Morfologia polínica de representantes da tribo Microlicieae (Melastomataceae) e suas implicações taxonômicas

Abstract

The tribe Microlicieae has undergone several changes in its circumscription throughout its taxonomic history, having been analyzed and morphologically described over time. The study by Versiane et al. (2021) proposed the inclusion of the genera Chaetostoma, Lavoisiera, Stenodon, and Trembleya within Microlicia sensu lato. The objective of the present study is to perform a morphological analysis of pollen grains from the genera Chaetostoma, Lavoisiera, Stenodon and Trembleya in order to obtain a palynological perspective on the new taxonomic circumscription of Microlicia s.l. Botanical material was obtained from specimens catalogued in the Herbarium of the Federal University of Goiás (UFG), through the collection of anthers or viable floral buds for analysis, using forceps and a stereomicroscope. The pollen grains of the analyzed Microlicieae species occur as monads, are isopolar, and small in size. The aperture system consists of three pseudocolpi alternating with three colpori, and in M. selaginea (under light microscopy) the occurrence of syncolpate colpori may be observed. Regarding shape, pollen grains range from prolate-spheroidal to perprolate, with a DP/DE ratio between 1.1 and 2.9. The polar diameter ranges from approximately 15.3 to 22.3 μm, and the equatorial diameter from 7.5 to 17.3 μm. Sexine ornamentation is variable and may be densely rugulate, rugulate, slightly rugulate, psilate, or psilate–rugulate. The results indicate that pollen grains of the family Melastomataceae do not differ markedly in their morphology, mainly expressing the presence of pseudocolpi alternating with colpori as a distinctive feature in the palynotaxonomy of the family. It is concluded that palynology represents an important tool in taxonomic studies, contributing to the reconstruction of evolutionary histories and to the proposal of new taxonomic circumscriptions.