While several studies have shown that invasive rats can have negative effects on island birds through predation (both direct predation and nest predation), other mechanisms for the effects of invasives on island biota have been given less attention. Here we explore another potential mechanism by which invasive rats can affect native island birds: the competitive use of common resources. We used stable isotope analyses to estimate the fraction of marine and terrestrial sources incorporated into the tissues of two species of passerines (Troglodytes cobbi, Troglodytidae; and Cinclodes antarcticus, Furnariidae) and Norway rats (Rattus norvegicus, Muridae) in the Falkland Islands. These two passerines are absent on islands where rats are present. We found significant incorporation of marine resources in the three species, with the highest incorporation in tissues of T. cobbi. This species appears to be one of the passerines most reliant on marine sources and the most marine member of the family Troglodytidae. We also used the results of these isotopic analyses to estimate the isotopic niche breadth of each of these species and the isotopic niche overlap among them. Rattus norvegicus had a large isotopic niche that overlapped broadly with those of the two passerine species. We propose that different ways of both depicting and estimating isotopic niche widths are complementary rather than alternative.Our results are consistent with the notion that invasive rats might have an impact on these two species of Falkland Island passerines by using common resources, but do not rule out the possibility that part of their effect is through direct predation.

Variability in snake venom composition has been frequently reported and correlated to the adaptability of snakes to environmental conditions. Previous studies report plasticity for the venom phenotype. However, these observations are not conclusive, as the results were based on pooled venoms, which present high individual variability. Here we tested the hypothesis of plasticity by influence of confinement and single diet type in the venom composition of 13 adult specimens of Bothrops atrox snakes, maintained under captivity for more than three years. Individual variability in venom composition was observed in samples extracted just after the capture of the snakes. However, composition was conserved in venoms periodically extracted from nine specimens, which presented low variability restricted to the less abundant components. In a second group, composed of four snakes, drastic changes were observed in the venom samples extracted at different periods, mostly related to snake venom metalloproteinases (SVMPs), the core function toxins of B. atrox venom, which occurred approximately between 400 and 500 days in captivity. These data show plasticity in the venom phenotype during the lifetime of adult snakes maintained under captive conditions. Causes or functional consequences involved in the phenotype modification require further investigations.

Motivation: Leaf traits represent an important component of plant functional strategies, and those related to carbon fixation and nutrient acquisition form the leaf economics spectrum. However, observations of functional leaf traits are underrepresented in tropical regions in comparison with those in temperate areas. Brazil, a country with continental scale and vast biodiversity is a timely example, where many biomes are impacted by human activities and climate change. However, leaf traits relevant to understand vegetation responses to these impacts remain poorly quantified for many species found in the country. We compiled an extensive data set of four functional leaf traits for native woody species occurring in the Brazilian territory. In addition to trait observations, sampling dates and geo-references were compiled and climatic parameters and soil properties of each sampling site were extracted from several databases. Main types of variables contained:The LT-Brazil data set contains 3,479, 1,216, 775 and 775 clean observations of leaf mass per area, leaf nitrogen (N) concentration per unit mass, leaf phosphorus (P) concentration per unit mass, and leaf N : P ratio, respectively, from native woody species, encompassing information of biome, vegetation, taxonomic data, geographical coordinates, climatic parameters, as well as soil properties. Spatial location and grain: We compiled trait observations from 223 sites under native vegetation distributed in all main biomes (i.e., Amazônia, Caatinga, Cerrado, Mata Atlântica, Pampa and Pantanal) across the Brazilian territory. Time period and grain: The data represent information published and/or sampled during the last 25 years.| 2137 MARIANO et Al.

BackgroundEnvironmental devastation threatens the survival of many species, including venomous snakes such as the South American rattlesnake Crotalus durissus terrificus. This observation is based on the decrease of snakes collected and donated to Brazilian research institutes. Nevertheless, some individuals have managed to survive and procreate. The question is how these snakes are adapting in these new environmental conditions.MethodsTo answer it, the carbon-13 level of rattlesnakes and their feed (either laboratory or wild mice) was evaluated by isotope-ratio mass spectrometry. Thus, rattle segments from 16 adults and 15 offspring of captive snakes, and of three wild newborn C. d. terrificus were evaluated as well as 17 Mus musculus mice captured in traps, four live feeder mice and the ration offered to mice at animal houses.ResultsThe isotopic exchange time of the captive adult snakes (n = 16) varied between 33 and 37 months and of captive-born animals (n = 15), until reaching a plateau of equilibrium, varied from 18 to 24 months. Regarding the captured Mus musculus (n = 17), 88.23% (n = 15) were from a C4 environment. Of the six rattle rings from offspring of captured C. d. terrificus, five were from a C4 environment, whereas of the 170 rattle rings studied, 60% originated from a C3 environment and 40% from a C4. The same carbon-13 values were found in captive snakes.ConclusionsBased on the present results, it can be inferred that most C. d. terrificus snakes (60%) fed animals from a C3 environment; birds consist of an alimentary alternative for snakes, as well as rodents, small reptiles and amphibians; different venom compositions among snakes from the same region may be related to the food type; the primary rattle of offspring reflects the maternal diet during gestation; and, finally, the different rattle rings indicate the alimentary history of these animals.Electronic supplementary materialThe online version of this article (doi:10.1186/1678-9199-20-53) contains supplementary material, which is available to authorized users.

In this article, by using carbon stable isotopes, we assessed the past and present land use influences that riparian areas are subject within agricultural landscapes. Emphasis is given to the understanding of the effects of the 2012 Brazilian Forest Act on such areas. We selected five riparian areas within a highly C4 dominated agricultural landscape. Three of them had 30 meters native riparian forest buffer (NRFB) and two of them had 8 meter and no NRFB. We used three 100 meter-transects located 5, 15 and 30 meters relative to stream channel to obtain soil samples (0 - 10 cm). All riparian areas presented soil carbon isotopic signatures that are not C3 (native forests) irrespective of having or not 30 meters NRFB. Two cases presenting less than 30 meters NRFB had higher C4 derived carbon contribution. All of the other three areas that followed the 30 meters NRFB presented, to some degree, C4 derived carbon, which was attributed to C4 organic matter deposition originated from cultivated areas and, in one case, to the persistence of former exotic grasses. With the 2012 Forest Act allowing narrower buffers (< 30 meters), we expect C4 contributions to soil organic matter to remain high in riparian areas and streams within agricultural landscapes dominated by C4 plants where 30 meter NRFB is no longer required. Such contributions will likely continue to have detrimental effects on stream water quality and biota.