Premise of the study: Because of their numbers, specimens in natural-history museums cannot be ignored when trying to answer one of the fundamental questions in science: What determines species diversity? The nonrandom nature of collecting does not allow most statistical tests or extrapolations of species estimates, or comparison of richness between areas (which, however, is still done frequently).
Methods: We present a simple simulation model, which starts from the assumption that collectors never collect the same species twice during collecting trips. The model allows the generation of the abundance distribution in a herbarium for any natural species abundance distribution, using a simple set of collecting strategies.
Key results: We show that, in essence, the strategy of "never collect the same species twice" is enough to generate the relative abundance distribution as found in a herbarium. We illustrate this using real plot and specimen data from two well-collected areas, one in central Guyana and one in Suriname.
Conclusions: Because of the oversampling of rare species, it is perhaps not possible to use museum data to reconstruct the community structure in the field or even estimate a proper diversity number other than the number of species in a region.