Discovering Brazilian cliff vascular flora on basaltic rock outcrops in Serra do Rio do Rastro, Santa Catarina

Resumen

Abstract Basaltic cliffs in southern Brazil support specialized plant communities shaped by extreme environmental conditions, high habitat heterogeneity, and spatial isolation. Despite their ecological importance, these environments remain poorly documented and are increasingly threatened by anthropogenic pressures. Here, we present the first comprehensive floristic inventory of the rupicolous vascular flora of the Serra do Rio do Rastro (SRR), Santa Catarina. A total of 317 species (204 genera and 71 families) were recorded, exceeding the floristic richness previously reported for other areas of the Aparados da Serra Geral region. Asteraceae (56 spp.) and Poaceae (31 spp.) were the most species-rich families, and herbaceous forms predominated (197 spp.). Twenty-one species are endemic to Santa Catarina, including Neocabreria catharinensis, which is documented here after a 64-year gap without herbarium records, and 20 species are officially recognized as threatened with extinction. Remarkably, 69.1% of species had no prior records in digital herbarium databases for the studied area, underscoring the value of targeted fieldwork for documenting biodiversity in understudied habitats. Our results identify the SRR as a biodiversity refuge of both regional and national significance, while exposing critical conservation gaps, particularly the absence of updated threat assessments for narrowly distributed taxa. We recommend the urgent integration of cliff ecosystems in conservation planning, supported by systematic monitoring, invasive species control, and regular updating of threatened species lists.