TY - JOUR A1 - Radchuk, Viktoriia A1 - Johst, Karin A1 - Groeneveld, Jürgen A1 - Turlure, Camille A1 - Grimm, Volker A1 - Schtickzelle, Nicolas T1 - Appropriate resolution in time and model structure for population viability analysis: Insights from a butterfly metapopulation JF - : an international journal N2 - The importance of a careful choice of the appropriate scale for studying ecological phenomena has been stressed repeatedly. However, issues of spatial scale in metapopulation dynamics received much more attention compared to temporal scale. Moreover, multiple calls were made to carefully choose the appropriate model structure for Population Viability Analysis (PVA). We assessed the effect of using coarser resolution in time and model structure on population dynamics. For this purpose, we compared outcomes of two PVA models differing in their time step: daily individual-based model (dIBM) and yearly stage-based model (ySBM), loaded with empirical data on a well-known metapopulation of the butterfly Boloria eunomia. Both models included the same environmental drivers of population dynamics that were previously identified as being the most important for this species. Under temperature change scenarios, both models yielded the same qualitative scenario ranking, but they quite substantially differed quantitatively with dIBM being more pessimistic in absolute viability measures. We showed that these differences stemmed from inter-individual heterogeneity in dIBM allowing for phenological shifts of individual appearance. We conclude that a finer temporal resolution and an individual-based model structure allow capturing the essential mechanisms necessary to go beyond mere PVA scenario ranking. We encourage researchers to carefully chose the temporal resolution and structure of their model aiming at (1) depicting the processes important for (meta)population dynamics of the species and (2) implementing the environmental change scenarios expected for their study system in the future, using the temporal resolution at which such changes are predicted to operate. KW - Temporal grain KW - Model complexity KW - Model comparison KW - Population dynamics KW - Individual-based model KW - Stage-based model Y1 - 2014 U6 - https://doi.org/10.1016/j.biocon.2013.12.004 SN - 0006-3207 SN - 1873-2917 VL - 169 SP - 345 EP - 354 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Lin, Yue A1 - Huth, Franka A1 - Berger, Uta A1 - Grimm, Volker T1 - The role of belowground competition and plastic biomass allocation in altering plant mass-density relationships JF - Oikos Y1 - 2014 U6 - https://doi.org/10.1111/j.1600-0706.2013.00921.x SN - 0030-1299 SN - 1600-0706 VL - 123 IS - 2 SP - 248 EP - 256 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Becher, Matthias A. A1 - Grimm, Volker A1 - Thorbek, Pernille A1 - Horn, Juliane A1 - Kennedy, Peter J. A1 - Osborne, Juliet L. T1 - BEEHAVE: a systems model of honeybee colony dynamics and foraging to explore multifactorial causes of colony failure JF - Journal of applied ecology : an official journal of the British Ecological Society N2 - BEEHAVE offers a valuable tool for researchers to design and focus field experiments, for regulators to explore the relative importance of stressors to devise management and policy advice and for beekeepers to understand and predict varroa dynamics and effects of management interventions. We expect that scientists and stakeholders will find a variety of applications for BEEHAVE, stimulating further model development and the possible inclusion of other stressors of potential importance to honeybee colony dynamics. KW - Apis mellifera KW - colony decline KW - cross-level interactions KW - feedbacks KW - foraging KW - modelling KW - multiple stressors KW - multi-agent simulation KW - predictive systems ecology KW - Varroa destructor Y1 - 2014 U6 - https://doi.org/10.1111/1365-2664.12222 SN - 0021-8901 SN - 1365-2664 VL - 51 IS - 2 SP - 470 EP - 482 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Grimm, Volker A1 - Augusiak, Jacqueline A1 - Focks, Andreas A1 - Frank, Beatrice M. A1 - Gabsi, Faten A1 - Johnston, Alice S. A. A1 - Liu, Chun A1 - Martin, Benjamin T. A1 - Meli, Mattia A1 - Radchuk, Viktoriia A1 - Thorbek, Pernille A1 - Railsback, Steven Floyd T1 - Towards better modelling and decision support: Documenting model development, testing, and analysis using TRACE JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - The potential of ecological models for supporting environmental decision making is increasingly acknowledged. However, it often remains unclear whether a model is realistic and reliable enough. Good practice for developing and testing ecological models has not yet been established. Therefore, TRACE, a general framework for documenting a model's rationale, design, and testing was recently suggested. Originally TRACE was aimed at documenting good modelling practice. However, the word 'documentation' does not convey TRACE's urgency. Therefore, we re-define TRACE as a tool for planning, performing, and documenting good modelling