TY - JOUR A1 - Groeneveld, Jürgen A1 - Johst, Karin A1 - Kawaguchi, So A1 - Meyer, Bettina A1 - Teschke, Mathias A1 - Grimm, Volker T1 - How biological clocks and changing environmental conditions determine local population growth and species distribution in Antarctic krill (Euphausia superba): a conceptual model JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - The Southern Ocean ecosystem is characterized by extreme seasonal changes in environmental factors such as day length, sea ice extent and food availability. The key species Antarctic krill (Euphausia superba) has evolved metabolic and behavioural seasonal rhythms to cope with these seasonal changes. We investigate the switch between a physiological less active and active period for adult krill, a rhythm which seems to be controlled by internal biological clocks. These biological clocks can be synchronized by environmental triggers such as day length and food availability. They have evolved for particular environmental regimes to synchronize predictable seasonal environmental changes with important life cycle functions of the species. In a changing environment the time when krill is metabolically active and the time of peak food availability may not overlap if krill's seasonal activity is solely determined by photoperiod (day length). This is especially true for the Atlantic sector of the Southern Ocean where the spatio-temporal ice cover dynamics are changing substantially with rising average temperatures. We developed an individual-based model for krill to explore the impact of photoperiod and food availability on the growth and demographics of krill. We simulated dynamics of local krill populations (with no movement of krill assumed) along a south-north gradient for different triggers of metabolic activity and different levels of food availability below the ice. We also observed the fate of larval krill which cannot switch to low metabolism and therefore are likely to overwinter under ice. Krill could only occupy the southern end of the gradient, where algae bloom only lasts for a short time, when alternative food supply under the ice was high and metabolic activity was triggered by photoperiod. The northern distribution was limited by lack of overwintering habitat for krill larvae due to short duration of sea ice cover even for high food content under the ice. The variability of the krill's length-frequency distributions varied for different triggers of metabolic activity, but did not depend on the sea ice extent. Our findings suggest a southward shift of krill populations due to reduction in the spatial sea ice extent, which is consistent with field observations. Overall, our results highlight the importance of the explicit consideration of spatio-temporal sea ice dynamics especially for larval krill together with temporal synchronization through internal clocks, triggered by environmental factors (photoperiod and food) in adult krill for the population modelling of krill. (C) 2015 Elsevier B.V. All rights reserved. KW - Dynamic energy budget theory KW - Individual based model KW - Southern Ocean KW - Sea ice KW - Climate change KW - Marine ecology Y1 - 2015 U6 - https://doi.org/10.1016/j.ecolmodel.2015.02.009 SN - 0304-3800 SN - 1872-7026 VL - 303 SP - 78 EP - 86 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Stillman, Richard A. A1 - Railsback, Steven Floyd A1 - Giske, Jarl A1 - Berger, Uta A1 - Grimm, Volker T1 - Making Predictions in a Changing World: The Benefits of Individual-Based Ecology JF - Bioscience N2 - Ecologists urgently need a better ability to predict how environmental change affects biodiversity. We examine individual-based ecology (IBE), a research paradigm that promises better a predictive ability by using individual-based models (IBMs) to represent ecological dynamics as arising from how individuals interact with their environment and with each other. A key advantage of IBMs is that the basis for predictions-fitness maximization by individual organisms-is more general and reliable than the empirical relationships that other models depend on. Case studies illustrate the usefulness and predictive success of long-term IBE programs. The pioneering programs had three phases: conceptualization, implementation, and diversification. Continued validation of models runs throughout these phases. The breakthroughs that make IBE more productive include standards for describing and validating IBMs, improved and standardized theory for individual traits and behavior, software tools, and generalized instead of system-specific IBMs. We provide guidelines for pursuing IBE and a vision for future IBE research. KW - ecology KW - fitness-maximization KW - individual-based KW - modeling KW - prediction Y1 - 2015 U6 - https://doi.org/10.1093/biosci/biu192 SN - 0006-3568 SN - 1525-3244 VL - 65 IS - 2 SP - 140 EP - 150 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Sundelof, Andreas A1 - Grimm, Volker A1 - Ulmestrand, Mats A1 - Fiksen, Oyvind T1 - Modelling harvesting strategies for the lobster fishery in northern Europe: the importance of protecting egg-bearing females JF - Population ecology KW - European lobster KW - Female moratorium KW - Individual-based model KW - Management KW - Minimum landing size KW - Yield per recruit (YPR) Y1 - 2015 U6 - https://doi.org/10.1007/s10144-014-0460-3 SN - 1438-3896 SN - 1438-390X VL - 57 IS - 1 SP - 237 EP - 251 PB - Springer CY - Tokyo ER - TY - JOUR A1 - Thiele, Jan C. A1 - Grimm, Volker T1 - Replicating and breaking models: good for you and good for ecology JF - Oikos N2 - There are two major limitations to the potential of computational models in ecology for producing general insights: their design is path-dependent, reflecting different underlying questions, assumptions, and data, and there is too little robustness analysis exploring where the model mechanisms explaining certain observations break down. We here argue that both limitations could be overcome if modellers in ecology would more often replicate existing models, try to break the models, and explore modifications. Replication comprises the re-implementation of an existing model and the replication of its results. Breaking models means to identify under what conditions the mechanisms represented in a model can no longer explain observed phenomena. The benefits of replication include less effort being spent to enter the iterative stage of model development and having more time for systematic robustness analysis. A culture of replication would lead to increased credibility, coherence and efficiency of computational modelling and thereby facilitate theory development. Y1 - 2015 U6 - https://doi.org/10.1111/oik.02170 SN - 0030-1299 SN - 1600-0706 VL - 124 IS - 6 SP - 691 EP - 696 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Topping, Christopher J. A1 - Alroe, Hugo Fjelsted A1 - Farrell, Katharine N. A1 - Grimm, Volker T1 - Per Aspera ad Astra: Through Complex Population Modeling to Predictive Theory JF - The American naturalist : a bi-monthly journal devoted to the advancement and correlation of the biological sciences N2 - Population models in ecology are often not good at predictions, even if they are complex and seem to be realistic enough. The reason for this might be that Occam's razor, which is key for minimal models exploring ideas and concepts, has been too uncritically adopted for more realistic models of systems. This can tic models too closely to certain situations, thereby preventing them from predicting the response to new conditions. We therefore advocate a new kind of parsimony to improve the application of Occam's razor. This new parsimony balances two contrasting strategies for avoiding errors in modeling: avoiding inclusion of nonessential factors (false inclusions) and avoiding exclusion of sometimes-important factors (false exclusions). It involves a synthesis of traditional modeling and analysis, used to describe the essentials of mechanistic relationships, with elements that arc included in a model because they have been reported to be or can arguably be assumed to be important under certain conditions. The resulting models should be able to reflect how the internal organization of populations change and thereby generate representations of the novel behavior necessary for complex predictions, including regime shifts. KW - complexity KW - error avoidance KW - agent-based models KW - model development KW - modest approach Y1 - 2015 U6 - https://doi.org/10.1086/683181 SN - 0003-0147 SN - 1537-5323 VL - 186 IS - 5 SP - 669 EP - 674 PB - Univ. of Chicago Press CY - Chicago ER -