Morphometric and Statistical Analysis of Pollen Morphology in Seven Woody Species of Betulaceae

Morphological characteristics of pollen grains, including shape, size, pore number, and exine thickness, vary significantly among species and enable the reliable use of palynological data in taxonomic studies. In this context, the present study investigates the pollen morphology of seven Betulaceae taxa (Alnus glutinosa, Betula pendula, Carpinus betulus, Carpinus orientalis, Corylus avellana, Corylus colurna, and Ostrya carpinifolia). Detailed morphometric measurements were carried out using Light Microscopy (LM), and high-resolution images were obtained using Scanning Electron Microscopy (SEM). For each taxon, thirty measurements were taken for the main pollen characters, including polar axis length (P), equatorial diameter (E), pore length (plg), pore width (plt), and exine thickness (Ex). Interspecific differences were evaluated using one-way ANOVA, Tukey’s HSD test, and Principal Component Analysis (PCA), and a diagnostic pollen identification key was developed for the investigated species. The results demonstrate statistically significant interspecific variation in pollen size, pore characteristics, and exine thickness. In the PCA ordination, the first principal component (PC1) was mainly associated with pollen size (P and E), clearly separating Carpinus betulus from the remaining taxa. The second principal component (PC2) was primarily related to pore length (plg) and contributed to the separation of Alnus glutinosa from the other small-pollen species. These results show that quantitative pollen morphological characters provide reliable criteria for distinguishing closely related Betulaceae taxa.