practice. TRACE documents should provide convincing evidence that a model was thoughtfully designed, correctly implemented, thoroughly tested, well understood, and appropriately used for its intended purpose. TRACE documents link the science underlying a model to its application, thereby also linking modellers and model users, for example stakeholders, decision makers, and developers of policies. We report on first experiences in producing TRACE documents. We found that the original idea underlying TRACE was valid, but to make its use more coherent and efficient, an update of its structure and more specific guidance for its use are needed. The updated TRACE format follows the recently developed framework of model 'evaludation': the entire process of establishing model quality and credibility throughout all stages of model development, analysis, and application. TRACE thus becomes a tool for planning, documenting, and assessing model evaludation, which includes understanding the rationale behind a model and its envisaged use. We introduce the new structure and revised terminology of TRACE and provide examples. (C) 2014 Elsevier B.V. All rights reserved. KW - Standardization KW - Good modelling practice KW - Risk assessment KW - Decision support Y1 - 2014 U6 - https://doi.org/10.1016/j.ecolmodel.2014.01.018 SN - 0304-3800 SN - 1872-7026 VL - 280 SP - 129 EP - 139 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Augusiak, Jacqueline A1 - Van den Brink, Paul J. A1 - Grimm, Volker T1 - Merging validation and evaluation of ecological models to 'evaludation': A review of terminology and a practical approach JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - Confusion about model validation is one of the main challenges in using ecological models for decision support, such as the regulation of pesticides. Decision makers need to know whether a model is a sufficiently good representation of its real counterpart and what criteria can be used to answer this question. Unclear terminology is one of the main obstacles to a good understanding of what model validation is, how it works, and what it can deliver. Therefore, we performed a literature review and derived a standard set of terms. 'Validation' was identified as a catch-all term, which is thus useless for any practical purpose. We introduce the term 'evaludation', a fusion of 'evaluation' and 'validation', to describe the entire process of assessing a model's quality and reliability. Considering the iterative nature of model development, the modelling cycle, we identified six essential elements of evaludation: (i) 'data evaluation' for scrutinising the quality of numerical and qualitative data used for model development and testing; (ii) 'conceptual model evaluation' for examining the simplifying assumptions underlying a model's design; (iii) 'implementation verification' for testing the model's implementation in equations and as a computer programme; (iv) 'model output verification' for comparing model output to data and patterns that guided model design and were possibly used for calibration; (v) 'model analysis' for exploring the model's sensitivity to changes in parameters and process formulations to make sure that the mechanistic basis of main behaviours of the model has been well understood; and (vi) 'model output corroboration' for comparing model output to new data and patterns that were not used for model development and parameterisation. Currently, most decision makers require 'validating' a model by testing its predictions with new experiments or data. Despite being desirable, this is neither sufficient nor necessary for a model to be useful for decision support. We believe that the proposed set of terms and its relation to the modelling cycle can help to make quality assessments and reality checks of ecological models more comprehensive and transparent. (C) 2013 Elsevier B.V. All rights reserved. KW - Model validation KW - Terminology KW - Decision support KW - Documentation KW - Ecological models KW - Risk assessment Y1 - 2014 U6 - https://doi.org/10.1016/j.ecolmodel.2013.11.009 SN - 0304-3800 SN - 1872-7026 VL - 280 SP - 117 EP - 128 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Meli, Mattia A1 - Palmqvist, Annemette A1 - Forbes, Valery E. A1 - Groeneveld, Jürgen A1 - Grimm, Volker T1 - Two pairs of eyes are better than one: Combining individual-based and matrix models for ecological risk assessment of chemicals JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - Current chemical risk assessment procedures may result in imprecise estimates of risk due to sometimes arbitrary simplifying assumptions. As a way to incorporate ecological complexity and improve risk estimates, mechanistic effect models have been recommended. However, effect modeling has not yet been extensively used for regulatory purposes, one of the main reasons being uncertainty about which model type to use to answer specific regulatory questions. We took an individual-based model (IBM), which was developed for risk assessment of soil invertebrates and includes avoidance