Isolated monoliths of granitic and/or gneissic rock rising abruptly from the surrounding landscape are known as inselbergs. Dome-shaped inselbergs are common throughout the Atlantic Forest in south-eastern Brazil, a region known as Sugarloaf Land (SLL). This study aimed to create the first checklist of vascular plant species occurring on lowland inselbergs in SLL, with a focus on vegetation islands. We used information from online databases, our own field sampling and data from previously-published studies. We found 548 vascular plant species (505 angiosperms; 43 ferns and lycophytes) belonging to 69 families and 212 genera. Of all identified species, 536 are native and 12 are naturalised.
We updated the information currently available in Flora do Brasil 2020, as 59% of the angiosperms and 63% of the ferns and lycophytes on our checklist were not previously characterised as occurring on rock outcrops. As a first step towards generating a Virtual Herbarium of lowland inselberg vascular plants, we added barcode vouchers with images available online for 75% of the total number of vascular species. In the official lists of endangered species, 115 angiosperms and five ferns and lycophytes are mentioned. However, the conservation status of many species have not yet been evaluated (77% angiosperms; 88% ferns and lycophytes), thus this list is an important step towards their conservation. The information provided herein is essential for management programmes related to rock outcrops in Brazil as they are facing serious threats to conservation.
A substantial fraction of stored freshwater available on neotropical inselbergs is impounded within the rosettes of bromeliads. Their high water retention capacity can potentially have an outcome on the inselberg community as well as on the surrounding environment. However, there are no studies measuring and extrapolating the water retention capacity of bromeliads from single observations to larger spatial scales. Using simple drone-based imagery, we were able to calculate and upscale the water tank capacity of Alcantarea distractila, a bromeliad genus which is widespread on inselbergs in Southeastern Brazil. Our results provide a firstarge scale quantification of the estimated availability of water tank reservoir of inselbergs, which highlights the potential provisional ecosystem service delivered by bromeliad species.
Granite and/or gneiss inselbergs are excellent examples of geomorphologically stable island habitats, considered as old, climatically buffered, infertile landscapes (OCBILs). However, unlike oceanic islands, their underlying drivers of diversity patterns remain to be investigated. Here, we studied 24 inselbergs in south-eastern Brazil, aiming to understand the role of landscape variables and environmental conditions in the assembly of the characteristic extremophilic mat vegetation communities. We found that beta diversity was largely explained by climatic variables, whereas species richness did not vary among inselbergs. Classic determinants of the diversity of island communities do not generally seem to apply to these plant assemblages. Overall, these communities change along a coast-to-inland gradient that captures increased seasonality with a replacement of more hydrophilic taxa by more drought-tolerant taxa. Changes in species composition in space involved strong species replacement, with several widespread genera locally represented on distinct inselbergs by different narrowly distributed species. Despite the deterministic sorting of taxa based on climatic conditions, a substantial fraction of the beta diversity remained unexplained. This underlines the importance of historical processes, which are easier to notice in stable OCBIL regions, such as range expansion, local extinction, dispersal constraints and allopatric speciation.
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