Author: Lena Roth
In her Master’s thesis, Lena Roth examined the growing popularity of importing and cultivating exotic fungi, as well as the associated risks when these species enter our ecosystems. To investigate this topic, genetic analyses, hybridisation experiments and eDNA studies using spore traps were carried out.
Mushroom cultivation is experiencing a boom worldwide, and with it, international trade in fungal mycelium is also on the rise: cultivated strains are transported across national borders and thus reach new geographical regions.
Fungi have various ways of escaping from cultivation systems into the natural environment, such as via spores or composted substrate. The ecological risks posed by this global exchange of fungal mycelium have so far received little attention, although there are already examples of fungi that have escaped from cultivation and are spreading invasively.
As part of Lena Roth’s Master’s thesis at SwissFungi, this risk was investigated in three commonly cultivated species: the lion’s mane mushroom (Hericium erinaceus), the caterpillar fungus (Cordyceps militaris) and the chestnut mushroom (Pholiota adiposa). Phylogenetic analyses showed that many strains derived from cultivation differ genetically from native strains. These differences reflect the different geographical origins of the respective source populations. In the case of H. erinaceus, this could even be demonstrated at species level: the cultivated strains examined did not belong to H. erinaceus s. str., but to H. asiaticum or H. carolinense. Cultivated and native strains of C. militaris also differed in their growth rates at various temperatures, suggesting that genetic differences between different populations can also be reflected in ecologically relevant traits. A hybridisation experiment involving C. militaris, conducted to investigate a further possible invasion mechanism, revealed no evidence of hybridisation between the strains studied; however, this does not rule out hybridisation under different conditions or between other lines.
Living mycelium in pure culture is largely not covered by current Swiss and international trade legislation on invasive organisms and therefore circulates largely unchecked. Furthermore, the information provided by traders regarding the origin of the mycelium often does not correspond to its actual genetic origin. If strains from cultivation are released into the environment, potentially alien genetic material comes into contact with native populations. As preventing introductions is significantly more effective than subsequently combating established invasions, these findings suggest that regulatory measures in the field of mushroom cultivation should be considered at this stage.