Food web complexity I: theoretical results
For centuries, biologists have been leaving their north-temperate, cold and species-poor homes to marvel at the extraordinary richness of species in the tropics. Nor has the contrast between the often capricious temperate climates and the warm and seemingly constant tropical ones escaped their notice. Not surprisingly, some of the earliest attempts to relate food web attributes to ecosystem function are embodied in the idea of some relationship between stability and complexity. But species richness as a measure of complexity and a benign, aseasonal climate as a measure of stability is only one of the many possible pairs of definitions. The hypothesis that complexity is related to stability causes contention, in part, because the definitions of stability and complexity are sufficiently vague to permit a plethora of intepretations. Elton (1958, pp. 145–153) gives six lines of evidence for his assertion that more complex ecosystems are more stable. His examples seem highly heterogeneous in the light of twenty years of hindsight. They contain, for example, comments on the cyclical behaviour of single-species population models, a statement that tropical systems are free from pest outbreaks and a discussion of how species-poor island faunas are susceptible to man’s attempts at introducing new species. But most contention stems from recent theoretical studies because these lead to the opposite hypothesis, namely, that complex systems will be less stable than simple ones.
KeywordsJacobian Matrix Interaction Strength Equilibrium Density Species Loss Predator Removal
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