Invasion Ecology
When species are carried beyond their native ranges by human activity, a few establish, spread, and reshape the ecosystems they enter; invasion ecology studies why some species become invasive and what consequences follow.
Definition
Invasion ecology is the study of the introduction, establishment, spread, and impacts of species outside their native ranges, and of the characteristics of both invaders and recipient ecosystems that determine invasion success.
Scope
This topic covers the stages of biological invasion from transport and introduction through establishment and spread, the traits of successful invaders and the invasibility of recipient communities, hypotheses such as enemy release and biotic resistance, and the ecological and economic impacts of invasive species. It draws on population, community, and biogeographic ecology to understand and anticipate invasions.
Core questions
- What stages must a species pass through to become invasive?
- Which traits make a species a successful invader?
- What makes some communities more invasible than others?
- What are the ecological consequences of biological invasions?
Key theories
- Invasion stages and the tens rule
- Invasion proceeds through a sequence of transport, introduction, establishment, and spread, with only a small fraction of introduced species passing each filter, a pattern summarised by the heuristic that roughly one in ten species succeeds at each stage.
- Enemy release and biotic resistance
- Introduced species may flourish because they escape the predators, parasites, and competitors that limited them at home (enemy release), while resident communities can resist invasion through their own diversity and interactions (biotic resistance).
Mechanisms
An invasion begins when human activity transports propagules beyond a species' native range; establishment then depends on surviving local conditions and reaching a self-sustaining population, which is more likely with high propagule pressure. Spread follows as the population grows and disperses across the landscape. Success is shaped by invader traits such as broad tolerance, rapid reproduction, and effective dispersal, and by properties of the recipient community, including disturbance, resource availability, and the strength of resident enemies and competitors. Impacts arise through competition, predation, hybridisation, disease transmission, and alteration of habitat and ecosystem processes.
Clinical relevance
Invasion ecology informs biosecurity, the prevention and control of invasive species, risk assessment for trade and transport, and the management of affected ecosystems. This is educational context, not management prescription.
History
Charles Elton's 1958 book founded the modern study of biological invasions. The field expanded rapidly from the 1980s as global trade accelerated species movements, developing frameworks for invasion stages, invader traits, and community invasibility, and increasingly addressing the contested question of how to evaluate and respond to invasion impacts.
Debates
- How to assess the impacts of invasions
- Ecologists debate how the ecological and economic impacts of invasive species should be measured and weighed, and whether some non-native species are unfairly vilified, while others stress the serious and irreversible harms many invasions cause.
Key figures
- Charles Elton
- Daniel Simberloff
- Mark Davis
- Julie Lockwood
Related topics
Seminal works
- elton1958
- lockwood2013
- simberloff2013
Frequently asked questions
- What is an invasive species?
- An invasive species is a non-native species that establishes, spreads, and causes ecological or economic harm in the region it has been introduced to.
- What is the enemy release hypothesis?
- The enemy release hypothesis proposes that introduced species can become abundant because they leave behind the predators, parasites, and competitors that controlled their populations in their native range.