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49 results for “trophic position”
Stomach contents (1977-1981) and stable isotopes (1994) from the Everglades, Florida, USA from the publication "Fishes in a seasonally pulsed wetland show spatiotemporal shifts in diet and trophic niche but not shifts in trophic position"
Stomach contents of fishes (1977-1981) and stable isotopes of fishes, invertebrates, and basal resources (1994) were collected from spikerush marsh, sawgrass ridge, and alligator pond habitats in Shark River Slough, Everglades National Park, Florida, USA. These data were used to quantify diet, trophic niche area, trophic position, basal resource use and how these metrics vary among size classes, seasons, and habitats. Data collection is complete. These data support Flood et al. (2023). Associated R code will be made available through Peter Flood's GitHub: https://github.com/pjflood/historic_everglades_aquatic_food_web. References: Flood, Peter J., William F. Loftus, and Joel C. Trexler. "Fishes in a seasonally pulsed wetland show spatiotemporal shifts in diet and trophic niche but not shifts in trophic position." Food Webs 34 (2023): e00265. https://doi.org/10.1016/j.fooweb.2022.e00265
FIG. 5 in Trophic position of some Late Devonian-Carboniferous (Mississippian) conodonts revealed on carbon organic matter isotope signatures: a case study of the East European basin
FIG. 5. — δ13Cdistribution along the facies profile plotted for dominating taxa (latest Famennian-middle Tournaisian; Kamenka River section org
FIG. 3 in Trophic position of some Late Devonian-Carboniferous (Mississippian) conodonts revealed on carbon organic matter isotope signatures: a case study of the East European basin
FIG. 3. — Distribution of δ13Cvalues among conodonts having different morphological types of P1 elements. Scale bar: 0.1 mm. org
FIG. 2 in Trophic position of some Late Devonian-Carboniferous (Mississippian) conodonts revealed on carbon organic matter isotope signatures: a case study of the East European basin
FIG. 2. — Lithology, biostratigraphy, and facies distribution of the Kamenka River section (Pechora Craton). Legend: 1, limestone; 2, clayey limestone; 3, clay; 4, cherty nodules; 5, flat lamination; 6, wavy lamination.
FIG. 1 in Trophic position of some Late Devonian-Carboniferous (Mississippian) conodonts revealed on carbon organic matter isotope signatures: a case study of the East European basin
FIG. 1. — Localization of the sites under consideration: A, Generalized map of Eastern Europe; rectangles mark the localities: 1, Pechora Craton; 2, Voronezh Anteclise (Kamenka Quarry and Russkiy Brod Quarry sections); 3, Ilmen Lake region (Chudovo section, Syas River section, Ilmen Lake borehole 8, Ilmen Lake section); 4, Chimbulat Quarry. B, Map of Pechora Craton; C, Scheme of outcrops' position in the Kozhva River basin.
Dataset for: Integrated trophic position as a proxy for food-web complexity
<div> <p>There are two distinct approaches to describing the distributions of biomass and species in food webs: one to consider them as discrete trophic levels (TLs); and the other to consider them as continuous trophic positions (TPs). Bridging the gap between these two perspectives presents a non-trivial challenge in integrating biodiversity and food-web structure.</p> <p>Food Network Unfolding (FNU) is a technique used to bridge this gap by partitioning the biomass of species into integer TLs to compute three complexity indices, namely vertical (<em>D</em><sub>V</sub>), horizontal (<em>D</em><sub>H</sub>), and range (<em>D</em><sub>R</sub>) diversity (<em>D</em> indices), through decomposition of Shannon's index <em>H'</em>. Using FNU, the food web (a network of species with unique TPs) is converted to a linear food chain (a biomass distribution at discrete TLs). This enables us to expect that the unfolded biomass within species decreases exponentially as the TL increases. Under this condition, the mean TL value in unfolded food chains is hypothesized to have an exponential relationship with the vertical diversity, <em>D</em><sub>V</sub>. To explore this, we implemented FNU and calculated <em>D</em> indices for food webs publicly available at EcoBase (<em>n</em> = 158) and calculated the integrated TP (iTP), defined as the biomass-weighted average TP of a given food web. The iTP corresponds to the mean TL in unfolded food chains and can be empirically measured through compound-specific isotope analysis of amino acids (CSIA-AA).</p> <p>Although our analysis is biased towards marine ecosystems, we revealed an exponential relationship between iTP and <em>D</em><sub>V</sub>, suggesting that iTP can serve as a measurable proxy for <em>D</em><sub>V</sub>. Furthermore, we found a positive correlation between the iTP observed in the total communities (total iTP) and the iTPs of partial communities consisting only of species with 2.0 ≤ TP < 3.0 (partial iTP; <em>r<sup>2</sup></em> = 0.48), suggesting that <em>D</em><sub>V</sub> can be predicted using partial iTP.</p> <p>Our findings suggest that the net effect of species diversity, excluding the effect of biomass (corresponding to <em>H'</em> − <em>D</em><sub>V</sub>), on food-web complexity can be revealed by combining CSIA-AA with biodiversity analysis (e.g., environmental DNA).</p> </div>
