Leaf venation network evolution across clades and scales

Leaf venation architecture varies greatly among living and fossil plants. However, we still have a limited understanding of when, why and in which clades new architectures arose and how they impacted leaf functioning. Using data from 1,000 extant and extinct (fossil) plants, we reconstructed approximately 400 million years of venation evolution across clades and vein sizes. Overall, venation networks evolved from having fewer veins and less smooth loops to having more veins and smoother loops, but these changes only occurred in small and medium vein sizes. The diversity of architectural designs increased biphasically, first peaking in the Paleozoic, then decreasing during the Cretaceous, then increasing again in the Cenozoic, when recent angiosperm lineages initiated a second and ongoing phase of diversification. Vein evolution was not associated with temperature and CO₂ fluctuations but was associated with insect diversification. Our results highlight the complexity of the evolutionary trajectory and potential drivers of venation network architecture.