Why Two Species Can’t Share the Same Niche: The Competitive Exclusion Principle
- In every ecosystem, species compete for limited resources such as food, water, space, and light.
- If two species depend on the same resource in the same way, one will eventually outcompete the other.
- This concept is known as the competitive exclusion principle.
Definition
Competitive exclusion principle
Two species cannot coexist indefinitely in the same ecological niche if resources are limiting.
Experimental Evidence: Tribolium Beetles
- Classic experiments with flour beetles (Tribolium castaneum and Tribolium confusum) illustrate competitive exclusion.
- When raised separately, both species thrived across a variety of temperature and humidity conditions.
- When raised together, one species consistently outcompeted the other, depending on environmental conditions.
Hint
Key Insight: The ability to outcompete rivals is context-dependent, small environmental shifts can alter competitive outcomes.
Self review
- How does competitive exclusion influence biodiversity in an ecosystem?
- Can you think of an example where human activity has disrupted the niches of species, leading to competitive exclusion?
