Pollen Morphology of Cotoneaster (Rosaceae) Species in Türkiye and Its Systematic Significance

Pollen morphology of 14 specimens from all nine Turkish native species along with one undescribed species of Cotoneaster was examined by light microscopy (LM) and scanning electron microscopy (SEM). The most frequent pollen types are trizonocolporate and tetracolporate, respectively and they occur together. Moreover, trisyncolporate, 3-parasyncolporate, 4-parasyncolporate, and pentacolporate pollen grains were observed in Cotoneaster for the first time in this study. Trizonocolporate pollen grains are radially symmetrical, isopolar, 22.5–35 × 26.25–42.5 μm in size and suboblate in shape. The amb is triangular, except C. integerrimus, which has a circular outline. Two endoaperture types can be distinguished. One is rectangular/square, the other is circular (endopore) and present only in C. integerrimus, C. melanocarpus and C. tomentosus. The exine pattern can be divided into two types, namely striate-perforate and rugulate-perforate. The quantitative pollen characteristics were analyzed using principal component analysis (PCA) and all pollen features were considered for hierarchical cluster analysis (HCA). Principal component analysis revealed that colpus width, endoaperture length, and endoaperture width are the most powerful metrical pollen traits in Cotoneaster identification. According to hierarchical cluster analysis, pollen traits enable division of Cotoneaster into two subgenera. The present study provides insights into pollen morphology of Cotoneaster, as well as its use for taxonomic purposes.