Abstract
<jats:p> The most famous chemicals produced by mushrooms are the psychedelic compound psilocybin from "magic mushrooms" and amatoxins from deadly poisonous mushrooms. These compounds are known to occur in multiple phylogenetically disjunct fungal lineages but have never been shown to co-occur within a single species. Here we show that the "dark magic mushroom" <jats:italic>Galerina indica</jats:italic> produces both psilocybin and amatoxins. Mass spectrometry revealed psilocybin and amatoxins in mushroom tissues, and genomic analyses identified corresponding biosynthetic genes. Phylogenetic analyses suggest that <jats:italic>G. indica</jats:italic> acquired psilocybin biosynthesis via horizontal gene transfer after amatoxin biosynthesis was already established, and that psilocybin biosynthesis was acquired twice independently within <jats:italic>Galerina.</jats:italic> Intriguingly, acquisition of psilocybin biosynthesis in <jats:italic>G. indica</jats:italic> may have coincided with reduced amatoxin potency. These findings reveal how horizontal gene transfer can combine powerful bioactive systems in a single species, potentially altering the ecological roles of both compound classes and the evolutionary fitness of the species. </jats:p>