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Träfflista för sökning "WFRF:(Perkins Guy) "

Sökning: WFRF:(Perkins Guy)

  • Resultat 1-7 av 7
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2.
  • Giménez-García, Angel, et al. (författare)
  • Pollination supply models from a local to global scale
  • 2023
  • Ingår i: Web Ecology. - 1399-1183. ; 23:2, s. 99-129
  • Tidskriftsartikel (refereegranskat)abstract
    • Ecological intensification has been embraced with great interest by the academic sector but is still rarely taken up by farmers because monitoring the state of different ecological functions is not straightforward. Modelling tools can represent a more accessible alternative of measuring ecological functions, which could help promote their use amongst farmers and other decision-makers. In the case of crop pollination, modelling has traditionally followed either a mechanistic or a data-driven approach. Mechanistic models simulate the habitat preferences and foraging behaviour of pollinators, while data-driven models associate georeferenced variables with real observations. Here, we test these two approaches to predict pollination supply and validate these predictions using data from a newly released global dataset on pollinator visitation rates to different crops. We use one of the most extensively used models for the mechanistic approach, while for the data-driven approach, we select from among a comprehensive set of state-of-The-Art machine-learning models. Moreover, we explore a mixed approach, where data-derived inputs, rather than expert assessment, inform the mechanistic model. We find that, at a global scale, machine-learning models work best, offering a rank correlation coefficient between predictions and observations of pollinator visitation rates of 0.56. In turn, the mechanistic model works moderately well at a global scale for wild bees other than bumblebees. Biomes characterized by temperate or Mediterranean forests show a better agreement between mechanistic model predictions and observations, probably due to more comprehensive ecological knowledge and therefore better parameterization of input variables for these biomes. This study highlights the challenges of transferring input variables across multiple biomes, as expected given the different composition of species in different biomes. Our results provide clear guidance on which pollination supply models perform best at different spatial scales-the first step towards bridging the stakeholder-Academia gap in modelling ecosystem service delivery under ecological intensification.
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3.
  • Harling, Guy, et al. (författare)
  • Interviewer-driven variability in social network reporting : results from health and aging in africa: a longitudinal study of an INDEPTH community (HAALSI) in South Africa
  • 2018
  • Ingår i: Field Methods. - : SAGE PUBLICATIONS INC. - 1525-822X .- 1552-3969. ; 30:2, s. 140-154
  • Tidskriftsartikel (refereegranskat)abstract
    • Social network analysis depends on how social ties to others are elicited during interviews, a process easily affected by respondent and interviewer behaviors. We investigate how the number of self-reported important social contacts varied within a single data collection round. Our data come from Health and Aging in Africa: a Longitudinal Study of an INDEPTH community (HAALSI), a comprehensive population-based survey of individuals aged 40 years and older conducted over 13 months at the Agincourt health and demographic surveillance site in rural South Africa. As part of HAALSI, interviewers elicited detailed egocentric network data. The average number of contacts reported by the 5,059 respondents both varied significantly across interviewers and fell over time as the data collection progressed, even after adjusting for respondent, interviewer, and respondent-interviewer dyad characteristics. Contact numbers rose substantially after a targeted interviewer intervention. We conclude that checking (and adjusting) for interviewer effects, even within one data collection round, is critical to valid and reliable social network analysis.
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4.
  • Mim, Carsten, et al. (författare)
  • Structure versus function : Are new conformations of pannexin 1 yet to be resolved?
  • 2021
  • Ingår i: The Journal of General Physiology. - : Rockefeller University Press. - 0022-1295 .- 1540-7748. ; 153:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Pannexin 1 (Panx1) plays a decisive role in multiple physiological and pathological settings, including oxygen delivery to tissues, mucociliary clearance in airways, sepsis, neuropathic pain, and epilepsy. It is widely accepted that Panx1 exerts its role in the context of purinergic signaling by providing a transmembrane pathway for ATP. However, under certain conditions, Panx1 can also act as a highly selective membrane channel for chloride ions without ATP permeability. A recent flurry of publications has provided structural information about the Panx1 channel. However, while these structures are consistent with a chloride selective channel, none show a conformation with strong support for the ATP release function of Panx1. In this Viewpoint, we critically assess the existing evidence for the function and structure of the Panx1 channel and conclude that the structure corresponding to the ATP permeation pathway is yet to be determined. We also list a set of additional topics needing attention and propose ways to attain the large-pore, ATP-permeable conformation of the Panx1 channel.
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5.
  • 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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6.
  • Perkins, Daniel M., et al. (författare)
  • Environmental Warming and Biodiversity-Ecosystem Functioning in Freshwater Microcosms : Partitioning the Effects of Species Identity, Richness and Metabolism
  • 2010
  • Ingår i: Integrative Ecology. - : Academic Press. - 9780123850058 ; 43, s. 177-209
  • Bokkapitel (refereegranskat)abstract
    • Predicting the effects of global warming on biodiversity–ecosystem functioning (B–EF) relationships is complicated by potential interactions among abiotic and biotic variables at multiple levels of organisation, including adaptation within regional species populations and changes in community composition and species richness. We investigated the capacity for assemblages of three freshwater invertebrate consumer species (Asellus aquaticus, Nemoura cinerea and Sericostoma personatum) from temperate (southern England) and boreal (northern Sweden) regions to respond to expected shifts in temperature and basal resources, and quantified rates of a key ecosystem process (leaf-litter decomposition). Predictions of assemblage metabolism, derived from allometric-body size and temperature scaling relationships, accounted for approximately 40% of the variance in decomposition rates. Assemblage species composition accounted for further variance, but species richness per se had no discernible effect. Regional differences were evident in rates of leaf decomposition across temperature and resource manipulations, and in terms of the processing efficiency of temperate and boreal consumers of the same species (i.e. after correcting for body size and metabolic capacity), suggesting that intraspecific variation among local populations could modulate B–EF effects. These differences have implications for extrapolating how environmental warming and other aspects of climate change (e.g. species range shifts) might affect important drivers of ecosystem functioning over large biogeographical scales.
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7.
  • Yvon-Durocher, Gabriel, et al. (författare)
  • Across ecosystem comparisons of size structure: methods, approaches and prospects
  • 2011
  • Ingår i: OIKOS. - : Nordic Ecological Society. - 0030-1299. ; 120:4, s. 550-563
  • Tidskriftsartikel (refereegranskat)abstract
    • Understanding how ecological communities are structured and how this may vary between different types of ecosystems is a fundamental question in ecology. We develop a general framework for quantifying size-structure within and among different ecosystem types (e. g. terrestrial, freshwater or marine), via the use of a suite of bivariate relationships between organismal size and properties of individuals, populations, assemblages, pair-wise interactions, and network topology. Each of these relationships can be considered a dimension of size-structure, along which real communities lie on a continuous scale. For example, the strength, slope, or elevation of the body mass-versus-abundance or predator size-versus-prey size relationships may vary systematically among ecosystem types. We draw on examples from the literature and suggest new ways to use allometries for comparing among ecosystem types, which we illustrate by applying them to published data. Finally, we discuss how dimensions of size-structure are interconnected and how we could approach this complex hierarchy systematically. We conclude: (1) there are multiple dimensions of size-structure; (2) communities may be size-structured in some of these dimensions, but not necessarily in others; (3) across-system comparisons via rigorous quantitative statistical methods are possible, and (4) insufficient data are currently available to illuminate thoroughly the full extent and nature of differences in size-structure among ecosystem types.
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  • Resultat 1-7 av 7

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