of highly contaminated areas, and contrasted it with a simpler, more standardized model, based on the generic metapopulation matrix model RAMAS. In the latter the individuals within a sub-population are not treated as separate entities anymore and the spatial resolution is lower. We explored consequences of model aggregation in terms of assessing population-level effects for different spatial distributions of a toxic chemical. For homogeneous contamination of the soil, we found good agreement between the two models, whereas for heterogeneous contamination, at different concentrations and percentages of contaminated area, RAMAS results were alternatively similar to IBM results with and without avoidance, and different food levels. This inconsistency is explained on the basis of behavioral responses that are included in the IBM but not in RAMAS. Overall, RAMAS was less sensitive than the IBM in detecting population-level effects of different spatial patterns of exposure. We conclude that choosing the right model type for risk assessment of chemicals depends on whether or not population-level effects of small-scale heterogeneity in exposure need to be detected. We recommend that if in doubt, both model types should be used and compared. Describing both models following the same standard format, the ODD protocol, makes them equally transparent and understandable. The simpler model helps to build up trust for the more complex model and can be used for more homogeneous exposure patterns. The more complex model helps detecting and understanding the limitations of the simpler model and is needed to ensure ecological realism for more complex exposure scenarios. (C) 2013 Elsevier B.V. All rights reserved. KW - Ecotoxicology KW - Folsomia candida KW - Mechanistic effect models KW - Soil invertebrates Y1 - 2014 U6 - https://doi.org/10.1016/j.ecolmodel.2013.07.027 SN - 0304-3800 SN - 1872-7026 VL - 280 SP - 40 EP - 52 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Gabsi, Faten A1 - Hammers-Wirtz, Monika A1 - Grimm, Volker A1 - Schaeffer, Andreas A1 - Preuss, Thomas G. T1 - Coupling different mechanistic effect models for capturing individual- and population-level effects of chemicals: Lessons from a case where standard risk assessment failed JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - Current environmental risk assessment (ERA) of chemicals for aquatic invertebrates relies on standardized laboratory tests in which toxicity effects on individual survival, growth and reproduction are measured. Such tests determine the threshold concentration of a chemical below which no population-level effects are expected. How well this procedure captures effects on individuals and populations, however, remains an open question. Here we used mechanistic effect models, combining individual-level reproduction and survival models with an individual-based population model (IBM), to understand the individuals' responses and extrapolate them to the population level. We used a toxicant (Dispersogen A) for which adverse effects on laboratory populations were detected at the determined threshold concentration and thus challenged the conservatism of the current risk assessment method. Multiple toxicity effects on reproduction and survival were reported, in addition to effects on the F1 generation. We extrapolated commonly tested individual toxicity endpoints, reproduction and survival, to the population level using the IBM. Effects on reproduction were described via regression models. To select the most appropriate survival model, the IBM was run assuming either stochastic death (SD) or individual tolerance (IT). Simulations were run for different scenarios regarding the toxicant's effects: survival toxicity, reproductive toxicity, or survival and reproductive toxicity. As population-level endpoints, we used population size and structure and extinction risk. We found that survival represented as SD explained population dynamics better than IT. Integrating toxicity effects on both reproduction and survival yielded more accurate predictions of population effects than considering isolated effects. To fully capture population effects observed at high toxicant concentrations, toxicity effects transmitted to the F1 generation had to be integrated. Predicted extinction risk was highly sensitive to the assumptions about individual-level effects. Our results demonstrate that the endpoints used in current standard tests may not be sufficient for assessing the risk of adverse effects on populations. A combination of laboratory population experiments with mechanistic effect models is a powerful tool to better understand and predict effects on both individuals and populations. Mechanistic effect modelling thus holds great potential to improve the accuracy of ERA of chemicals in the future. