[1][2][3] Invasive species may have greater phenotypic plasticity in important traits than their native competitors, allowing them to tolerate more environmental variation,[4] or exhibit the ability to evolve rapidly to adapt to their new conditions.
[14] An early study of the flowering plant Silene latifolia found that about 60% of its invasive populations in North America were free from herbivory, while 84% of those in its native Europe exhibited damage from at least one herbivore.
[18] In some cases, native pathogens, parasites and herbivores present significant biotic resistance to potential invasive species,[19][20] as do non-native enemies that may have arrived prior to the exotic plant.
[24] The ERH is closely related to two other important theories for invasive species success: the evolution of increased competitive ability (EICA) and novel weapons hypotheses (NWH).
[29][30][31] A final argument for the ERH lies in the success of biological control of some invasive species, in which herbivores or other enemies from their native environment are introduced to suppress population growth in their adopted range.
[32] For example, when conservationists sought to control the invasive St.-John's-wort (Hypericum perforatum) in North America, they imported a leaf herbivore (Chrysolina quadrigemina) from its native range in Europe.