Construction Of Food Webs Research Articles

Food-web construction and ecological effects of implementing non-traditional biomanipulation in eutrophic reservoirs in North-central China

ABSTRACT This study was undertaken to elucidate the food web structure and interspecific interactions in the lakes and reservoirs undergoing eutrophication and to assess the efficacy of lake-wide non-traditional biomanipulation (direct predation of cyanobacteria by proliferating planktivorous fish) for bloom management. Analyses of aquatic organisms and stable isotopes of basic food sources and consumers were performed for Zhangze Reservoir in North-central China. Additionally, an improved scheme based on plankton changes and interspecific interactions is proposed on this basis. Compared with other widely-studied eutrophic reservoirs, the δ 15N value of each component of the food web in Zhangze Reservoir was higher, the food chain was relatively long and the δ 13C range of fish consumers was narrower. Planktivorous fish consumed phytoplankton as their primary food source. However, the phytoplankton biomass and the percentage of cyanobacteria increased, and eutrophication did not improve. The findings concerning the composition of consumers and their food sources in Zhangze Reservoir indicate the urgent need to change the fish structure to optimise the structure of plankton community and mitigate phytoplankton overgrowth. The study findings provide a basis for the implementation of effective eutrophication management strategies in lakes and reservoirs where planktivorous fish are prevalent.

The Dietary Diversity of Holometabolous Insects and the Construction of Food Webs

The Dietary Diversity of Holometabolous Insects and the Construction of Food Webs

Brownification of freshwater promotes nitrogen-cycling microorganism growth following terrestrial material increase and ultraviolet radiation reduction

Brownification is an increasingly concerning phenomenon faced by aquatic ecosystems in the changing environments, and the microbiome plays an irreplaceable role in material circulation and food web construction. Insight into the influence of brownification on microbial communities is crucial from an ecological standpoint. In this study, we simulated brownification using a the mesocosm system and explored the relationship between the characteristics of microbial communities and brownification using excitation-emission matrix (EEM) fluorescence spectroscopy and ultraviolet (UV) spectroscopy combined with high-throughput amplicon sequencing techniques. The results showed that brownification reduced the richness of the microbial community and selectively promoted the growth of nitrogen-cycling microorganisms, including hgcI_clade, Microbacteriaceae, and Limnohabitans. Brownification affected microbial communities by altering the carbon source composition and underwater spectrum intensity; UV, blue, violet, and cyan light were significantly (p < 0.05) correlated with microbial community richness, and random forest analysis revealed that UV, C1 (microbial humic-like), and C3 (terrestrial humic-like) were the major factors significantly influencing microbiome variation. We found that brownification affected microorganisms in shallow lakes, especially nitrogen cycling microorganisms, and propose that controlling terrestrial material export is an effective strategy for managing freshwater brownification.

Typical scaled food web structure and total mercury enrichment characteristics in Xingkai Lake, China.

Different from the widely used constant discrimination factor Δ15N = 3.4‰ between two adjacent trophic positions (TPs), a scaled Δ15N framework for evaluating the TP of species was developed in 2014, that is, the Δ15N between two adjacent TPs decreases as the TP increases which is considered to be in closer conformity to the trophic cascade in the natural food web. In this study, we compared the two TP calculation methods and then reconsidered the evaluation of the trophic magnification factors (TMFs). Our results show that the TPscaled value is higher and the TMFs value is lower under the scaled Δ15N framework, indicating that the TMFs value under the constant Δ15N framework is often overestimated. We further constructed a diet proportion food web model, which shows that species with lower TP has higher contribution rate as food sources. In Xingkai Lake, the enrichment process of mercury in the food web is not strictly consistent with the diet proportion of the food web. Based on the diet proportion food web model and the mercury enrichment model, it can be found that the White shrimp (Exopalaemon modestus) is not only an important food source, but also the main source of mercury transmission in the food web. Overall, our findings have quantified the food web construction and thus facilitated a better understanding of the interaction between the diet proportion and the bio-concentration in the food web.