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved. KW - Individual-based modelling KW - TK/TD modelling KW - Daphnia magna KW - Risk assessment Y1 - 2014 U6 - https://doi.org/10.1016/j.ecolmodel.2013.06.018 SN - 0304-3800 SN - 1872-7026 VL - 280 SP - 18 EP - 29 PB - Elsevier CY - Amsterdam ER - TY - INPR A1 - Grimm, Volker A1 - Thorbek, Pernille T1 - Population models for ecological risk assessment of chemicals: Short introduction and summary of a special issue T2 - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog Y1 - 2014 U6 - https://doi.org/10.1016/j.ecolmodel.2014.01.017 SN - 0304-3800 SN - 1872-7026 VL - 280 SP - 1 EP - 4 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Cortes-Avizanda, Ainara A1 - Jovani, Roger A1 - Antonio Donazar, Jose A1 - Grimm, Volker T1 - Bird sky networks: How do avian scavengers use social information to find carrion? JF - Ecology : a publication of the Ecological Society of America N2 - The relative contribution of personal and social information to explain individual and collective behavior in different species and contexts is an open question in animal ecology. In particular, there is a major lack of studies combining theoretical and empirical approaches to test the relative relevance of different hypothesized individual behaviors to predict empirical collective patterns. We used an individual-based model to confront three hypotheses about the information transfer between social scavengers (Griffon Vultures, Gyps fulvus) when searching for carrion: (1) Vultures only use personal information during foraging ("nonsocial" hypothesis); (2) they create long chains of vultures by following both other vultures that are flying towards carcasses and vultures that are following other vultures that are flying towards carcasses ("chains of vultures" hypothesis); and (3) vultures are only attracted by other vultures that are sinking vertically to a carcass ("local enhancement" hypothesis). The chains of vultures hypothesis has been used in existing models, but never been confronted with field data. Testing is important, though, because these hypotheses could have different management implications. The model was parameterized to mimic the behavior and the densities of both Griffon Vultures and carcasses in a 10 000-km(2) study area in northeastern Spain. We compared the number of vultures attending simulated carcasses with those attending 25 continuously monitored experimental carcasses in the field. Social hypotheses outperformed the nonsocial hypothesis. The chains of vultures hypothesis overestimated the number of vultures feeding on carcasses; the local enhancement hypothesis fitted closely to the empirical data. Supported by our results, we discuss mechanistic and adaptive considerations that reveal that local enhancement may be the key social mechanism behind collective foraging in this and likely other avian scavengers and/or social birds. It also highlights the current need for more studies confronting alternative models of key behaviors with empirical patterns in order to understand how collective behavior emerges in animal societies. KW - carrion resources KW - foraging KW - group-living KW - pulsed resources KW - sociality KW - Spain KW - vultures Y1 - 2014 SN - 0012-9658 SN - 1939-9170 VL - 95 IS - 7 SP - 1799 EP - 1808 PB - Wiley CY - Washington ER - TY - JOUR A1 - McNair, Alistair Senior A1 - Nakagawa, Shinichi A1 - Grimm, Volker T1 - The evolutionary consequences of disrupted male mating signals: An agent-based modelling exploration of endocrine disrupting chemicals in the guppy JF - PLoS one N2 - Females may select a mate based on signalling traits that are believed to accurately correlate with heritable aspects of male quality. Anthropogenic actions, in particular chemicals released into the environment, are now disrupting the accuracy of mating signals to convey information about male quality. The long-term prediction for disrupted mating signals is most commonly loss of female preference. Yet, this prediction has rarely been tested using quantitative models. We use agent-based models to explore the effects of rapid disruption of mating signals. In our model, a gene determines survival. Males signal their level of genetic quality via a signal trait, which females use to select a mate. We allowed this system of sexual selection to become established, before introducing a disruption between the male signal trait and quality, which was similar in nature to that induced by exogenous chemicals. Finally, we assessed the capacity of the system to recover from this disruption. We found that within a relatively short time frame, disruption of mating signals led to a lasting loss of female preference. Decreases in mean viability at the population-level were also observed, because sexual-selection acting against newly arising deleterious mutations was relaxed. The ability of the population to recover from disrupted mating signals was strongly influenced by the mechanisms that promoted or maintained genetic diversity in traits under sexual selection. Our simple model demonstrates that environmental perturbations to the accuracy of male mating signals can result in a long-term loss of female preference for those signals within a few generations. What is more, the loss of this preference can have knock-on consequences