Curiously, diffuse knapweed's allelopathic chemicals were shown to have a deleterious effect on the North American competitors but were beneficial to its native competitors. While diffuse knapweed's native competitors are able to compete more effectively in the presence of allelopathic chemicals, the novel competitor's fitness is decreased. This situation provides an example of the effectiveness of the allelopathy mechanism benefiting from the ERH. The increased effectiveness of allelopathic chemicals cause diffuse knapweed to experience less competitive pressure. As a result, diffuse knapweed is able to establish more predominantly in this new area.