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451 results for “food webs”
Data from: Assessing the effect of predator control on an endangered goose population subjected to predator-mediated food web dynamics
1. Assessing the effectiveness of conservation actions to halt population declines is challenging when confounded by other factors. We assessed whether culling of red fox, a predator currently increasing in the sub-Arctic, contributed to recent recovery of the critically endangered Fennoscandian population of Lesser White-fronted Goose Anser erythropus, while controlling for potentially confounding food web dynamics. 2. Using 19 years of data, 10 before and 9 after the implementation of annual red fox culling, we estimated the effect of this action on annual performance of the goose population. We corrected for the potentially confounding effects of cyclic rodent dynamics and semi-domestic reindeer carrion abundance, both of which are expected to trigger predator functional and numerical responses, as well as for annual variation in spring phenology. 3. Goose reproductive success fluctuated in synchrony with the rodent cycle and was negatively related to abundant carrion. When accounting for these aspects of food web dynamics, there was no evidence for an effect of red fox culling on reproductive success. There was, however, a tendency for fox culling to increase adult survival. 4. Our analysis suggests that goose performance in their breeding area is influenced by fluctuating offspring predation, mediated by mainly natural (rodents) and partly anthropogenic (semi-domestic reindeer) dynamic components of the food web. 5. Synthesis and applications. The effect of a decade-long red fox culling on goose reproductive success and survival is currently uncertain. This is despite the fact that predation drives reproductive success through changes in rodent and reindeer carrion abundance. New management actions may consist of regulation of reindeer herd sizes and/or removal of carcasses to reduce the subsidizing effect of reindeer carrion on mesopredators. Getting robust evidence regarding the impact of red fox culling on population recovery depends on continuing research to disentangle food web dynamics and efficiency of management actions.
Data from: Land use alters trophic redundancy and resource flow through stream food webs
1. The changes to physical and chemical ecosystem characteristics as a response to pervasive and intensifying land use have the potential to alter the consumer-resource interactions and to rewire the flow of energy through entire food webs. 2. We investigated these structural and functional properties of food webs in stream ecosystems distributed across woodland, agricultural and urban areas in the Zagreb region of Croatia. We compared resource availability and consumer diet composition using stable isotope mixing models and tested how the isotopic variance of basal resources, primary consumers, macroinvertebrate predators, and other food-web characteristics change with different land use types. 3. Combination of increased loading and altered composition of nutrients, lower water discharge and higher light availability at urban sites likely promoted the contribution of aquatic macrophytes to diets of primary consumers. Macroinvertebrate predators shifted their diet, relying more on active filterers at urban sites relative to woodland and agricultural sites. Urban food webs also had lower trophic redundancy (i.e. fewer species at each trophic level) and a more homogenised energy flow from lower to higher trophic levels. There was no effect of land use on isotopic variation of basal resources, primary consumers or macroinvertebrate predators, but all these trophic groups at urban and agricultural sites were 15N-enriched relative to their counterparts in woodland stream food webs. 4. The physical and chemical ecosystem characteristics associated with intensive land use altered the resource availability, trophic redundancy and the flow of energy to other trophic levels, with potentially negative consequences for community dynamics and ecosystem functioning. These empirical findings indicate that reducing nutrient pollution, agricultural runoffs and maintaining riparian vegetation can mitigate the impacts of land use on structure and function of stream ecosystems.
Data from: Exceptional body sizes but typical trophic structure in a Pleistocene food web
In this study, we focused on the exceptionally large mammals inhabiting the Americas during the Quaternary period and the paramount role of body size in species ecology. We evaluated two main features of Pleistocene food webs: the relationship between body size and (i) trophic position and (ii) vulnerability to predation. Despite the large range of species sizes, we found a hump-shaped relationship between trophic position and body size. We also found a negative trend in species vulnerability similar to that observed in modern faunas. The largest species lived near the boundary of energetic constraints, such that any shift in resource availability could drive these species to extinction. Our results reinforce several features of megafauna ecology: (i) the negative relationship between trophic position and body size implies that large-sized species were particularly vulnerable to changes in energetic support; (ii) living close to energetic imbalance could favour the incorporation of additional energy sources, for example, a transition from a herbivorous to a scavenging diet in the largest species (e.g. Megatherium) and (iii) the interactions and structure of Quaternary megafauna communities were shaped by similar forces to those shaping modern fauna communities.
