Abstract
Nicotianagandarela Augsten & Stehmann (Solanaceae), sp. nov., a small ’tobacco’ known only from one locality at Serra do Gandarela, in the state of Minas Gerais, Brazil, is described and illustrated. It is morphologically characterized by its rosulate basal leaves, red corolla with a short tube not inflated at the apex, and the peculiar habitat, a shaded site under a rocky outcrop ledge along a forested stream. Phylogenetic analyses based on a combined dataset of nuclear (ITS) and plastid (ndhF, trnLF, and trnSG) DNA sequences revealed that the species belongs to the Nicotianasect.Alatae and is sister to the clade with the remaining species in the section. A key for the identification of Brazilian species of the section is given. The unusual habitat, the small population size, and the intense pressure of mining activities in the surroundings made the species assessed as Critically Endangered (CR), needing conservation efforts to avoid its extinction.
Highlights
Nicotiana L. is a Solanaceae genus known mostly because of tobacco (N. tabacum L.), a crop cultivated worldwide, but its diversity goes further
Due to the combined dataset produced higher-supported trees in both Maximum Likelihood (ML) and Bayesian inference (BI) methods than using nuclear and plastid regions independently, we described the results based on this supermatrix only
Phylogenetic trees generated showed that the samples collected in the Serra da Gandarela in Minas Gerais are genetically distinct from all known species of Nicotiana used in our analyses
Summary
Nicotiana L. is a Solanaceae genus known mostly because of tobacco (N. tabacum L.), a crop cultivated worldwide, but its diversity goes further. It is the fifth-largest genus in the family, with 82 species (Knapp 2020). The section comprises two cytogenetic groups: one displays chromosome number 2n = 20 and includes two species, N. longiflora Cav. and N. plumbaginifolia Viv., distributed from Argentina to the USA; the other presents chromosome number 2n = 18 and includes N. alata Link & Otto, N. bonariensis Lehm., N. forgetiana Hemsl., N. langsdorffii Weinm., N. mutabilis Stehmann & Semir and N. azambujae L. According to the plastid or nuclear markers used for the reconstruction, section diversification is proposed between 6.2 Ma and 7.7 Ma, respectively (Clarkson et al 2017)
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