Is invasion success explained by the enemy release hypothesis?
Article first published online: 4 JUN 2004
Volume 7, Issue 8, pages 721–733, August 2004
How to Cite
Colautti, R. I., Ricciardi, A., Grigorovich, I. A. and MacIsaac, H. J. (2004), Is invasion success explained by the enemy release hypothesis?. Ecology Letters, 7: 721–733. doi: 10.1111/j.1461-0248.2004.00616.x
- Issue published online: 4 JUN 2004
- Article first published online: 4 JUN 2004
- Editor, Marcel Rejmanek Manuscript received 9 March 2004 First decision made 19 April 2004 Manuscript accepted 29 April 2004
- Enemy inversion hypothesis;
- enemy of my enemy hypothesis;
- enemy release hypothesis;
- exotic species;
- increased susceptibility hypothesis;
- invasion success;
- non-indigenous species
A recent trend in invasion ecology relates the success of non-indigenous species (NIS) to reduced control by enemies such as pathogens, parasites and predators (i.e. the enemy release hypothesis, ERH). Despite the demonstrated importance of enemies to host population dynamics, studies of the ERH are split – biogeographical analyses primarily show a reduction in the diversity of enemies in the introduced range compared with the native range, while community studies imply that NIS are no less affected by enemies than native species in the invaded community. A broad review of the invasion literature implies at least eight non-exclusive explanations for this enigma. In addition, we argue that the ERH has often been accepted uncritically wherever (i) NIS often appear larger, more fecund, or somehow ‘better’ than either congeners in the introduced region, or conspecifics in the native range; and (ii) known enemies are conspicuously absent from the introduced range. However, all NIS, regardless of their abundance or impact, will lose natural enemies at a biogeographical scale. Given the complexity of processes that underlie biological invasions, we argue against a simple relationship between enemy ‘release’ and the vigour, abundance or impact of NIS.