Figure. Constrained ordination plot as produced from canonical correspondence analysis (CCA). The variability of environmental variables is summarized on Axis 1 and Axis 2 of the constrained biplot, explaining the variability of the trophic groups included in the red fox's diet. Trophic groups are shown with black line (unfilled) pyramids, whereas environmental variables are shown with black filled pyramids. Proximity and distance of response centroids to predictor centroids indicate positive and negative correlations between them, respectively. in Factors affecting the diet of the red fox (Vulpes vulpes) in a heterogeneous Mediterranean landscape
Figure. Constrained ordination plot as produced from canonical correspondence analysis (CCA). The variability of environmental variables is summarized on Axis 1 and Axis 2 of the constrained biplot, explaining the variability of the trophic groups included in the red fox's diet. Trophic groups are shown with black line (unfilled) pyramids, whereas environmental variables are shown with black filled pyramids. Proximity and distance of response centroids to predictor centroids indicate positive and negative correlations between them, respectively.
Figure 2. The relationship between relative gut length and trophic position for the 6 in Tissue pH and gut ecomorphology in six freshwater teleosts occupying different trophic levels
Figure 2. The relationship between relative gut length and trophic position for the 6 freshwater fish species. (a) Relative gut length is presented in percent of body length; (b) Relative gut length is presented in percent of total length. Averaged values of trophic position (TP) from the study by Zhang et al. (2013). Grey and black circle dots correspond to TP for stable isotope analysis (SIA) and for gut content analysis (GCA), respectively. Dashed line represents the linear fitting of relative gut length and TP for SIA, while solid line represents the linear fitting of relative gut length and TP for GCA.
Dataset for: Integrated trophic position as a proxy for food-web complexity
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Data from: The temporal window of ecological adaptation in postglacial lakes: a comparison of head morphology, trophic position and habitat use in Norwegian threespine stickleback populations
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Habitat corridors alter relative trophic position of fire ants
Habitat fragmentation disrupts species movement, leading to local extinctions and altered community structure. Habitat corridors, which connect isolated patches of habitat and facilitate movement between patches, provide a potential solution to these negative impacts. However, most studies to date have examined the movement of species alone without considering emergent effects on the community (e.g., altered trophic structure). We use large-scale, experimental landscapes and nitrogen stable isotopes ratios (delta-N-15) of a common generalist consumer (the fire ant, Solenopsis invicta) to determine how corridors affect trophic structure. Thus, because the fire ant is a species whose trophic position is flexible and whose diet typically reflects local prey availability, we assume that shifts in fire ants' trophic position between connected and isolated patches are likely to reflect shifts in patch trophic structure. We found that colonies in isolated patches had lower means and ranges of delta-N-15 than colonies in otherwise similar connected patches, suggesting that corridors may increase fire ants' trophic position and breadth, respectively. Previous work in our landscapes documented higher species richness of plants in connected than unconnected patches. Patch means of ant delta-N-15 were positively correlated with plant richness, suggesting that increased plant richness may influence the observed responses in fire ant delta-N-15. Together these results suggest that fragmentation may reduce trophic position and narrow trophic breadth of dietary generalists such as the fire ant. These shifts likely reflect an alteration of food webs in isolated patches. Our results suggest that corridors may be effective in preventing or reducing such alterations.
FIG. 6 in Trophic position of some Late Devonian-Carboniferous (Mississippian) conodonts revealed on carbon organic matter isotope signatures: a case study of the East European basin
FIG. 6. — Bivariate plot for bulk carbonate δ13Cand conodont δ13Cvalues. carb org
FIG. 4 in Trophic position of some Late Devonian-Carboniferous (Mississippian) conodonts revealed on carbon organic matter isotope signatures: a case study of the East European basin
FIG. 4. — Organic carbon isotope compositions of conodonts measured in the study.