Designing (for) Urban Food Webs

Interest is growing in designing resilient and ecologically rich urban environments that provide social and ecological benefits. Regenerative and biocentric designs fostering urban ecological habitats including food webs that provide ecosystem services for people and wildlife increasingly are being sought. However, the intentional design of urban landscapes for food webs remains in an early stage with few precedents and many challenges. In this paper, we explore the potential to design (for) urban food webs through collaborations between designers and ecologists. We start by examining the ecology and management of Jamaica Bay in New York City as a case study of an anthropogenic landscape where ecosystems are degraded and the integrity of extant food webs are intertwined with human agency. A subsequent design competition focusing on ecological design and management of this large-scale landscape for animal habitat and ecosystem services for people illustrates how designers approach this anthropogenic landscape. This case study reveals that both designing urban landscapes for food webs and directly designing and manipulating urban food webs are complicated and challenging to achieve and maintain, but they have the potential to increase ecological health of, and enhance ecosystem services in, urban environments. We identify opportunities to capitalize on species interactions across trophic structures and to introduce managed niches in biologically engineered urban systems. The design competition reveals an opportunity to approach urban landscapes and ecological systems creatively through a proactive design process that includes a carefully crafted collaborative approach to constructing ecologically functioning landscapes that can integrate societal demands. As designers increasingly seek to build, adapt, and manage urban environments effectively, it will be critical to resolve the contradictions and challenges associated with human needs, ecosystem dynamics, and interacting assemblages of species. Ecologists and designers are still discovering and experimenting with designing (for) urban food webs and fostering species interactions within them. We recommend generating prototypes of urban food webs through a learning-by-doing approach in urban development projects. Design and implementation of urban food webs also can lead to research opportunities involving monitoring and experiments that identify and solve challenges of food-web construction while supporting and encouraging ongoing management.

A meta food web for invertebrate species collected in a European grassland.

Patterns of feeding interactions between species are thought to influence the stability of communities and the flux of nutrients and energy through ecosystems. However, surprisingly few well-resolved food webs allow us to evaluate factors that influence the architecture of species interactions. We constructed a meta food web consisting of 714 invertebrate species collected over 9 years of suction and pitfall sampling campaigns in the Jena Experiment, a long-term grassland biodiversity experiment located in Jena, Germany. We summarize information on the 51,496 potential trophic links, which were established using information on diet specificity and species traits that typically constrain feeding interactions (trophic group, body size, and vertical stratification). The list of species identities, traits, and link-derivation rules will be useful not only for tests of plant diversity effects on food web structure within the Jena Experiment, but also for considering consistent construction of food webs from empirical data, and for comparisons of network structure across ecosystems. No copyright or proprietary restrictions are associated with the use of this data set other than citation of this Data Paper.

The robustness, link-species relationship and network properties of model food webs

New results are collected using the Webworld model which simulates evolutionary food web construction with population dynamics (Drossel et al., 2001 [1]). We show that it supports a link-species relationship of neither constant link-density nor constant connectance, and new properties for the food webs are calculated including clustering coefficients and stability in the sense of community robustness to species deletion. Time-series for more than 40 properties of the taxonomic and trophic webs are determined over the course of individual simulations. Robustness is found to be positively correlated with connectance, but negatively with diversity, and we study the long-term development of model webs including the distribution of extinction events in a simulation with 108 speciation events.

Stable-isotope analysis: a neglected tool for placing parasites in food webs.

Parasites are often overlooked in the construction of food webs, despite their ubiquitous presence in almost every type of ecosystem. Researchers who do recognize their importance often struggle to include parasites using classical food-web theory, mainly due to the parasites' multiple hosts and life stages. A novel approach using compound-specific stable-isotope analysis promises to provide considerable insight into the energetic exchanges of parasite and host, which may solve some of the issues inherent in incorporating parasites using a classical approach. Understanding the role of parasites within food webs, and tracing the associated biomass transfers, are crucial to constructing new models that will expand our knowledge of food webs. This mini-review focuses on stable-isotope studies published in the past decade, and introduces compound-specific stable-isotope analysis as a powerful, but underutilized, newly developed tool that may answer many unresolved questions regarding the role of parasites in food webs.

Do age-related changes in feeding habits of brown trout alter structural properties of food webs?

