The keystone species concept: a critical appraisal

The keystone concept has been widely applied in the ecological literature since the idea was introduced in 1969. While it has been useful in framing biodiversity research and garnering support in conservation policy circles, the terminology surrounding the concept has been expanded to the extent that there is considerable confusion over what exactly a keystone species is. Several authors have argued that the term is too broadly applied, while others have pointed out the technical and theoretical limitations of the concept. Here, we chart the history of the keystone concept’s evolution and summarise the plethora of different terms and definitions currently in use. In reviewing these terms, we also analyse the value of the keystone concept and highlight some promising areas of recent work.