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What is amensalism and examples

When defining the relationships that are established between the different species of living beings, we define a series of concepts that allow us to classify and study them. Perhaps the best known to the general public are competition, parasitism or symbiosis, but there are others such as commensalism, mutualism or amensalism that are usually known by people more specialized in these areas. In this AgroCorrn article we will define what amensalism is and some examples of it.

You may also be interested in: Interspecific relationships: types and examples
  1. What is amensalism: definition
  2. Difference between amensalism and competition
  3. Amensalism: examples

What is amensalism: definition

Amensalism, also known as antagonism , is the biological interaction , that is, between living beings, in which one of the members involved does not experience any alteration but prevents the development and survival of the other. In other words, the amensalism relationship takes place when a smaller or weaker species establishes an interaction with another stronger or larger species in which it is harmed, while the dominant one does not notice the existence of the other. Amensalism is important to study trophic chains or relationshipswithin ecosystems, such as predator-prey relationships. It also helps to understand the impacts of pests on agriculture or the growth of certain plants and species in that environment.

Normally, the way in which amensalism or antagonism takes place is that of the production of toxic substances by one of the members involved and that prevents other populations from developing or subsisting while they are around them. This interaction is very common within microorganisms.

As soon as an organism occupies a habitat, its survival instinct makes it do everything possible to prevent other species from being able to survive or living there. This interaction is not defined as positive for the organism, rather neutral and harmful for the species that are displaced .

In this other AgroCorrn article we talk extensively about interspecific relationships: types and examples .

Difference between amensalism and competition

Frequently, some relationships between species can be confused with others because of their similarity and this can be the case between amensalism and competition. Competition is a biological interaction in which a struggle is established between two organisms to obtain the same resources , which both need to satisfy their needs.

Therefore, competition is a relationship in which the convenience of one organism necessarily implies the detriment of the other, while in amensalism one of the organisms does not derive any benefit from the action , that is, it can be neutral or detrimental to the organism that is displaced.

Amensalism: examples

Amensalism relationships can be identified in all groups of living beings. Let’s look at some as examples of amensalism :


Since fungi do not photosynthesize, they must absorb simple and soluble nutrients from the environment. Because these nutrients are absorbed by the fungi in the environment, they are no longer available to other populations, therefore, they can compromise the existence of other species in the environment.

When a fungus interacts with another species it can secrete a chemical component of its metabolism that harms the other species. This occurs, for example, in the fungus Penicilium notatum , which secretes a substance capable of destroying many bacteria, penicillin. Penicillin was discovered by Alexander Fleming and is one of the most widely used antibiotics in the world. The relationship that this fungus establishes with the bacteria it inhibits is amensalism.


Among plants, an example of amensalism relationship is that of the American black walnut ( Juglans nigra ), which you will see in the image below, which produces a toxin known as juglone and which prevents the growth of other plants around it. This substance deprives other plants of the energy they need for photosynthesis and eventually causes their death, thus reducing competition for survival. Juglona is produced mainly in the buds, roots and hulls of the fruits.

There are planktonic algae that release a toxic substance, forming red spots in the ocean and that cause the death of marine animals or the leaves of pine trees that fall to the ground, which release a substance that prevents the germination of the seeds of other plants.


For example, some wild pigs when they are transferred to other habitats eat all the nutrients in their path and excrete their waste to wetlands, rivers or soils, polluting them and causing the death of many species and damage to agriculture. Another clear example occurred when rabbits were introduced to Australia for hunters, and it turns out that they ended up becoming a pest that makes it difficult for other species to exist. Another common example is when animals trample the grasses without using them at all, in many cases killing them.

If you want to read more articles similar to What is amensalism and examples , we recommend that you enter our Biology category .

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