Macroevolution of major clades is often studied by plotting their taxonomic diversity through time. It is equally informative, but less commonplace, to investigate how clades explore anatomical ‘design’ space by quantifying their morphological disparity through time. Counterintuitively, diversity and disparity are usually decoupled. Metazoan clades often reach their highest disparity relatively early in their evolution, while diversity is still low.
Oyston et al. show that this macroevolutionary rule of thumb holds true in a sample of major plant clades, and discuss the types of data and methodological approaches that will facilitate future work on plant disparity.