Unit 13 - Invasive Species

______: not native; have established themselves in large numbers or biomass outside of their native ranges and are self- reproducing.

Invasive

Once invasive species are _____, they are able to quickly grow, reproduce, and expand population size in a new area.

introduced

______: not originally found in the area; introduced from another place.

non-native

_____: see “non-native”.

Exotic

_____: any species likely to be detrimental or destructive and difficult to control or eradicate; CAN BE NATIVE.

Noxious

Invasiveness or noxiousness are related to, but not exactly the same as:

“Weedy”: non-cultivated species that proliferate in agricultural settings

Ruderal: species with traits allowing them to dwell in disturbed habitats

Abundant propagules

Evolutionary adaptation to new environment

Superior competitors

Hybrid vigor

Plasticity in responses

Filling empty niche in new environment

Preadaptation to new environment

Why do some species become invasive?

Many proposed explanations:

Fast growth

Rapid reproduction

High seed production in shorter intervals and high dispersal ability

Tolerance of a wide range of environmental conditions

Aggressive vegetative reproduction

Associations with humans or human activities

Characteristics of Invasive and Noxious Plants

Disturbed site

Species-poor community (Biotic Resistance Hypothesis)

Absence of natural enemies (Enemy Release Hypothesis)

Unique allelopathic or antimicrobial compounds (Novel Weapons Hypothesis)

What makes a community susceptible to invasion?

Proposed explanations

Disturbed site

Species-poor communities

What makes a community susceptible to invasion?

Contradictions to proposed explanations:

Invaders Alter ______

Ecosystem Processes