Field of Science

The Importance of Vouchers: Even Molecular Workers Need Herbaria

Those of you who have seen the Monty Python movie The Meaning of Life may recall a scene near the beginning where a woman is brought into a hospital to have a baby, only to have attention to her condition overshadowed by the attention lavished by the hospital staff on their expensive equipment and machines going "ping". Part of the joke, of course, is that a lot of their flashy machinery is completely unnecessary under normal circumstances, considering that women have been successfully having babies without it for as long as there have been women to have babies. The other part is that while we all see the ridiculousness of the situation in the movie, we still all fall for the flashy expensive option in real life. If we go to hospital ourselves, we still damn want the machine that goes "ping".

The proposed closure of the Utrecht Herbarium is actually just another example of a general trend of recent years towards the downsizing and reduction in prestige of natural history collections everywhere. In these days of biochemical assays and gene sequencers, many people, unfortunately including many university and museum directors, seem to find specimen collections just a little antiquarian and hokey. Surely modern genomic and proteomic techniques have rendered such things obsolete? No, they haven't. Molecular investigations don't remove the need for physical specimen storage. Indeed, they make it even more important than before.

Yesterday, I wrote on the importance of conserving type specimens. Type specimens are a special type of voucher specimen, and I thought I'd enlarge today on the significance of voucher specimens in general. A voucher is a representative specimen of the organisms used in a study, such as the specimen used as the source of DNA for a molecular study or a specimen collected as part of an ecological survey. Like type specimens, voucher specimens allow for the confirmation of the identity of the species referred to in the study. They therefore provide a backup against misleading results due to such things as misidentification, changing species concepts, etc.

Apparently one of the projects that has been going on at the Utrecht Herbarium involves the identification of native medicinal plants used in Suriname, so I'll take that as a hypothetical example. Imagine that a researcher working on one of these medicinal plants, call it the "big-leaved bungleflower", manages to extract an active compound from it that he dubs "ifeelfantasticin", and which shows a great deal of promise in medical tests. The problem is that no-one else is able to extract that compound from the big-leaved bungleflower, despite much effort. Despair seems inevitable, until someone decides to check the voucher specimens that the original researcher deposited from his original study. At that point, it becomes clear that the original researcher was not using specimens of big-leaved bungleflower as he had thought, but actually the similar purple-leaved bungleflower. Focus switches to the latter species, ifeelfantasticin is recovered once more, and medical history is made.

Without the voucher specimens, the error would have never been corrected so easily. Griffiths and Bates (2002) report on a real life example of voucher specimens allowing the explanation of unusual results, when a molecular study on New World vultures was seemingly unable to distinguish between greater (Cathartes melambrotus) and lesser (C. burrovianus) yellow-headed vultures. Re-examination of the original specimens indicated that some had been misidentified, including one specimen that had been deposited in a collection before the two species were recognised as distinct.

Unfortunately, all too many researchers still fail to deposit vouchers for studies (Agerer et al., 2000; Wheeler, 2003). Dennis (1960, as quoted in Agerer et al., 2000) commented that "records that cannot be verified are mere waste paper". The need for proper natural history collections remains as strong now as ever.


Agerer, R., J. Ammirati, P. Blanz, R. Courtecuisse, D. E. Desjardin, W. Gams, N. Hallenberg, R. Halling, D. L. Hawksworth, E. Horak, R. P. Korf, G. M. Mueller, F. Oberwinkler, G. Rambold, R. C. Summerbell, D. Triebel & R. Watling. 2000. Open letter to the scientific community of mycologists: “Always deposit vouchers”. Mycorrhiza 10 (2): 95-97.

Griffiths, C. S., & J. M. Bates. 2002. Morphology, genetics and the value of voucher specimens: an example with Cathartes vultures. Journal of Raptor Research 36 (3): 183-187.

Wheeler, T. A. 2003. The role of voucher specimens in validating faunistic and ecological research. Biological Survey of Canada (Terrestrial Arthropods) Document series no. 9. Ottawa.

1 comment:

  1. Not to say some specimens will be/are the only possible sources of dna or (systematic) ungathered information, e.g. when considered species are rare or already gone extinct, or when they live in remote areas.

    On the other hand, herbaria (or other natural collections) can also allow solving historical questions not possibly solvable by other means...


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