Species interactions: complex effects

Interactions within ecological communities usually involve many species and pose intriguing challenges for ecologists who wish to map and disentangle them. To simplify this task we often assume that the interactions do not change in strength or direction and that the identities of the key species remain the same. Species can be 'pigeon-holed' into convenient categories such as 'pollinator', 'competitor', 'pest' or even 'redundant' using these assumptions. This makes programs of conservation or pest management easier to implement, but is also ignores an emerging body of evidence that interactions between species vary between situations, places and times. In this chapter we will explore the complexity of effects that arise from changes in tereactions between species. We also consider how such effects may be modelled and predicted,a nd illustrate how ecological insight can be used to guide management decisions.