The split gill mushroom redefines biological diversity with over 23,000 mating types, which allows for extensive genetic combinations and reduces inbreeding. Outstripping others like the fairy inkcap mushroom, which has 143 mating types, the split gill mushroom boasts the highest number of sexual types known in any organism, aiding in its adaptability and survival. Found globally, barring Antarctica, these mushrooms thrive on decaying wood and have special gills that protect them during dry periods, allowing them to survive years without rain. Unlike most fungi, the split gill mushrooms around the world are so genetically similar that they're considered one species, a fact discovered by mycologist John Raper's groundbreaking research from the 1950s and 1960s.