Data from: Eating up the world's food web and the human trophic level
Trophic levels are critical for synthesizing species' diets, depicting energy pathways, understanding food web dynamics and ecosystem functioning, and monitoring ecosystem health. Specifically, trophic levels describe the position of species in a food web, from primary producers to apex predators (range, 1–5). Small differences in trophic level can reflect large differences in diet. Although trophic levels are among the most basic information collected for animals in ecosystems, a human trophic level (HTL) has never been defined. Here, we find a global HTL of 2.21, i.e., the trophic level of anchoveta. This value has increased with time, consistent with the global trend toward diets higher in meat. National HTLs ranging between 2.04 and 2.57 reflect a broad diversity of diet, although cluster analysis of countries with similar dietary trends reveals only five major groups. We find significant links between socio-economic and environmental indicators and global dietary trends. We demonstrate that the HTL is a synthetic index to monitor human diets and provides a baseline to compare diets between countries.
Data from: The effects of food web structure on ecosystem function exceeds those of precipitation
Ecosystems are being stressed by climate change, but few studies have tested food web responses to changes in precipitation patterns and the consequences to ecosystem function. Fewer still have considered whether results from one geographic region can be applied to other regions, given the degree of community change over large biogeographic gradients. We assembled, in one field site, three types of macroinvertebrate communities within water-filled bromeliads. Two represented food webs containing both a fast filter feeder-microbial and slow detritivore energy channels found in Costa Rica and Puerto Rico, and one represented the structurally simpler food webs in French Guiana, which only contained the fast filter feeder-microbial channel. We manipulated the amount and distribution of rain entering bromeliads, and examined how food web structure mediated ecosystem responses to changes in the quantity and temporal distribution of precipitation. Food web structure affected the survival of functional groups in general, and ecosystem functions such as decomposition and the production of fine particulate organic matter. Ecosystem processes were more affected by decreased precipitation than were the abundance of microorganisms and metazoans. In our experiments, the sensitivity of the ecosystem to precipitation change was primarily revealed in the food web dominated by the single filter feeder-microbial channel because other top-down and bottom-up processes were weak or absent. Our results show stronger effects of food web structure than precipitation change per se on the functioning of bromeliad ecosystems. Consequently, we predict that ecosystem function in bromeliads throughout the Americas will be more sensitive to changes in the distribution of species, rather than to the direct effects caused by changes in precipitation.
Data from: Eelgrass (Zostera marina) food web structure in different environmental settings
This study compares the structure of eelgrass (Zostera marina L.) meadows and associated food webs in two eelgrass habitats in Denmark, differing in exposure, connection to the open sea, nutrient enrichment and water transparency. Meadow structure strongly reflected the environmental conditions in each habitat. The eutrophicated, protected site had higher biomass of filamentous algae, lower eelgrass biomass and shoot density, longer and narrower leaves, and higher above to below ground biomass ratio compared to the less nutrient-enriched and more exposed site. The faunal community composition and food web structure also differed markedly between sites with the eutrophicated, enclosed site having higher biomass of consumers and less complex food web. These relationships resulted in a column shaped biomass distribution of the consumers at the eutrophicated site whereas the less nutrient-rich site showed a pyramidal biomass distribution of consumers coupled with a more diverse consumer community. The differences in meadow and food web structure of the two seagrass habitats, suggest how physical setting may shape ecosystem response and resilience to anthropogenic pressure. We encourage larger, replicated studies to further disentangle the effects of different environmental variables on seagrass food web structure.
