution, because unrealistic assumptions have to be made to derive the model, and it is not clear that the conclusions are robust to the relaxation of these assumptions.

[1]  J. Lawton,et al.  Dynamic complexity in predator-prey models framed in difference equations , 1975, Nature.

[2]  J. Krebs,et al.  INDIVIDUAL DECISIONS AND THE DISTRIBUTION OF PREDATORS IN A PATCHY ENVIRONMENT , 1988 .

[3]  A. Ōkubo,et al.  Di?usion and ecological problems: mathematical models , 1980 .

[4]  R. May,et al.  Host–parasitoid associations in patchy environments , 1990, Nature.

[5]  M. Hassell,et al.  The Dynamics of Optimally Foraging Predators and Parasitoids , 1979 .

[6]  A. Nicholson,et al.  The Balance of Animal Populations.—Part I. , 1935 .

[7]  M. Hassell,et al.  The Persistence of Host-Parasitoid Associations in Patchy Environments. II. Evaluation of Field Data , 1991, The American Naturalist.

[8]  L. Taylor,et al.  Synoptic Dynamics, Migration and the Rothamsted Insect Survey: Presidential Address to the British Ecological Society, December 1984 , 1986 .

[9]  R. May,et al.  STABILITY IN INSECT HOST-PARASITE MODELS , 1973 .

[10]  M. Hassell.  The dynamics of arthropod predator-prey systems. , 1979, Monographs in population biology.

[11]  Peter Chesson,et al.  Aggregation of Risk: Relationships Among Host-Parasitoid Models , 1986, The American Naturalist.

[12]  N. Rashevsky,et al.  Mathematical biology , 1961, Connecticut medicine.

[13]  Allan Stewart-Oaten,et al.  Aggregation by Parasitoids and Predators: Effects on Equilibrium and Stability , 1989, The American Naturalist.

[14]  Michael P. Hassell,et al.  Discrete and continuous insect populations in tropical environments , 1989 .

[15]  Robert M. May,et al.  HOST-PARASITOID SYSTEMS IN PATCHY ENVIRONMENTS: A PHENOMENOLOGICAL MODEL , 1978 .

[16]  A. Ives.  Density-Dependent and Density-Independent Parasitoid Aggregation in Model Host-Parasitoid Systems , 1992, The American Naturalist.

[17]  R. May,et al.  Stability and Complexity in Model Ecosystems , 1976, IEEE Transactions on Systems, Man, and Cybernetics.

[18]  R. May,et al.  Aggregation of Predators and Insect Parasites and its Effect on Stability , 1974 .

[19]  J. Waage,et al.  Arrestment responses of the parasitoid, Nemeritis canescens, to a contact chemical produced by its host, Plodia interpunctella , 1978 .

[20]  M. Hassell,et al.  Natural enemies may be a cause of discrete generations in tropical insects , 1987, Nature.

[21]  William Gurney,et al.  An Invulnerable Age Class and Stability in Delay-Differential Parasitoid-Host Models , 1987, The American Naturalist.

[22]  Peter Chesson,et al.  The Persistence of Host-Parasitoid Associations in Patchy Environments. I. A General Criterion , 1991, The American Naturalist.