What is the theory that says no two species can occupy the same niche at the same time in a particular locale if resources are limited?

The competitive exclusion principle is an ecological principle stating that when two competing life forms attempt to occupy the same niche, only one outcome is possible: One life form will drive out the other. If any members of the other remain, it is only because they have adapted, and are now living in a slightly different niche. The principle applies to all kinds of competitive agent, which includes both genetic and memetic life forms.

Why this is important

The competitive exclusion principle applies to the battle for niche succession that is going on right now between Homo sapiens (a genetic life form) and the modern corporation (a memetic life form). The niche is control of the biosphere. There can be only one winner. The loser will adapt by becoming the equivalent of a servant or slave to the winner. Our analysis argues that the modern large for-profit corporation has already won this epic battle on a global basis. This makes them the New Dominant Life Form.

As long as large for-profit corporations are dominant, the human system will exhibit short term behavior in general, since the goal of for-profit corporations is to maximize short term profits. This makes solving long term problems like sustainability impossible.

Application example: The epic battle of niche succession

Niche succession occurs when successful competition from one life form drives another life form out of the same niche. This occurs due to superior strategies, superior physical abilities, or both. Sometimes luck is a factor.

The diagram below illustrates the cycle of battles of niche succession. Instead of the way conventional evolution theory usually uses population for the niche limit (carrying capacity) and measure of niche fill, a life form’s rule set is used. The wavy horizontal dashed line is the number of rules needed for niche optimization. The line varies because except in Petri dishes, niches are always changing. The rising and falling curves are the Competitive Advantage Rules of different life forms. The one with the most control of the niche’s resources (which includes other life forms in the niche) is the dominant replicator. Except during transition there can be only one dominant replicator in a niche.

On the left, the diagram starts with the 1st dominant replicator almost at the limit. At the same time, the dominance of the 2nd dominant replicator starts growing from zero. As it grows, dominance of the 1st replicator falls even further and goes extinct. The 2nd dominant replicator evolves to fill the niche and enjoys exclusive control of the niche for awhile. Then another niche succession event begins, as the 3rd dominant replicator starts to grow. The cycle repeats over and over indefinitely.

Substitute Homo sapiens for the 2nd dominant replicator and the New Dominant Life Form for the 3rd one, and you have the niche succession event underway today. Approximately where we are is marked.

History of the principle

Here's how the principle was discovered:

“Georgyi Gause, the Russian microbiologist... interested in competition, discovered this principle. Gause inoculated a simple, finite culture with Paramecium, and... got logistic population growth. These Paramecium eat bacteria, and there is only so much food in a culture to support a certain number of Paramecium.

“Then he put two [different] species of Paramecium in the same culture. He got lowered growth rates of both populations. Even more interestingly, one species always drove the other to extinction.

“This led Gause to come forth with a famous ‘principle’ that would dominate ecological research for nearly the entire century: Two species that use resources exactly the same way cannot coexist. One will drive the other to extinction.” 1  

The data from one of Georgyi Gause’s actual experiments is shown. It tells a clear story.

Results of competition between two species of Paramecium with similar requirements. Both did well for four days. After that the species represented by the lower curve was driven to extinction in 17 days, while the other species thrived.

The Competitive Exclusion Principle allows us to see what’s really happening here. Two life forms, one genetic and one memetic, are battling for control of the biosphere. According to the principle, the loser must adapt to a different niche or go extinct. There are no other choices.

The modern corporation appeared only about two hundred years ago, at the dawn of the Industrial Revolution.

Over the last few hundred years, it appears that Homo sapiens has chosen adaptation rather than extinction, so he is now subservient to the modern corporation and its allies. Depending on your point of view, his new niche is a powerless employee and consumer, or a Corporatis profitis slave. Perhaps it’s all three. This transition is still in progress in the less industrialized areas of the world.

Once Homo sapiens ceded control of the biosphere to the New Dominant Life Form, an ecological niche succession event occurred. This has happened billions of times before in the genetic world, as one species overcame another in a struggle for survival in the same niche. It’s probably happened trillions of times in the memetic world.

(1) Source of quote. The graph was reconstructed from the very fuzzy one here.

Learning Outcomes

• Define the competitive exclusion principle

Resources are often limited within a habitat and multiple species may compete to obtain them. All species have an ecological niche in the ecosystem, which describes how they acquire the resources they need and how they interact with other species in the community. The competitive exclusion principle states that two species cannot occupy the same niche in a habitat. In other words, different species cannot coexist in a community if they are competing for all the same resources. An example of this principle is shown in Figure 1, with two protozoan species, Paramecium aurelia and Paramecium caudatum. When grown individually in the laboratory, they both thrive. But when they are placed together in the same test tube (habitat), P. aurelia outcompetes P. caudatum for food, leading to the latter’s eventual extinction.

Figure 1. Paramecium aurelia and Paramecium caudatum grow well individually, but when they compete for the same resources, the P. aurelia outcompetes the P. caudatum.

Resource Partitioning

Competitive exclusion may be avoided if one or both of the competing species evolves to use a different resource, occupy a different area of the habitat, or feed during a different time of day. The result of this kind of evolution is that two similar species use largely non-overlapping resources and thus have different microniches. This is called resource partitioning, and it helps the species coexist because there is less direct competition between them. These organisms coexist by minimizing direct competition.

The anole lizards found on the island of Puerto Rico are a good example of resource partitioning. In this group, natural selection has led to the evolution of different species that make use of different resources. The figure below shows resource partitioning among 11 species of anole lizards. Each species lives in its own preferred habitat, which is defined by type and height of vegetation (trees, shrubs, cactus, etc.), sunlight, and moisture, among other factors.

Figure 2. Resource partitioning among anole lizards

Watch this video to review competition and how populations share resources in a community:

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