Pollen morphology and species differentiation in selected species of Inuleae (Asteraceae)

The tribe Inuleae is widely distributed within Asteraceae and exhibits considerable morphological variation, which complicates species classification. Pollen morphology provides relatively stable features for species delimitation, yet comprehensive palynological data for many species remain limited. In this study, the pollen morphology of 19 species from eight genera of Inuleae was investigated using light microscopy (LM) and scanning electron microscopy (SEM), with a focus on 10 quantitative traits. Multivariate analyses, including principal component analysis (PCA) and hierarchical clustering analysis (HCA), showed that both pollen size and exine ornamentation contribute to interspecific differentiation. Differences were especially notable between Blumea and Carpesium, with the latter showing larger pollen grains and more slender, scattered spines. This research also presents first-time palynological descriptions of Blumea, Carpesium, Inula, Laggera, Pentanema, and Pterocaulon. Overall, the findings indicate that pollen morphological traits are informative for species differentiation and lay a foundation for further palynological classification within Inuleae.