It was isolated by chemists at the Upjohn company in 1955 from the mycelium and culture filtrates of a previously unknown actinomycete, Streptomyces filipinensis, that was discovered in a soil sample collected in the Philippine Islands.
This can occur naturally, such as in the mycelium of fungi during sexual reproduction, or artificially as formed by the experimental fusion of two genetically different cells.
As such, it could be a sociological term, but was actually coined by Alan Rayner and Norman Todd working at Exeter University in the late 1970s, to characterise a particular kind of zone line formed between wood-rotting fungal mycelia.
The environment was a major theme, including Eric Salzman's in-depth coverage of "Mysteries of the Mycelium" and on-going discussions of whether local snapping turtles (a/k/a "toropes") should be exterminated or celebrated.
Phlebopus tropicus has been shown to form a crust of mycelium around the roots of species of Citrus in Brazil covering colonies of the comstock mealybug Pseudococcus comstocki which attack the roots of these plants after they have been carried there by ants (Solenopsis saevissima var. moelleri); these mycelial crusts are called criptas by Brazilian writers.