Modelagem ecológica como ferramenta para a identificação de áreas prioritárias à conservação de Philodryas agassizii (Squamata, Dipsadidae) no Rio Grande do Sul

Abstract

The biodiversity is in global decline and the major threats are associated to anthropogenic activities, mainly related to environmental changes linked to land use. Specialist species in habitats are the most vulnerable species. The distribution and environmental requirements of the species are fundamental to establish conservation initiatives, however many of these information are still unknown. The predictive distribution models are useful for filling gaps regarding geographic distribution of species and environmental requirements. Philodryas agassizii is a snake species specialist in habitat, highly sensitive to environmental changes and possibly insufficient sampling. This species occurs in areas of grasslands of the Brazilian Cerrado and in biome Pampa of the Brazil, Uruguay and Argentina. The areas of the field, in turn, are among the most threatened in the world and need conservation efforts. For that reason, this study aimed to forecast the potential geographical distribution of the Philodryas agassizii in order to identify the most favorable areas to its occurrence and conservation status of the species. Through these data, proposed initiatives to preserve the species in the Rio Grande do Sul state. To achieve such objective, we inventoried the points of occurrence known for the species available in collections and bibliographies and we apply the method of modeling potential distribution, using bioclimatic and altitude matrices, with a resolution of 30 arc second, and the maximum entropy algorithm. From the resulting model, we consider areas with environmental suitability greater than 70% as priority for conservation of P. agassizi. From that cutoff point, we performed overlays with maps of soil use, conservation areas and Priority Areas for Conservation of Brazilian Biodiversity (PROBIO). The potential geographical distribution of the P. agassizii followed the so-called "savana corridor", with areas of higher suitability in northwestern Uruguay, center-west of the Rio Grande do Sul state (Brazil), southern of Minas Gerais state (Brazil) and Brasilia city (Brazil). The main threats to the species in Rio Grande do Sul are arising the replacement of natural cover by planting annual crops and forestry. Priority areas for conservation of P. agassizii are poor of conservation units, and it urges the establishment of new protected areas, in agreement with the priority areas for biodiversity conservation, provided for the report of PROBIO. Based on the need of disturbance regime to maintain the southern grasslands, we believe that extensive livestock farming is a practice compatible with biodiversity conservation and we discard the controlled use of fire, due to the negative effects on the fauna, mainly on the criptozoicas species, such as P. agassizii.