Pollen morphology of the monotypic genera Antherothamnus and Manuleopsis from southern Africa and the Madagascan Barthlottia (Scrophulariaceae): Taxonomic and phylogenetic implications

• Pollen morphology of genera Antherothamnus, Barthlottia, Manuleopsis, and species from six related genera from tribes Limoselleae and Scrophularieae, was studied using LM and SEM. • The pollen traits of seven species are described and illustrated for the first time. • UPGMA dendrograms based on palynomorphological data are presented. • Data obtained do not support a close relationship between Barthlottia and Manuleopsis. • Antherothamnus and Manuleopsis are well diagnosed on the pollen characters; pollen grains of Barthlottia are more similar to those of Scrophularia and Verbascum. Pollen morphology of Antherothamnus N.E.Br., Barthlottia Eb.Fisch., and Manuleopsis Thell. (Scrophulariaceae), three monotypic genera from southern Africa and Madagascar, was examined. Pollen grains of selected species of the closely related genera Chaenostoma Benth., Limosella L., Lyperia Benth., Scrophularia Tourn. ex L., Verbascum L., and Zaluzianskya F.W.Schmidt were also investigated (in total 21 taxa). The characters and photomicrographs of pollen grains of seven species ( Antherothamnus pearsonii, Barthlottia madagascariensis, Chaenostoma caeruleum, Ch. rotundifolium, Manuleopsis dinteri, Limosella aquatica , and L. grandiflora ) are presented for the first time. The research aimed to provide data on pollen characters and to evaluate the taxonomic significance of these data. Pollen morphology was studied using both light microscopy and scanning electron microscopy. Pollen grains are 3-colporate or rarely 4-colporate; small and medium-sized: polar axis ( P ) = 13.30–39.90 µm, equatorial diameter ( E ) = 11.97–34.58 µm; and suboblate to prolate ( P / E = 0.78–1.63) in shape. The outline in polar view (amb) is slightly 3-lobate, 3-lobate or rarely 4-lobate, triangular or circular. Colpi are long, wide or narrow, with acute or rounded, distinct or indistinct ends. Endoapertures are lolongate or lalongate, elliptic or circular. Exine sculpture is microreticulate or reticulate. UPGMA dendrograms based on palynomorphological data are presented. The diagnostic features of studied species included the shape and size of pollen grains, amb, length and width of the colpi and endoapertures, apocolpium and mesocolpium diameters, margo and exine thickness, and details of exine sculpture (lumina size and muri thickness) and aperture membranes. The data obtained do not support a close relationship between Barthlottia and Manuleopsis as they clearly differ in palynomorphological characters. At generic level, Antherothamnus and Manuleopsis are well diagnosed on the pollen characters. The pollen grains of Barthlottia are more similar to those of Scrophularia and Verbascum.