competition between two species is occurring when what happens

Daniel Parker

2 min read

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19-03-2025

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Interspecies competition, a fundamental ecological process, occurs when individuals of different species utilize the same limited resources. This competition can significantly impact the population dynamics, distribution, and evolution of the species involved. Understanding the conditions under which this competition arises is crucial for comprehending biodiversity and ecosystem stability.

The Key Ingredients: Niche Overlap and Resource Limitation

Two primary factors are necessary for interspecies competition to occur:

• Niche Overlap: Species compete when they share aspects of their ecological niche. A niche encompasses all the resources and conditions a species needs to survive and reproduce. This includes food sources, shelter, nesting sites, breeding territories, and even the preferred temperature range or pH level. The greater the overlap in the niches of two species, the greater the potential for competition.

• Resource Limitation: Competition only arises when resources are scarce. If resources are abundant, individuals of different species can coexist without directly competing. Competition intensifies when resources become limiting—meaning there's not enough to satisfy the needs of all individuals.

Types of Interspecies Competition

Interspecies competition manifests in several ways:

1. Exploitation Competition: This occurs indirectly. Individuals of different species reduce the availability of a shared resource through their consumption. For example, two plant species might compete for the same soil nutrients. The faster-growing plant will absorb more nutrients, leaving fewer for the slower-growing competitor.

2. Interference Competition: This is a more direct interaction. Individuals of one species actively prevent another species from accessing a resource. Examples include:

• Allelopathy: Plants releasing chemicals that inhibit the growth of neighboring plants.
• Territoriality: Animals defending territories that contain resources essential for survival and reproduction.
• Aggressive interactions: Physical fights or other aggressive behaviors between competing species.

Consequences of Interspecies Competition

The outcomes of interspecies competition can vary significantly:

• Competitive Exclusion: In some cases, one species outcompetes another, leading to the local extinction or exclusion of the weaker competitor. This is often seen when niches significantly overlap and resources are severely limited. Gause's principle of competitive exclusion illustrates this phenomenon.

• Resource Partitioning: Species may evolve to use different aspects of a resource, reducing direct competition. For example, different bird species might specialize in foraging at different heights within a tree, minimizing competition for the same insects.

• Character Displacement: Over time, competition can lead to evolutionary changes in the morphology, behavior, or physiology of competing species. This allows them to utilize resources differently and lessen the intensity of competition. Think of Darwin's finches—different beak sizes allow them to exploit different food sources.

• Coexistence: Under certain circumstances, species can coexist even with significant niche overlap. This may involve fluctuations in resource availability, environmental heterogeneity (patchy distribution of resources), or other factors that prevent one species from completely dominating the other.

Real-world Examples

Many examples illustrate interspecies competition:

• Lions and Hyenas: These African predators compete for similar prey, leading to frequent territorial disputes and aggressive interactions.

• Different plant species: Plants in a meadow often compete for sunlight, water, and nutrients. Taller plants might shade out shorter ones, reducing their access to sunlight.

• Barnacles: Different barnacle species competing for space on rocky intertidal zones demonstrate clear competitive exclusion and resource partitioning.

Conclusion: A Driving Force in Ecological Dynamics

Interspecies competition is a powerful force shaping ecological communities. It influences species distributions, abundances, and evolutionary trajectories. By understanding the mechanisms and consequences of interspecies competition, we gain valuable insights into the complex dynamics of ecosystems and the factors governing biodiversity. The interplay between niche overlap and resource limitation remains central to understanding when and how this critical ecological interaction unfolds.