Palinologia de espécies brasileiras de Stachytarpheta Vahl (Verbenaceae)

Abstract

Stachytarpheta Vahl is the second largest genus of the Verbenaceae family, comprising over a hundred species mainly distributed in the Neotropical region. Brazil concentrates the most richness for this genus, with around 80 species, many of them endemic and of rare occurrence. The genus underwent several changes in infrageneric classification, with a lack of consensus among different authors. Therefore, the present study aims to characterize the pollinic morphology of 33 representative species of the Stachytarpheta genus, belonging to the Stachytarpheta sect. Stachytarpheta and Stachytarpheta sect. Melasanthus sections, and to verify if the palynological data corroborates the circumscription of these species. For the palynological characterization, we used specimens stored in the Herbário Leopoldo Krieger at the Federal University of Juiz de Fora and one specimen grown in the Experimental Plant Station of the Biological Sciences Institute of the Federal University of Juiz de Fora. The palynological analyses were carried out with the aid of an optical microscope, before and after the acetolysis chemical treatment, and with a scanning electron microscope. Morphometric data were obtained from optical microscopy, with the aid of a micrometer eyepiece, and then subjected to statistical treatment. The results obtained allowed us to confirm that verrucate ornamentation, colpus aperture, and the presence of margin and membrane are common for the genus. Palynological characters linked to the margin and membrane are especially important for the circumscription of the studied species, and different morphological types were established, grouping species according to the shape of the pollen grains. For the Stachytarpheta sect. Stachytarpheta section, we established three morphological types based on the shapes seen in pollen grains. In the Stachytarpheta sect. Melasanthus section, the pollen grains had four different shapes. We highlight that, for the Stachytarpheta longispicata complex species, we found only two shapes.