@article{RaatzSchaelickeSieberetal.2018, author = {Raatz, Michael and Sch{\"a}licke, Svenja and Sieber, M. and Wacker, Alexander and Gaedke, Ursula}, title = {One man's trash is another man's treasure}, series = {Limnology and Oceanography: Methods}, volume = {16}, journal = {Limnology and Oceanography: Methods}, number = {10}, publisher = {Wiley}, address = {Hoboken}, issn = {1541-5856}, doi = {10.1002/lom3.10269}, pages = {629 -- 639}, year = {2018}, abstract = {Chemostat experiments are employed to study predator-prey and other trophic interactions, frequently using phytoplankton-zooplankton systems. These experiments often use population dynamics as fingerprints of ecological and evolutionary processes, assuming that the contributions of all major actors to these dynamics are known. However, bacteria are often neglected although they are frequently present. We argue that even without external carbon input bacteria may affect the experimental outcomes depending on experimental conditions and the physiological traits of bacteria, phytoplankton, and zooplankton. Using a static carbon flux model and a dynamic simulation model, we predict the minimum and maximum impact of bacteria on phytoplankton-zooplankton population dynamics. Under bacteria-suppressing conditions, we find that the effect of bacteria is indeed negligible and their omission justified. Under bacteria-favoring conditions, however, bacteria may strongly affect average biomasses of phytoplankton and zooplankton. The population dynamics may become highly complex, which may result in wrong interpretations when inferring processes (e.g., trait changes) from population dynamic patterns without considering bacteria. We provide suggestions to reduce the bacterial impact experimentally. Besides optimizing experimental conditions (e.g., the dilution rate) the appropriate choice of the zooplankton predator is decisive. Counterintuitively, bacteria have a larger impact if the predator is not bacterivorous as high bacterial biomasses and complex population dynamics arise via competition for nutrients with the phytoplankton. Only at least partial bacterivory minimizes the impact of bacteria. Our results help to improve the design of chemostat experiments and their interpretation, and advance the study of ecological and evolutionary processes in aquatic food webs.}, language = {en} } @article{SchaelickeHeimMartinCreuzburgetal.2020, author = {Sch{\"a}licke, Svenja and Heim, Silvia and Martin-Creuzburg, Dominik and Wacker, Alexander}, title = {Inter- and intraspecific differences in rotifer fatty acid composition during acclimation to low-quality food}, series = {Philosophical transactions of the Royal Society of London : B, Biological sciences}, volume = {375}, journal = {Philosophical transactions of the Royal Society of London : B, Biological sciences}, number = {1804}, publisher = {Royal Society}, address = {London}, issn = {0962-8436}, doi = {10.1098/rstb.2019.0644}, pages = {8}, year = {2020}, abstract = {Biochemical food quality constraints affect the performance of consumers and mediate trait variation among and within consumer species. To assess inter- and intraspecific differences in fatty acid retention and conversion in freshwater rotifers, we provided four strains of two closely related rotifer species,Brachionus calyciflorussensustricto andBrachionus fernandoi, with food algae differing in their fatty acid composition. The rotifers grazed for 5 days on eitherNannochloropsis limneticaorMonoraphidium minutum, two food algae with distinct polyunsaturated fatty acid (PUFA) profiles, before the diets were switched to PUFA-freeSynechococcus elongatus, which was provided for three more days. We found between- and within-species differences in rotifer fatty acid compositions on the respective food sources and, in particular, highly specific acclimation reactions to the PUFA-free diet. The different reactions indicate inter- but also intraspecific differences in physiological traits, such as PUFA retention, allocation and bioconversion capacities, within the genusBrachionusthat are most likely accompanied by differences in their nutritional demands. Our data suggest that biochemical food quality constraints act differently on traits of closely related species and of strains of a particular species and thus might be involved in shaping ecological interactions and evolutionary processes. This article is part of the theme issue 'The next horizons for lipids as 'trophic biomarkers': evidence and significance of consumer modification of dietary fatty acids'.