Os tabacos brasileiros (Nicotiana sect. Alatae, Solanaceae) revisitados à luz de estudos filogenéticos moleculares

Abstract

Nicotiana L. is a genus of Solanaceae of global relevance that has almost 100 species distributed among the Americas, Africa (one species), Australia and oceanic islands, with origin of diversification in South America, more especially related to the Andes. The genus is divided into 13 sections, and only one of them, N. sect. Alatae Goodsp., has diversified in the east of the South American continent, in the south and southeast of Brazil. This section, composed of ten species, is revisited in this study carried out in the light of integrative taxonomy, using primarily molecular phylogenetic studies and ecological niche modeling. The first chapter deals with the description of N. gandarela Augsten & Stehmann, a recently discovered and known species from a single population occurring in Serra do Gandarela in Minas Gerais, inhabiting shaded environments next to rock outcrops inside the forest. We performed, in addition to the description, the molecular phylogeny including several representatives of N. sect. Alatae and at least one representative from each of the other sections to verify the phylogenetic position of the species in the genus. Molecular data were obtained from Sanger sequencing, from nuclear (ITS) and chloroplast DNA regions (ndhf gene and trnL-trnF, trnS-trnG spacers). The results showed that it is the sister group of the other species in the section and that it is critically endangered. In the second chapter we investigated N. forgetiana l.s. species described in 1904, and whose name is used for all species of pink-flowered Nicotiana occurring in Serra Geral, in the states of Rio Grande do Sul and Santa Catarina. Previous ecology works suggested that the populations of these plants that occurred in the Aparados da Serra canyons actually constituted a different species from the one that occurs in the interior of the state of Rio Grande do Sul, in the ecotonal region between the mixed forest and the grasslands. from the top of the mountain. In this study, we used the chloroplast intergenic regions (trnS-trnG, rps12-rpl20 and rpl32-trnL) as well as 11 ecological niche modeling for the present and the past. Our findings indicated the existence of two monophyletic groups with robust support divided according to their morphological classification, where individuals in each group do not share haplotypes and there is no ecological niche overlap between groups. In agreement with previous morphometric studies, we confirmed that populations located on the edges of the plateaus of Santa Catarina and northeastern Rio Grande do Sul represent a distinct species. The two studies carried out provide evidence that the southern and southeastern regions of Brazil were the scene of important N. sect Alatae diversification processes and highlight that the group is an excellent model for evolutionary studies.