111 results found
O'Gorman EJ, Petchey OL, Faulkner KJ, et al., 2019, A simple model predicts how warming simplifies wild food webs, Nature Climate Change, Vol: 9, Pages: 611-616, ISSN: 1758-678X
Warming increases the metabolic demand of consumers1, strengthening their feeding interactions2. This could alter energy fluxes3,4,5 and even amplify extinction rates within the food web6,7,8. Such effects could simplify the structure and dynamics of ecological networks9,10, although an empirical test in natural systems has been lacking. Here, we tested this hypothesis by characterizing around 50,000 directly observed feeding interactions across 14 naturally heated stream ecosystems11,12,13,14,15. We found that higher temperature simplified food-web structure and shortened the pathways of energy flux between consumers and resources. A simple allometric diet breadth model10,16 predicted 68–82% of feeding interactions and the effects of warming on key food-web properties. We used model simulations to identify the underlying mechanism as a change in the relative diversity and abundance of consumers and their resources. This model shows how warming can reduce the stability of aquatic ecosystems by eroding the structural integrity of the food web. Given these fundamental drivers, such responses are expected to be manifested more broadly and could be predicted using our modelling framework and knowledge of how warming alters some routinely measured characteristics of organisms.
Brose U, Archambault P, Barnes AD, et al., 2019, Predator traits determine food-web architecture across ecosystems, NATURE ECOLOGY & EVOLUTION, Vol: 3, Pages: 919-927, ISSN: 2397-334X
Patrick CJ, McGarvey DJ, Larson JH, et al., 2019, Precipitation and temperature drive continental-scale patterns in stream invertebrate production, Science Advances, Vol: 5, Pages: eaav2348-eaav2348, ISSN: 2375-2548
Secondary production, the growth of new heterotrophic biomass, is a key process in aquatic and terrestrial ecosystems that has been carefully measured in many flowing water ecosystems. We combine structural equation modeling with the first worldwide dataset on annual secondary production of stream invertebrate communities to reveal core pathways linking air temperature and precipitation to secondary production. In the United States, where the most extensive set of secondary production estimates and covariate data were available, we show that precipitation-mediated, low-stream flow events have a strong negative effect on secondary production. At larger scales (United States, Europe, Central America, and Pacific), we demonstrate the significance of a positive two-step pathway from air to water temperature to increasing secondary production. Our results provide insights into the potential effects of climate change on secondary production and demonstrate a modeling framework that can be applied across ecosystems.
Aspin TWH, Hart K, Khamis K, et al., 2019, Drought intensification alters the composition, body size, and trophic structure of invertebrate assemblages in a stream mesocosm experiment, Freshwater Biology, Vol: 64, Pages: 750-760, ISSN: 0046-5070
Predicted trends towards more intense droughts are of particular significance for running water ecosystems, as the loss of critical stream habitat can provoke sudden changes in biodiversity and shifts in community structure. However, analysing ecological responses to the progressive loss of stream habitat requires a continuous disturbance gradient that can only be generated through large‐scale manipulations of streamflow.In the first experiment of its kind, we used large artificial stream channels (mesocosms) as analogues of spring‐fed headwaters and simulated a gradient of drought intensity that encompassed flowing streams, disconnected pools, and dry streambeds. We used breakpoint analysis to analyse macroinvertebrate community responses to intensifying drought, and identify the taxa and compositional metrics sensitive to small changes in drought stress.We detected breakpoints for >60% of taxa, signalling sudden population crashes or irruptions as drought intensified. Abrupt changes were most pronounced where riffle dewatering isolated pools. In the remnant wetted habitat, we observed a shift to larger body sizes across the community, primarily driven by irruptions of predatory midge larvae and coincident population collapses among prey species (worms and smaller midges).Our results suggest that intense predation in confined, fragmented stream habitat can lead to unexpected changes in body sizes, challenging the conventional wisdom that droughts favour the small. Pool fragmentation might thus be the most critical stage of habitat loss during future droughts, as the point at which impacted rivers and streams begin to exhibit major shifts in fundamental food web properties.
Sampson A, Ings N, Shelley F, et al., 2019, Geographically widespread C-13-depletion of grazing caddis larvae: A third way of fuelling stream food webs?, FRESHWATER BIOLOGY, Vol: 64, Pages: 787-798, ISSN: 0046-5070
Ma A, Lu X, Gray C, et al., 2019, Ecological networks reveal resilience of agro-ecosystems to changes in farming management, NATURE ECOLOGY & EVOLUTION, Vol: 3, Pages: 260-+, ISSN: 2397-334X
Tiegs SD, Costello DM, Isken MW, et al., 2019, Global patterns and drivers of ecosystem functioning in rivers and riparian zones, Science Advances, Vol: 5, ISSN: 2375-2548
River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.
