Pollen morphology of the genera and (Coreopsideae, Asteraceae): implications for taxonomy.

and are two closely related genera in Asteraceae, tribe Coreopsideae whose limits need to be clarified. Pollen morphology has been useful for delimitation at the genus level in this family. To better define these genera, the morphology of pollen grains was observed and measured using light and scanning electron microscopy. The pollen grains of 25 species of and were acetolyzed and analyzed. Pollen is tricorporate in most of the species studied, although in a few species in , grains were found to be hexacolporate. The most outstanding differentiating characters among species of and are colpus length (greater in ) and shape of spines (conical in ). In addition, lalongate ora are larger in than in . A PCA analysis of thirteen pollen characters, identified species of in a discrete group and as an outlier. These distinctive attributes in pollen morphology support the idea that pollen morphology is useful for delimitation at the generic level in the clade. Further evidence from other sources, genetic or anatomical, might contribute to demarcating and , and provide insight into the family's evolutionary history.