Little evidence for release from herbivores as a driver of plant invasiveness from a multi-species herbivore-removal experiment

Enemy release is frequently posed as a main driver of invasiveness of alien species. However, an experimental multi-species test examining performance and herbivory of invasive alien, non-invasive alien and native plant species in the presence and absence of natural enemies is lacking. In a common garden experiment in Switzerland, we manipulated exposure of seven alien invasive, eight alien non-invasive and fourteen native species from six taxonomic groups to natural enemies (invertebrate herbivores), by applying a pesticide treatment under two diff erent nutrient levels. We assessed biomass production, herbivore damage and the major herbivore taxa on plants. Across all species, plants gained signifi cantly greater biomass under pesticide treatment. However, invasive, non-invasive and native species did not diff er in their biomass response to pesticide treatment at either nutrient level. Th e proportion of leaves damaged on invasive species was signifi cantly lower compared to native species, but not when compared to non-invasive species. However, the diff erence was lost when plant size was accounted for. Th ere were no diff erences between invasive, non-invasive and native species in herbivore abundance. Our study off ers little support for invertebrate herbivore release as a driver of plant invasiveness, but suggests that future enemy release studies should account for diff erences in plant size among species.