Distribuição espaço-temporal de anfíbios anuros em uma localidade da Serra do Sudeste, Pampa Gaúcho

Abstract

Brazil has the greatest diversity of amphibians in the world, however, studies of these animals are still scarce, mainly in the Pampa biome. This study aimed to: i) determine the richness and the composition of the assemblage of frogs at a site in the Southeast Mountain, in Pampa gaucho, ii) determine the similarity between the species in the habitat use patterns, iii) determine vocalization season of males and tadpoles occurence and, iv) test which abiotic variables have the greatest influence on the temporal patterns of richness and abundance of this assembledge. The study was conducted from August 2012 to July 2013 in Sao Sepe city, Rio Grande do Sul. We sampled monthly nine water bodies (i.e. five permanent ponds, a temporary pond, a permanent swamp, an ephemeral stream and a permanent river). The number of adults was estimated based on breeding activity of males, while the tadpoles were collected by netting all the edge of the water bodies. We recorded 25 species of amphibians belonging to six families: Alsodidae (1), Bufonidae (3), Hylidae (8), Leptodactylidae (11), Microhylidae (1) and Odontophrynidae (1) however only 18 vocalized on sampled water bodies. The most abundant species in adult phase was Dendropsophus minutus, followed by Scinax granulatus and Physalaemus gracilis meanwhile the most constant larvae was Dendropsophus minutus. We recorded five reproductive modes, being the reproductive mode 1 more abundant, followed by mode 11, a common pattern reported to open areas . Temporal overlap created four groups. Hypsiboas pulchellus and Physalaemushenselii had high temporal segregation compared to other species, as males of these species vocalized mainly in the colder months of the year, while males Elachistocleis bicolor, Physalaemus cuvieri and Scinax fuscovarius typically vocalized in the warmer months. Tadpoles of Dendropsophus minutus were more constant, being found throughout the sampling period. Species richness was positively correlated with air temperature, while the abundance was best described by air temperature and moon phase. The Akaike selection criterion had the strongest model to predict the temporal variation in species richness the temperature of the air and to predict the variation in the abundance of males in breeding activity, the model that included the air temperature and the moon phase. The spatial overlap created two groups. Dendropsophus minutus and Scinax granulatus used the greatest number of water bodies while Melanophryniscus pachyrhyunus and Pseudopaludicola falcipes used the ephemeral stream and permanent river, respectively. Understanding how the assembledges of frogs respond to environmental stimulus is ve ry important to create efficient conservation plans, since the Pampa biome is suffering great defacement by agriculture and deflorestation. Despite the temporal and spatial overlap are high, there was complementarity between the groups of species, where species with high temporal overlap had low spatial overlap and vice versa.