Performance of non-native species within marine reserves

Conservation of biodiversity is a major aim of marine reserves; however the effects of reserves on non-native species, a major threat to biodiversity globally, is not widely known. Marine reserves could resist non-native species due to enhanced native diversity and biomass that heightens biotic resistance. Or non-native species could be enhanced by reserves by at least three mechanisms, including protection from harvesting, increased fishing pressure outside reserves facilitating invasions at a regional scale and increasing the exposure of reserves to more potential invaders, and increased propagule pressure from human visitation. We exhaustively searched the literature and found 13 cases that contained quantitative data on non-native species inside and outside marine reserves. In no cases did reserves resist non-native species. Of the seven cases where reserves were established prior to the arrival of the non-native species, five had no effect on the non-native species and two enhanced non-native species. Of the six cases where reserves were established in areas that had pre-existing non-native species, two had no effect on the non-native species and four enhanced the non-native species. These results suggest that while non-native species do equally well or better within marine reserves, too few data are currently available to draw broad, general conclusions regarding the effects of marine reserves on non-native species. Management plans for marine reserves rarely include guidelines for preventing or managing non-native species. If the trends we have detected here are supported by future studies, non-native species should be a priority for management of marine reserves