@article{MartinCzesnyWahletal.2016, author = {Martin, Benjamin T. and Czesny, Sergiusz and Wahl, David H. and Grimm, Volker}, title = {Scale-dependent role of demography and dispersal on the distribution of populations in heterogeneous landscapes}, series = {Oikos}, volume = {125}, journal = {Oikos}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0030-1299}, doi = {10.1111/oik.02345}, pages = {667 -- 673}, year = {2016}, abstract = {Both dispersal and local demographic processes determine a population's distribution among habitats of varying quality, yet most theory, experiments, and field studies have focused on the former. We use a generic model to show how both processes contribute to a population's distribution, and how the relative importance of each mechanism depends on scale. In contrast to studies only considering habitat-dependent dispersal, we show that predictions of ideal free distribution (IFD) theory are relevant even at landscape scales, where the assumptions of IFD theory are violated. This is because scales that inhibit one process, promote the other's ability to drive populations to the IFD. Furthermore, because multiple processes can generate IFDs, the pattern alone does not specify a causal mechanism. This is important because populations with IFDs generated by dispersal or demography respond much differently to shifts in resource distributions.}, language = {en} } @article{GrimmAugusiakFocksetal.2014, author = {Grimm, Volker and Augusiak, Jacqueline and Focks, Andreas and Frank, Beatrice M. and Gabsi, Faten and Johnston, Alice S. A. and Liu, Chun and Martin, Benjamin T. and Meli, Mattia and Radchuk, Viktoriia and Thorbek, Pernille and Railsback, Steven Floyd}, title = {Towards better modelling and decision support: Documenting model development, testing, and analysis using TRACE}, series = {Ecological modelling : international journal on ecological modelling and engineering and systems ecolog}, volume = {280}, journal = {Ecological modelling : international journal on ecological modelling and engineering and systems ecolog}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0304-3800}, doi = {10.1016/j.ecolmodel.2014.01.018}, pages = {129 -- 139}, year = {2014}, abstract = {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.}, language = {en} } @misc{SiblyGrimmMartinetal.2013, author = {Sibly, Richard M. and Grimm, Volker and Martin, Benjamin T. and Johnston, Alice S. A. and Kulakowska, Katarzyna and Topping, Christopher J. and Calow, Peter and Nabe-Nielsen, Jacob and Thorbek, Pernille and DeAngelis, Donald L.}, title = {Representing the acquisition and use of energy by individuals in agent-based models of animal populations}, series = {Methods in ecology and evolution : an official journal of the British Ecological Society}, volume = {4}, journal = {Methods in ecology and evolution : an official journal of the British Ecological Society}, number = {2}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {2041-210X}, doi = {10.1111/2041-210x.12002}, pages = {151 -- 161}, year = {2013}, abstract = {Agent-based models (ABMs) are widely used to predict how populations respond to changing environments. As the availability of food varies in space and time, individuals should have their own energy budgets, but there is no consensus as to how these should be modelled. Here, we use knowledge of physiological ecology to identify major issues confronting the modeller and to make recommendations about how energy budgets for use in ABMs should be constructed. Our proposal is that modelled animals forage as necessary to supply their energy needs for maintenance, growth and reproduction. If there is sufficient energy intake, an animal allocates the energy obtained in the order: maintenance, growth, reproduction, energy storage, until its energy stores reach an optimal level. If there is a shortfall, the priorities for maintenance and growth/reproduction remain the same until reserves fall to a critical threshold below which all are allocated to maintenance. Rates of ingestion and allocation depend on body mass and temperature. We make suggestions for how each of these processes should be modelled mathematically. Mortality rates vary with body mass and temperature according to known relationships, and these can be used to obtain estimates of background mortality rate. If parameter values cannot be obtained directly, then values may provisionally be obtained by parameter borrowing, pattern-oriented modelling, artificial evolution or from allometric equations. The development of ABMs incorporating individual energy budgets is essential for realistic modelling of populations affected by food availability. Such ABMs are already being used to guide conservation planning of nature reserves and shell fisheries, to assess environmental impacts of building proposals including wind farms and highways and to assess the effects on nontarget organisms of chemicals for the control of agricultural pests.