"But how true that is, I do not know": the influence of written sources on the medicinal use of fungi across the western borderlands of the former Soviet Union.

Fungi have been used for medicinal purposes for many centuries. This study, based on 35 historical written sources and 581 in-depth semi-structured interviews from eight countries in the western borderlands of the former Soviet Union, investigates the medicinal use of fungi by local communities. We compared the taxa and uses obtained from fieldwork and historical sources with works that advocated fungi use within Soviet herbals, representing the centralised medical system. During fieldwork, we identified eight locally used fungi and one lichen. The highest numbers of medicinal uses were documented in Russia, Estonia and Ukraine. Studies published before the Soviet era listed 21 fungal taxa and one lichen species used in the study region. However, only six of these taxa were mentioned as used by people in our field studies (Amanita muscaria, Boletus edulis, Lycoperdon, Morchella, Phallus impudicus and Cetraria islandica). Notably, these same six taxa were consistently endorsed in Soviet herbals. Of the remaining three taxa recorded in the fieldwork, none were mentioned in historical written sources. However, they were promoted either in Soviet herbals (Inonotus obliquus, Kombucha) or later popular publications (Cantharellus cibarius). This highlights the significant influence of written sources on the use of fungi for medicinal purposes within the studied local communities.