}, language = {en} } @article{SchaelickeSobischMartinCreuzburgetal.2019, author = {Sch{\"a}licke, Svenja and Sobisch, Lydia-Yasmin and Martin-Creuzburg, Dominik and Wacker, Alexander}, title = {Food quantity-quality co-limitation}, series = {Freshwater biology}, volume = {64}, journal = {Freshwater biology}, number = {5}, publisher = {Wiley}, address = {Hoboken}, issn = {0046-5070}, doi = {10.1111/fwb.13272}, pages = {903 -- 912}, year = {2019}, abstract = {Food quantity and quality are highly variable in natural systems. Therefore, their interplay and the associated effects on consumer population growth are important for predator-prey interactions and community dynamics. Experiments in which consumers were exposed to elemental nutrient limitations along food quantity gradients suggest that food quality effects on consumer performance are relevant only at high food quantities. However, elemental nutrients act differently on physiological processes than biochemical nutrients. So far, the interactive effects of food quantity and biochemical compounds on consumer performance have been insufficiently studied. We studied interactive effects of food quantity and biochemical food quality on population growth, including fecundity and survival, of the freshwater rotifer Brachionus calyciflorus. We hypothesised that these life history traits are differently affected by the availability of biochemical nutrients and that food quality effects gain importance with increasing food quantity. In a first experiment, we established food quantity and quality gradients by providing rotifers with different concentrations of a low-quality food, the sterol-free cyanobacterium Synechococcus elongatus, supplemented with increasing amounts of cholesterol. In a second experiment, food quantity and quality gradients were established by providing different proportions of two prey species differing in biochemical food quality, i.e. S.elongatus and the lipid-rich alga Nannochloropsis limnetica, at different total food concentrations. We found that the effects of cholesterol supplementation on population growth increased with increasing food quantity. This interactive effect on population growth was mainly due to food quality effects on fecundity, as effects on survival remained constant along the food quantity gradient. In contrast, when feeding on the mixed algal diet, the food quality effect associated with increasing the proportion of the high-quality alga did not change along the food quantity gradient. The data on survival and fecundity demonstrate the missing interactive effect of food quantity and quality on population growth, as both traits were oppositely affected. Survival was affected by food quality primarily at low food quantity, whereas food quality effects on fecundity were stronger at high food quantity. Our results highlight the significance of essential biochemicals in mediating the interactive effects of food quantity and quality on population growth. The interplay between food quantity and biochemical food quality limitation seems to influence resource allocation patterns in order to optimise survival or reproduction, which may strongly affect population dynamics in variable environments. As opposed to exploring the function of a single nutrient via supplementation, using algae mixtures allowed us to assess food quality effects on consumer performance in a more natural context by taking potential interactive effects of multiple co-limiting nutrients into account.}, language = {en} } @misc{SchaelickeTeubnerMartinCreuzburgetal.2019, author = {Sch{\"a}licke, Svenja and Teubner, Johannes and Martin-Creuzburg, Dominik and Wacker, Alexander}, title = {Fitness response variation within and among consumer species can be co-mediated by food quantity and biochemical quality}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {806}, issn = {1866-8372}, doi = {10.25932/publishup-44225}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-442256}, pages = {11}, year = {2019}, abstract = {In natural heterogeneous environments, the fitness of animals is strongly influenced by the availability and composition of food. Food quantity and biochemical quality constraints may affect individual traits of consumers differently, mediating fitness response variation within and among species. Using a multifactorial experimental approach, we assessed population growth rate, fecundity, and survival of six strains of the two closely related freshwater rotifer species Brachionus calyciflorus sensu stricto and Brachionus fernandoi. Therefore, rotifers fed low and high concentrations of three algal species differing in their biochemical food quality. Additionally, we explored the potential of a single limiting biochemical nutrient to mediate variations in population growth response. Therefore, rotifers fed a sterol-free alga, which we supplemented with cholesterol-containing liposomes. Co-limitation by food quantity and biochemical food quality resulted in differences in population growth rates among strains, but not between species, although effects on fecundity and survival differed between species. The effect of cholesterol supplementation on population growth was strain-specific but not species-specific. We show that fitness response variations within and among species can be mediated by biochemical food quality. Dietary constraints thus may act as evolutionary drivers on physiological traits of consumers, which may have strong implications for various ecological interactions.