An invasive amphibian drives antipredator responses in two prey at different trophic positions
<p>Generalist invasive predators consume prey at different trophic levels and generate drastic changes in local communities. However, the long-term effects of predation may be reduced by eco-evolutionary responses of native populations. The capacity of prey species distributed across the trophic network to develop antipredator responses may determine the ecosystem potential to buffer against the invader. The African clawed frog is a major invader on several continents. Because of its large size, generalist diet, and aquatic lifestyle, we predicted the development of antipredator responses in prey species at different trophic levels. We tested for behavioral shifts between populations within and outside the invasive range in the herbivorous snail Physella acuta and the predatory heteropteran, the backswimmer Notonecta glauca. We detected antipredator responses in both prey species. In sympatry, P. acuta stayed higher in the water column, while N. glauca spent more time swimming underwater and less time surfacing when the predator cues were present. In allopatry, P. acuta dived deeper and N. glauca spent more time surfacing and stayed longer still underwater. In both species, sympatric populations showed evidence of olfactory recognition of the frog. Our results show that the introduction of a top predator like Xenopus laevis in the pond ecosystem drives behavioral antipredator responses in species across the trophic network. Eco-evolutionary processes may allow some degree of long-term resilience of pond communities to the invasion of X. laevis.</p>
Data from: Trophic position and niche overlap of an Asian weatherfish (Misgurnus bipartitus), western tubenose goby (Proterorhinus semilunaris), and native benthic fish species
<p>The dataset belonging to the paper "Trophic position and niche overlap of an Asian weatherfish (<i>Misgurnus bipartitus</i>), western tubenose goby (<i>Proterorhinus semilunaris</i>), and native benthic fish species" published in Aquatic Invasions (paper in press; doi link will be added later), is provided here. The dataset consists of δ13C and δ15N (‰) stable isotope ratios of taxa of fish, macroinvertebrates, plants, alga, and soil. If applicable, the length of the taxon was included. Below, methodological information is provided on the study site, the sampling process, the sampling preparation, and the stable isotope analysis. For references, see the published paper in Aquatic Invasions.</p><p> </p><p><i>Study site</i></p><p>The study site concerned a section of the lowland brook Tungelroysebeek (51°14.38'N, 005°52.086'E – 51°14.26'N, 005°47.77'E) near the village Tungelroy in the Province of Limburg, the Netherlands. This brook of 35 km length has several tributaries before discharging into the River Meuse. Over most of its course, the brook was meandering and had a well-developed riparian and hydrophyte vegetation. During sampling the mean water temperature was 16.0 °C, conductivity 664 µS/cm, pH 7.3, water velocity 0.2 m/s, depth 70 cm, and Secchi depth 60 cm. The brook width ranged between 5-8 m and its bed substrate predominantly consisted of sand.</p><p> </p><p><i>Sampling</i></p><p>Samples of fish, macroinvertebrates, macrophytes, dead organic material, and bottom soil substrate were collected in October 2019. The samples were collected in the stretch of the brook that is denoted in Fig. 1 of the paper. Fish were caught using handheld electrofishing equipment (Bretschneider EFGI 650). After catching, the fish were euthanized using a neutralized benzocaine solution of 100 mg l-1. Macroinvertebrates were collected using 70x55 cm dip nets with a mesh size of 1 mm. Helophytes, floating-leaved, and submerged aquatic macrophytes were collected by hand. Soil samples were collected by means of a hollow soil sampling tube with a diameter of 5 cm. A Nikon SMZ800 stereo microscope with a 10-63 magnification was used for the identification of small macroinvertebrates.</p><p> </p><p><i>Sample preparation </i></p><p>All samples were transported to the laboratory and stored separately at -18° C until preparation. To obtain muscle samples a piece of 0.5-1 cm of the dorsal tissue of each fish was dissected. Muscle tissue samples were dissected from fish, crayfish, and unionid mussels. Other macroinvertebrates were stored alive for two days at 5 °C to empty their intestinal contents. Subsequently, these invertebrates were rinsed with tap water and then with demineralized water before processing. From unionid mussels, muscle tissue of a similar size was dissected. Of small mollusks, all soft body tissues were used. For small mollusks and other macroinvertebrates, individuals of the same species were pooled to obtain enough material (0.22-0.26 mg) for analyses. For crayfish, muscle tissue of the abdomen was used while the intestine