Rarity patterns and the conservation status of tree species in South American savannas

Abstract

The interest in quantifying rare species has been increasing, but less attention has been paid to analysing their conservation status. Here, we used the Rabinowitz method based on geographical range, habitat specificity and population size to classify 2,203 tree species of South American savannas (SAS). We considered species with narrow (stenochoric) or wide (eurychoric) geographic range respectively occurring in up to 10% or over of the latitudinal belts in the SAS, specialist (stenoecious) or generalist (euryoecious) species occurring in one or more ecoregions, respectively, and locally scarce or abundant populations of species with low or high numbers of records within a grid cell of 1° latitude by 1° longitude, respectively. We then quantified species which only occur inside protected areas (PAs), in and outside PAs, or only outside PAs. Of the 2,203 species, 49.25% were rare, 40.35% stenochoric, 14.12% stenoecious and 56.15% had a scarce population. The Cerrado (433) followed by Caatinga (259), Campos Rupestres montane savanna (256), Bahia interior forests (189) and Guiana savanna (154) had the highest number of rare species. Only 6.44% species only occurred inside PAs, 83.79% in and outside PAs and 9.75% only outside PAs. Unprotected species are mostly geographically restricted with ecoregion specialists, and have small population sizes. The number of protected species are is positively correlated with the number of records within them. The establishment of PAs should focus on both core and disjunct savannas to encompass all ecoregions in order to ensure the conservation of species and the range of evolutionary processes in SAS.