Inselbergs from Brazilian Atlantic Forest: high biodiversity refuges of vascular epiphytes from Espírito Santo

Inselbergs are old outcrops, characterized by large expanses of open rocks and by distinct environmental filters. Many studies have been carried out on inselberg’s flora in the last decades. In contrast, vascular epiphytes received little attention compared to lithophytic groups. We aimed to investigate the role of inselbergs of the Espírito Santo as a refuge for epiphytic flora in Atlantic Forest in southeastern Brazil. In addition, we provide and discuss data on taxonomic representativeness, endemism, and threat status of the epiphyte species We used a combination of two online national databases of flora, species data collected by the authors and previously published studies. We record 266 species of vascular epiphytes (220 angiosperms; 43 ferns and three lycophytes), belonging to 89 genera and 18 families. Of these, three species (two orchids and one bromeliad) are restricted on Vellozia stems and represent an exceptional case of epiphyte-phorophyte specificity. For these species, we propose the term “specialist rock epiphytes”. The richest families were Orchidaceae, followed by Bromeliaceae and Polypodiaceae, while Vriesea, Acianthera, Epidendrum, Maxillaria, Peperomia, and Tillandsia represent the richest genera. The Espírito Santo inselbergs host endangered, endemic species, and a high number of species (77.0%) that are typical of the surrounding forest core of the Atlantic Forest, reinforcing the relevance of these xeric ecosystems as refuges for vascular epiphytes and that sometimes constitute the only chances of survival for native species epiphytes.