C4.1.13 Resource competition between endemic and invasive species Notes

Invasive Species Disrupt Ecosystems by Outcompeting Endemic Species

1. Invasive species often outcompete endemic species for limited resources, leading to significant ecological disruptions.
2. This competition can result in population declines, habitat displacement, and long-term ecosystem instability.

Example

1. Cane toads in Australia, which outcompete native species is an example of an invasive species.
2. More on this later...

Endemic vs. Invasive Species

Endemic Species

1. Naturally occurring in a specific region.
2. Highly adapted to local environmental conditions.
3. Often have specialized niches and rely on balanced ecosystem interactions.

Invasive Species

1. Non-native species are introduced, often by human activity.
2. Spread rapidly and can disrupt native ecosystems.
3. Often lack natural predators in their new environment.

The Competitive Exclusion Principle

1. If an invasive species has a competitive advantage, it can displace endemic species by:
   1. Outcompeting for Resources: Taking over food, water, or breeding sites.
   2. Occupying a Broader Niche: Exploiting more resources than native species.
   3. Reproducing More Rapidly: Growing in population faster than endemic competitors.

A Local Example: The Cane Toad in Australia

1. The Cane Toad (Rhinella marina) was introduced to Australia in 1935 to control agricultural pests.
2. Instead of helping, it became an invasive species, rapidly spreading across northern and eastern Australia.
3. Why Cane Toads Outcompete Native Species:
   1. Broad Diet: Generalist feeders, eating insects, small mammals, and even amphibians.
   2. Rapid Reproduction: A single female can lay up to 30,000 eggs at a time.
   3. Toxicity: Produces a potent toxin, killing most predators that try to eat them.
   4. High Adaptability: Thrives in diverse habitats, from wetlands to urban areas.

Impact on Endemic Species

The competitive advantages of cane toads have caused severe ecological damage, particularly for Australia’s native amphibians, reptiles, and predators.

1. Predation & Poisoning: Native predators (e.g., snakes, lizards, quolls) die after consuming toxic cane toads.
2. Resource Depletion: Outcompete native amphibians for food and breeding sites, reducing local populations.
3. Ecosystem Disruption: Declines in native predators and prey disrupt food webs, altering ecosystem balance.

Why Do Invasive Species Succeed?

1. Invasive species thrive in new environments because they often:
   1. Lack Natural Predators or Pathogens that would control their populations.
   2. Have High Reproductive Rates, allowing for rapid expansion.
   3. Possess Broad Ecological Niches, making them highly adaptable.
   4. Show Resistance to Environmental Stresses, such as drought or pollution.

The Role of Human Activity

Human activities, such as global trade and travel, have accelerated the spread of invasive species.

1. Unintended Consequences:
   1. Many introduced species lack ecological assessments, leading to uncontrolled spread.
   2. Human-modified environments (e.g., deforestation, urbanization) create new opportunities for invasives.

Managing Invasive Species

1. Controlling invasive species is difficult but necessary for biodiversity conservation.
2. Strategies include:
   1. Biological Control: Introducing natural predators or pathogens to reduce invasive populations.
   2. Chemical Control: Using pesticides or toxins, though this can harm non-target species.
   3. Physical Removal: Manually capturing or eradicating invasive species.
   4. Prevention: Implementing policies to prevent the introduction of new invasive species.

Reflection and Broader Implications

1. The competition between endemic and invasive species underscores the delicate balance of ecosystems.
2. Invasive species not only threaten biodiversity but also impact ecosystem services, such as water purification and soil fertility.