Microhabitat use is an important component of anuran behavior in both the tadpole and the adult stages. It is potentially influenced by phylogeny and extant ecological factors acting as selective pressures, such as predation, competition, or physical habitat properties. We aimed to test whether patterns of microhabitat use vary among species, habitats and sites, and how much of this variation can be explained by phylogenetic relatedness. We collected data on microhabitat use at five different sites, where we obtained a total of 4,230 records of individual tadpoles of 34 species in 15 genera and 7 families, and a total of 1,163 records of adult individuals of 39 species in 16 genera and 8 families. Mantel tests conducted to relate species dissimilarities in microhabitat use and phylogenetic relatedness indicated a weak but significant relationship for adult anurans, and no relationship for tadpoles. Our results suggest that microhabitat use is a plastic and variable trait, overcoming phylogenetic signal in tadpoles. In adult anurans, very little of the variation in microhabitat use can be explained by phylogenetic relatedness. Microhabitat use is not a good predictor of phylogeny, but it may be a very interesting subject to study natural selection and adaptation.

Phenotypic plasticity can improve fitness in unstable environments and can be expressed in many traits, such as life history attributes, growth and behavioural features. Microhabitat choice can have important consequences for development and survival of aquatic organisms and is expected to vary in response to stimuli, such as predation risk, food availability and temperature. At seasonal sites, microhabitat availability and associated benefits may change from season to season, which might lead to altered patterns of microhabitat use by tadpoles. We investigated this hypothesis in 17 streams from two localities in south-eastern Brazil. We tested whether water level drops significantly during the dry season, whether lower water level results in altered microhabitat availability and whether predation risk changes between seasons, based on predator density. We then tested whether tadpoles change their pattern of microhabitat use, their spatial niche breadth (given by diversity of used microhabitats) and spatial niche overlap (in the case of co-occurring species). We were able to include in our analyses tadpoles of four species of Hylidae, that occurred throughout both seasons. Stream depth decreased in the dry season, but microhabitat availability remained relatively stable in many streams, and predator density did not change significantly. Tadpoles of three out of the four species studied were more abundant during the dry season, which may be an adaptation to adjust time of metamorphosis to the rainy season. Tadpoles changed their patterns of microhabitat use between seasons, although the potential causing factors investigated did not seem to be responsible. Tadpole plasticity in microhabitat use may indicate the existence of selective pressures that vary through time and space and are still not well understood.