was removed. The stems, leaves, and roots of individual plants were pooled. </p><p>After preparation, all samples were stored at -80 °C until freeze drying. Freeze drying was carried out at -90 °C for 24-48 hours for fish and macroinvertebrate samples. Plant, dead organic material, and soil samples were freeze dried at least 48 hours. After freeze drying, the samples were grounded with aluminum balls, for 2 min at 30 rpm, using a Retsch MM 400. Subsequently, the grounded samples were weighted in tin cups (Elemental Microanalysis 8 x 5 mm) and prepared for isotope analyses. For the fish and invertebrate samples, 0.22-0.26 mg was weighted. For plants and soil, separate samples were weighted for carbon (10 mg) and nitrogen (40 mg) analyzes. </p><p> </p><p><i>Stable isotope analyses</i></p><p>Carbon and nitrogen stable isotopes were measured using a Thermo Scientific FLASH 2000 HT Elemental Analyzer with a Thermo Scientific DELTA V Advantage Next Generation Isotope Ratio mass spectrometer. Reference gasses were calibrated with the IAEA standards (IAEA-N-2 and IAEA-CH-6), with a maximum deviation of 0.15‰. As an internal standard control, caffeine was used and the 13C/12C and 15N/14N of every sample were determined (in ‰). The isotope ratios (R) δ13C and δ15N are relative to Vienna PDB and atmospheric N2 and were calculated by:</p><p> </p><p>δ13C or δ15N = (Rsample/Rstandard − 1) * 1000</p><p> </p><p>Abstract </p><p>Co-occurring and morphologically similar species have adapted to differential niches for minimizing competition. An invasive alien species can occupy an 'empty niche' in introduced ranges. Alternatively, the invader may occupy an overlapping niche and compete with native species to a certain degree. In a Western European lowland brook with high nutrient loads, we studied a benthic community of five fish species, including two alien species: an Asian weatherfish (<i>Misgurnus bipartitus</i>) and the western tubenose goby (<i>Proterorhinus semilunaris</i>). The native species concerned stone loach (<i>Barbatula barbatula</i>), spined loach (<i>Cobitis taenia</i>), and gudgeon (<i>Gobio gobio</i>). Because of the unknown effects of the invaders on native benthic fish species, the trophic position, isotopic niche overlap, and potential food competition among these species were identified using nitrogen and carbon stable isotopes. The trophic levels of the five fish species indicated that they are secondary consumers. Body size of native fish species correlated significantly negative with their δ15N (‰) signature, in contrast with the invaders indicating that the latter are generalists. Significant isotopic niche overlap was observed among all benthic species. The degree of niche overlap of <i>M. bipartitus </i>was the highest (91.8%) with the <i>G. gobio</i>. <i>Proterorhinus semilunaris</i> had the highest degree of niche overlap (91.2%) with the (<i>B. barbatula</i>. It was notable that the observed niche overlap between the native <i>B. barbatula </i>and <i>C. taenia</i> was high (99.2%). Overlap between <i>M. bipartitus</i> and <i>P. semilunaris</i> was low (8.9% overlap), indicating little resource competition between these alien species. Native species showed wider isotopic niches than the invaders. Bayesian mixing models revealed that native and alien species slightly differ in their main diet. The results suggest that the invaders are plastic in their resource use, leading to niche differentiation and promoting co-existence of benthic fish species.</p>
Stable isotopes unravel the feeding mode-trophic position relationship in trematode parasites
<div class="WordSection1"> <p><span>1. Stable isotopes have been sporadically used over the last two decades to characterise host-parasite trophic relationships. The main reason for this scarcity is the lack of an obvious pattern in the ratio of nitrogen stable isotope values (<i>δ</i><sup>15</sup>N) of parasites in comparison to their host tissues, which would be key to understand any host-parasite system dynamics. </span></p> <p><span>2. To circumvent this, we focused on a single snail host, <i>Zeacumantus subcarinatus</i>, and three of its trematode parasites. </span></p> <p><span>3. We used stable isotopes to investigate each host-trematode trophic relationship and shed light on the mechanisms utilised by the parasite to reroute its hosts' biomass. </span></p> <p><span>4. All our trematodes were found to be <sup>15</sup>N-enriched compared to their host, with their <i>δ</i><sup>15</sup>N values strongly related to their feeding behaviours: passive vs active. It was possible to 'rank' these parasite species and assess their 'relative' trophic position using <i>δ</i><sup>15</sup>N values. We also demonstrated that including a broader range of samples (e.g. host food and faeces, multiple parasite life stages) helped understand the metabolic mechanisms used by the various participants, and that using carbon stable isotope values and C:N ratios allowed to identify an important lipid requirement of these trematode parasites. Finally, we show how critical it is to not ignore parasitic infections as they can have a great influence on their host's trophic position.</span></p> <p><span>5. We have shown that by focussing on a single host species and a single taxonomic group of parasites, we can remove a certain amount of variation recorded by broader isotope studies. We hope that these data will ultimately improve our ability to place parasites in food webs, and thus improve our understanding of the connections and interactions that dictate food web dynamics. </span></p> </div>
