Composição e estrutura de comunidade de anfíbios anuros em uma área de pampa no município de São Gabriel, RS

Abstract

The Pampa Biome is unique to the southern portion of South America. In Brasil, it is present only in Rio Grande do Sul State, presents poorly sampled regions and is considered a very threatened biome. Although it is considered a Biome rich in biodiversity, it has one of the lowest percentage of protected area. Depending on the few studies conducted in the region, knowledge about frogs in this biome is still scarce and fragmentary. This study aimed to determine the composition and community structure of frogs in an area of Pampa, through parameters such as diversity, richness, habitat use and temporal occurrence of species in an open area of Pampa Biome. The study was conducted between January 2009 and February 2010 in the State Foundation for Agricultural Research in São Gabriel, RS. The community of amphibians has been observed in pools and ponds (permanent, semi-permanent and temporary). Were carried out 58 visits (373 hours of sampling effort) monitoring one or two environments per night. The search of exemplars was conducted by survey method in breeding site. We recorded 21 species, distributed in six families: Bufonidae (1 sp.) Cycloramphidae (1 sp.) Hylidae (8 spp.) Leiuperidae (5 spp.), Leptodactylidae (5 spp.) and Microhylidae (1sp.) . The recorded frogs represents about 23% of the species found in RS and is usually associated with open areas in this state and in neighboring countries. Ten species were considered frequent, seven were common and four were rare in relation to the constancy of occurrence. These categories were not associated with the type of reproduction of some species. Three reproductive modes (1, 30 11e), were recorded and about 57% of species use mode 1, which appears to be related to the homogeneity of the area. The of activity circannual vocalization analysis of frogs showed high correlation to the sinusoidal model reflecting the monthly variation of the photoperiod, which accounted for 70% of the seasonal variation of the data. The largest number of frog species in calling activity occurred in months with longer photoperiods (spring and summer) and lower activity in the winter months, with short photoperiod. This may be related to the appropriate environmental conditions for species reproduction. The frogs in the city of São Gabriel was compared by analysis of similarity with other four municipalities in different regions. São Gabriel showed higher similarity (about 70%) with the municipality of Candiota (Região da Campanha), this might happen due to the location of the municipalities, located in a region of meeting of two vegetation types, sharing fragments of the Sul-riograndense Plateau