Documenting biodiversity with digital data: comparing and contrasting the efficacy of specimen-based and observation-based approaches.

Digitized herbarium specimens and iNaturalist observations provide invaluable plant biodiversity data. Combining these two data sources could create a more holistic representation of local biodiversity; however, understanding biases inherent to each is critical to determine how to best combine and utilize these data. We examined how the interpretation of taxonomic and phylogenetic diversity, naturalized species detection, and spatiotemporal coverage differ when using herbarium and iNaturalist data alone and together. We also examined how these patterns vary among areas with different degrees of collecting and community science efforts. Across areas, diversity was higher when data sources were combined, and complementary spatiotemporal coverage between data sources indicates that combining these data is useful; however, biases unique to each data source should be considered during analyses. Naturalized species detection, diversity patterns, and spatial biases varied by area, indicating that local context impacts our current views of biodiversity and should shape future monitoring. Our findings suggest that continued digitization and georeferencing of the herbarium records will help provide critical information about biodiversity, but a strategic collection of both specimens and iNaturalist observations moving forward will ensure that we are capturing biodiversity change in real time, helping us track responses to environmental change.