Resource partitioning is the process where species seeking similar, scarce resources divide them to minimize direct competition. This division is a concept in community ecology that allows different species to coexist in the same habitat, supporting greater biodiversity. By finding unique ways to access necessities, organisms avoid the intense struggle that would occur if they all pursued the same resources in the same way.
Mechanisms of Resource Partitioning
The methods species use to partition resources are varied. One mechanism is spatial partitioning, where species use different locations within a habitat. For example, several species of anole lizards may live in the same forest, but some inhabit the forest floor, others live on tree trunks, and still others reside high in the canopy.
Species also divide resources through dietary partitioning by consuming different types or sizes of the same food source. In the mountains of Colorado, different species of bumblebees have proboscis (tongue) lengths that correspond to the corolla lengths of different native flowers. This specialization allows each bee species to efficiently gather nectar from a specific set of plants.
A third method is temporal partitioning, which involves using the same resource but at different times. Some predators might hunt during the day while others hunt at night, allowing them to pursue the same prey without constantly crossing paths. Certain desert plants are more successful during wet years, while others thrive in dry years, a form of partitioning based on environmental conditions.
Common Ecological Results
Successful resource partitioning directly facilitates the coexistence of multiple species. By minimizing the overlap in resource needs, species that would otherwise be strong competitors can live together. This allows for a more diverse and stable ecosystem, as more species can occupy a habitat without one driving the others to local extinction.
This coexistence is a result of reduced interspecific competition—the rivalry between different species for the same resources. While partitioning does not eliminate competition, it lessens its intensity. The pressure on each species is lowered, meaning they do not suffer the same negative consequences, like reduced growth or reproduction, that occur under direct competitive stress.
A significant outcome is niche specialization, or niche differentiation. As species partition resources, they become more specialized in their habits and physical traits to better exploit their portion of the resource. This leads to the development of narrower ecological niches, which are the specific roles and requirements an organism has within its environment.
Character Displacement as an Evolutionary Result
Over evolutionary timescales, resource partitioning can lead to character displacement. This occurs when the physical differences between competing species are more pronounced in areas where they live together (sympatry) than where they live apart (allopatry). These changes are evolutionary responses to competition, as natural selection favors individuals with traits that reduce resource overlap.
A well-documented example involves Darwin’s finches in the Galápagos Islands. Where two competing finch species coexist, their beak sizes show divergence, with one species evolving a deeper beak for large seeds and the other a shallower beak for smaller seeds. On islands where only one of the species exists, its beak size is intermediate, suited for a wider variety of seeds.
Clarifying Non-Results and Misconceptions
It is important to understand what resource partitioning does not cause. The process is often misunderstood in several ways:
- It prevents competitive exclusion. The principle of competitive exclusion states that two species competing for the exact same limited resources cannot coexist, as one will eventually eliminate the other. Partitioning is the mechanism that allows species to avoid this outcome.
- It does not increase the total amount of resources. The process is strictly about how existing resources are divided. The total food, water, or space remains the same, but the way it is accessed changes to allow for more efficient use by more species.
- It does not eliminate all competition. Partitioning reduces competition to a level where coexistence becomes possible. However, some degree of overlap and competitive pressure often remains between the species.
- It promotes species survival. By enabling coexistence, successful partitioning helps sustain biodiversity. It is a strategy for survival, not a process that leads to the extinction of a competing species.