Rupestrian Grassland Vegetation, Diversity, and Origin

Abstract

Rupestrian grasslands (campos rupestres) are tropical landscapes consisting of a mosaic of herbaceous and shrubby physiognomies on quartzite or ironstone that occur in highlands , usually above 900 m. These landscapes encompass a high diversity of habitats , under different environmental conditions, such as on rock outcrops dominated by desiccation-tolerant species, as well as grasslands and shrublands dominated by resprouter species. Therefore, water availability is one of the most significant selective pressures on rock outcrops, while fire is more important on grasslands and shrublands. Poaceae and Velloziaceae are the two dominant plant families in terms of cover area. There is predominance of hemicryptophytes, chamaephytes, and phanerophytes. Autochory is the main dispersal syndrome and contributes to high plant endemism. Floristic and vegetation structural patterns are affected by geology, geography, habitat, and disturbance. Rupestrian grasslands are Old Stable Landscapes and high specialization, phylogenetic conservatism, and low dispersal ability characterize most lineages in these landscapes. Rather than plant refuges during the warmer and moister Pleistocene interglacial periods, highlands have probably worked as refuges for fire-sensitive lineages since the expansion of fire-prone savannas (cerrados) in the late Tertiary. Most lineages from these mountain ranges then diversified during the Quaternary as rupestrian grasslands were finely fragmented by fire-prone landscapes. The fragmented and rich biodiversity in rupestrian grasslands is naturally vulnerable to anthropogenic disturbances. Therefore, protected areas even if small, scattered along the whole landscape, will help to protect them for a while. However, areas suitable for rupestrian grasslands will probably be greatly reduced in the next few decades as seasonality increases. This scenario calls for immediate ex situ conservation measures.