Two new rupicolous species of Tibouchina (Melastomataceae) from the Parque Nacional da Chapada dos Guimarães, Mato Grosso, Brazil

Two new species of Melastomataceae, Tibouchina caducifolia and T. dispar , are described from the Parque Nacional da Chapada dos Guimarães (PNCG), Mato Grosso, Brazil. Both show characters typical of the Southern clade of Tibouchina , including stamens with villose filaments and villose pedoconnective appendages, suggesting that they likely belong to this clade, although they have not yet been included in a phylogenetic analysis. Morphological descriptions, high‐resolution photographs, scanning electron micrographs, photographic plates, distribution maps, and preliminary conservation assessments are provided. Comparisons with morphologically similar taxa are included, highlighting diagnostic traits that facilitate identification. Additionally, we present a detailed account on the globoid or fusiform stem galls that are frequently observed on the basal portions of the branches in T. caducifolia , and represent a conspicuous feature that may assist in the recognition of the species. Both species are endemic to the PNCG, occurring in rupestrian savannas (‘cerrado rupestre') and associated rupestrian grasslands (‘campos rupestres'), with restricted ranges and specialized rupestrian habitats. Due to the limited number of georeferenced records and insufficient data on population size, trends, and response to fire, both species are preliminarily assessed as ‘Data Deficient' (DD) according to IUCN criteria. These findings reinforce sandstone outcrops in the Cerrado of central Brazil as centers of plant diversity and endemism, underscoring the importance of continued taxonomic research in underexplored areas.