Data from: Challenging trophic position assessments in complex ecosystems: calculation method, choice of baseline, trophic enrichment factors, season and feeding guild do matter. A case study from Marquesas Islands coral reefs
<p>Assessments of ecosystem functioning are a fundamental ecological challenge and an essential foundation for ecosystem-based management. An understanding of species trophic positions (TP) is essential to characterize food web architecture. However, despite the intuitive nature of the concept, empirically estimating TP is a challenging task due to the complexity of trophic interaction networks. Various alternative methods are proposed to assess TPs, including different approaches to account for the different sources of organic matter at the base of the food web (the "baseline"). However, it is often not clear which methodological approach and which baseline choices are the most reliable. Using an ecosystem-wide assessment of a tropical reef (Marquesas Islands, French Polynesia, with available data for 70 coral reef invertebrate and fish species), we tested whether different commonly used TP estimation methods yield similar results and, if not, whether it is possible to identify the most reliable method. We found significant differences in TP estimates of up to 1.7 TP for the same species, depending on the method and the baseline used. When using bulk stable isotope data, the choice of the baseline significantly impacted TP values. Indeed, while δ<sup>15</sup>N values of macroalgae led to consistent TP estimates, those using phytoplankton generated unrealistically low TP estimates. The use of a conventional enrichment factor (i.e. 3.4 ‰) or a "variable" enrichment factor (i.e. according to feeding guilds) also produced clear discrepancies between TP estimates. Regarding the use of different calculation methods, TPs obtained with δ<sup>15</sup>N values of source amino acids (compound specifics isotope analysis) were close to those assessed with macroalgae, but evidenced the opposite seasonal pattern, with significantly lower TPs in winter than in summer for the majority of assessed species, with particularly pronounced differences for lower TP species. We use the observed differences to discuss possible drivers of the diverging TP estimates and the potential ecological implications.</p>
Body size, trophic position, and the coupling of different energy pathways across a saltmarsh landscape
<p>Here, we listed the bulk stable isotope values (δ13C and δ15N) and body size measurements of organisms that were analyzed in the manuscript "Body size, trophic position, and the coupling of different energy pathways across a saltmarsh landscape", published in Limnology and Oceanography Letters. Our dataset is a compilation of samplings obtained by the Southern Louisiana marsh food webs project within the Coastal Waters Consortium (CWC) II (Lopez-Duarte et al. 2017a [https://doi.org/10.7266/N7XS5SGD], Lopez-Duarte et al. 2017b [https://doi.org/10.7266/N79W0CJW], Polito et al. 2019 [https://doi.org/10.7266/n7-6277-1216]). The dataset consists of 1563 individual samples from 77 taxa, including basal sources (plants, phytoplankton, detritus, and microphytobenthos), fishes, invertebrates (insects, crustaceans, and spiders), infauna, seaside sparrows (Ammospiza maritima), and marsh rice rats (Oryzomys palustris). Samplings were conducted in three sites, Bay Sansbois, Bay Batiste, and West Pointe à la Hache, located in northeastern Barataria Bay. Bay Sansbois and Bay Batiste were sampled in May and October 2015, and May 2016, whereas West Pointe à la Hache was sampled only in May 2016. Body size measurements are available for 59% of all samples (52 taxa) while δ13C and δ15N are available for all samples.</p>
Data from: Challenging trophic position assessments in complex ecosystems: calculation method, choice of baseline, trophic enrichment factors, season and feeding guild do matter. A case study from Marquesas Islands coral reefs
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Body size, trophic position, and the coupling of different energy pathways across a saltmarsh landscape
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