Symbiosis

Definition

A close, long-term biological interaction between two or more organisms of different species. In entomology and ecology, the term encompasses the full spectrum of outcomes: mutualism (both partners benefit), commensalism (one benefits, the other is unaffected), and parasitism (one benefits at the expense of the other). The interaction is typically obligate or highly persistent across generations, distinguishing it from transient associations such as predation or incidental phoresy.

Etymology

From Greek syn- (together) + biosis (living), coined by Heinrich Anton de Bary in 1879

Example

Leaf-cutting ants (Atta spp.) cultivate specialized fungal gardens within their nests; the ants provide leaf substrate and exclude competing fungi, while the fungus serves as the colony's sole food source—a classic mutualistic symbiosis.

Related Terms

• mutualism
• commensalism
• Parasitism
• Phoresy
• xenobiosis
• domatia
• Symbiont

Usage Notes

Specialists often use 'symbiosis' in the broad de Bary sense (any persistent interspecific living together), though popular and some textbook usage restricts it to mutualism. When precision matters, specify the outcome category. Contrast with 'phoresy' (transport without metabolic dependence) and 'xenobiosis' (temporary social parasitism). Many insect symbioses involve microbial partners (gut microbiota, intracellular bacteria) rather than visible macroscopic associates.