}, language = {en} } @article{MartinJagerNisbetetal.2013, author = {Martin, Benjamin T. and Jager, Tjalling and Nisbet, Roger M. and Preuss, Thomas G. and Hammers-Wirtz, Monika and Grimm, Volker}, title = {Extrapolating ecotoxicological effects from individuals to populations - a generic approach based on Dynamic Energy Budget theory and individual-based modeling}, series = {Ecotoxicology}, volume = {22}, journal = {Ecotoxicology}, number = {3}, publisher = {Springer}, address = {Dordrecht}, issn = {0963-9292}, doi = {10.1007/s10646-013-1049-x}, pages = {574 -- 583}, year = {2013}, abstract = {Individual-based models (IBMs) predict how dynamics at higher levels of biological organization emerge from individual-level processes. This makes them a particularly useful tool for ecotoxicology, where the effects of toxicants are measured at the individual level but protection goals are often aimed at the population level or higher. However, one drawback of IBMs is that they require significant effort and data to design for each species. A solution would be to develop IBMs for chemical risk assessment that are based on generic individual-level models and theory. Here we show how one generic theory, Dynamic Energy Budget (DEB) theory, can be used to extrapolate the effect of toxicants measured at the individual level to effects on population dynamics. DEB is based on first principles in bioenergetics and uses a common model structure to model all species. Parameterization for a certain species is done at the individual level and allows to predict population-level effects of toxicants for a wide range of environmental conditions and toxicant concentrations. We present the general approach, which in principle can be used for all animal species, and give an example using Daphnia magna exposed to 3,4-dichloroaniline. We conclude that our generic approach holds great potential for standardized ecological risk assessment based on ecological models. Currently, available data from standard tests can directly be used for parameterization under certain circumstances, but with limited extra effort standard tests at the individual would deliver data that could considerably improve the applicability and precision of extrapolation to the population level. Specifically, the measurement of a toxicant's effect on growth in addition to reproduction, and presenting data over time as opposed to reporting a single EC50 or dose response curve at one time point.}, language = {en} } @article{MartinJagerNisbetetal.2013, author = {Martin, Benjamin T. and Jager, Tjalling and Nisbet, Roger M. and Preuss, Thomas G. and Grimm, Volker}, title = {Predicting population dynamics from the properties of individuals - a cross-level test of dynamic energy budget theory}, series = {The American naturalist : a bi-monthly journal devoted to the advancement and correlation of the biological sciences}, volume = {181}, journal = {The American naturalist : a bi-monthly journal devoted to the advancement and correlation of the biological sciences}, number = {4}, publisher = {Univ. of Chicago Press}, address = {Chicago}, issn = {0003-0147}, doi = {10.1086/669904}, pages = {506 -- 519}, year = {2013}, abstract = {Individual-based models (IBMs) are increasingly used to link the dynamics of individuals to higher levels of biological organization. Still, many IBMs are data hungry, species specific, and time-consuming to develop and analyze. Many of these issues would be resolved by using general theories of individual dynamics as the basis for IBMs. While such theories have frequently been examined at the individual level, few cross-level tests exist that also try to predict population dynamics. Here we performed a cross-level test of dynamic energy budget (DEB) theory by parameterizing an individual-based model using individual-level data of the water flea, Daphnia magna, and comparing the emerging population dynamics to independent data from population experiments. We found that DEB theory successfully predicted population growth rates and peak densities but failed to capture the decline phase. Further assumptions on food-dependent mortality of juveniles were needed to capture the population dynamics after the initial population peak. The resulting model then predicted, without further calibration, characteristic switches between small-and large-amplitude cycles, which have been observed for Daphnia. We conclude that cross-level tests help detect gaps in current individual-level theories and ultimately will lead to theory development and the establishment of a generic basis for individual-based models and ecology.}, language = {en} }