Abstract
<title>Abstract</title> <p> The genera of the tribe Beslerieae (Gesneriaceae) exhibit remarkable diversity in growth forms, flowers, and fruits, making the identification of morphological synapomorphies challenging. Among them, <italic>Anetanthus</italic> Hiern ex Benth. & Hook.f., <italic>Besleria</italic> Plum ex L., and <italic>Tylopsacas</italic> Leeuwenb. remain poorly known, with unclear morphological relationships to their closest relatives. Here, we investigated whether pollen morphology can improve the characterization of Beslerieae taxa. We analyzed pollen from 20 Brazilian species of <italic>Anetanthus</italic> , <italic>Besleria</italic> , and <italic>Tylopsacas</italic> distributed in the Amazon and Atlantic Forest biomes. Pollen grains were acetolyzed, measured, and examined using light, scanning, and transmission electron microscopy. Qualitative characters were described, and quantitative data were analyzed using descriptive and multivariate statistics. The pollen grains are monads, isopolar, small, circular to subtriangular amb, and range from oblate to prolate. The apertures are 3-colpate, 3-(4)-colpate, or 3-colporate; long, short, or very short ectoaperture and narrow to wide; with or without margo, rounded or tapered at the polar ends; endoapertures circular or lolongate. The exine is microreticulate, microreticulate-rugulate, rugulate, or rugulate-perforate, with the sexine consistently thicker than the nexine. Variation in aperture type and exine ornamentation distinguished most species and confirmed the eurypalynous nature of Beslerieae, although these characters did not differentiate the analyzed genera. Our findings demonstrate that pollen morphology is more informative for species delimitation than for generic circumscription, reinforcing the systematic value of palynological characters for closely related and sympatric species. In contrast, no pollen morphological patterns were associated with the geographic distribution of the species. </p>