Fungi produce diverse metabolites, including psilocybin and related tryptamine-derived compounds called psiloids, which have antimicrobial, antifungal, antifeedant, or psychoactive properties. The high nitrogen allocation to psiloids in mushrooms, along with convergent evolution and horizontal gene transfer, suggests a selective benefit, but no precise ecological roles have been experimentally determined. Structural and functional similarities of psiloids to serotonin, an essential neurotransmitter in animals, indicate they may enhance fungal fitness through interference with serotonergic processes, though other mechanisms have been proposed. This review examines literature on psilocybin ecology and proposes potential adaptive advantages psiloids may confer to fungi.
Various fungi across multiple phyla produce psychoactive compounds like psilocybin, ibotenic acid, muscimol, and lysergic acid amides, which affect human neurotransmitter receptors to cause profound psychological effects. These substances appear in mushroom-forming genera such as Psilocybe and Amanita, as well as ergot-producing Claviceps and insect-pathogenic Massospora. Ecologically, psychedelics may deter predators or aid spore dispersal. Biosynthetic enzymes are encoded in metabolic gene clusters that can spread via horizontal gene transfer, leading to a patchy distribution among species. The renewed study of these compounds presents both opportunities and challenges for science and society.