Horizontal gene transfer is the passing of genes sideways between lineages, instead of down from parent to offspring. In psilocybin mushrooms it explains a puzzle: the compound appears in genera that are not closely related. A 2018 study sequenced Psilocybe cyanescens, Gymnopilus dilepis and Panaeolus cyanescens, found the same gene cluster in each, and argued it had jumped between fungal lineages (Reynolds et al., 2018).
A 2024 study refined the timing. It estimated that psilocybin production first arose in Psilocybe and passed to other mushrooms four or five times between about 40 and 9 million years ago, though one of its datasets leaves open an earliest origin in Panaeolus (Bradshaw et al., 2024).
Not every case needs the same route. Psilocybin has also been found in cicadas infected by Massospora, insect-killing fungi that are not mushrooms, possibly made by a different pathway (Boyce et al., 2019). How many species outside Psilocybe carry the cluster is still unknown, because few have been sequenced.
Sources
- Reynolds et al., 2018, Evolution Letters
- Bradshaw et al., 2024, PNAS
- Boyce et al., 2019, Fungal Ecology
Last checked .