Aspin TWH, Khamis K, Matthews TJ, et al., 2019, Extreme drought pushes stream invertebrate communities over functional thresholds, GLOBAL CHANGE BIOLOGY, Vol: 25, Pages: 230-244, ISSN: 1354-1013
Perkins DM, Durance I, Edwards FK, et al., 2018, Bending the rules: exploitation of allochthonous resources by a top-predator modifies size-abundance scaling in stream food webs, Ecology Letters, Vol: 21, Pages: 1771-1780, ISSN: 1461-023X
Body mass–abundance (M‐N) allometries provide a key measure of community structure, and deviations from scaling predictions could reveal how cross‐ecosystem subsidies alter food webs. For 31 streams across the UK, we tested the hypothesis that linear log‐log M‐N scaling is shallower than that predicted by allometric scaling theory when top predators have access to allochthonous prey. These streams all contained a common and widespread top predator (brown trout) that regularly feeds on terrestrial prey and, as hypothesised, deviations from predicted scaling increased with its dominance of the fish assemblage. Our study identifies a key beneficiary of cross‐ecosystem subsidies at the top of stream food webs and elucidates how these inputs can reshape the size‐structure of these ‘open’ systems.
Isaac NJB, Brotherton PNM, Bullock JM, et al., 2018, Defining and delivering resilient ecological networks: Nature conservation in England, JOURNAL OF APPLIED ECOLOGY, Vol: 55, Pages: 2537-2543, ISSN: 0021-8901
Woodward G, 2018, Bending the rules: exploitation of allochthonous resources by atop-predator modiﬁes size-abundance scaling in stream foodwebs, Ecology Letters, ISSN: 1461-023X
Thompson MSA, Brooks SJ, Sayer CD, et al., 2018, Large woody debris "rewilding" rapidly restores biodiversity in riverine food webs, JOURNAL OF APPLIED ECOLOGY, Vol: 55, Pages: 895-904, ISSN: 0021-8901
Andujar C, Arribas P, Gray C, et al., 2017, Metabarcoding of freshwater invertebrates to detect the effects of a pesticide spill, Molecular Ecology, Vol: 27, Pages: 146-166, ISSN: 0962-1083
Biomonitoring underpins the environmental assessment of freshwater ecosystems and guides management and conservation. Current methodology for surveys of (macro)invertebrates uses coarse taxonomic identification where species‐level resolution is difficult to obtain. Next‐generation sequencing of entire assemblages (metabarcoding) provides a new approach for species detection, but requires further validation. We used metabarcoding of invertebrate assemblages with two fragments of the cox1 “barcode” and partial nuclear ribosomal (SSU) genes, to assess the effects of a pesticide spill in the River Kennet (southern England). Operational taxonomic unit (OTU) recovery was tested under 72 parameters (read denoising, filtering, pair merging and clustering). Similar taxonomic profiles were obtained under a broad range of parameters. The SSU marker recovered Platyhelminthes and Nematoda, missed by cox1, while Rotifera were only amplified with cox1. A reference set was created from all available barcode entries for Arthropoda in the BOLD database and clustered into OTUs. The River Kennet metabarcoding produced matches to 207 of these reference OTUs, five times the number of species recognized with morphological monitoring. The increase was due to the following: greater taxonomic resolution (e.g., splitting a single morphotaxon “Chironomidae” into 55 named OTUs); splitting of Linnaean binomials into multiple molecular OTUs; and the use of a filtration‐flotation protocol for extraction of minute specimens (meiofauna). Community analyses revealed strong differences between “impacted” vs. “control” samples, detectable with each gene marker, for each major taxonomic group, and for meio‐ and macrofaunal samples separately. Thus, highly resolved taxonomic data can be extracted at a fraction of the time and cost of traditional nonmolecular methods, opening new avenues for freshwater invertebrate biodiversity monitoring and molecular ecolo
O'Gorman EJ, Zhao L, Pichler DE, et al., 2017, Unexpected changes in community size structure in a natural warming experiment, NATURE CLIMATE CHANGE, Vol: 7, Pages: 659-+, ISSN: 1758-678X
Bohan D, Dumbrell A, Raybould A, et al., 2017, Next-generation global biomonitoring: large-scale, automated reconstruction of ecological networks, Trends in Ecology and Evolution, Vol: 32, Pages: 477-487, ISSN: 1872-8383
We foresee a new global-scale, ecological approach to biomonitoring emerging within the next decade that can detect ecosystem change accurately, cheaply, and generically. Next-generation sequencing of DNA sampled from the Earth’s environments would provide data for the relative abundance of operational taxonomic units or ecological functions. Machine-learning methods would then be used to reconstruct the ecological networks of interactions implicit in the raw NGS data. Ultimately, we envision the development of autonomous samplers that would sample nucleic acids and upload NGS sequence data to the cloud for network reconstruction. Large numbers of these samplers, in a global array, would allow sensitive automated biomonitoring of the Earth’s major ecosystems at high spatial and temporal resolution, revolutionising our understanding of ecosystem change.
