A influência da área de poças e seus descritores ambientais sobre a estrutura de comunidades de anfíbios anuros em áreas campestres do Rio Grande do Sul, Brasil

Abstract

Size and habitat heterogeneity are among the main factors that determine the species richness, structure and composition of plants and animal communities. However, the distinction between them is essential to discriminate which of those descriptors have influence on the local patterns registered. In this work, we tested in separate the effect of the area and the environmental heterogeneity of ponds on communities of amphibians in natural grasslands of Rio Grande do Sul, Brazil. Sampling was carried out from September to November 2014, Spring, time of greater activity anurofauna in southern Brazil. The sample consisted of a daytime part, in which tadpoles were collected, and a night part when we employed active survey at breeding sites. In addition, local environmental characteristics were collected, such as physical-chemical water quality and structure of emergent vegetation and the edge of the ponds, as well as the presence of fish. We also collected environmental features of the landscape such as type of surrounding matrix and distance the forest. We identified 35 species of frogs belonging to five families: Bufonidae, Hylidae, Leptodactylidae, Microhylidae and Odontophrinidae. The ponds area analysis on the species richness we observed absence of influence of this factor, therefore, with increasing area of ponds wealth is not likely to increase significantly. On the other hand, local environmental factors such as pH, percentage of plant extract emerging number of plant extracts and water were significantly associated with increased richness of frogs. Indeed, the characteristics of the vegetation in the pools may be related to species richness as the increase in the percentage of emergent vegetation provides greater amounts of microhabitats, and thus more resources for egg laying and protection of the larvae. The presence of fish proved to be a non-limiting factor for the species richness of frogs, since the analysis where we test the effect of local environmental factors and the landscape on the composition of species of frogs, was inconclusive due to low explanation of environmental factors local retained in the model, which retained only 17% of the variance of the data on 1st axis and 7% on 2nd axis. The absence of significant influence on the size of ponds on the wealth of frogs shows how important are these water bodies to the conservation of frogs communities, even if they are small, smaller than those protected by Brazilian law.