Amensalism

There are two modes of ammensalism: antibiosis and competition. The organisms in both cases do not benefit, but one suffers.

1. Antibiosis

The word antibiosis, coined by Vuillemin in 1889-1890, is obtained from the French word ‘antibiosis,’ meaning an antagonistic relationship between organisms.

Thus, in antibiosis, one organism produces substances that harm other organisms. These substances can include toxins, chemicals, or metabolic byproducts that inhibit the growth or survival of neighboring species.

An example of antibiosis is the release of antibiotics by certain fungi, which can hinder the growth of bacteria in the surrounding environment.

2. Competition

This form of ammensalism arises when one organism actively competes with another for resources, leading to a negative impact on the latter. While the competing organism benefits from this interaction, the other organism is suppressed or inhibited.

Competition can exist between an inferior and a superior species or between similar or different species.

An example of competition is allelopathy in plants, where one plant species releases chemicals that impede the growth of neighboring plants, giving itself a competitive advantage.

There are several practical examples of amensalism in nature.

Black Walnut Trees and Nearby Plants

Black walnut trees (Juglans nigra) release a compound called juglone into the soil, which inhibits the growth of many nearby plant species. While the black walnut tree is unaffected by the presence of these neighboring plants, they experience decreased growth due to the allelopathic effects of juglone.

Eucalyptus and Other Plants

Certain trees, like the eucalyptus, release chemicals that inhibit the germination and development of other plant species in their vicinity, a phenomenon known as allelopathy. It produces oils that prevent the growth of most other plants beneath its canopy, creating a zone devoid of competing vegetation.

Penicillium and Bacteria

The mold Penicillium produces penicillin, which acts as an antibiotic. In its natural environment, it secretes penicillin into the surroundings, inhibiting the growth of nearby bacteria. While the mold is unaffected by the bacteria, its antibiotic properties create a zone of inhibition, affecting bacterial populations.

Elephants and Small Burrowing Animals

The movement of large herbivores like elephants can inadvertently disturb burrowing animals such as ground-dwelling rodents. The heavy footsteps of these large animals can collapse burrows, disrupt nests, or even harm the burrowing animals directly. While the herbivores continue their activities without hindrance, the burrowing animals experience negative consequences.

Ammensalism plays an essential role in shaping the dynamics of our ecosystems. While not as noticeable as mutualism or predation, ammensalism contributes significantly to biodiversity by creating unique niches for species to thrive. This one-sided interaction influences ecological succession, directing the path of ecosystem development.

Ammensalism helps manage resource allocation and reduces intense competition by inhibiting competitors, fostering a more balanced coexistence.

Furthermore, ammensal interactions enhance the resilience of ecosystems, making them better equipped to withstand disturbances. Recognizing and understanding ammensalism is essential for effective conservation and management strategies, ensuring the long-term health and stability of the ecosystems.

Amensalism is the exact opposite of commensalism.

Amensalism is a (0,-) interaction in which one organism remains unaffected, and the other is harmed. At the same time, commensalism is a (0,+) interaction in which one organism neither benefits nor is harmed, and the other organism derives benefit.