Pollen morphology and its systematic relevance in Senega Spach (Polygalaceae)

Polygalaceae is a monophyletic family within Fabales comprising approximately 1,200 species distributed among 28 genera. The genus Senega Spach was recently recircumscribed after the segregation of Polygala L., resulting in a more natural delimitation of the group. This study aims to characterize pollen morphology in representatives of Senega and evaluate the systematic relevance of pollen characters for species recognition and infrageneric classification. Pollen grains of 36 species of Senega, representing 2 subgenera and 11 infrageneric sections, were analyzed using light microscopy (LM) and scanning electron microscopy (SEM). Pollen grains were prepared using the acetolysis method, and morphological, qualitative, semiquantitative, and quantitative characters were analyzed. Multivariate analyses, including Principal Coordinates Analysis (PCoA), PERMANOVA, and UPGMA clustering, were performed based on Gower distance to evaluate patterns of pollen morphological variation among species and infrageneric groups. Species of Senega exhibit monad, isopolar, predominantly medium-sized pollen grains, mainly varying from prolate-spheroidal to subprolate. Pollen grains are mostly zonocolporate, with aperture number ranging from 8 to 13 colpori. Endoapertures are mainly lalongate and may become endocingulate in several species. Exine ornamentation varies among psilate, scabrate, rugulate, and reticulate patterns, with scabrate ornamentation being the most frequent condition. A parasyncolporate condition was observed in S. atropurpurea, and granular sexine in the polar area was recorded in selected species. Multivariate analyses revealed significant differences between subgenera and among sections of subg. Senega, although PCoA and UPGMA indicated partial overlap and limited correspondence with the current infrageneric classification. The results demonstrate that pollen morphology provides valuable characters for species recognition in Senega, while also indicating that pollen data should be interpreted as complementary evidence in integrative taxonomic and phylogenetic studies of Polygalaceae.