Modeling the spatial distribution of the endemic and threatened palm shrub Syagrus glaucescens (Arecaceae)

Abstract

This study tests the use of accessible geoprocessing techniques to identify and describe the distribution of Syagrus glaucescens, a threatened palm shrub endemic to rupestrian fields (high-altitude grasslands) of the southern Espinhaço Range, in Minas Gerais, Brazil. A hundred and ninety five occurrence points and 24 absence points of S. glaucescens were recorded on a GPS device during field trips. Free databases of eight abiotic variables for the surveyed area were also used. Ninety-eight of the occurrence points were used to generate a spectral signature in ArcView to identify variables best characterizing S. glaucescens’ distribution area and produce a probability map. The species’ distribution was strongly associated to rocky outcrops whose geological composition is Quartzite Filite and Conglomerates, above 1.000 m of altitude, with declivities of 5-30%. When the accuracy of the probability map was tested, 87.63% of the 97 occurrence points used fitted areas of very high occurrence probability on the map, while 100% of the 24 non-occurrence points matched areas of null probability; therefore confirming the high accuracy of the model in predicting the occurrence of S. glaucescens. Although the altitudinal grasslands of Espinhaço are areas of great biodiversity and high degree of plant species endemism, they remain poorly studied. Thus, this model can be a helpful tool in designing management and conservation strategies not only for S. glaucescens but also for other species associated to rocky outcrops of such environment.

Key words: rupestrian fields, rocky outcrops, habitat modeling.