Small herbaria contribute unique biogeographic records to county, locality, and temporal scales

Abstract

Premise: With digitization and data sharing initiatives underway over the last 15 years, an important need has been prioritizing specimens to digitize. Because duplicate specimens are shared among herbaria in exchange and gift programs, we investigated the extent to which unique biogeographic data are held in small herbaria vs. these data being redundant with those held by larger institutions. We evaluated the unique specimen contributions that small herbaria make to biogeographic understanding at county, locality, and temporal scales.

Methods: We sampled herbarium specimens of 40 plant taxa from each of eight states of the United States of America in four broad status categories: extremely rare, very rare, common native, and introduced. We gathered geographic information from specimens held by large (≥100,000 specimens) and small (<100,000 specimens) herbaria. We built generalized linear mixed models to assess which features of the collections may best predict unique contributions of herbaria and used an Akaike information criterion-based information-theoretic approach for our model selection to choose the best model for each scale.

Results: Small herbaria contributed unique specimens at all scales in proportion with their contribution of specimens to our data set. The best models for all scales were the full models that included the factors of species status and herbarium size when accounting for state as a random variable.

Conclusions: We demonstrated that small herbaria contribute unique information for research. It is clear that unique contributions cannot be predicted based on herbarium size alone. We must prioritize digitization and data sharing from herbaria of all sizes.

Keywords: Index Herbariorum; North American Network of Small Herbaria; Small Collections Network; biodiversity collection; biogeography; herbarium; natural history collection; rare plant; specimen; voucher.

Figure 1

Number of specimen records included in this study’s primary analysis data set that were contributed by large (≥100,000 specimens) and small herbaria (<100,000 specimens) in each participating state.

Figure 2

Number of specimen records included in this study’s primary analysis data set that were contributed by large (≥100,000 specimens) and small herbaria (<100,000 specimens) in each participating state, faceted by scale of uniqueness (county, locality, temporal) and species status category (S1, S2, common native, introduced).

Figure 3

Assessment of model validity in predicting the probability that a specimen represents unique information at different biogeographic scales by comparing (A) observed specimen records and (B) probability in observed data to (C) probability predicted by model. Given that the herbarium size class and species status of a specimen are inherent attributes of the specimen,this figure illustrates the scale of biogeographic uniqueness at which a particular specimen might be expected to contribute.