Palinkas Z, Kiss J, Zalai M, et al., 2017, Effects of genetically modified maize events expressing Cry34Ab1, Cry35Ab1, Cry1F, and CP4 EPSPS proteins on arthropod complex food webs, Ecology and Evolution, Vol: 7, Pages: 2286-2293, ISSN: 2045-7758
Four genetically modified (GM) maize (Zea mays L.) hybrids (coleopteran resistant, coleopteran and lepidopteran resistant, lepidopteran resistant and herbicide tolerant, coleopteran and herbicide tolerant) and its non-GM control maize stands were tested to compare the functional diversity of arthropods and to determine whether genetic modifications alter the structure of arthropods food webs. A total number of 399,239 arthropod individuals were used for analyses. The trophic groups’ number and the links between them indicated that neither the higher magnitude of Bt toxins (included resistance against insect, and against both insects and glyphosate) nor the extra glyphosate treatment changed the structure of food webs. However, differences in the average trophic links/trophic groups were detected between GM and non-GM food webs for herbivore groups and plants. Also, differences in characteristic path lengths between GM and non-GM food webs for herbivores were observed. Food webs parameterized based on 2-year in-field assessments, and their properties can be considered a useful and simple tool to evaluate the effects of Bt toxins on non-target organisms.
Yvon-Durocher G, Hulatt CJ, Woodward G, et al., 2017, Long-term warming amplifies shifts in the carbon cycle of experimental ponds, NATURE CLIMATE CHANGE, Vol: 7, Pages: 209-+, ISSN: 1758-678X
Lakes and ponds cover only about 4% of the Earth’s non-glaciated surface1, yet they represent disproportionately large sources of methane and carbon dioxide2, 3, 4. Indeed, very small ponds (for example, <0.001 km2) may account for approximately 40% of all CH4 emissions from inland waters5. Understanding how greenhouse gas emissions from aquatic ecosystems will respond to global warming is therefore vital for forecasting biosphere–carbon cycle feedbacks. Here, we present findings on the long-term effects of warming on the fluxes of GHGs and rates of ecosystem metabolism in experimental ponds. We show that shifts in CH4 and CO2 fluxes, and rates of gross primary production and ecosystem respiration, observed in the first year became amplified over seven years of warming. The capacity to absorb CO2 was nearly halved after seven years of warmer conditions. The phenology of greenhouse gas fluxes was also altered, with CO2 drawdown and CH4 emissions peaking one month earlier in the warmed treatments. These findings show that warming can fundamentally alter the carbon balance of small ponds over a number of years, reducing their capacity to sequester CO2 and increasing emissions of CH4; such positive feedbacks could ultimately accelerate climate change.
Jackson M, Weyl O, Altermatt F, et al., 2016, Chapter twelve - recommendations for the next generation of global freshwater biological monitoring tools, Advances in Ecological Research, Vol: 55, Pages: 615-636, ISSN: 0065-2504
Biological monitoring has a long history in freshwaters, where much of the pioneering work in this field was developed over a hundred years ago – but few of the traditional monitoring tools provide the global perspective on biodiversity loss and its consequences for ecosystem functioning that are now needed. Rather than forcing existing monitoring paradigms to respond to questions they were never originally designed to address, we need to take a step back and assess the prospects for novel approaches that could be developed and adopted in the future. To resolve some of the issues with indicators currently used to inform policymakers, we highlight new biological monitoring tools that are being used, or could be developed in the near future, which (1) consider less-studied taxonomic groups; (2) are standardised across regions to allow global comparisons, and (3) measure change over multiple time points. The new tools we suggest make use of some of the key technological and logistical advances seen in recent years – including remote sensing, molecular tools, and local-to-global citizen science networks. We recommend that these new indicators should be considered in future assessments of freshwater ecosystem health and contribute to the evidence base for global to regional (and national) assessments of biodiversity and ecosystem services: for example, within the emerging framework of the Intergovernmental Platform on Biodiversity and Ecosystem Services.