Data from: Linking songbird nest predation to seedling density: sugar maple masting as a resource pulse in a forest food web
The ecological literature presents considerable evidence for top-down forcing on the maintenance of species diversity. Yet, in temperate forests, bottom-up forces often exert a strong influence on ecosystem functioning. Here, we report on the indirect influence of a pulsed resource, sugar maple (Acer saccharum) seed production, on nest survival in a migratory songbird. We hypothesized that seed production in year t would determine daily nest survival rate in year t + 1 through its effects on seed-eating rodents. We used the density of sugar maple seedlings (with cotyledons) in year t + 1 as a proxy for seed production in year t and predicted that it would be inversely related to songbird nest survival the same year. We estimated the density of sugar maple seedlings, eastern chipmunk (Tamias striatus) activity, and daily nest survival rate in the ovenbird (Seiurus aurocapilla) over four successive years in a northern hardwood forest of New Brunswick, Canada. Seedling density varied by two orders of magnitude between years, whereas an index of chipmunk activity changed by an order of magnitude. Both variables were positively correlated and negatively correlated to daily nest survival rate. A logistic-exposure model including only seedling density received the greatest level of support (lowest AICc). Previous studies have reported the effect of sugar maple masting on seed-eating rodent populations, but the strong link we report between seedling density and songbird nest survival is novel. A nocturnal seed-eating nest predator, deer mouse (Peromyscus maniculatus), was not considered in our models, which may explain why chipmunk was not the best predictor of daily nest survival rate. The trophic linkages we observed are remarkably strong for a temperate forest ecosystem and might become more prevalent in northeastern North America, at least on calcium-rich soils, with the loss of large-diameter beech trees as a result of beech bark disease.
Data from: Reduced tillage, but not organic matter input, increased nematode diversity and food web stability in European long-term field experiments
Soil nematode communities and food web indices can inform about the complexity, nutrient flows and decomposition pathways of soil food webs, reflecting soil quality. Relative abundance of nematode feeding and life-history groups are used for calculating food web indices, i.e. maturity index (MI), enrichment index (EI), structure index (SI) and channel index (CI). Molecular methods to study nematode communities potentially offer advantages compared to traditional methods in terms of resolution, throughput, cost and time. In spite of such advantages, molecular data have not often been adopted so far to assess the effects of soil management on nematode communities and to calculate these food web indices. Here, we used high-throughput amplicon sequencing to investigate the effects of tillage (conventional vs reduced) and organic matter addition (low vs high) on nematode communities and food web indices in ten European long-term field experiments and we assessed the relationship between nematode communities and soil parameters. We found that nematode communities were more strongly affected by tillage than by organic matter addition. Compared to conventional tillage, reduced tillage increased nematode diversity (23% higher Shannon diversity index), nematode community stability (12% higher MI), structure (24% higher SI), and the fungal decomposition channel (59% higher CI), and also the number of herbivorous nematodes (70% higher). Total and labile organic carbon, available K and microbial parameters explained nematode community structure. Our findings show that nematode communities are sensitive indicators of soil quality and that molecular profiling of nematode communities has the potential to reveal the effects of soil management on soil quality.
Data from: Exploring the temporal variability of a food web using long-term biomonitoring data
Ecological communities are constantly being reshaped in the face of environmental change and anthropogenic pressures. Yet, how food webs change over time remains poorly understood. Food web science is characterized by a trade-off between complexity (in terms of the number of species and feeding links) and dynamics. Topological analysis can use complex, highly resolved empirical food web models to explore the architecture of feeding interactions but is limited to a static view, whereas ecosystem models can be dynamic but use highly aggregated food webs. Here, we explore the temporal dynamics of a highly resolved empirical food web over a time period of 18 years, using the German Bight fish and benthic epifauna community as our case study. We relied on long-term monitoring ecosystem surveys (from 1998 to 2015) to build a metaweb, i.e. the meta food web containing all species recorded over the time span of our study. We then combined time series of species abundances with topological network analysis to construct annual food web snapshots. We developed a new approach, "node-weighted" food web metrics by including species abundances to represent the temporal dynamics of food web structure, focusing on generality and vulnerability. Our results suggest that structural food web properties change through time; however, binary food web structural properties may not be as temporally variable as the underlying changes in species composition. Further, the node-weighted metrics enabled us to detect that food web structure was influenced by changes in species composition during the first half of the time series and more strongly by changes in species dominance during the second half. Our results demonstrate how ecosystem surveys can be used to monitor temporal changes in food web structure, which are important ecosystem indicators for building marine management and conservation plans.
