Let's see how imortant these fungi are in the diet of some mammals. These burrowing animals expose fine roots, dump spore laden feces, thus provide easy infection of roots. Orchid mycorrhizal fungi are unusual in that they do make cellulases and ligases. Furthermore, orchids are unusual in being able to utilize trehalose, a 5C sugar generally used by fungi but not plants. Orchid seeds are extremely tiny and must inititate a mr relationship to germinate and establish.
Some orchids parasitize first fungus, and have to establish new association to live longer.
Instead, they are viewed as assemblages of different species, each present in response to its own physiological requirements and a particular set of environmental conditions.