Pollen morphology of 16 species of Fritillaria L. and its taxonomic implications

Fritillaria spp. have an abundance of germplasm resources, but there is still controversy over the delimitation of some species. The morphological characteristics of pollen are important for classification and evolutionary research. In this study, we assessed the pollen morphology of 16 samples from 11 species covering four subgenera. The pollen is subprolate, prolate or perprolate, mostly with bilateral symmetry, monosulcate almost up to the poles, oblong-ellipsoidal in equatorial view and suborbicular in polar view. A total of ten exine sculpturing types (striate-reticulate, rugulate-reticulate, perforate, reticulate-perforate, psilate-perforate, suprareticulate, reticulate, microreticulate, macroreticulate and granular), and eight sulcus membrane ornamentation types (psilate, rugulate, granulate, granulate-striate, verrucate, verrucate-granulate, plicate-granular and macrogranular) were observed across these species. The apex of the sulcus was sharp or round. The murus consisted of single- or multiple-line particles and a more or less verrucate-granulate mesh was observed in some species. Combined with molecular evidence, pollen sculpture patterns appear to reflect phylogenetic relationships and are useful for delimiting species or subsections. Using the characteristic pollen morphology of all the examined species, we also analysed evolutionary trends and taxonomic implications while discussing the application of pollen morphology in the classification of cultivars. These data provide palynological evidence for understanding similarities and relationships within the Fritillaria genus.