Perfluoroalkyl substances (PFAS) are a complex group of anthropogenic compounds with exceptional properties. Due to their high persistence and mobility, they have caused ubiquitous environmental ...contamination and in part accumulate in the food chain. In the general population, diet is the main source of PFAS exposure, with the important sources fish and meat. As a vegan diet implies the complete exclusion of any animal products, it might be expected that vegans have lower blood levels of PFAS compared to omnivores. Furthermore, lower levels of cholesterol is one of the well-documented nutritional effects in vegans, but cholesterol levels were also found to be associated with higher PFAS levels in epidemiological studies.
To examine the relations of internal PFAS levels and the levels of cholesterol in vegans and omnivores, the cross-sectional “Risks and Benefits of a Vegan Diet” (RBVD) study was used involving 36 vegans and 36 omnivores from Berlin/Germany. Nine perfluoroalkyl substances were quantified in plasma using a triple-stage quadrupole mass spectrometer.
Lower median plasma concentrations were found in vegans compared to omnivores for perfluorooctane sulfonic acid (PFOS) (2.31 vs. 3.57 ng/ml, respectively; p = 0.02) and for perfluorononanoic acid (PFNA) (<0.25 vs. 0.41 ng/ml, respectively; p < 0.0001). No significant differences of the median concentrations were observed for perfluorooctanoic acid (PFOA) (1.69 vs. 1.44 ng/ml, respectively, p = 0.26) and perfluorohexane sulfonic acid (PFHxS) (1.96 vs. 1.79 ng/ml, respectively; p = 0.70). The strongest correlations with food groups, derived from a food frequency questionnaire, were observed between levels of PFOA and water consumption (in case of the total study population, n = 72), and between levels of PFOS as well as PFNA and the consumption of ‘meat and meat products’ (in case of the omnivores, n = 36). Levels of Low Density Lipoprotein (LDL) cholesterol were confirmed to be considerably lower in vegans compared to omnivores (86.5 vs. 115.5 mg/dl, respectively; p = 0.001), but no associations between the four main PFAS and LDL cholesterol were observed (all p > 0.05) at the low exposure level of this study.
According to the results of our study, a vegan diet may be related to lower PFAS levels in plasma. We highlight the importance of the adjustment of dietary factors like a vegan diet in case of epidemiological studies dealing with the impact of PFAS on the levels of blood lipids.
The giant panda feeds almost exclusively on bamboo, a diet highly enriched in lignin and cellulose, but is characterized by a digestive tract similar to carnivores. It is still large unknown if and ...how the giant panda gut microbiota contributes to lignin and cellulose degradation. Here we show the giant pandas' gut microbiota does not significantly contribute to cellulose and lignin degradation. We found that no operational taxonomic unit had a nearest neighbor identified as a cellulolytic species or strain with a significant higher abundance in juvenile than cubs, a very low abundance of putative lignin and cellulose genes existed in part of analyzing samples but a significant higher abundance of genes involved in starch and hemicellulose degradation in juveniles than cubs. Moreover, a significant lower abundance of putative cellulolytic genes and a significant higher abundance of putative α-amylase and hemicellulase gene families were present in giant pandas than in omnivores or herbivores.
Understanding environmental drivers of species diversity has become increasingly important under climate change. Different trophic groups (predators, omnivores and herbivores) interact with their ...environments in fundamentally different ways and may therefore be influenced by different environmental drivers. Using random forest models, we identified drivers of terrestrial mammals' total and proportional species richness within trophic groups at a global scale. Precipitation seasonality was the most important predictor of richness for all trophic groups. Richness peaked at intermediate precipitation seasonality, indicating that moderate levels of environmental heterogeneity promote mammal richness. Gross primary production (GPP) was the most important correlate of the relative contribution of each trophic group to total species richness. The strong relationship with GPP demonstrates that basal‐level resource availability influences how diversity is structured among trophic groups. Our findings suggest that environmental characteristics that influence resource temporal variability and abundance are important predictors of terrestrial mammal richness at a global scale.
We determined the total and relative species richness of terrestrial mammals within different trophic groups (i.e. predators, omnivores and herbivores) at a global scale. We used random forest models to identify environmental drivers that explain species richness within the three trophic groups. We found that precipitation seasonality was the most important driver of raw species richness for all three trophic groups, while GPP was the most important driver of the relative contribution of each trophic group to total species richness.
