Composição e uso do habitat da herpetofauna em mosaicos naturais (campo-mata ciliar) em uma área de pampa do Rio Grande do Sul

Abstract

The Pampa biome consists of grasslands and forest vegetation types, whose dynamics and importance to the conservation of herpetofauna are poorly studied. The aim of this study was: i) to characterize the herpetofauna associated with forest and grasslands in the central region of Rio Grande do Sul throughout the richness, abundance and constancy of occurrence of the species, ii) determine whether the field and riparian forest differ in structure herpetofauna, and iii) test whether patterns of species richness and abundance can be explained by variables representing environmental heterogeneity. Sampling was conducted using pitfall traps, totaling 40 buckets of 30 liters, distributed in five sets by radial physiognomy (mixed grasslands of Andropogoneae and composed, as well as riparian vegetation). The spacing between the buckets of each set was five meters, the distance between the sets was at least 500m and samples were taken for four days/month from January 2011 to November 2012. For statistical analysis we used ANOSIM, Principal Component Analysis (PCA) and Multiple Linear Regression. We recorded 32 species (17 of amphibians and 15 of reptiles) distributed in ten families, five of amphibians and five families of reptiles: Bufonidae (2), Odontophrynidae (1), Hylidae (3), Leptodactylidae (10), Microhylidae (1), Amphisbaenidae (1), Colubridae (10) Gymnophthalmidae (1) Scincidae (1) and Teiidae (2). At least one recorded species of reptile, Calamodontophis paucidens, is considered threatened (vulnerable) internationally and regionally. In fact, the ANOSIM showed that grasslands and riparian forest differed in structure herpetological community (R = 0.73, p = 0.008). According to Principal Component Analysis (PCA) performed in the warm season, the first two axes explained 76.31% of the data variation of environmental heterogeneity (the first and second accumulated 52.27% 24.04% respectively). In the cold season, the first two axes explained 80.01% of the variation of environmental data, and (the first axis accounted for 66.18% and the second 13.83%, respectively). Regression analysis indicated that for amphibians any of the descriptors was able to explain the variation wealth and abundance in any of the seasons (hot and cold). For reptiles analysis indicated that abundance and richness in the warm season were positively related to the first axis of PCA. For the cold season, abundance and richness for reptiles species was negatively related to the first axis of the PCA. The analysis of similarities indicating that these phytophysiognomies are essential for the conservation of the local herpetofauna. The results obtained in this study represent an important contribution on the distribution of amphibians and reptiles in Pampa gaucho and may stimulate future studies on habitat requirements of species and comparisons with different phytophysiognomies in the region.