for mean population fitness. Y1 - 2014 U6 - https://doi.org/10.1371/journal.pone.0103100 SN - 1932-6203 VL - 9 IS - 7 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Pavlova, Viola A1 - Nabe-Nielsen, Jacob A1 - Dietz, Rune A1 - Svenning, Jens-Christian A1 - Vorkamp, Katrin A1 - Riget, Frank Farso A1 - Sonne, Christian A1 - Letcher, Robert J. A1 - Grimm, Volker T1 - Field metabolic rate and PCB adipose tissue deposition efficiency in East Greenland polar bears derived from contaminant monitoring data JF - PLoS one N2 - Climate change will increasingly affect the natural habitat and diet of polar bears (Ursus maritimus). Understanding the energetic needs of polar bears is therefore important. We developed a theoretical method for estimating polar bear food consumption based on using the highly recalcitrant polychlorinated biphenyl (PCB) congener, 2,2',4,4',55-hexaCB (CB153) in bear adipose tissue as an indicator of food intake. By comparing the CB153 tissue concentrations in wild polar bears with estimates from a purposely designed individual-based model, we identified the possible combinations of field metabolic rates (FMR) and CB153 deposition efficiencies in East Greenland polar bears. Our simulations indicate that if 30% of the CB153 consumed by polar bear individuals were deposited into their adipose tissue, the corresponding FMR would be only two times the basal metabolic rate. In contrast, if the modelled CB153 deposition efficiency were 10%, adult polar bears would require six times more energy than that needed to cover basal metabolism. This is considerably higher than what has been assumed for polar bears in previous studies though it is similar to FMRs found in other marine mammals. An implication of this result is that even relatively small reductions in future feeding opportunities could impact the survival of East Greenland polar bears. Y1 - 2014 U6 - https://doi.org/10.1371/journal.pone.0104037 SN - 1932-6203 VL - 9 IS - 8 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Martin, Benjamin A1 - Jager, Tjalling A1 - Nisbet, Roger M. A1 - Preuss, Thomas G. A1 - Grimm, Volker T1 - Limitations of extrapolating toxic effects on reproduction to the population level JF - Ecological applications : a publication of the Ecological Society of America N2 - For the ecological risk assessment of toxic chemicals, standardized tests on individuals are often used as proxies for population-level effects. Here, we address the utility of one commonly used metric, reproductive output, as a proxy for population-level effects. Because reproduction integrates the outcome of many interacting processes (e.g., feeding, growth, allocation of energy to reproduction), the observed toxic effects in a reproduction test could be due to stress on one of many processes. Although this makes reproduction a robust endpoint for detecting stress, it may mask important population-level consequences if the different physiological processes stress affects are associated with different feedback mechanisms at the population level. We therefore evaluated how an observed reduction in reproduction found in a standard reproduction test translates to effects at the population level if it is caused by hypothetical toxicants affecting different physiological processes (physiological modes of action; PMoA). For this we used two consumer-resource models: the Yodzis-Innes (YI) model, which is mathematically tractable, but requires strong assumptions of energetic equivalence among individuals as they progress through ontogeny, and an individual-based implementation of dynamic energy budget theory (DEB-IBM), which relaxes these assumptions at the expense of tractability. We identified two important feedback mechanisms controlling the link between individual- and population-level stress in the YI model. These mechanisms turned out to also be important for interpreting some of the individual-based model results; for two PMoAs, they determined the population response to stress in both models. In contrast, others stress types involved more complex feedbacks, because they asymmetrically stressed the production efficiency of reproduction and somatic growth. The feedbacks associated with different PMoAs drastically altered the link between individual- and population-level effects. For example, hypothetical stressors with different PMoAs that had equal effects on reproduction had effects ranging from a negligible decline in biomass to population extinction. Thus, reproduction tests alone are of little use for extrapolating toxicity to the population level, but we showed that the ecological relevance of standard tests could easily be improved if growth is measured along with reproduction. KW - Daphnia KW - dynamic energy budget KW - ecological risk assessment KW - ecotoxicology KW - ontogenetic symmetry KW - physiological mode of action KW - PMoA KW - population dynamics KW - reproduction test KW - Yodzis-Innes Y1 - 2014 U6 - https://doi.org/10.1890/14-0656.1 SN - 1051-0761 SN - 1939-5582 VL - 24 IS - 8 SP - 1972 EP - 1983 PB - Wiley CY - Washington ER -