Influência do uso do solo na diversidade de anfíbios anuros nos Campos Sulinos do Rio Grande do Sul, Brasil

Abstract

The degradation of natural ecosystems due to land use changes is becoming accentuated, altering the structure, composition or ecosystem processes, as well as negatively affecting biodiversity. Among vertebrates, amphibians present singularities that make them sensitive to environmental changes and consequently appropriate models for assessing habitat integrity. Herein, we want to understand the patterns of diversity in a scenario of degradation and extensive replacement of native grasslands by crops in southernmost Brazil, measuring the ability of amphibians to respond to land use. Thus, we tested possible changes in species richness, taxonomic composition, and structure of anuran communities. The study was carried out along the Campos Sulinos of the state of Rio Grande do Sul, by sampling pond-dwelling anurans along the grassland ecosystems of the Mata Atlântica and Pampa biomes. We sampled a total of 238 ponds were sampled only once, 153 in extensive livestock areas on native grassland and 85 ponds in agricultural areas, by using ‘the survey at breeding sites’ method. We recorded 36 anuran species distributed in seven families, with higher species richness in the livestock over native grassland than in the agricultural areas. Besides, we found a significant nestedness pattern associated with agricultural area, indicating a non-random process of community simplification by species loss. In addition, we recovered seven anuran species as indicators of land uses: five species as indicators of native grasslands with livestock, and two as indicator of agricultural areas. Generalist species were persistent and dominant in agricultural areas while habitat specialists disappeared. We recorded by multivariate analysis that land use was a significant factor explaining the community structure segregation among land uses, regardless the natural variation registered at local and regional scales. In this context, we emphasize the importance of natural grassland for the conservation of anurofauna in the nonforest landscape of subtropical region, since maintenance of diverse communities is dramatically simplified by land use changes. Moreover, we emphasized that the traditional extensive livestock farming on native grasslands can be considered a buffer for freshwater environments due to few changes in the native matrix. Therefore, this land use needs strategical incentives that help the conservation of the biodiversity in the grasslands, such as parallel multiinstitutional actions with the productive sector.