Ogy and fnhum.2014.00074 various theories have been proposed to explain such phenomenon [1?]. Niche-basedPLOS ONE | DOI:10.1371/journal.pone.0152494 April 6,1 /Stable Isotopes and Diet of Small Mammalspermits was provided by Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renov eis (IBAMA #14428-2, IBAMA #31941-1). The authors thank Funda o order LY2510924 Florestal for allowing them to work in the protected fpsyg.2017.00209 areas. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing NVP-AUY922 web Interests exist.approaches postulates that co-occurring species are required to exhibit ecological differences in at least one niche dimension, such as space use [5] or food preferences [6]. In other words, niche theory predicts that two species cannot share exactly the same niche; otherwise, one must be excluded by competition, which constrains the number of coexisting species in biological communities [7]. Indeed, many examples of niche differentiation between co-occurring species have supported this idea in diverse taxonomic groups [8]. However, understand how so many species partition resources and the underlying mechanisms allowing coexistence in highly diverse tropical communities is still an open issue in modern ecology, which has challenged ecologists for more than half a century [1]. Nutritional or trophic dimension is the most explored niche component in ecological studies [8]. As animals acquire and assimilate resources for growth and reproduction, trophic niche dimension is directly related to the average fitness of organisms [9]. Therefore, trophic partitioning between co-occurring species can favor coexistence via lessening the niche overlap and the intensity of interspecific competition [10]. Diet partitioning can arise via many types of ecological differences between species, but studies have focused mainly in interspecific differences in functional traits and space use among community members [8]. Body size is a key trait in ecological interactions, and can be a surrogate of resource use and energetics for many animal groups. Size is directly related of how organisms experience the environment, impacting on its fitness and performance [11]. In this line, the spatial scaling law postulates that interspecific differences in size will result in sufficiently distinct niches that allow the persistence of competitors [12]. For instance, body size can constraint the type and size of food resources that can be explored (e.g. gape limitation). Hence, divergences in body size among community members can constitute an underlying mechanism of niche partitioning [13, 14]. In turn, the spatial arrangement of species also can lead to niche divergence (e.g. use of different vertical strata in forests). Studies in diverse taxonomic groups have shown that even subtle differences in foraging microhabitats between sympatric species can potentially buffer competition intensity and favor species’ coexistence [15]. Small mammals are promising study models to investigate trophic relations in tropical communities because they constitute a diverse group, with conspicuous interspecific variations in body size and microhabitat use, and consume a broad range of food resources [16]. The Atlantic forests in South America holds one of the greatest diversity of small mammals in the Neotropics, harboring more than 120 species of rodents and marsupials [17], with up to 23 sp.Ogy and fnhum.2014.00074 various theories have been proposed to explain such phenomenon [1?]. Niche-basedPLOS ONE | DOI:10.1371/journal.pone.0152494 April 6,1 /Stable Isotopes and Diet of Small Mammalspermits was provided by Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renov eis (IBAMA #14428-2, IBAMA #31941-1). The authors thank Funda o Florestal for allowing them to work in the protected fpsyg.2017.00209 areas. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist.approaches postulates that co-occurring species are required to exhibit ecological differences in at least one niche dimension, such as space use [5] or food preferences [6]. In other words, niche theory predicts that two species cannot share exactly the same niche; otherwise, one must be excluded by competition, which constrains the number of coexisting species in biological communities [7]. Indeed, many examples of niche differentiation between co-occurring species have supported this idea in diverse taxonomic groups [8]. However, understand how so many species partition resources and the underlying mechanisms allowing coexistence in highly diverse tropical communities is still an open issue in modern ecology, which has challenged ecologists for more than half a century [1]. Nutritional or trophic dimension is the most explored niche component in ecological studies [8]. As animals acquire and assimilate resources for growth and reproduction, trophic niche dimension is directly related to the average fitness of organisms [9]. Therefore, trophic partitioning between co-occurring species can favor coexistence via lessening the niche overlap and the intensity of interspecific competition [10]. Diet partitioning can arise via many types of ecological differences between species, but studies have focused mainly in interspecific differences in functional traits and space use among community members [8]. Body size is a key trait in ecological interactions, and can be a surrogate of resource use and energetics for many animal groups. Size is directly related of how organisms experience the environment, impacting on its fitness and performance [11]. In this line, the spatial scaling law postulates that interspecific differences in size will result in sufficiently distinct niches that allow the persistence of competitors [12]. For instance, body size can constraint the type and size of food resources that can be explored (e.g. gape limitation). Hence, divergences in body size among community members can constitute an underlying mechanism of niche partitioning [13, 14]. In turn, the spatial arrangement of species also can lead to niche divergence (e.g. use of different vertical strata in forests). Studies in diverse taxonomic groups have shown that even subtle differences in foraging microhabitats between sympatric species can potentially buffer competition intensity and favor species’ coexistence [15]. Small mammals are promising study models to investigate trophic relations in tropical communities because they constitute a diverse group, with conspicuous interspecific variations in body size and microhabitat use, and consume a broad range of food resources [16]. The Atlantic forests in South America holds one of the greatest diversity of small mammals in the Neotropics, harboring more than 120 species of rodents and marsupials [17], with up to 23 sp.
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