The species Boana bischoffi and Boana marginata are endemic to the Atlantic Forest, where they often occur in sympatry. There is a large gap in the knowledge of natural history of both species. In this study, we aimed to describe and compare the diet composition of B. bischoffi and B. marginata in the southern domain of the Brazilian Atlantic Forest. We analyzed the gastrointestinal contents of 43 individuals of B. bischoffi and 30 individuals of B. marginata. Both showed a high trophic niche overlap (0.90 O jk ). The most important prey categories for both species belonged to the orders Araneae and Coleoptera. The species niche breadth (Bsta) varied from 0.35 to 0.42, suggesting a generalist feeding behavior for both species. Our data provide unprecedented information on these species' food composition, contributing to a better knowledge of the natural history of neotropical anurans. Dieta e sobreposição de nicho trófico deBoana bischoffi e Boana marginata (Anura: Hylidae) no sul do Brasil Resumo: As espécies Boana bischoffi e Boana marginata, são endêmicas da Mata Atlântica onde frequentemente ocorrem em simpatria. Existe uma grande lacuna no conhecimento da história natural de ambas as espécies. Nesse estudo, nosso objetivo foi descrever e comparar a composição da dieta de B. bischoffi e B. marginata no limite sul da Mata Atlântica brasileira. Analisamos o conteúdo gastrointestinal de 43 indivíduos de B. bischoffi e 30 indivíduos de B. marginata. Ambas apresentaram elevada sobreposição de seus nichos tróficos (0,90 O jk ). As categorias de presas mais importantes para ambas as espécies pertenciam as ordens Araneae e Coleoptera. A amplitude de nicho das espécies (Bsta) variou de 0,35 a 0,42, sugerindo comportamento alimentar generalista para ambas. Nossos dados trazem informações inéditas sobre a composição alimentar destas espécies, contribuindo para um maior conhecimento da história natural dos anuros neotropicais.
Despite the current increase in studies on the diet of neotropical anurans, few of them take a comparative approach between syntopic species. The objective of this study was to compare the diet of four syntopic species of the genus Physalaemus. The collections occurred between November 2014 and January 2016 in a preserved area of the subtropical Atlantic Forest in southern Brazil. We compared the gastrointestinal content of 109 individuals distributed in the species Physalaemus biligonigerus, P. cuvieri, P. gracilis and P. henselii. We measured the Index of Relative Importance of each prey category and calculated trophic niche breadth using the Levins’ index (Bsta) and trophic niche overlap using the Pianka’s index (Ojk). We also applied compositional analysis to evaluate feeding specializations. Formicidae was the most important prey category for P. biligonigerus (IRI = 88.5%) and P. gracilis (IRI = 39.1%). For P. henselii and P. cuvieri, the most important category was Isopoda (IRI = 51.7% and 57.9%, respectively), followed by Formicidae (IRI = 34.9% and 24.8%). Isopoda was also important in the diet of P. gracilis (IIR = 28.6%), followed by Araneae (IIR = 22.6%). The trophic niche breadth of the four species was narrow, all smaller than 0.32, and the lowest was recorded for P. biligonigerus (0.04). The trophic niche overlap was higher between P. biligonigerus and P. cuvieri (96%), and between P. gracilis and P. henselii (95%). Only P. gracilis presented a significant level of feeding specialization. The differences in their diets suggest different uses of the resources, which could relate to different ways of exploring the microhabitat.
In this study, we observed that burrows of Rhinella dorbignyi (Duméril & Bibron, 1841) are distributed in a non-random manner in the habitat, suggesting a microhabitat selection for digging. This conclusion was based on a characterization of 36 burrows and surrounding micro-habitat. We established a 1 m x 1 m quadrat with the burrow in its central point (n=36) to measure the percentage (density) and the average heights of grasses, herbs, and shrubs. All measurements were repeated in two unused quadrats (without burrows) to evaluate the available microhabitat (n=72). The burrows are built in specific areas of the habitat with a higher percentage of grass, taller herbs, lower density of shrubs and low shaded sites than the founded at control sites. Based on three-dimensional models of the interior of the burrow (n=15), we observed that all of them were constructed with an elliptical opening that opens into a narrow channel perpendicular to the ground. Channels had a mean maximum diameter of 38 mm and a mean minimum diameter of 18 mm. The mean length of the burrows is 182 mm, and the mean volume is 95 mL.
Climatic conditions and microhabitat characteristics, such as the substrate and type of vegetation, influence the choice of male anurans for calling sites that optimize their reproductive success. We evaluated the structure and selection of vocalization microhabitat of 17 individuals of Phyllomedusa distincta Lutz, 1950 and 25 of Boana leptolineata (Braun & Braun, 1977), in a subtropical forest in southern Brazil. We measure the height of the perch, the distance between the perch and the edge of the body of water and the structure of the microhabitat of quadrants used by individuals. The same attributes were measured in the quadrants available (but not used) by the individuals. We classified the microhabitats by visual estimate, assigning percentages of coverage for each quadrant by herbaceous, shrub, tree and wetland vegetation. We observed that both species selected their microhabitat, since the characteristics of the quadrants occupied by the individuals were different from those available. Phyllomedusa distincta was more associated with heterogeneous microhabitats, while B. leptolineata occurred in environments with greater coverage of tree strata. Additionally, we observed that both species used shrubs more frequently as a perch site. The selection of these microhabitat characteristics must be associated with strategies to optimize the use of the reproductive habitat, based on the morphological and behavioral characteristics of the species. Finally, it is possible to infer that the differences observed in the microhabitat structure selected by the species can facilitate the coexistence of both in the context of the heterogeneity of the environment.
The Sinos River encompasses a wide area of natural habitats and, at the same time, supports one of the highest population densities of southern Brazil. Consequently, natural habitats along the Basin present a high degree of habitat disturbance. Despite of the existence of threatened species, information about diversity of amphibians in that area is scarce. Thus, we aimed to catalogue the amphibian species of the Sinos River Basin from records in scientific collections and compilation of published articles. We recorded 52 species, all with geographic coordinates validated at the collection point, indicating that the Sinos River Basin harbours about 50% of the amphibian species of the State of Rio Grande do Sul. Three anuran species were classified as having some degree of threat: Melanophryniscus cambaraensis, Melanophryniscus dorsalis and Thoropa saxatilis. We also expected other 18 species with a high probability of occurrence in the Basin. This work shows that, despite the intense human impact, the Sinos River Basin has a relevant role for the maintenance of a considerable fraction of the amphibian biodiversity in southern Brazil.
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