Flowering plants show a high diversity of pollen morphology. This diversity is assumed to reflect not only variations in the underlying design, but also stress imposed by ecological conditions related to pollen survival and germination. Both components are expected to constrain accumulation of pollen disparity.
Yu et al. perform a combination of phylogeny-based and statistical tests, demonstrating that pollen disparity in Ericaceae did not evolve steadily but pulsed over the time, clearly decoupling it from the relative constant-rate pattern of species diversification inferred. In pollen morphospace, most major clades appeared to occupy distinct neighbouring regions, and the distribution of species showed a strong central tendency.
Yu, Y., Schneider, H., Li, D.-Z., & Wang, H. (2019). Evolutionary constraints on disparity of ericaceous pollen grains. Annals of Botany, 123(5), 805–813. https://doi.org/10.1093/aob/mcy212