The sequences alignment used for building the Apocynaceae phylogeny.

Investigating species diversification patterns of hyperdiverse lineages is essential for understanding their species diversity accumulation and the historical assembly of floristic components in biodiversity hotspots where they have radiated. Apocynaceae plays a significant role in several hotspots, and is one of the two families with pollinia. Previous studies have hypothesized that species with pollinia could have higher diversification rate, but it remains inadequately explored in the Apocynaceae. Using a robust phylogeny covering 22 of the 25 tribes, this study investigated the possible association between diversification of the Apocynaceae and pollinia. We found that the Apocynaceae originated at 59.03 Ma. The region encompassing India, Indochina, and Western Malesia was main source for the Apocynaceae migrations. We detected a diversification rate increase at the node in which pollinia started to evolve, starting at the Oligocene-Miocene boundary. Trait-related diversification analyses also showed that species with pollinia had a higher speciation rate than those without. However, according to the HiSSE results, the presence of pollinia alone did not explain this difference. Our results suggest that pollinia could be one of the traits contributing to the diversification rate acceleration. Other biotic and abiotic factors should be considered along with the pollinia in the future studies.