High-resolution paleobiome reconstructions highlight ecological and historical dynamics underpinning global terrestrial vertebrate diversity

Past climate change has repeatedly reshaped Earth's biomes, yet how their expansion and contraction influence biodiversity patterns through time remains unclear. Competing hypotheses propose that either historical biome area has a strong influence on diversity, or that biodiversity responds rapidly to environmental change, such that present-day biome area and energy are sufficient to explain diversity patterns. Progress in testing these ideas has been limited by sparse and inconsistent proxy data and the coarse resolution of existing paleoclimate models. Here, we reconstructed global biome histories for the Cenozoic (66-0 Ma) by downscaling five different paleoclimate simulations. Estimates of change in biome area through time were generally consistent among alternative climate models and with the empirical proxy record. Accounting for variation among models, we found that present-day area and energy were consistently better predictors of vertebrate diversity than historical measures. These findings suggest biodiversity tracks the ecological limits set by shifting biomes, leaving sparse legacy of past dynamics. Our results highlight the importance of integrating multiple paleoclimate reconstructions when assessing the historical drivers of biodiversity.