The study of pollen grains as a contribution to the taxonomy of Nissolia (Leguminosae–Papilionoideae–Dalbergieae)

Nissolia has one of the most complex taxonomic histories of the informal Adesmia clade. In order to find additional taxonomic relevant characters for this genus, we studied the pollen morphology, ultrasculpture, and ultrastructure of 21 species and a single variety of Nissolia using light, scanning, and electron transmission microscopy. Additionally, a principal component analysis was performed to elucidate patterns of quantitative data variation among species concerning the most recent molecular data. Three pollen types are described based on mesocolpium sexine ornamentation. Furthermore, pollen grain size and shape, class of endoaperture, ultrasculpture of the operculum, membrane, and apocolpium sexine were informative pollen features for species recognition and delimitation in Nissolia. We conclude that pollen morphology and pollen types are related to species and phylogenetic distribution in Nissolia, providing valuable characters for taxonomic studies in the Adesmia clade.