An update to the palynotaxonomy of the Brazilian species of Aeschynomene sensu stricto and the recently circumscribed genus Ctenodon (Leguminosae - Papilionoideae - Dalbergieae)

Pollen morphology and ultrasculpture are variable features and important tools to aid the taxonomy and systematics of Aeschynomene sensu stricto and the recently circumscribed genus Ctenodon. We performed a palynotaxonomy study of pollen morphology and ultrasculpture of nine species of Aeschynomene and 13 species of Ctenodon using light, scanning and electron transmission microscopy, and provided novel data for seven species. Additionally, principal components analysis was performed to elucidate patterns of quantitative data variation between species. Pollen is isopolar (rarely apolar and pantocolporate), small to medium in size, oblate to prolate, 3-zonocolporate or 3-parassyncolporate/3-syncolporate (only in A. americana) with a colporus with margo (the margo was rarely absent), membrane or/and operculum (the operculum was rarely absent), and a rugulate-perforate or nanoreticulate to reticulate sexine. Two pollen types are recognised, one for each genus, based on ultrasculpture variation of the colporus operculum, membrane and margo, and the mesocolpium and apocolpium sexine combined with endoaperture features. The eurypalynous morphology supports the current circumscription of these genera and their phylogenetic relationships.