“Magic mushrooms” are consumed recreationally and for medicinal purposes around the world. These fungi gained their fame as “magic” because they produce chemical compounds (called psilocybin and psilocin) which have psychedelic effects.
The most famous species of these mushrooms, due to their global distribution and ease of cultivation, is Psilocybe cubensis, known primarily from its preferred habitat of dung-laden fields. It was first described from Cuba, but is found throughout the world.
However, there has been a long-standing question about its evolutionary history. Where did it originate, and how did it move around the globe?
We described a new species of magic mushroom in South Africa and Zimbabwe, now named Psilocybe ochraceocentrata, which has allowed us to investigate this question.
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Our disciplines are mycology (the study of fungi) and evolutionary biology. In a recent paper, we report on what P. ochraceocentrata may tell us about the possible wild origins of Psilocybe cubensis.
Our findings used sophisticated methods to test whether P. cubensis could have arrived in the Americas along with European colonisation and cattle, a long standing hypothesis proposed by the Mexican mycologist and ethnomycologist Gastón Guzmán. We also investigated other possible scenarios, such as dispersal by environmental factors like wind, or ancient biological means such as large herbivore or insect migration.
Before this study, P. ochraceocentrata was already regularly collected. But it was assumed either to be P. cubensis or P. natalensis, sold under the name “Natal Super Strength“.
We have created a framework of unambiguous identification. Ultimately, our work does not fully resolve the evolutionary history question. But it provides a guide for future study to fully understand where these fungi evolved and how they may have travelled the world.
Knowing the origin of a species is important as it explains how historical, geological and climate factors shape the current distribution of life on Earth. This can be important for understanding how some traits evolved in response to their environment, where a species may become invasive, or possibly where to look for closely related species with traits of interest for medicinal research.
How was the study performed?
Fieldwork conducted over decades in Zimbabwe by researcher Cathy Sharp, and further observations in South Africa, yielded multiple collections of mushrooms similar to P. cubensis. All were associated with the dung of herbivores, including animals native to Africa. Some Psilocybe mushrooms use dung as a food source.
Our work showed that these “cubensis look-a-likes” were superficially similar but differed microscopically and at a molecular level. We chose to investigate this relationship further. Our approach involved:
- field collection – studying specimens from the wild
- genomics of museum specimens (museomics) – using molecular techniques on historically important specimens
- phylogenetics – using genetic data to reconstruct how species are related through common ancestry
- molecular dating – estimating a general time frame when two species may have diverged from one another
- ecological niche modelling – predicting where a species can live based on environmental conditions.
This allowed us to study the natural history of P. cubensis and its close relative Psilocybe ochraceocentrata.
We found that P. ochraceocentrata and P. cubensis may have had a common ancestor living about 1.56 million years ago.
This corresponds with the global expansion of grasslands and the distribution of grazing herbivores. The world at this time would have been populated with migrating herbivores. Coprophilic fungi (fungi that grow on animal dung) could have moved with them globally, and then begun to evolve along independent paths.
Origin story
To complement our taxonomic and dating investigations, we wanted to see if we could find a plausible origin of P. cubensis. In previous studies, the lead author had identified that the closest relatives of P. cubensis all had native distributions across the Asian continent. There was very little overlap with species from the Americas.
With the addition of P. ochraceocentrata as the sister taxon (the closest relative), it became far more reasonable to suggest its evolutionary history is centred in Africa or Asia, not the Americas.
To test this, we used publicly available data from the popular public “citizen science” repository for biodiversity monitoring, iNaturalist. We then used mathematical modelling to hypothesise where these organisms might have occurred hundreds of thousands to millions of years ago.
Our work showed a lot of variability across time but partially favoured tropical and subtropical regions where large animals roamed. From this, we proposed a few scenarios of how P. cubensis split from the ancestor it shared with P. ochraceocentrata and became globally dispersed.
One theory is a natural disturbance via unknown animal or environmental vectors. In other words, something may have changed the environment and disrupted the population. For example, dung beetles could have eaten dung that had fungal spores in it, and could have crossed the ocean, taking the fungus with them. Or the spores may have been carried across the ocean on the wind. This is known to have happened with other fungi, such as Podospora.
Another possibility is migration via the Bering land bridge between Eurasia and the Americas. This is how many plants and animals moved between the continents.
Guzmán proposed that P. cubensis likely originated in Africa and was transported to the Americas via cattle transport during the colonisation events of the 1400s and 1500s. Our work suggests that this route was also possible.
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The most likely scenario would be multiple introductions, and spore dispersal between populations in the Americas to retain genetic diversity.
What’s missing
Africa is one of the most biodiverse continents, and yet it is the most under-sampled for fungal diversity, due in part to a historical sampling bias of fungi from other parts of the world.
When it comes to Psilocybe, fewer than ten species are officially described from the African continent. Worldwide about 165 species are known.
Further studies are needed across the continent, to describe and map local fungal diversity and improve on current knowledge. Knowing more about the mushrooms that occur in a region tells us more about the ecology of the area, which is key to conservation efforts.
Natural history museums and herbariums were critical for this work and serve as an immeasurable biodiversity resource representing hundreds of years of scientific effort that both scientists and the general public can access.
Breyten Van der Merwe, PhD student, Stellenbosch University
Alexander Bradshaw, Postdoc, mycologist and evolutionary biologist, Clark University
