As I explained in a previous post, one of THE things to do in London in 1789 was to visit botanist Joseph Banks’s exhibition of specimens that he collected on James Cook’s first expedition around the world. Today plant specimens rarely captivate the public the way they did 222 years ago, but they remain essential as “vouchers for the truth” in the apt words of Richard Fortey. Unfortunately this is not always acknowledged and too often plant species are reported without voucher specimens. “But surely well-trained, experienced botanists know the flora and so don’t need to collect.” Yeah, well ... I know from experience that occasionally the following things can happen.
Misidentification: This happens to everyone at some point, at times for good reason. Some groups of plants are notoriously difficult to segregate into species, especially if one finds individuals growing in unusual conditions. I’ve made misidentifications and have corrected some by my colleagues. Without vouchers it’s impossible to fix such errors.
Typos: I’ve found this kind of mistake most often in plot data entered from messy field forms. A mis-typed or mis-read code produces a new species for the area! Unfortunately it usually isn’t feasible to collect vouchers for all species in every plot.
Taxonomic revision: Plant classifications are often revised, especially as new methods of analysis become available. What we consider one species today may become five in the future. If there is a voucher, a correct new name can be assigned.
Variation: There can be significant morphological variation within a species and proper species characterization requires specimens from throughout its geographic range. Plant descriptions in the literature that are based on adequate material make plant identification easier for all of us! Thus it is critical to collect and to deposit specimens in well-curated accessible facilities.
These are all convincing arguments, but a botanist faced with heat, bugs, hunger, bad roads, thunderstorms and vehicle problems may be tempted to forego yet another collection. Don’t do it! Think about the great botanist Joseph Banks who, though stuck in a little ship for three years, persevered and how it led to fame, fortune and influence. That should give you the energy you need to collect the essential “vouchers for the truth”.
[The importance of vouchers is covered more thoroughly by Vicki Funk in 100 uses for a herbarium: Well, at least 72.]