A voucher specimen is preserved material deposited in a collection, usually a fungarium, as evidence for a study, a record or a name. If a later researcher doubts what species was tested, the voucher lets them look again, including with DNA. The Canadian National Mycological Herbarium says its specimens serve as vouchers for research, scientific names and living cultures.
Missing vouchers are a known weakness of psilocybin research. A 2022 review judged many older chemical reports doubtful because the material was rarely kept as a voucher others could re-examine (Bradshaw et al., 2022). It found psilocybin identified in only about 45 accepted Psilocybe species.
Vouchers can overturn old results. Inocybe calamistrata was once reported to contain psilocybin, but later studies found none and described the original method as prone to false positives (Kosentka et al., 2013). A 2024 study re-examined a fungarium specimen labelled Psilocybe quebecensis and redetermined it as P. caerulipes (Bradshaw et al., 2024). A result tied to a voucher can be checked; one without a voucher has to be taken on trust.
Sources
- Bradshaw et al., 2022, Applied and Environmental Microbiology
- Kosentka et al., 2013, PLoS One
- Bradshaw et al., 2024, PNAS
- GBIF dataset: Canadian National Mycological Herbarium
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