Understanding how communities are structured through space and time is essential to the conservation of biodiversity and ecosystem function, especially as climate change rapidly transforms our planet. Of the many biological responses to climate change, changes in phenology–the timing of life history events–are among the most dramatic. However, how phenological responses vary within species across climatic and geographic space remains understudied. Here, we investigated the changes in plant reproductive phenology over the last 100 years across the Eastern United States, encompassing a latitudinal gradient of 25 degrees. Harnessing the power of citizen science facilitated by a fully digitized flora and custom developed tools (www.CrowdCurio.com), we examined the buds, flowers, and fruits of over 10,000 herbarium specimens of 30 widely distributed species.
Results/Conclusions
We find that flowering phenology has advanced significantly over the last 100 years. Also, we demonstrate a latitudinal gradient in phenological sensitivity to spring temperatures, where northern populations tended to be more responsive to warming. This corresponded to a latitudinal increase in climate change. Furthermore, northern habitats experienced higher intra-annual fluctuations in temperature. In conclusion, we find that populations exposed to high inter/intra-annual variations in temperature have evolved to be more responsive to temperature cues to initiate phenological events. With climate change, we predict convergence in flowering times across species ranges, which may lead to increased gene flow and result in genetic homogenization. Such disruption of phenology will likely impact species survival and community diversity, and may have widespread consequences on critical ecosystem processes.