When you travel to a far and away place, it always is an exhilarating experience to find a species of fungus you have never seen. They fill the mind with wonder and appreciation, because up until that point, to you that fungus did not exist. You soon realize that this new fungus is the result of millions and millions of years of constant evolutionary pressures. Further still, you fathom that this species is just a small subset of its common ancestors, with the notion that 99% of all species that have evolved on Earth are indeed extinct. Some traits this species has in its repertoire has helped it to be extant, rather than extinct. You then entertain yourself, trying to pinpoint those traits and explain how they interact with the environment. You scour textbooks and online resources and learn that this species specializes in the lignin breakdown of a genus of trees only found in Central America. You think to yourself, “That’s why I have never seen this before! It is limited to the distribution of the trees it breaks down.” Though, what is sometimes even more thought provoking is when you are hiking thousands of miles away from your own native forest floor, and you find a species you know. This was the case for Schizophyllum commune, the common split gill. Instead of trying to understand what is limiting this species distribution you instead question what traits make these fungi occur in several ecosystems all over the place.
The traits associated with Schizophyllum commune that allow it to exist everywhere are as widespread as its distributions itself. For one, this species has a wide feeding niche. It can both parasitize and decompose several different tree genera. These first described traits helps this species compete everywhere. Parasitic decomposers have a competitive edge over fungi that are strictly decomposers because they can colonize the tree, competing for space and resources before the tree is dead. There are several latent fungal decomposers that lie dormant in living trees until the tree dies, but S. commune goes right to work once it penetrates the tree's outer tissue. The second series of traits help this species live in diverse ecosystems, and help them persist throughout the year.
These next traits enhance its xeromorphic lifestyle, or its ability to retain and store water most efficiently. It’s genus name Schizophyllum stems from the Greek, schizo; to split and phyllon; leaf, and refers to the gills split edge. When desiccation events are imminent, the dry weather promotes this species gills to curve inward, which protect the hymenial surface, ultimately reducing water loss. Physiologically, this curvature occurs as the thinner-walled hyphae shrink through desiccation, while the other gilled, clamped tissue loses water less readily and remains turgid. Another xeromorphic trait that was recently brought to light is its fuzzy cap surface.
A little more than a year ago during another encounter with this species, I wondered how a fuzzy cap would enhance a species fitness. At the time, I couldn’t find anything and concluded that fuzziness could be a random conserved mutation that doesn’t have an ecological or physiological function. Well, I couldn’t be more wrong. An individual of S. commune experiencing a dry period for a long enough duration, will enter a dormant state in which metabolic activity comes to a halt. Once it rains, or an intrigued mycologist with a water bottle quenches the individual, that fuzzy cap surface comes into play by absorbing large quantities of water. In fact, a dried fruiting body of this species can be stored for years and can reanimate when placed in a moist environment. I’ve heard of different spores and seeds that can stand the test of time but actual fruiting bodies?! Yet again I am left shook after understanding fungal adaptations. In just 2-3 hours after this fungus breaks dormancy, its releases potential offspring in the form of spores.
I’ve seen this species in western NY, just north of Georgia in the southern Appalachia, and in central Costa Rica during the dry season. I now know why. Schizophyllum commune readily competes for space and resources by having a huge feeding niche and has evolved adaptations that allow it to live in both dry and wet environments. It also has fruiting bodies that last for years, and can reanimate once suitable conditions become present. S. commune is an amazing species that has earned the right to global dominance. May its teachings also be a testament on how to always remain open minded even after you come up with a conclusion. A year ago, I thought a fuzzy cap didn’t have an ecological function. There is no place for stubbornness or egoism if you truly want to cultivate a greater understanding of the forest floor.