Invasive

Definition

Describes a non-native organism that has been introduced to a new region, established self-sustaining populations, and spreads widely enough to cause ecological disruption, economic damage, or harm to human health. In entomology and arachnology, the term distinguishes between merely 'introduced' species (present but not spreading) and those actively expanding their range with measurable impacts. The progression from introduction to naturalization to invasion is often gradual and context-dependent, with the same species behaving invasively in some habitats but not others.

Etymology

From Latin invadere, 'to go into, enter upon, fall upon, attack,' from in- 'into' + vadere 'to go, walk.'

Example

The spotted lanternfly (Lycorma delicatula) is considered invasive in the eastern United States because it spreads rapidly, damages grapevines and hardwoods through heavy feeding, and disrupts native food webs; in its native range in China, it is not invasive because natural enemies and co-evolved host relationships keep populations in check.

Synonyms

• invader
• pest species (when causing economic harm)

Related Terms

• introduced
• naturalized
• non-native
• range expansion
• Biological control
• quarantine pest
• establishment
• propagule pressure
• invasion biology

Usage Notes

Specialists distinguish 'invasive' from merely 'non-native' or 'exotic'—a species must demonstrate spread and impact to qualify. The term is sometimes applied prematurely to recently introduced species before evidence of harm accumulates. Some ecologists reserve 'invasive' for species affecting biodiversity specifically, using 'pest' or 'nuisance species' for economically damaging organisms with limited ecological impact. Regulatory usage (e.g., quarantine lists) may label species 'invasive' based on potential rather than demonstrated impact. The adjective modifies both the organism ('invasive ant') and the process ('invasive spread').