@article{SperfeldMartinCreuzburgWacker2012,
  author    = {Sperfeld, Erik and Martin-Creuzburg, Dominik and Wacker, Alexander},
  title     = {Multiple resource limitation theory applied to herbivorous consumers Liebig's minimum rule vs. interactive co-limitation},
  series = {Ecology letters},
  volume    = {15},
  journal   = {Ecology letters},
  number    = {2},
  publisher = {Wiley-Blackwell},
  address   = {Malden},
  issn      = {1461-023X},
  doi       = {10.1111/j.1461-0248.2011.01719.x},
  pages     = {142 -- 150},
  year      = {2012},
  abstract  = {There is growing consensus that the growth of herbivorous consumers is frequently limited by more than one nutrient simultaneously. This understanding, however, is based primarily on theoretical considerations and the applicability of existing concepts of co-limitation has rarely been tested experimentally. Here, we assessed the suitability of two contrasting concepts of resource limitation, i.e. Liebigs minimum rule and the multiple limitation hypothesis, to describe nutrient-dependent growth responses of a freshwater herbivore (Daphnia magna) in a system with two potentially limiting nutrients (cholesterol and eicosapentaenoic acid). The results indicated that these essential nutrients interact, and do not strictly follow Liebigs minimum rule, which consistently overestimates growth at co-limiting conditions and thus is not applicable to describe multiple nutrient limitation of herbivorous consumers. We infer that the outcome of resource-based modelling approaches assessing herbivore population dynamics strongly depends on the applied concept of co-limitation.},
  language  = {en}
}
@article{MartinCreuzburgOexleWacker2014,
  author    = {Martin-Creuzburg, Dominik and Oexle, Sarah and Wacker, Alexander},
  title     = {Thresholds for sterol-limited growth of Daphnia magna: A comparative approach using 10 different sterols},
  series = {Journal of chemical ecology},
  volume    = {40},
  journal   = {Journal of chemical ecology},
  number    = {9},
  publisher = {Springer},
  address   = {Dordrecht},
  issn      = {0098-0331},
  doi       = {10.1007/s10886-014-0486-1},
  pages     = {1039 -- 1050},
  year      = {2014},
  abstract  = {Arthropods are incapable of synthesizing sterols de novo and thus require a dietary source to cover their physiological demands. The most prominent sterol in animal tissues is cholesterol, which is an indispensable structural component of cell membranes and serves as precursor for steroid hormones. Instead of cholesterol, plants and algae contain a variety of different phytosterols. Consequently, herbivorous arthropods have to metabolize dietary phytosterols to cholesterol to meet their requirements for growth and reproduction. Here, we investigated sterol-limited growth responses of the freshwater herbivore Daphnia magna by supplementing a sterol-free diet with increasing amounts of 10 different phytosterols and comparing thresholds for sterol-limited growth. In addition, we analyzed the sterol composition of D. magna to explore sterol metabolic constraints and bioconversion capacities. We show that dietary phytosterols strongly differ in their potential to support somatic growth of D. magna. The dietary threshold concentrations obtained by supplementing the different sterols cover a wide range (3.5-34.4 mu g mg C-1) and encompass the one for cholesterol (8.9 mu g mg C-1), indicating that certain phytosterols are more efficient in supporting somatic growth than cholesterol (e.g., fucosterol, brassicasterol) while others are less efficient (e.g., dihydrocholesterol, lathosterol). The dietary sterol concentration gradients revealed that the poor quality of particular sterols can be alleviated partially by increasing dietary concentrations, and that qualitative differences among sterols are most pronounced at low to moderate dietary concentrations. We infer that the dietary sterol composition has to be considered in zooplankton nutritional ecology to accurately assess potential sterol limitations under field conditions.},
  language  = {en}
}
@article{KoussoroplisSchaelickeRaatzetal.2019,
  author    = {Koussoroplis, Apostolos-Manuel and Sch{\"a}licke, Svenja and Raatz, Michael and Bach, Moritz and Wacker, Alexander},
  title     = {Feeding in the frequency domain},
  series = {Ecology letters},
  volume    = {22},
  journal   = {Ecology letters},
  number    = {7},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {1461-023X},
  doi       = {10.1111/ele.13267},
  pages     = {1104 -- 1114},
  year      = {2019},
  abstract  = {Theory predicts that resource variability hinders consumer performance. How this effect depends on the temporal structure of resource fluctuations encountered by individuals remains poorly understood. Combining modelling and growth experiments with Daphnia magna, we decompose the complexity of resource fluctuations and test the effect of resource variance, supply peak timing (i.e. phase) and co-limiting resource covariance along a gradient from high to low frequencies reflecting fine- to coarse-grained environments. Our results show that resource storage can buffer growth at high frequencies, but yields a sensitivity of growth to resource peak timing at lower ones. When two resources covary, negative covariance causes stronger growth depression at low frequencies. However, negative covariance might be beneficial at intermediate frequencies, an effect that can be explained by digestive acclimation. Our study provides a mechanistic basis for understanding how alterations of the environmental grain size affect consumers experiencing variable nutritional quality in nature.},
  language  = {en}
}