Predation, apparent competition, and the structure of prey communities

摘要: Abstract It is argued that alternate prey species in the diet of a food-limited generalist predator should reduce each other's equilibrial abundances, whether or not they directly compete. Such indirect, interspecific interactions are labeled apparent competition . Two examples discussed which an observed pattern habitat segregation was at first interpreted as evidence for direct competition, but later resulting from shared predation. In order to study consequences predator-mediated isolation other complicating factors, model community analyzed there no among prey. An explicit necessary condition coexistence derived case one feeding on many species. This has several interesting properties: (1) Prey with high relative values parameter r “keystone” community; (2) can be excluded by “diffuse” competition; (3) large changes niche breadth need correspond density; (4) trophic level whole regulated predator, yet its constituent both and available resources; (5) increased productivity may either increase, decrease, leave unchanged number (6) decrease density-independent mortality diversity. These conclusions seem robust growth equations incorporation satiation. By contrast, adding refugia switching weakens these conclusions. If satiated switched, elements ij comprising matrix have signs opposite long-term effect j upon i The natural selection discussed. Unless , K tightly coupled, within will tend abundance