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Sökning: WFRF:(Petchey Owen L.)

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1.
  • O'Gorman, Eoin J., et al. (författare)
  • Impacts of Warming on the Structure and Functioning of Aquatic Communities : Individual-to Ecosystem-Level Responses
  • 2012
  • Ingår i: Advances in Ecological Research, Vol 47. - : Elsevier. - 9780123983152 ; , s. 81-176
  • Bokkapitel (refereegranskat)abstract
    • Environmental warming is predicted to rise dramatically over the next century, yet few studies have investigated its effects in natural, multi-species systems. We present data collated over an 8-year period from a catchment of geothermally heated streams in Iceland, which acts as a natural experiment on the effects of warming across different organisational levels and spatiotemporal scales. Body sizes and population biomasses of individual species responded strongly to temperature, with some providing evidence to support temperature size rules. Macroinvertebrate and meiofaunal community composition also changed dramatically across the thermal gradient. Interactions within the warm streams in particular were characterised by food chains linking algae to snails to the apex predator, brown trout These chains were missing from the colder systems, where snails were replaced by much smaller herbivores and invertebrate omnivores were the top predators. Trout were also subsidised by terrestrial invertebrate prey, which could have an effect analogous to apparent competition within the aquatic prey assemblage. Top-down effects by snails on diatoms were stronger in the warmer streams, which could account for a shallowing of mass-abundance slopes across the community. This may indicate reduced energy transfer efficiency from resources to consumers in the warmer systems and/or a change in predator-prey mass ratios. All the ecosystem process rates investigated increased with temperature, but with differing thermal sensitivities, with important implications for overall ecosystem functioning (e.g. creating potential imbalances in elemental fluxes). Ecosystem respiration rose rapidly with temperature, leading to increased heterotrophy. There were also indications that food web stability may be lower in the warmer streams.
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3.
  • Pennekamp, Frank, et al. (författare)
  • Biodiversity increases and decreases ecosystem stability
  • 2018
  • Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 563:7729, s. 109-
  • Tidskriftsartikel (refereegranskat)abstract
    • Losses and gains in species diversity affect ecological stability(1-7) and the sustainability of ecosystem functions and services(8-13). Experiments and models have revealed positive, negative and no effects of diversity on individual components of stability, such as temporal variability, resistance and resilience(2,3,6,11,12,14). How these stability components covary remains poorly understood(15). Similarly, the effects of diversity on overall ecosystem stability(16), which is conceptually akin to ecosystem multifunctionality(17,18), remain unknown. Here we studied communities of aquatic ciliates to understand how temporal variability, resistance and overall ecosystem stability responded to diversity (that is, species richness) in a large experiment involving 690 micro-ecosystems sampled 19 times over 40 days, resulting in 12,939 samplings. Species richness increased temporal stability but decreased resistance to warming. Thus, two stability components covaried negatively along the diversity gradient. Previous biodiversity manipulation studies rarely reported such negative covariation despite general predictions of the negative effects of diversity on individual stability components(3). Integrating our findings with the ecosystem multifunctionality concept revealed hump- and U-shaped effects of diversity on overall ecosystem stability. That is, biodiversity can increase overall ecosystem stability when biodiversity is low, and decrease it when biodiversity is high, or the opposite with a U-shaped relationship. The effects of diversity on ecosystem multifunctionality would also be hump- or U-shaped if diversity had positive effects on some functions and negative effects on others. Linking the ecosystem multifunctionality concept and ecosystem stability can transform the perceived effects of diversity on ecological stability and may help to translate this science into policy-relevant information.
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4.
  • Petchey, Owen L., et al. (författare)
  • The ecological forecast horizon, and examples of its uses and determinants
  • 2015
  • Ingår i: Ecology Letters. - 1461-023X .- 1461-0248. ; 18:7, s. 597-611
  • Tidskriftsartikel (refereegranskat)abstract
    • Forecasts of ecological dynamics in changing environments are increasingly important, and are available for a plethora of variables, such as species abundance and distribution, community structure and ecosystem processes. There is, however, a general absence of knowledge about how far into the future, or other dimensions (space, temperature, phylogenetic distance), useful ecological forecasts can be made, and about how features of ecological systems relate to these distances. The ecological forecast horizon is the dimensional distance for which useful forecasts can be made. Five case studies illustrate the influence of various sources of uncertainty (e.g. parameter uncertainty, environmental variation, demographic stochasticity and evolution), level of ecological organisation (e.g. population or community), and organismal properties (e.g. body size or number of trophic links) on temporal, spatial and phylogenetic forecast horizons. Insights from these case studies demonstrate that the ecological forecast horizon is a flexible and powerful tool for researching and communicating ecological predictability. It also has potential for motivating and guiding agenda setting for ecological forecasting research and development.