Planktonic Food Web Structure at a Coastal Site
<p>Fluorescent Labeled Bacteria (FLB) Uptake Experiment- whole (unfiltered) seawater (WSW) was collected on the HOE Legacy 2A cruise near station ALOHA, Hawaii. Water was collected from the Niskin into 3, 2.3L bottles. FLBs were added to the bottles, and 100ml was removed and preserved from each bottle at T0. Bottles were incubated on-deck for 1h, at which point another 100ml was preserved from each bottle. Preserved samples were filtered onto 2.0um blackened polycarbonate filters and stained with DAPI. Slides were stored at -20C. </p>
Data from: Exploring trophic role similarity and phylogenetic relatedness between species in food webs
<p>Understanding the mechanism shaping species assemblage is a fundamental goal in ecology. In the past two hypotheses have been suggested. One is the filtering hypothesis where environmental factors select for species of similar traits such that they co-occurring in similar niches. The other is the competitive exclusion hypothesis where related species are driven far apart by competition such that they over-disperse across different niches. Here, we investigate the relationship between species assemblage and their phylogenetic relatedness from the network perspective by using five different ecosystems ranging from oceans to an inland lake. We quantified the similarity in species'network positions in a food web and cluster them into different trophic role groups; and from an on-line database we quantified their phylogenetic distances. We then investigated whether related species tend to under or overdisperse across different trophic role groups. In general, our result suggests the environmental filtering process is the dominant force shaping the species assemblage of those ecosystems. However, there are some possible cases where related species are driven by competition such that they evolve to adopt different trophic roles in relatively closed ecosystems.</p>
Resource-driven colonization by cod in a high Arctic food web
Climate change is commonly associated with many species redistributions and the influence of other factors may be marginalized, especially in the rapidly warming Arctic. The Barents Sea, a high latitude large marine ecosystem in the Northeast Atlantic has experienced above average temperatures since the mid 2000's with divergent bottom temperature trends at sub-regional scales. Concurrently, the Barents Sea stock of Atlantic cod Gadus morhua, one of the most important commercial fish stocks in the world, increased following a large reduction in fishing pressure and expanded north of 80°N. We examined the influence of food availability and temperature on cod expansion using a comprehensive data set on cod stomach fullness stratified by sub-regions characterized by divergent temperature trends. We then tested whether food availability, as indexed by cod stomach fullness, played a role in cod expansion in sub-regions that were warming, cooling or showed no trend. The greatest increase in cod occupancy occurred in three northern sub-regions with contrasting temperature trends. Cod apparently benefited from initial high food availability in these regions that previously had few large-bodied fish predators. The stomach fullness in the northern sub-regions declined rapidly after a few years of high cod abundance, suggesting that the arrival of cod caused a top down effect on the prey base. Prolonged cod residency in the northern Barents Sea is, therefore, not a certainty.
