One of my favorite journalists, Michael Pollan, had a mentor who once said “As a journalist, you want to be a short-term visionary. If you’re a long-term visionary, no one will know what in the hell you’re talking about and nobody will read you. You just want to see around one corner.” The same might be true of scientists. Some of the greatest scientists in history were ahead of their time. Galileo championed heliocentrism in the early 1600s and was put under house arrest for it by the Catholic Church for the last decade of his life. Alfred Wegener proposed the theory of continental drift in 1915, which laid the foundation for modern plate tectonics. But since he couldn’t quite explain why the continents moved, despite the clear observational evidence that they did, he was ridiculed and ostracized from the scientific community. A lesser-known example is that of a Swiss botanist named Simon Schwendener, who suggested the radical hypothesis that lichens are composite organisms made of fungi living in symbiosis with algae. Schwendener proposed the idea in 1867, a decade after Darwin published his magnum opus On the Origin of Species in 1859. One of Schwendener’s contemporaries, William Nylander, a lichenologist who was the first to realize the impact of air pollution on lichen growth, went so far as to call him “stultitia Schwendeneriana”—Schwendener the simpleton. An article in The Atlantic described the attitude among biologists of the time: “…many biologists were gripped by the idea of nature as a gladiatorial arena, shaped by conflict. Against this zeitgeist, the concept of cohabitating, cooperative organisms found little purchase.” While Schwendener’s idea was premature, it was proved factual before the end of his life, unlike Galileo and Wegener.
Nearly all organisms live in symbiosis with other organisms, but few to the extent of lichens. The relationship is generally mutually beneficial—the fungus benefits from the food supplied by the algae (or sometimes cyanobacteria, formerly referred to as blue-green algae) through photosynthesis, and the algae benefits from the protection the fungus provides from predators and sunlight which can dry it out. Together, they also gather moisture and nutrients from the environment. However, in some lichens, the fungus may get the better end of the bargain. The algal partner can usually live outside of the lichen in wetter ecosystems, such as streams, ponds, or wet soil. The fungal partner becomes dependent on the algae for food and cannot live off of decaying organisms like other fungi. For this reason, some scientists think the relationship between lichenized fungi and algae is actually a controlled form of parasitism.
Lichens are diverse. They can be green, bright yellow, red, orange, black, brown, and gray. There are four main shapes of lichens: crustose (crust-like and grow tight to the surface it’s attached to), foliose (leaf-like structures), squamulose (tightly clustered pebble-like units), and fruticose (free-standing branching tubes). Scientists estimate lichens cover approximately 8 percent of Earth’s land surface. There are at least 18,000 species, but taxonomists estimate that between 17–30% of all fungus species are capable of becoming lichens. Since it’s believed there are over 1.5 million fungi species, there could be upwards of 250,000 lichen species.
Lichens may represent an extroverted example of symbiosis among individual organisms, but nearly all organisms require some level of mutualism to survive. The idea of individuality in biology is becoming less and less consistent with the varieties and relationships of life. Perhaps animals should no longer be considered individuals by anatomical or physiological criteria because a diversity of symbionts are present and functional in completing metabolic pathways and serving various other functions. In line with this idea, a new term has entered the scientific community’s jargon: holobiont. “Holos” is the Greek word for “whole”. Holobionts are the multicellular eukaryote plus its colonies of persistent symbionts. Holobionts are the sum of relationships between organisms, big and small. In this way, we may be more like lichens than we thought. As Merlin Sheldrake writes in the book Entangled Life, perhaps “There have never been individuals. We are all lichens.”