Shifts in phenology and species ranges restructure the flowering season across North America

This is a Preprint and has not been peer reviewed. This is version 3 of this Preprint. You must log in to post a comment. There are no comments or no comments have been made public for this article. This is a Preprint and has not been peer reviewed. This is version 3 of this Preprint. Add a Comment You must log in to post a comment. Comments There are no comments or no comments have been made public for this article. Global change is altering the phenology and geographic ranges of flowering species, with potentially profound consequences for the timing and composition of floral resources and the seasonal structure of ecological communities. However, shifts in flowering phenology and species distributions have historically been studied in isolation due to disciplinary silos and limited data, leaving critical gaps in our understanding of their combined effects. To address this, we used millions of herbarium and occurrence records to model phenological and range shifts for 2,837 plant species in the United States across historical, recent, and projected climate and land cover conditions, enabling us to scale responses from species to communities, and from local to continental geographies. Our analysis reveals that communities are shifting toward earlier, longer flowering seasons in most biomes, with co-flowering species richness increasing at the edges of the season and declining at historical peaks—trends projected to intensify under ongoing environmental trends. Although these shifts operate concurrently, they affect different aspects of the flowering season: phenological changes primarily alter seasonality—its start, end, and duration—and co-flowering diversity at the edges of the season, while range shifts more strongly influence co-flowering species richness during historical seasonal peaks, and attributes tied to community composition, such as patterns of flowering synchrony among co-occurring species. Together, these results demonstrate that shifts in phenology and species ranges act synergistically to restructure the flowering seasons across North America, revealing wide variation in the pace and magnitude of change among biomes. https://doi.org/10.32942/X28W5Z Life Sciences species distributions, flowering phenology, no-analogue communities, community reassembly, ecological scales, climate change Published: 2025-04-08 04:23 Last Updated: 2025-10-24 07:27 CC-BY Attribution-NonCommercial 4.0 International Conflict of interest statement: None Data and Code Availability Statement: The underlying data used in the analyses will be made publicly available on Dryad upon completion of the peer review process. All code underlying the analyses will also be made publicly accessible through Zenodo upon completion of the peer review process. Language: English