Phylogenetic evaluation of pollen and orbicule morphology in Rosaceae tribe Neillieae (subfamily Amygdaloideae)

Palynological characteristics were examined in Rosaceae tribe Neillieae, comprising the genera Neillia, Physocarpus and Stephanandra. Physocarpus insularis and some taxa of Spiraea were also examined to evaluate the potential usefulness of pollen traits in taxonomic and phylogenetic studies of Rosaceae. Pollen grains of Neillieae are monads, tricolporate, small to medium in size [polar axis (P) = 13.4–45.8 μm, equatorial diameter (E) = 14.3–39.9 μm] and oblate to prolate in shape (P/E = 0.68–1.70). Sexine ornamentation in Neillia and Stephanandra is perforate, whereas Physocarpus and Spiraea have striate pollen. Spherical orbicules with a central perforation (donut-shaped) were consistently found in Neillieae, but these were absent in P. insularis and all taxa of Spiraea. Our palynological results provide strong evidence for the merging of Neillia and Stephanandra, and pollen morphological data supported the recent phylogenetic hypothesis that P. insularis should be a member of Spiraea.