Competition is a key force shaping ecosystems. It occurs between different species (interspecific) or within the same species (intraspecific), affecting population dynamics and resource use. Understanding competition helps explain species distributions, community structures, and evolutionary adaptations.
The competitive exclusion principle states that species competing for the same resources can't coexist long-term. This concept drives resource partitioning, where species divide resources to reduce competition. It impacts biodiversity and influences how ecological communities form and change over time.
Interspecific vs Intraspecific competition
Types and Characteristics of Competition
- Interspecific competition occurs between individuals of different species competing for the same limited resources in an ecosystem (food, water, space)
- Intraspecific competition takes place between individuals of the same species vying for similar resources within a population (mates, nesting sites)
- Competition affects population growth rates, survival, and reproductive success of competing species or individuals
- Intensity of competition influenced by resource availability, population density, and niche overlap between species
- Competition leads to evolutionary adaptations, including character displacement and resource specialization
- Character displacement results in greater differences between competing species over time
- Resource specialization allows species to utilize different aspects of shared resources
Measuring Competition's Effects
- Effects of competition on populations measured through changes in:
- Birth rates
- Death rates
- Overall population size over time
- Experimental methods to study competition:
- Removal experiments remove one species to observe effects on others
- Addition experiments introduce new competitors to observe impacts
- Mathematical models used to predict competitive outcomes:
- Lotka-Volterra competition model
- Resource ratio theory
Competitive exclusion principle
Core Concept and Assumptions
- Competitive exclusion principle states two species competing for the same limiting resource cannot coexist indefinitely in the same habitat
- Also known as Gause's principle, named after Russian ecologist Georgy Gause
- Assumes species have identical ecological niches and environmental conditions remain constant
- Species with slight advantage in resource utilization eventually outcompetes and excludes other species from shared habitat
- Leads to local extinction of less competitive species, potentially reducing biodiversity
Ecological Implications and Exceptions
- Important for understanding:
- Species distributions (why certain species are found in some areas but not others)
- Community assembly (how ecological communities form and change over time)
- Evolution of ecological niches (how species adapt to reduce competition)
- Exceptions to competitive exclusion can occur due to:
- Environmental heterogeneity (varied habitats allow species to partition resources)
- Predation (keeps populations in check, preventing complete exclusion)
- Mutualistic interactions (species benefit each other, allowing coexistence)
Resource partitioning for coexistence
Mechanisms of Resource Partitioning
- Resource partitioning allows competing species to use different parts of a shared resource or utilize the resource at different times or in different ways
- Reduces direct competition for limited resources, enabling species with similar ecological niches to coexist
- Occurs along various dimensions:
- Spatial (using different parts of the habitat)
- Temporal (active at different times)
- Dietary (consuming different food items)
- Often leads to niche differentiation and specialization among competing species over evolutionary time
- Promotes biodiversity by allowing multiple species to occupy similar habitats without exclusion
Examples and Ecological Significance
- Examples of resource partitioning:
- Anole lizards in the Caribbean using different parts of trees
- Warblers feeding at different heights in coniferous forests
- African savanna grazers feeding on different parts of grass plants
- Significance in ecology:
- Explains high diversity in seemingly homogeneous environments (coral reefs, rainforests)
- Helps predict community responses to environmental changes
- Informs conservation strategies for maintaining biodiversity
Competition's impact on diversity
Competition and Community Structure
- Competition plays crucial role in shaping community composition and influencing species diversity
- Intense competition can reduce species diversity through competitive exclusion, particularly in stable environments with limited resources
- Intermediate levels of competition may promote species coexistence and increase diversity by preventing dominance by a single species
- Influences relative abundance and distribution of species within a community, affecting overall community structure
- Effects on diversity moderated by:
- Environmental heterogeneity (varied habitats support more species)
- Disturbance regimes (periodic disturbances create opportunities for less competitive species)
- Trophic interactions (predators can prevent competitive exclusion)
Evolutionary Consequences and Conservation Implications
- Competition drives evolutionary processes:
- Character displacement (species evolve differences to reduce competition)
- Adaptive radiation (diversification of species to fill different niches)
- Contributes to diversification of species over time, creating new ecological opportunities
- Understanding competitive interactions essential for:
- Predicting community responses to environmental changes (climate change, habitat loss)
- Developing effective conservation strategies (maintaining habitat diversity, managing invasive species)
- Informs restoration ecology practices for recreating diverse, stable ecosystems