Data from: Calcium and strontium stable isotopes reveal similar behaviors of essential Ca and non-essential Sr in stream food webs
<p>Recent studies showed the potential of stable isotopes of the macronutrient calcium (δ<sup>44/40</sup>Ca) and non-essential strontium (δ<sup>88/86</sup>Sr) as new trophic level indicators in terrestrial vertebrates and marine teleost fishes. In this study, we tested whether similar Ca and Sr isotopic fractionation trends existed in macroinvertebrate dominated stream food webs compared to vertebrates despite their physiological differences. We have determined the δ<sup>44/40</sup>Ca and δ<sup>88/86</sup>Sr values as well as the <sup>87</sup>Sr/<sup>86</sup>Sr ratios of stream macroinvertebrates and of small gobies and of their potential metal sources (stream water, periphyton, terrestrial plant litter) collected in May and November 2018 in upper and lower reaches of two streams in the Lake Biwa catchment, central Japan.</p> <p>The data are organized in different spreadsheets for each sample type (Rock cobbles, Stream water, Periphyton, Plant litter, Aquatic macroinvertebrates, fishes). Each spreadsheet contains information of the sample type including stream name (Ado, Yasu), stream location (Upper, Lower), sampling month (May, November), where relevant the order and scientifc name of specimens, the δ<sup>44/40</sup>Ca and δ<sup>88/86</sup>Sr values with two standard deviations, the <sup>87</sup>Sr/<sup>86</sup>Sr ratios with two standard errors, the Ca and Sr concentrations and the calculated log(Sr/Ca) ratios of the samples.</p>
Impacts on food web properties of island invertebrate communities vary between different human land uses
<p><span>Human land use is of growing concern for island ecosystems. Besides direct impacts on biodiversity, land uses can alter the functioning and structure of ecosystems. Central to this are impacts on food webs. The release of additional nutrients from human origin, habitat homogenization, or environmental filtering due to human land use can change the diet of individual consumer species (i.e., their trophic niches) and the distribution and overlap of trophic niches within a food web. However, it remains largely unclear whether the effects on food web properties vary between the different and predominant human land uses present on islands. Here, we investigated the impact of two dominant human land uses on small oceanic islands (i.e., urban and tourism development) and tested if and how different land uses on islands affect food web structure. To disentangle human land uses, we investigated islands, which were either privately owned by a tourist facility (i.e., exclusively tourism land use) or experienced urban development from the local population (i.e., urban land use), or remained uninhabited, serving as reference sites free of direct land use. Using stable isotope analysis, we show that isotope signature, trophic (isotopic) niches, and overall food web properties of the investigated island invertebrate communities were significantly changed under both land use regimes. While trophic diversity was reduced and trophic niche widths increased under tourism land use, the investigated food webs showed reduced trophic diversity at the food web base and a more uneven trophic niche distribution under urban land use. In summary, these findings show that different human land uses can have contrasting impacts on oceanic island food webs. As oceanic islands experience rapidly growing human land conversion, our results indicate that they may also face increasing yet unpredictable long-term changes in food web dynamics.</span></p>
Even short-term revegetation complicates soil food webs and strengths their links with ecosystem functions
<p>Degradation of dryland ecosystems is a worldwide problem caused by climate change and human activities. To restore these degraded ecosystems, governments have implemented projects that often include revegetation, but we still lack an understanding of how soil food webs and ecosystem functions are affected by revegetation. By conducting a large-scale revegetation experiment under two degradation intensities (low and high) on the Inner Mongolian degraded grassland, we tested the effects of revegetation on primary producers (plants), key components of soil food webs (bacteria, fungi, and nematodes), and ecosystem functions (soil C and N mineralization). After 4 years, revegetation greatly increased the biomass of plants and soil bacteria and fungi but had less effects on soil nematode functional groups. Revegetation increased vegetation and bacterial diversities and soil C and N mineralization rates, altered the structures of vegetation and soil microbial communities, but did not affect fungal or nematode diversity. The stronger effects of revegetation on plants, soil bacteria, soil fungi, and soil nematodes in plots with low degradation intensity than in plots with high degradation intensity indicated that future revegetation efforts should consider the degree