“The Evolution and Ecology of Psilocybin in Nature”, 2023-05-18 ():
Fungi produce diverse metabolites that can have antimicrobial, anti-fungal, anti-feedant, or psychoactive properties. Among these metabolites are the tryptamine-derived compounds psilocybin, its precursors, and natural derivatives (collectively referred to as psiloids), which have played large roles in human society and culture. The high allocation of nitrogen to psiloids in mushrooms, along with evidence of convergent evolution and horizontal transfer of psilocybin genes, suggest they provide a selective benefit to some fungi.
However, no precise ecological roles of psilocybin have been experimentally determined. The structural and functional similarities of psiloids to serotonin, an essential neurotransmitter in animals, suggest that they may enhance the fitness of fungi through interference with serotonergic processes.
However, other ecological mechanisms of psiloids have been proposed. Here, we review the literature pertinent to psilocybin ecology and propose potential adaptive advantages psiloids may confer to fungi.
[Keywords: psilocybin, fungi, evolutionary chemical ecology, neurotransmitters, serotonin, specialized metabolites]
…Given its neuroactive properties, psilocybin may increase spore dispersal distance by altering the behavior of animals visiting the mushroom and expanding their travel radius…Most psilocybin-producing mushrooms have firm-to-tender flesh, making them potential targets for fungivores. Mycophagy pressures have likely driven the evolution of multiple defensive strategies, such as the production of toxic metabolites (2015), including psilocybin…Yet despite convergent evolution in multiple mushroom-forming fungi and an insect pathogen, and its relatively simple biosynthesis compared to other specialized metabolites, psilocybin has not been found in filamentous Ascomycota or yeasts.
…Specific animals that prey on and compete with psilocybin-producing fungi likely exert pressures that are partially mitigated by psilocybin. Existing evidence suggests invertebrates are likely to have driven the emergence and dispersal of the psilocybin pathway, although it is possible that primates also played a role at more recent timescales. The alternate production of psilocybin and other neuroactive metabolites in fungi further suggests psilocybin is targeted to animals, and also that its benefits may be temporary and interchangeable with other neuroactive compounds in the ongoing animal-fungal chemical arms race. Psiloids’ chemical properties give them a unique relationship with animal physiology, allowing them to avoid digestive degradation and access the central nervous system in ways other tryptamines cannot. Psilocybin has a particular affinity for serotonin receptors, but also dopamine and other receptor types, potentially having wide-ranging neuroactive effects across different animal phyla. Psiloids may also function through mechanisms beyond neuroactivity, including as precursors to complex chemical structures with potential anti-fungivory properties via digestive and nutritional interference. The fitness benefits of psilocybin to fungi may come in the form of reduced predation or improved spore dispersal, and different mechanisms may be at play in different circumstances. These questions will be addressed by direct experimentation that we expect will lead to novel insights into the genetics, chemistry, and ecology of fungal psychedelics.