There is increasing scientific awareness of the intricate and essential ways in which different organisms depend on one another biochemeically. Termites could not eat wood without bacteria in their digestive tracts. Humans are likewise dependent upon the huge variety of microorganisms that comprise our microbiome.
Dichanthelium lanuginosum takes such intricacy a step further. It is a grass that lives in very hot soils – such as those in Yellowstone Park. ot only does it depend upon a fungus for its heat resistance, that fungus depends in turn upon a virus. Remove either the fungus or the virus and the grass can no longer live in its ordinary niche. Apparently, something similar has been observed in some tomato plants.
The example demonstrates just how shockingly complex the combination of biochemistry, ecology, and evolutionary biology really is.
Source: MÃ¡rquez et al. “A Virus in a Fungus in a Plant: Three-Way Symbiosis Required for Thermal Tolerance.” Science 26 January 2007: Vol. 315. no. 5811, pp. 513 – 515.