Lecture #9 Invasive Species

Invasive species

• Non-native species introduced to an ecosystem that spread rapidly, outcompete native species, and cause ecological/economic harm

Potential invasive species effects on biodiversity/ecosystems

• Outcompeting native species

• Reduces biodiversity

• Spreads disease

• Changes habitats

What is the invasion process

• Multi-stage process where a non-native species is introduced to a new area, establishes a population, and then spreads, potentially causing negative impacts

4 stages of the invasion process

• Dispersal → Colonization → Establishment → Spread

Dispersal

• Geographic barriers

• Propagule pressure

• Random chance

Colonization

• Abiotic local environment

• Propagule pressure

Establishment

• Biotic local environment

• Genetic variation of species

• Species traits

Spread

• Dispersal ability

• Fertility

• Phenotypic plasticity

Propagule Pressure

• The quantity (number of individuals) and frequency (how often) a non-native species is introduced to a new environment. It is a key factor in determining whether an invasive species will successfully establish itself.

Biotic Resistance Hypothesis

• Biotic composition of the recipient community repels invaders

• Ecosystems with high biodiversity are more resistant against invaders

• Diverse, stable communities with strong competition and full resource use are better at resisting invasions

• Interaction scale = community

Enemy Release Hypothesis

• Invaders lose enemies during the invasion process, giving them a competitive advantage

• Lack of enemies in exotic environment gives an advantage to invasive species

• Suggests that when a plant is introduced to a new region, it escapes its natural enemie

• Interaction scale = population

Which native community should prevent invaders?

• 2nd bc it is more diverse

Based on the enemy-release hypothesis, do you think this plant is native to Europe or North America?

• SInce it faces less damage in North America, that’s likely its introduced range - meaning this species is native to Europe