Calea comprises 157 species that occur in the Neotropics. The genus is organized into eight subgenera and 18 sections. Calea sect. Meyeria consists of eight species occurring exclusively in south-central Brazil. In this study, pollen grains from these eight species were sampled from herborized flower buds in pre-anthesis. Pollen samples were acetolyzed, measured, and photographed under a light microscope. Unacetolyzed pollen grains were examined under a scanning electron microscope. The results were used to characterize pollen morphology and construct a palynotaxonomic key for Calea sect. Meyeria. The analyzed pollen grains were monads, isopolar, usually medium-sized, oblate spheroidal, tricolporate, with lalongate endoaperture, the sexine echinate and thicker than the nexine, and six spines in the apocolpium region. The eight species have very similar pollen grains, but some characters are informative for this section, namely pollen size, polar area, sexine ornamentation, and endoaperture characteristics. Despite the similarity of the pollen grains, palynological analysis was able to contribute to the delimitation of Calea species, providing new information for species distinction within Calea sect. Meyeria.

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