Museum specimens can potentially be used to determine the relative abundance of species in the wild in places that have not been surveyed for their biodiversity or places that may have changed due to human impacts. A previous study (Daru et al. 2017) of biases in herbarium collections emphasized that such relationships between field inventories and museum collections were unknown. In this study, we compared the abundance of tree species in the wild in various North American states, including Massachusetts, Connecticut, North Carolina, Georgia, Florida, California, Oregon, and Washington, with the number of herbarium specimens of these species collected in the same states. Tree species abundance was determined using the Forest Inventory and Analysis (FIA) Program of the U.S. Forest Service, and number of herbarium specimens was determined using newly available online catalogues.
Results/Conclusions
For individual states, there was a strong correlation (R²= 0.25-0.48) between log-transformed abundance of tree species in the wild and number of herbarium specimens: species common in the wild had more herbarium specimens than species that were rare in the wild. However, common species were under-represented in museum collections relative to their abundance in the wild (often less than 20% of expected), and rare species were substantially over-represented (often more than 10-50 times expected). Collectors presumably seek out rare species and rare microhabitats, and field surveys probably have a more limited spatial extent than museum collections. Strong correlations between counts of museum records and independently estimated field abundance suggests that relative abundance of museum specimens can be used to infer relative abundance of species in locations with museum records but few field surveys. Museum specimens might also be useful for inferring relative abundance in past communities before they were transformed by climate change and human activities. However, scientists must be aware of the strong tendency for museum collections to under-collect common species and to over-collect rare species. As new museum collections become available on-line, this method could be used to estimate relative abundances of other plant and animal taxa.