Zhao L, Moore J, O'Gorman EJ, et al., 2016, Weighting and indirect effects identify keystone species in food webs, Ecology Letters, Vol: 19, Pages: 1032-1040, ISSN: 1461-0248
Species extinctions are accelerating globally, yet the mechanisms that maintain local biodiversity remain poorly understood. The extinction of species that feed on or are fed on by many others (i.e. ‘hubs’) has traditionally been thought to cause the greatest threat of further biodiversity loss. Very little attention has been paid to the strength of those feeding links (i.e. link weight) and the prevalence of indirect interactions. Here, we used a dynamical model based on empirical energy budget data to assess changes in ecosystem stability after simulating the loss of species according to various extinction scenarios. Link weight and/or indirect effects had stronger effects on food-web stability than the simple removal of ‘hubs’, demonstrating that both quantitative fluxes and species dissipating their effects across many links should be of great concern in biodiversity conservation, and the potential for ‘hubs’ to act as keystone species may have been exaggerated to date.
Droughts are intensifying across the globe with potentially devastating implications for freshwater ecosystems. We used new network science approaches to investigate drought impacts on stream food webs and explored potential consequences for web robustness to future perturbations. The substructure of the webs was characterized by a core of richly connected species surrounded by poorly connected peripheral species. Although drought caused the partial collapse of the food webs, the loss of the most extinction-prone peripheral species triggered a substantial rewiring of interactions within the networks’ cores. These shifts in species interactions in the core conserved the underlying core/periphery substructure and stability of the drought-impacted webs. When we subsequently perturbed the webs by simulating species loss in silico, the rewired drought webs were as robust as the larger, undisturbed webs. Our research unearths previously unknown compensatory dynamics arising from within the core that could underpin food web stability in the face of environmental perturbations.
Woodward G, Bonada N, Brown LE, et al., 2016, The effects of climatic fluctuations and extreme events on running water ecosystems, Philisophical Transactions of the Royal Society B, Vol: 371, ISSN: 0962-8436
Most research on the effects of environmental change in freshwaters hasfocused on incremental changes in average conditions, rather than fluctuationsor extreme events such as heatwaves, cold snaps, droughts, floodsor wildfires, which may have even more profound consequences. Suchevents are commonly predicted to increase in frequency, intensity and durationwith global climate change, with many systems being exposed toconditions with no recent historical precedent. We propose a mechanisticframework for predicting potential impacts of environmental fluctuationson running-water ecosystems by scaling up effects of fluctuations from individualsto entire ecosystems. This framework requires integration of four keycomponents: effects of the environment on individual metabolism, metabolicand biomechanical constraints on fluctuating species interactions,assembly dynamics of local food webs, and mapping the dynamics of themeta-community onto ecosystem function. We illustrate the framework bydeveloping a mathematical model of environmental fluctuations on dynamicallyassembling food webs. We highlight (currently limited) empiricalevidence for emerging insights and theoretical predictions. For example,widely supported predictions about the effects of environmental fluctuationsare: high vulnerability of species with high per capita metabolic demandssuch as large-bodied ones at the top of food webs; simplification of foodweb network structure and impaired energetic transfer efficiency; andreduced resilience and top-down relative to bottom-up regulation of foodweb and ecosystem processes. We conclude by identifying key questionsand challenges that need to be addressed to develop more accurate and predictivebio-assessments of the effects of fluctuations, and implications offluctuations for management practices in an increasingly uncertain world.
O'Gorman EJ, Ólafsson Ó, Demars BOL, et al., 2016, Temperature effects on fish production across a natural thermal gradient, Global Change Biology, Vol: 22, Pages: 3206-3220, ISSN: 1365-2486
Global warming is widely predicted to reduce the biomass production of top predators, or even result in species loss. Several exceptions to this expectation have been identified, however, and it is vital that we understand the underlying mechanisms if we are to improve our ability to predict future trends. Here, we used a natural warming experiment in Iceland and quantitative theoretical predictions to investigate the success of brown trout as top predators across a stream temperature gradient (4–25 °C). Brown trout are at the northern limit of their geographic distribution in this system, with ambient stream temperatures below their optimum for maximal growth, and above it in the warmest streams. A five-month mark-recapture study revealed that population abundance, biomass, growth rate, and production of trout all increased with stream temperature. We identified two mechanisms that contributed to these responses: (1) trout became more selective in their diet as stream temperature increased, feeding higher in the food web and increasing in trophic position; and (2) trophic transfer through the food web was more efficient in the warmer streams. We found little evidence to support a third potential mechanism: that external subsidies would play a more important role in the diet of trout with increasing stream temperature. Resource availability was also amplified through the trophic levels with warming, as predicted by metabolic theory in nutrient-replete systems. These results highlight circumstances in which top predators can thrive in warmer environments and contribute to our knowledge of warming impacts on natural communities and ecosystem functioning.
