When the novelty wears off: Enemy spillover drives plant invasion success

Abstract

Integrating plant physiological traits (ideal weed hypothesis) and interactions with enemies (enemy release hypothesis) may be key to understanding plant invasions. Contrary to enemy release, recent evidence suggests that invasive plants often accumulate generalist enemies due to the same r-selected physiological traits that often drive invasive success. Despite high enemy loads, successful invasive plants can remain dominant due to high growth rates rather than due to lack of damage. Consequently, generalist herbivore and pathogen populations may be amplified by invaders and can spillover onto native plants, with these indirect interactions disproportionately affecting native rather than invasive plant species via apparent competition. Where this occurs, the generalist enemies of invasive plants may instead be hidden allies that amplify invader success and impacts.