The species within any given ecosystem can be broadly described as either endemic or alien according to their origin

• Endemic species are those which are native to a defined geographic region (i.e. indigenous animals)
  

• Alien species are those that have been transferred from their natural habitat to a new environment
  

• If an alien species should have a detrimental effect upon the pre-existing food chains, it is classified as invasive
  

Invasive species possess several advantages that allow them to displace endemic species via competitive exclusion:

• They typically possess a large fundamental niche (can occupy a wider area than the endemic species)
  

• They will often have faster reproduction rates (are capable of forming a larger population than endemic species)
  

• They commonly lack a predator capable of limiting their survival (due to being introduced into a foreign environment)
  

• They may possess certain features that are suited to the new environment (e.g. more aggression, better foraging, etc.)
  

Example: Red Fox

• The red fox was introduced to Australia following European colonisation and rapidly became an apex predator
  

• The red fox shares a common diet with the native quoll (a carnivorous marsupial) and occupies a similar niche
  

• Since the introduction of foxes, quoll populations have declined dramatically and certain species are now considered endangered
  

• In certain areas, foxes are now being actively targeted for eradication in order to protect quoll populations
  

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