of degradation. Revegetation also increased the interactions among plants, soil food webs, and ecosystem functions, indicating that the revegetation-induced changes in soil food webs could facilitate the recovery of soil nutrients and vegetation productivity in degraded grasslands. Synthesis and applications. Overall, the effects of revegetation were stronger on plants (primary producers) and soil microorganisms (intermediate trophic levels) than on soil nematodes (higher trophic levels), and even short-term revegetation increased the complexity of soil food webs and strengthened their relationships with soil functions in degraded grasslands. These results highlight the effects of restoration on multiple trophic levels in degraded drylands, and suggest that some aspects of plant-soil interactions in global drylands could be rapidly improved by appropriate restoration.</p>
Transfer efficiency of carbon, nutrients, and PUFAs in planktonic food webs under different environmental conditions
<p>We investigated the transfer of essential substances (carbon, nutrients, and polyunsaturated fatty acids) through plankton communities in 30 Polish lakes with different trophic status in the middle of summer. The results of our study revealed that different essential substances were transferred from phytoplankton to zooplankton with varying efficiencies. The average TTE of C, N, P, and the sum of ω-3 PUFA were 6.55%, 9.82%, 15.82%, 20.90%, respectively. Our results also show a large mismatch between the elemental and biochemical compositions of zooplankton and their food during the peak of the summer stagnation, which may further promote the accumulation of essential substances. There were also large differences in TTEs between trophic conditions, with the highest efficiencies in oligotrophic lakes and the lowest in dystrophic and eutrophic lakes. Therefore, our study indicates that disturbances like eutrophication and dystrophication similarly decrease the TTE of essential substances between phytoplankton and zooplankton in freshwater food webs.</p>
The influence of nutrient enrichment on riverine food web function and stability
<p>Nutrient enrichment of rivers and lakes has been increasing rapidly over the past few decades, primarily because of agricultural intensification. Although nutrient enrichment is known to drive excessive algal and microbial growth, which can directly and indirectly change the ecological community composition, the resulting changes in food web emergent properties are poorly understood. We used ecological network analysis (ENA) to examine the emergent properties of 12 riverine food webs across a nutrient enrichment gradient in the Manawatu, New Zealand. We also derive Keystone Sensitivity Indices to explore whether nutrients change the trophic importance of species in a way that alters the resilience of the communities to further nutrient enrichment or floods. Nutrient enrichment resulted in communities composed of energy inefficient species with high community (excluding microbes) respiration. Community respiration was several times greater in enriched communities and this may drive hypoxic conditions even without concomitant changes in microbial respiration. Enriched communities exhibited weaker trophic cascades, which may yield greater robustness to energy flow loss. Interestingly, enriched communities were also more structurally and functionally affected by species sensitive to flow disturbance making these communities more vulnerable to floods. </p>
Supplementary material 1 from: Lefort M, Wratten S, Cusumano A, Varennes Y, Boyer S (2017) Disentangling higher trophic level interactions in the cabbage aphid food web using high-throughput DNA sequencing. Metabarcoding and Metagenomics 1: e13709. https://doi.org/10.3897/mbmg.1.13709
OSR aphid mummy collection. Sampling location and size / Amplification success of mummies' DNA extracts by Illumina sequencing.
Data from: Untangling the complex food webs of tropical rainforest streams.
<p>This submission encompasses biological data sampled in five stream stretches at the Cananeia watershed in São Paulo State (Brazil) in 2019.</p> <p>The dataset includes:</p> <p>1) Individually measured data from invertebrates and fish.</p> <p>2) Gut content data from fish species.</p> <p>3) Stable Isotopes data from animals and basal resources.</p> <p>4) A literature compilation of trophic interactions for the species in the dataset.</p>
Data: Trait-based food web model reveals the underlying mechanisms of biodiversity-ecosystem functioning relationships
<p>Data and code related to 'Trait-based food web model reveals the underlying mechanisms of biodiversity-ecosystem functioning relationships' to reproduce figures and analyses.</p>
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
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DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
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The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.