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5.
  • Petchey, Owen L., et al. (författare)
  • Trophically Unique Species Are Vulnerable to Cascading Extinction
  • 2008
  • Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 171:5, s. 568-579
  • Tidskriftsartikel (refereegranskat)abstract
    • Understanding which species might become extinct and the consequences of such loss is critical. One consequence is a cascade of further, secondary extinctions. While a significant amount is known about the types of communities and species that suffer secondary extinctions, little is known about the consequences of secondary extinctions for biodiversity. Here we examine the effect of these secondary extinctions on trophic diversity, the range of trophic roles played by the species in a community. Our analyses of natural and model food webs show that secondary extinctions cause loss of trophic diversity greater than that expected from chance, a result that is robust to variation in food web structure, distribution of interactions strengths, functional response, and adaptive foraging. Greater than expected loss of trophic diversity occurs because more trophically unique species are more vulnerable to secondary extinction. This is not a straightforward consequence of these species having few links with others but is a complex function of how direct and indirect interactions affect species persistence. A positive correlation between a species’ extinction probability and the importance of its loss defines high-risk species and should make their conservation a priority.
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6.
  • Plebani, Marco, et al. (författare)
  • Substratum-dependent responses of ciliate assemblages to temperature: a natural experiment in Icelandic streams
  • 2015
  • Ingår i: Freshwater Biology. - : Wiley-Blackwell. - 0046-5070. ; 60:8, s. 1561-1570
  • Tidskriftsartikel (refereegranskat)abstract
    • Ciliate assemblages play a significant role in the microbial food web. The effects of environmental temperature on assemblage composition may be influenced by abiotic factors such as seasonality and disturbance, but the effects of temperature on ciliate assemblages found on different substrata have not been explored. Sandy bottoms and submerged rocks harbour dissimilar ciliate assemblages, and it might be expected that their ciliate assemblages will respond differently to temperature. We studied how alpha diversity, beta diversity and total biomass of ciliate protist assemblages found on sandy bottoms and submerged rocks differed in 13 geothermally heated streams in Iceland whose mean temperatures range from 5 to 20 degrees C. We recorded number of operational taxonomic units (OTUs) and measured the size of cells in ciliate assemblages from both substrata. Effects of temperature on natural ciliate assemblages were substratum dependent. On rock surfaces, both total ciliate biomass and alpha diversity declined with increasing temperature, and beta diversity increased with increasing temperature difference due to OTU nestedness (assemblages from warm streams being composed chiefly of subsets of the OTUs found in colder streams). In sandy substrata, however, ciliate assemblage composition was independent of temperature. Substratum-specific responses may be due to differences in mechanical disturbance, nutrient availability or exposure to invertebrate grazers. Rock-surface assemblages may be more exposed to the flow and retain less nutrient than those of sandy substratum; thus, they may be more strongly resource limited and more responsive to direct effects of temperature on metabolism. Alternatively, rock-surface assemblages may be more exposed to grazing by invertebrates, which intensifies with temperature. Our study highlights the need to account for environmental context such as substratum type to fully understand the effect of temperature on microbial assemblages in streams. Future increases in global temperatures may affect fresh waters differently depending on their prevalent substratum. Those dominated by hard substrata may have their ciliate assemblages, and thus, food-web structures and ecosystem functioning more strongly affected by warming relative to systems dominated by soft substrata.
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7.
  • Pontarp, Mikael, et al. (författare)
  • Community trait overdispersion due to trophic interactions : concerns for assembly process inference
  • 2016
  • Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - 0962-8452 .- 1471-2954. ; 283:1840
  • Tidskriftsartikel (refereegranskat)abstract
    • The expected link between competitive exclusion and community trait over-dispersion has been used to infer competition in local communities, and trait clustering has been interpreted as habitat filtering. Such community assembly process inference has received criticism for ignoring trophic interactions, as competition and trophic interactions might create similar trait patterns. While other theoretical studies have generally demonstrated the importance of predation for coexistence, ours provides the first quantitative demonstration of such effects on assembly process inference, using a trait-based ecological model to simulate the assembly of a competitive primary consumer community with and without the influence of trophic interactions. We quantified and contrasted trait dispersion/clustering of the competitive communities with the absence and presence of secondary consumers. Trophic interactions most often decreased trait clustering (i.e. increased dispersion) in the competitive communities due to evenly distributed invasions of secondary consumers and subsequent competitor extinctions over trait space. Furthermore, effects of trophic interactions were somewhat dependent on model parameters and clustering metric. These effects create considerable problems for process inference from trait distributions; one potential solution is to use more process-based and inclusive models in inference.
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8.
