BIO3082 Lecture Notes - Lecture 22: Invasive Species, Introgression, Habitat Destruction
Lecture 22 – Invasive Species
What is an Invasive Species?
• A species that has been introduced to an area outside of its native range
o Successfully established
o Expanded their geographic range: expands its range across the area
o Something that has been transported somewhere → established →
spread
▪ Don’t need to show a negatively ecological impact
• Large human impact in global change
o Habitat loss and change
o Global environmental change
o Over-exploitation of biodiversity
o Invasive species
• Need to undergo sequential stages in order to invade
Stage
Barrier
Transport
• Have to overcome geographic barrier (native → non-
native range)
• Survival barrier
Introduction
• Disembarkation (e.g. from luggage) /release from captivity
Establishment
• Relies on positive population growth
o Birth rate needs to exceed death rate
• Need to survive and reproduce
Spread
• Dispersal element – in order to successfully invade
• Environmental – need to adapt and cope
Ecological and Economic impacts of Invasive Species
• Economic Impacts
o Annual economic cost:
▪ Australia: $6.8 billion AUD
▪ Worldwide: $1.5 trillion AUD
o Direct and indirect costs
▪ Production loss in agriculture, aquaculture and forestry
▪ Loss of recreational and tourism activities
▪ Human health: parasites, bacteria, viruses
▪ Prevention and control: biosecurity, management, eradication
• Ecological Impacts
o Genetic
▪ Hybridisation and introgression
o Individual
▪ Alter fitness or traits of individuals
• E.g. shifts in morphology or behaviour
o Population
▪ Predation (largest impact – on offshore islands) – larger role in
extinction
▪ Competition, physical impact
o Community
▪ Disrupt/alter communities and food webs
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