Characteristics of native predators are more important than those of alien prey in determining the success of biotic resistance in marine systems.
Predator-driven biotic resistance is known to be more effective in marine systems than in terrestrial and freshwater environments. However, there is little consensus about when such resistance can be expected to succeed or fail. Here, we reviewed case studies that investigated interactions between native marine predators and alien prey, with the aim of establishing which characteristics are important in determining the outcome of such interactions. Four potential biotic resistance outcome scenarios were identified, with these scenarios progressing from a state of no resistance to successful resistance, i.e. when an alien species is successfully excluded from the native community. Characteristics of native predators and alien prey that likely affect the outcome of biotic resistance were identified, and their presence and absence were noted for each case study. The outcome of each native predator-alien prey interaction was assigned to one of the four biotic resistance outcome scenarios, based on the conclusion of the original study. Multivariate statistics were used to examine potential differences in the suites of characteristics typifying each outcome scenario. These characteristics were found to differ significantly among scenarios, with failure of predator-driven biotic resistance occurring in cases where the alien prey typically had high fecundity, high recruitment and substantial dispersal potential. Conversely, successful biotic resistance was related to the characteristics of native predators including high abundance, strong predation pressure on alien prey, coupled with high feeding rates. This research emphasises the need to integrate information from both trophic groups to strengthen predictions about the outcomes of novel predator-prey interactions.