Timing and magnitude of Phanerozoic plant diversification are linked to paleogeography and atmospheric CO2

The evolution of plant diversity through Phanerozoic time is often understood as a succession of dominating evolutionary floras. Following the onset of land plant expansion and diversification in the Silurian to Middle Devonian, these include the successive dominance of plant ecosystems by spore-bearing plants (Paleophytic flora), gymnosperms (Mesophytic flora), and angiosperms (Cenophytic flora). The succession of these floras is associated with major evolutionary innovations in plant growth forms, physiology and reproductive systems, allowing for new strategies to utilize resources and diversify. In concert with biological innovation, environmental conditions over the Phanerozoic have strongly varied due to plate tectonic rearrangements of continents and topography, together with variation in atmospheric CO₂ and climate. However, our understanding of how biological innovation and environmental changes interacted to shape the diversity of land plants through deep time is limited by a fragmentary geologic record of both plant diversity and environmental conditions.

Here, we reconstruct high-resolution climatologies (0.5° in longitude and latitude) over the last 470 million years using the fully coupled atmosphere-ocean general circulation model HadCM3 [1], the landscape evolution model goSPL [2], and the mechanistic climate downscaling algorithm CHELSA [3]. Applying the trait-based plant diversity model TREED [4] we then investigate how paleogeographic changes, variation in atmospheric CO₂, and climate conditions shaped the Phanerozoic plant diversification. Combining the model-based diversity reconstruction with an analysis of 140,000 plant fossil occurrences from the Paleobiology Database, we show that Phanerozoic plant genus originations were strongly associated with variation in atmospheric CO₂ and the tectonic supercontinent cycle, both limiting terrestrial resource and niche availability, and modulating the efficiency of environmental heterogeneity to generate diversity. We further show that the angiosperm terrestrial revolution is unique not only due to the intrinsic diversification potential of flowering plants, but also because of the exceptional environmental opportunities following the Pangea supercontinent breakup.

 

[1] P. J. Valdes, et al., The BRIDGE HadCM3 family of climate models: HadCM3@Bristol v1.0. Geoscientific Model Development 10 (10), 3715–3743 (2017), doi:10.5194/gmd-10-3715-2017, https://gmd.copernicus.org/articles/10/3715/2017/

[2] T. Salles, et al., Landscape dynamics and the Phanerozoic diversification of the biosphere. Nature 624 (7990), 115–121 (2023), doi: 10.1038/s41586-023-06777-z, https://www.nature.com/articles/s41586-023-06777-z

[3] D. N. Karger, et al., Climatologies at high resolution for the earth’s land surface areas. Scientific Data 4 (1), 170122 (2017), doi:10.1038/sdata.2017.122, https://www.nature.com/articles/sdata2017122

[4] J. Rogger, et al., TREED (v1.0): a trait- and optimality-based eco-evolutionary vegetation model for the deep past and the present (2025), doi:10.5194/egusphere-2025-6002, https://egusphere.copernicus.org/preprints/2025/egusphere-2025-6002/