This study compared biodiversity between Eastern Asia and Eastern North America by analyzing 10 plant genera with sister clades in each region. For 7 of the 10 pairs, the Eastern Asian clade had longer branch lengths, indicating faster molecular evolution, and more species. Regression analysis found a positive relationship between molecular evolution rate and species richness. The results provide evidence that higher rates of molecular evolution in Eastern Asia may have led to more rapid speciation, contributing to its greater plant diversity compared to Eastern North America.