The aim of this study was to quantify changes in food webs based on ontogenetic dietary shifts of a top fish predator (here brown trout Salmo trutta L.). Here, the food web of a river in Central Spain (River Tormes) was studied to test the hypothesis that food web structural properties may change according to age-related changes in feeding habits of brown trout. Thus, the food web was established separately for age-0, age-1 and age-2 brown trout using a forward procedure (individual, modular and river networks); next the complete trophic networks were established. Overall, the networks were characterized by generalist predators with numerous prey types; specialized feeding was limited to a low number of taxa. Food web structural properties (number of links, connectance and linkage density) had the highest values in the age-1 scenario. The highest trophic level (i.e. the highest number of energy steps) was also found in the age-1 scenario, but the lowest in the age-0 scenario. Vulnerability and generalization tend to be higher in age-1 and age-0 scenarios, respectively. The present study exemplifies that age-specific brown trout predation on invertebrate predators emerged as the key factor to understand the changes in food web structural properties among age scenarios. I conclude that ontogenetic dietary shifts of brown trout promote changes in food web structural properties. This conclusion underscores the importance of considering different life history stages of species (i.e. to cover their ontogenetic dietary shifts) in food web construction.

Enriching Search Queries to Construct Comprehensive Concept Maps for Online Inquiries: A Case Study of a Food Web

Concept maps have recently been widely applied to pedagogical tasks, such as eliciting the acquired knowledge of students or scaffolding their online inquiry with a knowledge structure. Moreover, there is a growing need to develop an assistance mechanism that supports concept map construction due to the increasing volume of learning resources available online. The aim of this study is to develop a query expansion-based approach to assist students in efficiently retrieving appropriate knowledge from the Internet and constructing more comprehensive concept maps. The validity of the proposed approach is measured through a comparison of its results of a food web construction with those from a biology textbook. It is demonstrated that the proposed approach can provide sound results that are close to expert skeleton concept maps. The findings show that query expansion can help expand search queries, and can serve as a great source of inspiration for the construction of comprehensive concept maps.

Joining the dots: An automated method for constructing food webs from compendia of published interactions

Food webs are important tools for understanding how complex natural communities are structured and how they respond to environmental change. However their full potential has yet to be realised because of the huge amount of resources required to construct them de novo. Consequently, the current catalogue of networks that are suitable for rigorous and comparative analyses and theoretical development still suffers from a lack of standardisation and replication.Here, we present a novel R function, WebBuilder, which automates the construction of food webs from taxonomic lists, and a dataset of trophic interactions. This function works by matching species against those within a dataset of trophic interactions, and ‘filling in’ missing trophic interactions based on these matches. We also present a dataset of over 20,000 freshwater trophic interactions, and use this and four well-characterised freshwater food webs to test the method.The WebBuilder function facilitates the generation of food webs of comparable quality to the most detailed published food webs, but at a fraction of the research effort or cost. Furthermore, it matched and often outperformed a selection of predictive models, which are currently among the best, in terms of capturing key properties of empirical food webs. The method is simple to use, systematic and, perhaps most importantly, reproducible, which will facilitate (re-) analysis and data sharing. Although developed and tested on a sample of freshwater food webs, this method could easily be extended to cover other types of ecological interactions (such as mutualistic interactions).

Un‐nesting DNA Russian dolls – the potential for constructing food webs using residual DNA in empty aphid mummies

Constructing food-web assemblages comprising parasitoid wasps involves large field collections of hosts followed by labour-intensive rearing of the insects to evaluate the rates of parasitism along with morphological or molecular identification of the parasitoid species. This article presents research towards a new molecular method for the practical and accurate construction of aphid-based food webs. We hypothesize that parasitoid and hyperparasitoid DNA left inside aphid mummies after emergence of these third and fourth trophic-level guilds can be simultaneously detected using universal polymerase chain reaction (PCR) primers for nonspecific DNA amplification in combination with single-stranded conformation polymorphism (SSCP) analysis. Such a protocol theoretically allows food-web construction to be performed with no a priori knowledge of the species present. Moreover, the use of empty mummies circumvents rearing and minimizes labour and time in the field and laboratory. To test our hypothesis, we conducted DNA analyses on laboratory-produced parasitized aphids (mummies) from Myzus persicae and Brevicoryne brassicae (two important aphid pest species) after exposure to the parasitoid Diaeretiella rapae and the hyperparasitoid Asaphes vulgaris. DNA is amplifiable in empty aphid mummies for as long as 3weeks after parasitoid emergence. However, the simultaneous identification of several species in a single mummy sample was rare, which hinders the accurate inference of trophic links. DNA quality and relative quantity, together with preferential amplification, are potential explanations of current results. Technical refinements are needed to ensure full reliability and detection of complex trophic links. The use of PCR-SSCP for food-web construction is novel, and its potential to include an important number of different species is yet to be fully explored.

