Schweiger and Schweiger (2024) recently proposed that evolution of greater photosynthetic capacity in C3 plant species may be linked to increased species diversification. Here I argue that this conclusion is premature because their methods cannot reliably estimate diversification rate or ancestral trait values. Reanalyzing the data set using model-based phylogenetic comparative methods reveals no evidence that photosynthetic capacity is associated with diversification rates among C3 plant genera.

Schweiger and Schweiger (2024) recently proposed that evolution of greater photosynthetic capacity in C3 plant species may be linked to increased species diversification. Here I argue that this conclusion is premature because their methods cannot reliably estimate diversification rate or ancestral trait values.