Population, community and ecosystem effects of exotic herbivores: A growing global concern

Exotic herbivores represent a serious threat to native biodiversity, producing large scale changes in native communities and altering ecosystem processes. In this special issue, we present a series of case studies and reviews from different areas of the world that highlight (1) the consequences of herbivore introductions are a global problem; (2) they can result in wholesale shifts in the distribution of dominant plants on the landscape and; (3) the effects of herbivore introductions extend from the population to the community and ecosystem level. These studies suggest that introduced herbivores often retard ecosystem recovery after disturbance, facilitate invasion of plant species and can act as selective agents on native plant communities. These studies also suggest that several topics, including facilitation between exotic herbivores and exotic plants and animals (i.e., invasional meltdown) and the effect of exotic herbivores on ecosystem processes, require more research attention. Overall the papers in this special feature suggest that introduced herbivores are a global problem with wide-ranging ecological and evolutionary effects.