Tracking hidden dimensions of plant biogeography from herbaria

Plants are diverse, but investigating their ecology and evolution in nature across geographic and temporal scales to predict how species will respond to global change is challenging. With their geographic and temporal breadth, herbarium data provide physical evidence of the existence of a species in a place and time. The remarkable size of herbarium collections along with growing digitization efforts around the world and the possibility of extracting functional traits and geographic data from preserved plant specimens makes them invaluable resources for advancing our understanding of changing species distributions over time, functional biogeography, and conserving plant communities. Here, I synthesize core aspects of plant biogeography that can be gleaned from herbaria along changing distributions, attributes (functional biogeography), and conservation biogeography across the globe. I advocate for a collaborative, multisite, and multispecies research to harness the full potential of these collections while addressing the inherent challenges of using herbarium data for biogeography and macroecological investigations. Ultimately, these data present untapped resources and opportunities to enable predictions of plant species' responses to global change and inform effective conservation planning.