Diet diversity among five co-existing fish species in a tropical river: integration of dietary and stable isotope data

Diets were estimated from stomach contents and the MixSIR model using stable isotope values for five co-existing and abundant benthic fishes in relation to potential prey from a riffle habitat in a tropical river in eastern Thailand. Collectively, aquatic insects were of greatest dietary importance based on stomach contents and, except for one fish species, predicted from the MixSIR. The most prominent functional feeding insect groups in fish diets were collector-filterers and scrapers and, to a lesser extent, predators. MixSIR predicted shrimp to be the most important single dietary constituent for all fishes in contrast to stomach contents, which indicated they are a major item for only one species. MixSIR predicted plant material to be more important in fish diets than stomach contents where the composition of detritus was a concern. Differences in temporal feeding schedules, prey availability, species adaptations and others are important in understanding diet and in the construction of food webs. Stable isotope and dietary analysis provides a more accurate assessment of the food web structure and dynamics of tropical river ecosystems than either method alone.

Moorea BIOCODE barcode library as a tool for understanding predator–prey interactions: insights into the diet of common predatory coral reef fishes

Identifying species involved in consumer- resource interactions is one of the main limitations in the construction of food webs. DNA barcoding of prey items in predator guts provides a valuable tool for characterizing trophic interactions, but the method relies on the avail- ability of reference sequences to which prey sequences can be matched. In this study, we demonstrate that the COI sequence library of the Moorea BIOCODE project, an ecosystem-level barcode initiative, enables the identifi- cation of a large proportion of semi-digested fish, crusta- cean and mollusks found in the guts of three Hawkfish and two Squirrelfish species. While most prey remains lacked diagnostic morphological characters, 94% of the prey found in 67 fishes had (98% sequence similarity with BIOCODE reference sequences. Using this species-level prey identification, we demonstrate how DNA barcoding can provide insights into resource partitioning, predator feeding behaviors and the consequences of predation on ecosystem function.

Principles from community and metapopulation ecology: application to fungal entomopathogens

Fungal entomopathogens are often studied within the context of their use for biological control, yet these natural enemies are also excellent subjects for studies of ecological interactions. Here, we present selected principles from community ecology and discuss these in relation to fungal entomopathogens. We discuss the relevance of apparent competition, food web construction, intraguild predation and density-mediated and trait-mediated indirect effects. Although current knowledge of community interactions involving fungal entomopathogens are limited, fungal entomopathogens can be important, interactive members of communities and the activities of fungal entomopathogens should be evaluated in the context of ecological principles. We also discuss aspects of metapopulation ecology and the application of these principles to fungal entomopathogens. Knowledge of ecological interactions is crucial if we are to understand and predict the effects of fungal entomopathogens on host populations and understand the interactions among fungal entomopathogens and other organisms in the communities in which they occur.

A ‘bottom-up’ approach to food web construction

The ability to comprehend trophic (nutritional) relationships and food web dynamics is an essential part of environmental literacy. However, students face severe difficulties in grasping the variety of causal patterns in food webs. We propose a curriculum for comprehending trophic relations in elementary school. The curriculum allows students to construct a food web using real data and following guidelines for the identification of organisms and their food preferences. The curriculum was applied to 22 fourth graders of an elementary school in Nicosia, Cyprus. Another 24 fourth graders participated as control group. Children of the experimental group managed to construct quite precise and complicate webs, including a large number of species and drawing multiple trophic connections between them. However, difficulties in grasping aspects of the functional and behavioural characteristics of food webs remained after the learning intervention. We conclude that the proposed curriculum could serve as an introductory basis for studying food webs, but it should be accompanied with a series of activities for more explicit consideration of the function and behaviour of food webs in order to offer a compete educational account for comprehending trophic relations.

