The east coast of Brazil comprises an extensive area inserted in the Tropical Atlantic Domain and is represented by sandy plains of beach ridges commonly known as Restingas. The coastal environments are unique and house a rich amphibian fauna, the geographical distribution patterns of which are incipient. Biogeographical studies can explain the current distributional patterns and provide the identification of natural biogeographical units. These areas are important in elucidating the evolutionary history of the taxa and the areas where they occur. The aim of this study was to seek natural biogeographical units in the Brazilian sandy plains of beach ridges by means of distribution data of amphibians and to test the main predictions of the vicariance model to explain the patterns found. We revised and georeferenced data on the geographical distribution of 63 anuran species. We performed a search for latitudinal distribution patterns along the sandy coastal plains of Brazil using the non-metric multidimensional scaling method (NMDS) and the biotic element analysis to identify natural biogeographical units. The results showed a monotonic variation in anuran species composition along the latitudinal gradient with a break in the clinal pattern from 23°S to 25°S latitude (states of Rio de Janeiro to São Paulo). The major predictions of the vicariance model were corroborated by the detection of four biotic elements with significantly clustered distribution and by the presence of congeneric species distributed in distinct biotic elements. The results support the hypothesis that vicariance could be one of the factors responsible for the distribution patterns of the anuran communities along the sandy coastal plains of eastern Brazil. The results of the clusters are also congruent with the predictions of paleoclimatic models made for the Last Glacial Maximum of the Pleistocene, such as the presence of historical forest refugia and biogeographical patterns already detected for amphibians in the Atlantic Rainforest.

Áreas compostas por matrizes florestadas e sistemas agroflorestais podem minimizar os efeitos da fragmentação ao conectar remanescentes de vegetação nativa. Neste estudo, avaliou-se a biomassa de quatro grupos de artrópodes cursores que ocorrem na matriz de seringal e nos fragmentos florestais em estádios iniciais e avançados de regeneração, com intuito de verificar a permeabilidade da monocultura (Hevea brasiliensis) e sua possível utilização como área de conexão entre fragmentos florestais isolados. Oito pontos aleatórios foram marcados nas três fitofisionomias e quatro armadilhas foram instaladas em cada ponto. Os artrópodes capturados foram separados por grandes grupos (ordem) e sua biomassa (peso úmido) foi determinada. As ordens escolhidas foram Araneae, Dermaptera, Blattaria e Isopoda. Araneae e Isopoda foram mais abundantes no seringal, enquanto Dermaptera e Blattaria nos fragmentos. Os valores de biomassa apresentaram maior amplitude de variação entre os pontos amostrais dos fragmentos do que os pontos do seringal. Não foi detectada diferença significativa considerando as três fitofisionomias, contudo, ao analisar as interações entre os níveis do fator (três fitofisionomias comparadas dois a dois), foi verificada significância entre fragmentos em estádio avançado de regeneração e plantações de seringal. A menor biomassa apresentada pelo seringal pode indicar a sua ineficiência para a conexão dos remanescentes de mata.

Contribution of environmental variables to anuran community structure in the Caatinga Domain of Brazil. To ascertain the influence of environmental variables on the structure of anuran communities, we conducted tests to determine which variables best explain the spatial distribution patterns of different communities of anurans in a rocky, montane environment characterized mainly by open habitats and gallery forests. The study area is the Sete Passagens State Park in the State of Bahia, Brazil, an area included in the Chapada Diamantina Region and in the Caatinga Morphoclimatic Domain. We sampled 20 plots (60 × 25 m) during two rainy seasons, and measured 13 environmental variables. The environmental matrix was reduced to four synthetic axes through the principal component analysi, and the anuran community matrix was reduced to a synthetic axis through the nonmetric multidimensional scaling method. We tested the association between environmental axes (independent variables) and community composition (dependent variable) using a multiple regression analysis. The single axis significantly associated with the species of anurans found in any given plot is Principal Component 1, in which the major contributors to variation are factors involving vegetation structure, listed in descending order, as follow: percentage of leaf litter, density of trees, canopy height, soil moisture, and percentage of understory, shrub, and herb layers. The ordination of the anuran community showed an environmental gradient from the Campo Rupestre to Semideciduous Forest patches, characterized mainly by the gradual increase of layering in the vegetation.