Outstanding plant endemism levels strongly support the recognition of campo rupestre provinces in mountaintops of eastern South America

Aim The Brazilian campo rupestre is a vegetation associated to ancient mountaintops in eastern South America, spread mainly over disjunct areas of the Espinhaco Range and the Chapada dos Veadeiros. These areas hold outstanding levels of plant diversity and endemism, but despite their uniqueness they have been neglected in recent bioregionalizations for the Neotropical region. Given their particular levels of species richness and endemism, we here test the recognition of these as distinct bioregions within the Chacoan dominion. Location Mountaintops of eastern South America. Methods We listed 1,748 angiosperm species endemic to the campo rupestre of the Espinhaco Range and Chapada dos Veadeiros regions, based on the data gathered from the Brazilian Flora 2020 Project. We extracted all occurrence information available from GBIF (the Global Biodiversity Information Facility) for such list and also for a polygon gathering all the study area, including information from adjacent vegetations. Data went through standard cleaning procedures and a network clustering analysis was performed to delimitate the boundaries of the new bioregions. Results Our data strongly support the recognition of two distinct bioregions along the Espinhaco Range, but none in the Chapada dos Veadeiros. Given their high levels of endemism and singularity within the Chacoan dominion, we formalize two provinces associated to campo rupestre in the Espinhaco Range, naming them as ``Chapada Diamantina{''} and ``Southern Espinhaco{''} provinces. Within the latter province, three districts are also recognized, based on this and previous studies: ``Diamantina Plateau{''}, ``Grao-Mogol{''} and ``Iron Quadrangle{''} districts. Main conclusions The formalization of new and previously described bioregions highlights the campo rupestre as a vegetation harbouring outstanding levels of species richness and endemism in South America, contributing to a better understanding of biogeographical patterns in the Neotropics. Also, as we follow the International Code of Area Nomenclature as a device to standardize recognition of bioregions, this shall facilitate further biogeographical and conservation studies in these areas. Further assessments with new and revisited data are needed to enable minor scale bioregionalization within the Chacoan dominion. (AU)