The World’s Most Common Mushroom?
According to Wikipedia the Common Split Gill (Schizophyllum commune) is the world's most widely distributed mushroom, occurring on every continent except Antarctica. It is found predominantly from autumn to spring on dead wood, in coniferous and deciduous forest.
Often when fungi appear to be similar but occur on widely separated continents, DNA analysis shows that their genetic separation is so great that they should be classified as distinct species. Thanks to the work of John Raper and colleagues at Harvard University over two decades from the 1950s to the 1970s we know that Schizophyllum commune is one species worldwide. Roper and friends collected Split Gill mushrooms from all over the world. From germinated spores they grew mycelia and showed that as two strains are of different mating types they were able to mate with one another. They also discovered that Schizophyllum commune has more than 28,000 sexes, an adaptation that minimizes the risk of siblings mating and hence maximizes the genetic diversity by achieving nearly 100% outbreeding with new genetic stock.
Although European and US guidebooks list it as inedible, this is apparently due to differing standards of taste rather than known toxicity, being regarded with little culinary interest due to its tough texture. S. commune is, in fact, edible and widely consumed in Mexico and elsewhere in the tropics.