Enemy Release

Thu, 02 Apr 2026 00:00:00 +0000

The enemy release hypothesis (ERH) proposes that invasive species succeed in their introduced range because they have escaped from the co-evolved natural enemies — specialist herbivores, parasites, pathogens, and competitors — that limit their population in their native range [@keane2002]. Without these constraints, the introduced organism’s population grows unchecked, reaching densities it could never achieve at home.

Enemy release is the most widely cited explanation for why a species that is unremarkable in its native community becomes dominant when introduced elsewhere. Japanese knotweed illustrates the mechanism precisely: in Japan, over 180 insect species and 40 fungal pathogens attack it, limiting its growth to one competitor among many on volcanic soils. In Europe and North America, none of these specialists exist. The plant grows without constraint, forming dense monocultures that exclude native vegetation.

InvasionBiology on emsenn.net

Enemy Release