Distributed along the east coast of South America, the Atlantic Forest Domain houses a widespread Inselberg region, which is inserted in the southeastern rim of the Brazilian Shield along the Serra do Mar and Serra da Mantiqueira. Among the most conspicuous elements of these inselbergs is Velloziaceae, which comprises heliophyte plants adapted to xeric conditions and to specific substrates. Five genera, Acanthochlamys, Barbacenia, Barbaceniopsis, Vellozia and Xerophyta, and approx. 250 species, distributed mostly in an amphiatlantic pattern, are currently recognized within the family. Barbacenia s.l. (including Aylthonia, Barbacenia, Burlemarxia, and Pleurostima), encompasses about 100 species, exclusively Neotropical, that occur predominantly in the Espinhaço Range and Central Plateau of Brazil. The genus is supported for double sheath in leaf vascular bundles and presence of corona. In recent phylogenetic reconstructions, Barbacenia was recovered as two major clades characterized by the environmental and geographical occurrence, the Atlantic Forest Inselbergs clade (AFI clade) and the Campos Rupestres (CR) clade. Whereas the available analyses did not include all Barbacenia species that occur in AFI, more evidence and a wider sampling are necessary to infer its evolutionary and biogeographic history. Therefore, the aims of the present study were: (i) to reconstruct the phylogenetic relationships of Barbacenia using a wider taxon sampling for Barbacenia AFI group; (ii) to estimate divergence times, reconstruct the ancestral areas and compare the morphological diversity of Barbacenia lineages; and (iii) to conduct a taxonomic treatment of Barbacenia AFI group. The phylogenetic analysis presented in this study recovered the same lineages mentioned above (Barbacenia AFI and CR). Morphological stasis was found in Barbacenia AFI clade, and possibly environmental heterogeneity combined with different paleovegetational dynamics during the Plio-Pleistocene influenced the morphological disparity between AFI and CR clades. In addition, niche conservatism in interplay with paleovegetation dynamics during the global Miocene cooling and Pleistocene climatic oscillations likely played an important role in the diversification and distribution of modern Barbacenia lineages. In taxonomic revision of Barbacenia AFI clade, we recognized twelve taxa and described two new species, Barbacenia amphirupia and B. maritime. This monograph included a complete list of synonyms, anatomical and morphological descriptions, identification key, information on the conservation, geographic distribution, habitat, phenology, and taxonomic comments of all species. This Master's thesis highlights the importance of phylogenetic, biogeographic and taxonomic studies in the discovery of hidden diversity, highlighting large sample gaps on the biodiversity of the Brazilian Atlantic Forest Inselbergs and Campos Rupestres, environments with high species richness and endemisms. These studies are particularly important to provide a knowledge base for the conservation and maintenance of biodiversity

Distributed along the east coast of South America, the Atlantic Forest Domain houses a widespread Inselberg region, which is inserted in the southeastern rim of the Brazilian Shield along the Serra do Mar and Serra da Mantiqueira. Among the most conspicuous elements of these inselbergs is Velloziaceae, which comprises heliophyte plants adapted to xeric conditions and to specific substrates. Five genera, Acanthochlamys, Barbacenia, Barbaceniopsis, Vellozia and Xerophyta, and approx. 250 species, distributed mostly in an amphiatlantic pattern, are currently recognized within the family. Barbacenia s.l. (including Aylthonia, Barbacenia, Burlemarxia, and Pleurostima), encompasses about 100 species, exclusively Neotropical, that occur predominantly in the Espinhaço Range and Central Plateau of Brazil. The genus is supported for double sheath in leaf vascular bundles and presence of corona. In recent phylogenetic reconstructions, Barbacenia was recovered as two major clades characterized by the environmental and geographical occurrence, the Atlantic Forest Inselbergs clade (AFI clade) and the Campos Rupestres (CR) clade. Whereas the available analyses did not include all Barbacenia species that occur in AFI, more evidence and a wider sampling are necessary to infer its evolutionary and biogeographic history. Therefore, the aims of the present study were: (i) to reconstruct the phylogenetic relationships of Barbacenia using a wider taxon sampling for Barbacenia AFI group; (ii) to estimate divergence times, reconstruct the ancestral areas and compare the morphological diversity of Barbacenia lineages; and (iii) to conduct a taxonomic treatment of Barbacenia AFI group. The phylogenetic analysis presented in this study recovered the same lineages mentioned above (Barbacenia AFI and CR). Morphological stasis was found in Barbacenia AFI clade, and possibly environmental heterogeneity combined with different paleovegetational dynamics during the Plio-Pleistocene influenced the morphological disparity between AFI and CR clades. In addition, niche conservatism in interplay with paleovegetation dynamics during the global Miocene cooling and Pleistocene climatic oscillations likely played an important role in the diversification and distribution of modern Barbacenia lineages. In taxonomic revision of Barbacenia AFI clade, we recognized twelve taxa and described two new species, Barbacenia amphirupia and B. maritime. This monograph included a complete list of synonyms, anatomical and morphological descriptions, identification key, information on the conservation, geographic distribution, habitat, phenology, and taxonomic comments of all species. This Master's thesis highlights the importance of phylogenetic, biogeographic and taxonomic studies in the discovery of hidden diversity, highlighting large sample gaps on the biodiversity of the Brazilian Atlantic Forest Inselbergs and Campos Rupestres, environments with high species richness and endemisms. These studies are particularly important to provide a knowledge base for the conservation and maintenance of biodiversity