Non-Native, Non-Naturalised Plants Suffer Less Herbivory Than Native Plants Across European Botanical Gardens

AimThe enemy release hypothesis states that the invasion success of non-native species is partly due to their escape from natural enemies, e.g., herbivores. Large-scale studies of herbivory using multiple species across multiple sites are needed to test the generality of herbivory release in non-native plants.LocationEurope.MethodsWe carried out leaf-herbivory surveys from 2007 to 2021 in 15 botanical gardens ranging in latitude from 47 degrees N (Switzerland) to 63 degrees N (Norway) to investigate how herbivory levels differed between (i) native and non-native species, and (ii) native and non-naturalised or naturalised species.ResultsOverall, we found that herbivory levels were lower on non-native than native species. In addition, we found that non-naturalised plants suffered less herbivory than natives and that naturalised plants showed similar levels of herbivory to native plants.Main ConclusionsWe find broad support for lower herbivory of non-native plant species compared to natives. However, the stronger reduction in herbivory for non-naturalised plants suggests that herbivore release may be transient and less pronounced for naturalised non-native species that have become abundant and integrated into resident communities. This has implications for the management of naturalised non-native plants, which are performing well in their non-native ranges despite suffering comparable herbivory levels to native species.