  • Pontarp, Mikael, et al. (författare)
  • Ecological opportunity and predator-prey interactions : linking eco-evolutionary processes and diversification in adaptive radiations
  • 2018
  • Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 285:1874
  • Tidskriftsartikel (refereegranskat)abstract
    • Much of life's diversity has arisen through ecological opportunity and adaptive radiations, but the mechanistic underpinning of such diversification is not fully understood. Competition and predation can affect adaptive radiations, but contrasting theoretical and empirical results show that they can both promote and interrupt diversification. A mechanistic understanding of the link between microevolutionary processes and macroevolutionary patterns is thus needed, especially in trophic communities. Here, we use a trait-based eco-evolutionary model to investigate the mechanisms linking competition, predation and adaptive radiations. By combining available micro-evolutionary theory and simulations of adaptive radiations we show that intraspecific competition is crucial for diversification as it induces disruptive selection, in particular in early phases of radiation. The diversification rate is however decreased in later phases owing to interspecific competition as niche availability, and population sizes are decreased. We provide new insight into how predation tends to have a negative effect on prey diversification through decreased population sizes, decreased disruptive selection and through the exclusion of prey from parts of niche space. The seemingly disparate effects of competition and predation on adaptive radiations, listed in the literature, may thus be acting and interacting in the same adaptive radiation at different relative strength as the radiation progresses.
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9.
  • Pontarp, Mikael, et al. (författare)
  • Inferring community assembly processes from macroscopic patterns using dynamic eco-evolutionary models and Approximate Bayesian Computation (ABC)
  • 2019
  • Ingår i: Methods in Ecology and Evolution. - : John Wiley & Sons. - 2041-210X .- 2041-210X. ; 10:4, s. 450-460
  • Forskningsöversikt (refereegranskat)abstract
    • Statistical techniques exist for inferring community assembly processes from community patterns. Habitat filtering, competition, and biogeographical effects have, for example, been inferred from signals in phenotypic and phylogenetic data. The usefulness of current inference techniques is, however, debated as a mechanistic and causal link between process and pattern is often lacking, and evolutionary processes and trophic interactions are ignored.Here, we revisit the current knowledge on community assembly across scales and, in line with several reviews that have outlined challenges associated with current inference techniques, we identify a discrepancy between the current paradigm of eco-evolutionary community assembly and current inference techniques that focus mainly on competition and habitat filtering. We argue that trait-based dynamic eco-evolutionary models in combination with recently developed model fitting and model evaluation techniques can provide avenues for more accurate, reliable, and inclusive inference. To exemplify, we implement a trait-based, spatially explicit eco-evolutionary model and discuss steps of model modification, fitting, and evaluation as an iterative approach enabling inference from diverse data sources.Through a case study on inference of prey and predator niche width in an eco-evolutionary context, we demonstrate how inclusive and mechanistic approaches-eco-evolutionary modelling and Approximate Bayesian Computation (ABC)-can enable inference of assembly processes that have been largely neglected by traditional techniques despite the ubiquity of such processes.Much literature points to the limitations of current inference techniques, but concrete solutions to such limitations are few. Many of the challenges associated with novel inference techniques are, however, already to some extent resolved in other fields and thus ready to be put into action in a more formal way for inferring processes of community assembly from signals in various data sources.
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10.
  • Rall, Bjoern C., et al. (författare)
  • Universal temperature and body-mass scaling of feeding rates
  • 2012
  • Ingår i: Philosophical Transactions of the Royal Society B: Biological Sciences. - : Royal Society Publishing. - 1471-2970. ; 367:1605, s. 2923-2934
  • Tidskriftsartikel (refereegranskat)abstract
    • Knowledge of feeding rates is the basis to understand interaction strength and subsequently the stability of ecosystems and biodiversity. Feeding rates, as all biological rates, depend on consumer and resource body masses and environmental temperature. Despite five decades of research on functional responses as quantitative models of feeding rates, a unifying framework of how they scale with body masses and temperature is still lacking. This is perplexing, considering that the strength of functional responses (i.e. interaction strengths) is crucially important for the stability of simple consumer-resource systems and the persistence, sustainability and biodiversity of complex communities. Here, we present the largest currently available database on functional response parameters and their scaling with body mass and temperature. Moreover, these data are integrated across ecosystems and metabolic types of species. Surprisingly, we found general temperature dependencies that differed from the Arrhenius terms predicted by metabolic models. Additionally, the body-mass-scaling relationships were more complex than expected and differed across ecosystems and metabolic types. At local scales (taxonomically narrow groups of consumer-resource pairs), we found hump-shaped deviations from the temperature and body-mass-scaling relationships. Despite the complexity of our results, these body-mass-and temperature-scaling models remain useful as a mechanistic basis for predicting the consequences of warming for interaction strengths, population dynamics and network stability across communities differing in their size structure.
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