Competition in ecosystems describes a fundamental interaction where organisms vie for limited resources. These resources, such as food, water, light, space, or mates, are not infinite, leading to a struggle among individuals. This interaction influences the structure and dynamics of natural communities, shaping how populations grow and interact within their environment.
Types of Ecological Competition
Competition manifests in different ways depending on the relationship between the competing organisms. One form is intraspecific competition, which occurs among individuals belonging to the same species. For example, a group of pine trees growing closely together in a forest will compete for available sunlight and nutrients in the soil. This type of competition directly impacts the growth and survival rates within a single population.
The other form is interspecific competition, which involves individuals from different species. Consider a grassland ecosystem where both zebras and wildebeest graze on similar types of grasses. Both species require the same food source, leading to a direct rivalry for available forage. This interaction can influence the distribution and abundance of both species within that shared habitat.
How Organisms Compete
Organisms can compete through indirect or direct means to secure necessary resources. Exploitative competition, also known as resource competition, represents an indirect interaction. Individuals consume or utilize shared resources, reducing availability for others without direct confrontation. For instance, a large population of deer grazing on vegetation depletes that food source, leaving less for other herbivores.
In contrast, interference competition involves direct interaction where one organism actively prevents another from accessing resources. This can be observed when a larger, more established plant shades out smaller seedlings, blocking their access to sunlight. Similarly, two male birds might physically fight over a prime nesting site, directly preventing one another from occupying that space. These direct confrontations determine which individuals or species gain access to the contested resource.
Outcomes of Competition
Competition can lead to several distinct ecological outcomes, shaping biodiversity over time. The competitive exclusion principle describes a situation where two species competing for the exact same limited resource cannot coexist indefinitely. One species will invariably be more efficient at utilizing the resource, eventually leading to the local elimination of the less successful competitor.
To avoid such exclusion, species often develop strategies like resource partitioning, which allows for coexistence. This involves species evolving to use different aspects of a shared resource, or using the same resource at different times or locations. For example, various species of warblers may forage for insects in different parts of the same tree, effectively dividing the resource. This specialization reduces direct competition, allowing multiple species to persist in the same area.
Character displacement is an evolutionary outcome where traits of competing species diverge more significantly in areas where they overlap. On islands where two similar finch species coexist, their beak sizes might differ considerably to allow them to eat different-sized seeds. On islands where only one of these species lives, its beak size might be intermediate, reflecting a broader diet. This divergence minimizes competitive pressure, facilitating their continued presence together.
Competition also influences population dynamics, affecting growth rates, survival, and the carrying capacity of an environment. Intense competition can slow population growth and even cause declines, while reduced competition might allow populations to expand closer to the maximum number of individuals an environment can support.
Examples of Competition in Nature
Competition is widely observed across various ecosystems, illustrating these principles in action. In a dense forest, tall trees compete intensely for sunlight, extending their canopies to capture as much light as possible while shading out smaller, understory plants. They also vie for water and nutrients absorbed from the soil through their extensive root systems.
Among animals, competition for prey is a common scenario, especially between predators with overlapping diets. Lions and spotted hyenas, for instance, frequently compete for large ungulates like zebras and wildebeest on the African savannas. While both hunt, they often scavenge from each other’s kills, directly contesting the same food source. This competition can influence hunting strategies and pack sizes in both species.
Territorial animals often engage in direct competition for suitable breeding grounds or foraging areas. Many bird species, such as robins, establish territories during breeding season, defending them vigorously against other individuals of the same species. Securing a good territory provides access to mates, nesting sites, and sufficient food to raise young, directly impacting reproductive success.
Even at the microscopic level, competition plays a role. Different bacterial strains growing in a petri dish or within a host organism will compete for available nutrients and space. Some bacteria produce antimicrobial compounds to inhibit the growth of competitors. This microbial rivalry influences which species dominate and can have significant implications for health or environmental processes.