Comparative Pollen Morphology of Selected Species of DC. and Cass. and Its Taxonomic Significance.

The pollen morphology of 20 species from and Cass. was investigated using a light microscope (LM) and scanning electron microscopy (SEM) to explore their taxonomic significance. This study showed that pollen grains of these species were usually tricolporate, rarely tetracolporate (). Nine pollen types were distinguishable through the exine sculpture characters and the number of apertures. It was easily distinguished from species of s. str. by its much smaller size (15.04 μm × 15.07 μm) and sparse and longer spines (24 spines, spine length 4.23 μm) with acute apex, which suggest that might not belong to the genus s. str. The palynological characteristics indicated that Section and Section of were not monophyletic groups. The pollen morphology differentiation of clade is consistent with the interspecific relationship revealed by the molecular phylogenetic tree. However, the pollen morphology of the clade is inconsistent with the interspecific relationship based on molecular phylogenetic analysis. This palynology research can only partly support the previously published molecular phylogeny of s. str.