}, language = {en} } @article{SchaelickeTeubnerMartinCreuzburgetal.2019, author = {Sch{\"a}licke, Svenja and Teubner, Johannes and Martin-Creuzburg, Dominik and Wacker, Alexander}, title = {Fitness response variation within and among consumer species can be co-mediated by food quantity and biochemical quality}, series = {Scientific Reports}, volume = {9}, journal = {Scientific Reports}, publisher = {Macmillan Publishers Limited}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-019-52538-2}, pages = {9}, year = {2019}, abstract = {In natural heterogeneous environments, the fitness of animals is strongly influenced by the availability and composition of food. Food quantity and biochemical quality constraints may affect individual traits of consumers differently, mediating fitness response variation within and among species. Using a multifactorial experimental approach, we assessed population growth rate, fecundity, and survival of six strains of the two closely related freshwater rotifer species Brachionus calyciflorus sensu stricto and Brachionus fernandoi. Therefore, rotifers fed low and high concentrations of three algal species differing in their biochemical food quality. Additionally, we explored the potential of a single limiting biochemical nutrient to mediate variations in population growth response. Therefore, rotifers fed a sterol-free alga, which we supplemented with cholesterol-containing liposomes. Co-limitation by food quantity and biochemical food quality resulted in differences in population growth rates among strains, but not between species, although effects on fecundity and survival differed between species. The effect of cholesterol supplementation on population growth was strain-specific but not species-specific. We show that fitness response variations within and among species can be mediated by biochemical food quality. Dietary constraints thus may act as evolutionary drivers on physiological traits of consumers, which may have strong implications for various ecological interactions.}, 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} } @phdthesis{Schaelicke2020, author = {Sch{\"a}licke, Svenja}, title = {Consumer traits and trait variation under the influence of biochemical food quality}, school = {Universit{\"a}t Potsdam}, pages = {136}, year = {2020}, abstract = {The earth's ecosystems undergo considerable changes characterized by human-induced alterations of environmental factors. In order to develop conservation goals for vulnerable ecosystems, research on ecosystem functioning is required.. Therefore, it is crucial to explore organismal interactions, such as trophic interaction or competition, which are decisive for key processes in ecosystems. These interactions are determined by the performance responses of organisms to environmental changes, which in turn, are shaped by the organism's functional traits. Exploring traits, their variation, and the environmental factors that act on them may provide insights on how ecological interactions affect populations, community structures and dynamics, and thus ecosystem functioning. In aquatic ecosystems, global warming intensifies phytoplankton blooms, which are more frequently dominated by cyanobacteria. As cyanobacteria are poor in polyunsaturated fatty acids (PUFA) and sterols, this compositional change alters the biochemical food quality of phytoplankton for consumer species with potential effects on ecological interactions. Within this thesis, I studied the effects of biochemical food quality on consumer traits and performance responses at the phytoplankton-zooplankton interface using different strains of two closely related generalist rotifer species Brachionus calyciflorus and Brachionus fernandoi and three phytoplankton species that differ in their biochemical food quality, i.e. in their content and composition of PUFA and sterols. In a series of laboratory feeding experiments I found that biochemical food quality affected rotifer's performance, i.e. fecundity, survival, and population growth, across a broad range of food quantities. Biochemical food quality constraints, which are often underestimated as influencing environmental factors, had strong impacts on performance responses. I further explored the potential of biochemical food quality in mediating consumer response variation between species and among strains of one species. Co-limitation by food quantity and biochemical food quality resulted in differences in performance responses, which were more pronounced within than between rotifer species. Furthermore, I demonstrated that the body PUFA compositions of rotifer species and strains were differently affected by the dietary PUFA supply, which indicates inter- and intraspecific differences in physiological traits, such as PUFA retention, allocation, and/or bioconversion capacity, within the genus Brachionus. This indicates that dietary PUFA are involved in shaping traits and performance responses of rotifers. This thesis reveals that biochemical food quality is an environmental factor with strong effects on individual traits and performance responses of consumers. Biochemical food quality constraints can further mediate trait and response variation among species or strains. Consequently, they carry the potential to shape ecological interactions and evolutionary processes with effects on community structures and dynamics. Trait-based approaches, which include food quality research, thus may provide further insights into the linkage between functional diversity and the maintenance of crucial ecosystem functions.}, language = {en} }