C4.1D Invasive species and testing for competition

Invasive Species Can Outcompete Endemic Species for Limited Resources

1. An invasive species is a non-native species that spreads and harms the ecosystem it enters.
2. When it needs the same limited resources as an endemic species, the two compete directly for food, space, water, or breeding sites.
3. If the invader wins that competition, native populations decline and can be displaced from their habitat.

Example

• The cane toad in Australia is a classic invasive species, and we return to it in detail below.

Endemic and Invasive Species Differ in Origin and Behaviour

1. Endemic species
   1. Occur naturally in a specific region and nowhere else.
   2. Are highly adapted to local conditions and often fill a narrow niche.
2. Invasive species
   1. Are non-native and are usually introduced by human activity.
   2. Spread rapidly and disrupt native ecosystems.
   3. Often lack natural predators or parasites in the new environment.

A Competitive Advantage Lets Invaders Displace Natives

1. An invasive species with a competitive advantage can displace endemic species in three main ways.
   1. Outcompeting for resources: taking a larger share of food, water, or breeding sites.
   2. Exploiting more resources: using a wider range of food or habitat than the native species can.
   3. Reproducing faster: building up a large population more quickly than its endemic competitor.