Symbiosis, Commensalism, and

Mutualism

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Introduction

Mutualism ("Symbiosis)

Commensalism

Other websites on Mutualism and Commensalism

Symbiosis, in its common usage, is a beneficial relationship between two species. However there is no universally accepted technical definition of the term symbiosis. The translation of symbiosis from the Greek literally means "living together." Therefore any relationship between two species could be considered symbiosis including both positive and negative interactions. The different forms of symbiosis each have their own names. Some of the different combinations are

+ and + = Mutualism. Both species benefit by the interaction between the two species.

+ and 0 = Commensalism. One species benefits from the interaction and the other is unaffected.

+ and - = One species benefits from the interaction and the other is adversely affected. Examples are predation, parasitism, and disease.

- and - = Competition. Both species are adversely affected by the interaction.

This technical definition is the most commonly accepted and the one used in these web pages. Some people assert that the species must physically touch each other and divide symbiosis into mutualism, commensalism, and parasitism.

However, if you want to use symbiosis as equivalent to mutualism, there is nothing wrong with it so long as everyone understands what you mean by "symbiosis."

This page deals only with mutualism and commensalism. Predation and competition are treated on separate pages of Nearctica.