Using Environmental Variables to Predict the Structure of Deep-sea Arctic Fish Communities: Implications for Food Web Construction

ABSTRACTUnderstanding trophic interaction within deep-sea marine communities is critically important as commercial exploitation increases in the Arctic. Undoubtedly, the Arctic marine environment will be subject to the same environmental and human stressors as its southern counterparts and, as a result, community stability is vulnerable. The objectives of this study were to test the predictive power of environmental variables on fish community composition using redundancy analysis and to determine if this information could be used to differentiate distinct trophic communities throughout the Davis Strait/Baffin Bay region. This analysis used data collected in benthic surveys from 2000 to 2004, and results indicate that water temperature, latitude, and depth strongly influence the distribution of fish species in this region. Latitude and water temperature were strongly negatively correlated, and the majority of species were distributed along the low latitude/high temperature to high latitude/low temperature gradient. Some fish species were more highly correlated with depth. Proportions of most by-catch species differed between northern and southern regions at each depth range. Since community structure changes gradually along environmental gradients, perhaps it is more appropriate to describe the communities as shifting their trophic status along environmental gradients rather than as distinct communities with distinct food webs in a specific region of the Arctic.

Pasture and grazing land: assessment of sustainability using invertebrate bioindicators

Impacts of practices frequently used to manage Australian pastures are reviewed with the aim of determining which groups are responsive to changes in grazing regime, fertiliser use, pasture types, tree clearing, pesticide use, liming and irrigation. Invertebrate groups sensitive to pasture management regimes may be potential candidates for use as bioindicators of ecological sustainability of these pasture types. This review concentrates on the more intensively utilised temperate pastures of southern Australia, as very little work has been done on the impact of the grazing animal and pasture management on invertebrate fauna on the extensive rangelands of the arid and semiarid zones. Background to the relative importance of invertebrates in the functioning of the pasture ecosystem is given. This has culminated in the construction of food webs for two temperate perennial pastures (an unfertilised, native and a fertilised, sown pasture) at Armidale, NSW, for which there is comprehensive data available. Invertebrate bioindicators of pasture sustainability emerged from the consideration of grazing lands and invertebrate responses. Currently, only four groups would seem to be likely candidates as bioindicators of sustainability of pastures. These are soil nematodes, earthworms, protozoa and Collembola. The main difficulty in monitoring these groups is that it requires specialist expertise, and services provided by commercial laboratories for routine biological soil tests are still in their infancy. There are gaps in our knowledge of how invertebrate fauna react to the pressing issues of soil acidity and salinity.

Intricate Webs in the Rain Forest

ECOLOGY/EVOLUTION The processes maintaining the high diversity of tropical rain-forest organisms remain a central focus of ecological research. Quantifying the trophic interactions between species via the construction of food webs is a key to understanding the structuring of these communities and the relative abundances of their components. Lewis et al. constructed quantitative food webs for leaf-mining insects, their food plants, and their parasitoids for a rain forest in Belize. This analysis, involving 93 leaf miner species, 84 parasitoid species, and 71 species of host plants at three different seasons, is the most comprehensive one to date. The leaf miners were fastidious in their choice of plant, whereas the parasitoids tended to be catholic, attacking a range of insects. The analysis suggests that herbivorous insect species might indirectly influence each other's abundance and population dynamics, with the more abundant species having greater effects on the less abundant ones. — AMS J. Anim. Ecol. 71 , 855 (2002).

Studying insect diversity in the tropics.

Understanding the extent and causes of insect diversity in the humid tropics is one of the major challenges in modern ecology. We review some of the current approaches to this problem, and discuss how future progress may be made. Recent calculations that there may be more than 30 million species of insect on earth have focused attention on the magnitude of this problem and stimulated several new lines of research (although the true figure is now widely thought to be between five and ten million species). We discuss work based on insecticidal logging surveys; studies of herbivore and parasitoid specificity; macroecological approaches; and the construction of food webs. It is argued that progress in estimating insect diversity and in understanding insect community dynamics will be enhanced by building local inventories of species diversity, and in descriptive and experimental studies of the trophic structure of communities. As an illustration of work aimed at the last goal, we discuss the construction and analysis of quantitative host-parasitoid food webs, drawing on our work on leaf miner communities in Central America.