Pollen Morphology of Haplopappus and Related Genera (Compositae—astereae)

Pollen grains of Haplopappus and related genera in the subtribe Solidaginae from North and South America were examined by light and scanning electron microscopy. The grains are consistently tricolporate and echinate. Some genera can be distinguished by pollen size, spine length, and number of spine rows between colpi. Based on these characters, the divergence of Benitoa from other members of the subtribe, as indicated by its morphology and secondary chemistry, is supported. Additionally, the recently suggested absence of a close relationship between Pyrrocoma and Oonopsis is indicated by their contrasting pollen types. This study demonstrates the potential of pollen studies in distinguishing some taxonomic groups in the Astereae.