Ecology Chapter: Competition and Resources

Definitions

• Competition: A struggle between organisms for resources (e.g., food, water, shelter, mates) in a shared environment.
• Interspecific competition: Competition between different species.
• Intraspecific competition: Competition between individuals of the same species.

Types of Competition

• Exploitative competition: Organisms compete indirectly for a limited resource.
• Interference competition: Organisms directly interact to compete for a resource, often through aggressive behavior.

Resource Partitioning

• Resource partitioning: The division of limited resources by species to reduce competition, leading to niche specialization.
• Examples: Different bird species foraging at different levels in a forest canopy or diverse sizes of fish feeding on different sized prey.
• Niche overlap: Areas of overlap in resource use.

Competitive Exclusion Principle

• Competitive exclusion principle: Two species competing for the same limiting resource cannot coexist indefinitely in the same ecological niche. One species will eventually outcompete the other.
• Implications: One species may be driven to local extinction or adapt and evolve to utilize different resources.

Outcomes of Competition

• Character displacement: Evolutionary divergence in physical traits due to competition for resources, e.g., beak size differences in finch species across islands. This reduces overlap in their resource consumption, allowing coexistence.

Factors Influencing Competition

• Resource availability: Abundance and distribution of resources significantly impacts competition intensity. Scarcity of resources increases competition.
• Environmental conditions: Factors like temperature and water availability influence competition intensity by altering resource availability.
• Population density: Higher population densities lead to greater intraspecific competition due to increased demands on resources.
• Species diversity: Richer communities with more species often exhibit lower competition intensity as resources are more partitioned.

Key Concepts in Competition

• Fundamental niche: The total theoretical range of resources a species could exploit if there were no limiting factors, including competitors.
• Realized niche: The actual range of resources a species exploits in the presence of competitors. This is always smaller than the fundamental niche.

Competition and Community Structure

• Competition is a major driver of community structure, influencing species distribution, abundance, and diversity.
• It shapes community composition, with species better adapted to competition establishing dominance.

Models of Competition

• Lotka-Volterra competition models: Mathematical models predicting outcomes of competition between two species, including parameters for competition coefficients and species' inherent growth rates.

Applications of Competition Studies

• Conservation biology: Understanding competition aids in conservation strategies by identifying species competing for resources, potentially affecting conservation success.
• Invasive species management: Identifying competitors for invasive species informs eradication or management techniques.
• Agriculture: Understanding plant competition informs crop management practices for maximizing yields.

Evolutionary Significance of Competition

• Evolutionary arms races: Competition drives coevolutionary changes, where species adapt to enhance competitive ability and minimize the negative impacts of competition.