Huddart JEA, Thompson MSA, Woodward G, et al., 2016, Citizen science: from detecting pollution to evaluating ecological restoration, Wiley Interdisciplinary Reviews: Water, Vol: 3, Pages: 287-300, ISSN: 2049-1948
Gill RJ, Baldock KCR, Brown MJF, et al., 2016, Protecting an Ecosystem Service: Approaches to Understanding and Mitigating Threats to Wild Insect Pollinators, Advances in Ecological Research, Vol: 54, Pages: 135-206, ISSN: 0065-2504
Insect pollination constitutes an ecosystem service of global importance, providing significant economic and aesthetic benefits as well as cultural value to human society, alongside vital ecological processes in terrestrial ecosystems. It is therefore important to understand how insect pollinator populations and communities respond to rapidly changing environments if we are to maintain healthy and effective pollinator services. This chapter considers the importance of conserving pollinator diversity to maintain a suite of functional traits and provide a diverse set of pollinator services. We explore how we can better understand and mitigate the factors that threaten insect pollinator richness, placing our discussion within the context of populations in predominantly agricultural landscapes in addition to urban environments. We highlight a selection of important evidence gaps, with a number of complementary research steps that can be taken to better understand: (i) the stability of pollinator communities in different landscapes in order to provide diverse pollinator services; (ii) how we can study the drivers of population change to mitigate the effects and support stable sources of pollinator services and (iii) how we can manage habitats in complex landscapes to support insect pollinators and provide sustainable pollinator services for the future. We advocate a collaborative effort to gain higher quality abundance data to understand the stability of pollinator populations and predict future trends. In addition, for effective mitigation strategies to be adopted, researchers need to conduct rigorous field testing of outcomes under different landscape settings, acknowledge the needs of end-users when developing research proposals and consider effective methods of knowledge transfer to ensure effective uptake of actions.
Gill RJ, Woodward G, 2016, Networking our way to better ecosystem service provision, Trends in Ecology & Evolution, Vol: 31, Pages: 105-115, ISSN: 0169-5347
The ecosystem services (EcoS) concept is being used increasingly to attach values to natural systems and the multiple benefits they provide to human societies. Ecosystem processes or functions only become EcoS if they are shown to have social and/or economic value. This should assure an explicit connection between the natural and social sciences, but EcoS approaches have been criticized for retaining little natural science. Preserving the natural, ecological science context within EcoS research is challenging because the multiple disciplines involved have very different traditions and vocabularies (common-language challenge) and span many organizational levels and temporal and spatial scales (scale challenge) that define the relevant interacting entities (interaction challenge). We propose a network-based approach to transcend these discipline challenges and place the natural science context at the heart of EcoS research.
Bohan DA, Pocock MJO, Woodward G, 2016, Ecosystem Services: From Biodiversity to Society, Part 2 PREFACE, Publisher: ELSEVIER ACADEMIC PRESS INC, ISBN: 978-0-08-100978-9
Dumbrell AJ, Kordas RL, Woodward G, 2016, Preface
Dumbrell AJ, Kordas RL, Woodward G, 2016, ADVANCES IN ECOLOGICAL RESEARCH Large-Scale Ecology: Model Systems to Global Perspectives PREFACE, Publisher: ELSEVIER ACADEMIC PRESS INC, ISBN: 978-0-08-100935-2
Chauvet E, Ferreira V, Giller PS, et al., 2016, Litter Decomposition as an Indicator of Stream Ecosystem Functioning at Local-to-ontinental Scales: Insights from the European RivFunction Project, ADVANCES IN ECOLOGICAL RESEARCH, VOL 55: LARGE-SCALE ECOLOGY: MODEL SYSTEMS TO GLOBAL PERSPECTIVES, Editors: Dumbrell, Kordas, Woodward, Publisher: ELSEVIER ACADEMIC PRESS INC, Pages: 99-182, ISBN: 978-0-08-100935-2
Gray C, Hildrew AG, Lu X, et al., 2016, Recovery and Nonrecovery of Freshwater Food Webs from the Effects of Acidification, ADVANCES IN ECOLOGICAL RESEARCH, VOL 55: LARGE-SCALE ECOLOGY: MODEL SYSTEMS TO GLOBAL PERSPECTIVES, Editors: Dumbrell, Kordas, Woodward, Publisher: ELSEVIER ACADEMIC PRESS INC, Pages: 475-534, ISBN: 978-0-08-100935-2
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