Palynotaxonomy of Neotropical species of Paullinia L. (Sapindaceae)

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Paullinia is the second-largest genus within the Sapindaceae, with approximately 200 species. It predominantly comprises lianas that inhabit humid forests, mainly the Amazon and Atlantic forests in Brazil. This study aimed to characterize the pollen morphology of 60 species of Paullinia, examining the potential of pollen characters as morphological markers to support the systematics of the genus. The pollen material was obtained from exsiccatae of flower buds from major herbaria. Pollen grains were acetolyzed, measured, described, and illustrated using light microscopy. Scanning electron microscopy was used for accurate descriptions of surface features. The analyzed characters included pollen shape, size, aperture type and number, and exine ornamentation. The similarity of pollen characters between species was analyzed using hierarchical cluster analysis and principal component analysis. The results showed that pollen grains of Paullinia species are shed in monads, heteropolar in most species and isopolar in some others, medium or large in size, oblate or suboblate, and 3- or 3-4-porate, with perforate sexine ornamentation in most species and microreticulate in some others. Multivariate analyses revealed that pollen morphology is informative and holds taxonomic potential, enabling grouping based on the similarity of the unique pollen characters of the genus. Species dispersion on the PCA biplot showed that the five clusters formed by HCA were robust, suggesting that quantitative and qualitative pollen characters exhibit consistency with regard to the similarity species. The palynological findings presented here contribute to enhancing our understanding of the morphological characters, aiding in the taxonomy and systematics of the genus.