The broad negative consequences of habitat degradation on biodiversity have been studied, but the complex effects of natural–agricultural landscape matrices remain poorly understood. Here we used ...stable carbon and nitrogen isotopes to detect changes in mammal resource and habitat use and trophic structure between preserved areas and human-modified landscapes (HMLs) in a biodiversity hot spot in South America. We classified mammals into trophic guilds and compared resource use (in terms of C₃- and C₄-derived carbon), isotopic niches, and trophic structure across the 2 systems. In HMLs, approximately one-third of individuals fed exclusively on items from the agricultural matrix (C₄), while in preserved areas, ∼68% depended on forest remnant resources (C₃). Herbivores, omnivores, and carnivores were the guilds that most incorporated C₄ carbon in HMLs. Frugivores maintained the same resource use between systems (C₃ resources), while insectivores showed no significant difference. All guilds in HMLs except insectivores presented larger isotopic niches than those in preserved areas. We observed a complex trophic structure in preserved areas, with increasing δ15N values from herbivores to insectivores and carnivores, differing from that in HMLs. This difference is partially explained by species loss and turnover and mainly by the behavioral plasticity of resilient species that use nitrogen-enriched food items. We concluded that the landscape cannot be seen as a habitat/nonhabitat dichotomy because the agricultural landscape matrix in HMLs provides mammal habitat and opportunities for food acquisition. Thus, favorable management of the agricultural matrix and slowing the conversion of forests to agriculture are important for conservation in this region.
Invasive species are one of the main threats to biodiversity worldwide and the processes enabling their establishment and persistence remain poorly understood. In generalist consumers, plasticity in ...diet and trophic niche may play a crucial role in invasion success. There is growing evidence that invasive ants, in particular, occupy lower trophic levels in their introduced range compared to the native one, but evidences remain fragmented. We conducted stable isotope analysis at five locations distributed on two continents to infer the trophic position of the invasive ant Formica paralugubris in the native and introduced part of the range. This species forms large colonies and can be a voracious predator while feeding on sugar‐based resources as well. Whereas native populations had trophic positions comparable to that of an omnivore, the introduced populations varied from being honeydew specialists to top predators, or omnivore. Where other ant species co‐occurred, there was no overlap in their trophic niches, and F. paralugubris occupied the lower position, suggesting that trophic displacement may enable the coexistence of different ant species. Taken together, our results suggest that shifts in diet associated with changes in the trophic niche of introduced species might mediate invasion success and enable long‐term coexistence with native species.
The estimation of the relative roles of environment, space, and their interactions in structuring community composition is one of the central topics of community ecology. I conducted a quantitative ...review to determine if the degree of species sorting (SS) by the abiotic environment varied predictably between organism types and ecosystems. SS was quantified as the relative fraction of community variation that is explained by environmental variables. I integrated data from 326 variation partition analyses in a generalized linear model, and found that a mean of 26.1% (minimum 0%, maximum 88%) of the variance in community composition was explained by environmental variables. I also found that organism body size and dispersal group were not related to the degree of SS. SS varied among trophic positions, being highest in autotrophs and omnivores and lowest in herbivores and decomposers. SS also varied among ecosystem types: it was lowest in lakes and highest in estuaries and marine environments. Studies using abundance data showed a higher degree of SS than studies based on presence-absence data. SS was lower when data sets were analyzed by spatial filters instead of by polynomials. These results suggest that although significant among-group differences emerged for trophic position and ecosystem type, variation in SS across body sizes or across different dispersal groups was relatively unpredictable. Nonetheless, these findings shed light on how the degree of SS varies across ecosystems or organism groups and may give important insights into the magnitude of environmental effects on biotic communities in a changing environment.
Despite becoming one of the main pressures on aquatic ecosystems globally, understanding of the ecological impacts of altered water‐level regimes in lakes lags far behind that of other human ...disturbances (e.g. eutrophication, acidification). We employed a multifaceted approach to explore the potential importance of water‐level fluctuations (WLF) for the structure and functioning of littoral zones and multiple trait responses of primary producers and benthic consumers across a range of natural lakes. We found that lakes with high WLF had significantly more coarse littoral substrata with less coverage of macrophyte vegetation in the shallows than in lakes with low WLF. Lakes with high WLF also had greater proportions of motile diatom species and omnivorous benthic invertebrates in shallow waters, altered taxonomic and trophic structure of benthic consumers and more homogeneous algal and benthic invertebrate assemblages. Variation along the littoral depth gradient needs to be examined when assessing the impacts of hydrological pressures in lakes. We found that depth interacted with WLF in its effects on habitat structure and mediated the response of both producer and consumer benthic assemblages to WLF. Our results indicate that amplified WLF significantly affect both the structure and functioning of lake ecosystems. Given the growing importance of WLF as an increasingly pervasive pressure on lake ecosystems worldwide, our findings have important implications for the conservation and management of global aquatic biodiversity. Inclusion of both biological traits and sampling along a depth gradient in existing and in future monitoring programmes could improve significantly the ability to detect and predict effects of altered patterns of WLF on lake ecosystems.
The complex relationships that exist between terrestrial mammals and their habitats make African ecosystems highly interactive environments. Anthropogenic activities including climate change have ...altered geochemical cycles, which influence nutrient availability and deficiency at local, regional and global scales. As synergistic and antagonistic interactions occur between essential elements at both deficiency and excess concentrations, the differences in feeding strategy between trophically distinct groups of terrestrial vertebrates are likely to influence the degree to which overall nutrient needs are met or may be deficient. The overall aim of this study was to investigate and compare quantitative differences of nine essential elements in terrestrial vertebrates occupying different trophic levels within two protected areas; Tswalu Kalahari Reserve (TKR) and Manyeleti Nature Reserve (MNR) South Africa, using faeces as an analytical matrix. Results from linear mixed effects models highlight that concentrations varied widely between individuals. Overall, measured concentrations above their respective means were evident for B and Mn in herbivores, Fe in omnivores and Cu, Co, Fe, Se and Zn in carnivores. Measured concentrations of Mo and Ni did not differ significantly between trophic groups. Although site-specific differences were evident for specific elements, measured mean concentrations of B, Co, Cu, Fe, Mo, Ni, Se and Zn were significantly higher overall at the MNR study site compared to the TKR site. This is the first study to non-invasively assess essential element concentrations across trophic levels in free ranging African wildlife species within protected areas of the savannah biome. Combined with the assessment of environmental matrices, this approach can be used as an effective diagnostic tool for the assessment of animal welfare and the management of protected areas globally.
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•Essential element availability or deficiency difficult to establish in wildlife.•Trophic level differences investigated non-invasively by faecal sampling.•Patterns were evident within sites, but absolute values differed between sites.•Species-specific and essential element interactions need further investigation.•Broad application of a non-invasive approach for protected area management.
Estimating trophic structures is a common approach used to retrieve information regarding energy pathways, predation, and competition in complex ecosystems. The application of amino acid (AA) ...compound-specific nitrogen (N) isotope analysis (CSIA) is a relatively new method used to estimate trophic position (TP) and feeding relationships in diverse organisms. Here, we conducted the first meta-analysis of δ¹⁵N AA values from measurements of 359 marine species covering four trophic levels, and compared TP estimates from AA-CSIA to literature values derived from food items, gut or stomach content analysis. We tested whether the AA trophic enrichment factor (TEF), or the ¹⁵N enrichment among different individual AAs is constant across trophic levels and whether inclusion of δ¹⁵N values from multiple AAs improves TP estimation. For the TEF of glutamic acid relative to phenylalanine (Phe) we found an average value of 6.6 ‰ across all taxa, which is significantly lower than the commonly applied 7.6 ‰. We found that organism feeding ecology influences TEF values of several trophic AAs relative to Phe, with significantly higher TEF values for herbivores compared to omnivores and carnivores, while TEF values were also significantly lower for animals excreting urea compared to ammonium. Based on the comparison of multiple model structures using the metadata of δ¹⁵N AA values we show that increasing the number of AAs in principle improves precision in TP estimation. This meta-analysis clarifies the advantages and limitations of using individual δ¹⁵N AA values as tools in trophic ecology and provides a guideline for the future application of AA-CSIA to food web studies.
•The study articulated a range of mechanisms by which meat eaters reduce dissonance•These mechanisms were applied to explain omnivores’ reactions to vegetarians•It was hypothesized that vegetarians ...would increase dissonance among meat eaters•This dissonance would be reduced in whatever way possible•Five experiments showed that meat eaters reacted to vegetarians by reducing dissonance
Meat eaters face dissonance whether it results from inconsistency (“I eat meat; I don’t like to hurt animals”), aversive consequences (“I eat meat; eating meat harms animals”), or threats to self image (“I eat meat; compassionate people don’t hurt animals”). The present work proposes that there are a number of strategies that omnivores adopt to reduce this dissonance including avoidance, dissociation, perceived behavioral change, denial of animal pain, denial of animal mind, pro-meat justifications, reducing perceived choice, and actual behavioral change. The presence of vegetarians was speculated to cause meat eating to be a scrutinized behavior, remind meat eaters of their discomfort, and undermine the effectiveness of these strategies. It was therefore hypothesized that exposure to a description of a vegetarian would lead omnivores to embrace dissonance-reducing strategies. Supporting this hypothesis, participants who read a vignette about a vegetarian denied animal mind more than participants who read about a gluten-free individual. It was also hypothesized that omnivores would be sensitive to individual differences between vegetarians and would demonstrate using dissonance-reducing strategies more when the situation failed to provide cognitions consonant with eating meat or to reduce dissonant cognitions. Four experiments supported this prediction and found that authentic vegetarians, vegetarians freely making the decision to abandon meat, consistent vegetarians, and anticipating moral reproach from vegetarians produced greater endorsement of dissonance-reducing strategies than their counterpart conditions.
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