TY - JOUR A1 - Klauschies, Toni A1 - Vasseur, David A. A1 - Gaedke, Ursula T1 - Trait adaptation promotes species coexistence in diverse predator and prey communities JF - Ecology and evolution N2 - Species can adjust their traits in response to selection which may strongly influence species coexistence. Nevertheless, current theory mainly assumes distinct and time-invariant trait values. We examined the combined effects of the range and the speed of trait adaptation on species coexistence using an innovative multispecies predator–prey model. It allows for temporal trait changes of all predator and prey species and thus simultaneous coadaptation within and among trophic levels. We show that very small or slow trait adaptation did not facilitate coexistence because the stabilizing niche differences were not sufficient to offset the fitness differences. In contrast, sufficiently large and fast trait adaptation jointly promoted stable or neutrally stable species coexistence. Continuous trait adjustments in response to selection enabled a temporally variable convergence and divergence of species traits; that is, species became temporally more similar (neutral theory) or dissimilar (niche theory) depending on the selection pressure, resulting over time in a balance between niche differences stabilizing coexistence and fitness differences promoting competitive exclusion. Furthermore, coadaptation allowed prey and predator species to cluster into different functional groups. This equalized the fitness of similar species while maintaining sufficient niche differences among functionally different species delaying or preventing competitive exclusion. In contrast to pre- vious studies, the emergent feedback between biomass and trait dynamics enabled supersaturated coexistence for a broad range of potential trait adaptation and parameters. We conclude that accounting for trait adaptation may explain stable and supersaturated species coexistence for a broad range of environmental conditions in natural systems when the absence of such adaptive changes would preclude it. Small trait changes, coincident with those that may occur within many natural populations, greatly enlarged the number of coexisting species. KW - Coadaptation KW - equalizing and stabilizing mechanisms KW - maintenance of functional diversity KW - niche and fitness differences KW - supersaturated species coexistence KW - trait convergence and divergence Y1 - 2016 U6 - https://doi.org/10.1002/ece3.2172 SN - 2045-7758 PB - John Wiley & Sons, Inc. ER - TY - JOUR A1 - Klauschies, Toni A1 - Vasseur, David A. A1 - Gaedke, Ursula T1 - Trait adaptation promotes species coexistence in diverse predator and prey communities JF - Ecology and evolution N2 - Species can adjust their traits in response to selection which may strongly influence species coexistence. Nevertheless, current theory mainly assumes distinct and time-invariant trait values. We examined the combined effects of the range and the speed of trait adaptation on species coexistence using an innovative multispecies predator-prey model. It allows for temporal trait changes of all predator and prey species and thus simultaneous coadaptation within and among trophic levels. We show that very small or slow trait adaptation did not facilitate coexistence because the stabilizing niche differences were not sufficient to offset the fitness differences. In contrast, sufficiently large and fast trait adaptation jointly promoted stable or neutrally stable species coexistence. Continuous trait adjustments in response to selection enabled a temporally variable convergence and divergence of species traits; that is, species became temporally more similar (neutral theory) or dissimilar (niche theory) depending on the selection pressure, resulting over time in a balance between niche differences stabilizing coexistence and fitness differences promoting competitive exclusion. Furthermore, coadaptation allowed prey and predator species to cluster into different functional groups. This equalized the fitness of similar species while maintaining sufficient niche differences among functionally different species delaying or preventing competitive exclusion. In contrast to previous studies, the emergent feedback between biomass and trait dynamics enabled supersaturated coexistence for a broad range of potential trait adaptation and parameters. We conclude that accounting for trait adaptation may explain stable and supersaturated species coexistence for a broad range of environmental conditions in natural systems when the absence of such adaptive changes would preclude it. Small trait changes, coincident with those that may occur within many natural populations, greatly enlarged the number of coexisting species. KW - Coadaptation KW - equalizing and stabilizing mechanisms KW - maintenance of functional diversity KW - niche and fitness differences KW - supersaturated species coexistence KW - trait convergence and divergence Y1 - 2016 U6 - https://doi.org/10.1002/ece3.2172 SN - 2045-7758 VL - 6 SP - 4141 EP - 4159 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Klauschies, Toni A1 - Isanta-Navarro, Jana T1 - The joint effects of salt and 6PPD contamination on a freshwater herbivore JF - The science of the total environment : an international journal for scientific research into the environment and its relationship with man N2 - Using sodium chloride (NaCl) for de-icing roads is known to have severe consequences on freshwater organisms when washed into water bodies. N-(1,3-dimethylbutyl)-N '-phenyl-p-phenylenediamine, also known as 6PPD, is an antiozonant mainly found in automobile tire rubber to prevent ozone mediated cracking or wear-out. Especially the ozonated derivate, 6PPD-quinone, which is washed into streams after storm events, has been found to be toxic for coho salmon. Studies on other freshwater organisms could not confirm those findings, pointing towards distinct species-specific differences. Storm events result in greater run-offs from all water-soluble contaminants into freshwater bodies, potentially enhancing the concentrations of both chloride and 6PPD during winter. Here we show that these two contaminants have synergistic negative effects on the population growth of the rotifer Brachionus calyciflorus, a common freshwater herbivore. Hence, while only high concentrations of 6PPD and even higher concentrations of 6PPD-quinone, beyond environmentally relevant concentrations, had lethal effects on rotifers, the addition of NaCl enhanced the sensitivity of the rotifers towards the application of 6PPD so that their negative effects were more pronounced at lower concentrations. Similarly, 6PPD increased the lethal effect of NaCl. Our results support the species-specific toxicity of 6PPD and demonstrate a synergistic effect of the antiozonant on the toxicity of other environmentally relevant stressors, such as road salt contamination. KW - Anthropogenic impact KW - Car tire rubber KW - Environmental stressor KW - Rotifer KW - Sodium chloride KW - 6PPD quinone Y1 - 2022 U6 - https://doi.org/10.1016/j.scitotenv.2022.154675 SN - 0048-9697 SN - 1879-1026 VL - 829 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ceulemans, Ruben A1 - Gaedke, Ursula A1 - Klauschies, Toni A1 - Guill, Christian T1 - The effects of functional diversity on biomass production, variability, and resilience of ecosystem functions in a tritrophic system JF - Scientific Reports N2 - Diverse communities can adjust their trait composition to altered environmental conditions, which may strongly influence their dynamics. Previous studies of trait-based models mainly considered only one or two trophic levels, whereas most natural system are at least tritrophic. Therefore, we investigated how the addition of trait variation to each trophic level influences population and community dynamics in a tritrophic model. Examining the phase relationships between species of adjacent trophic levels informs about the strength of top-down or bottom-up control in non-steadystate situations. Phase relationships within a trophic level highlight compensatory dynamical patterns between functionally different species, which are responsible for dampening the community temporal variability. Furthermore, even without trait variation, our tritrophic model always exhibits regions with two alternative states with either weak or strong nutrient exploitation, and correspondingly low or high biomass production at the top level. However, adding trait variation increased the basin of attraction of the high-production state, and decreased the likelihood of a critical transition from the high- to the lowproduction state with no apparent early warning signals. Hence, our study shows that trait variation enhances resource use efficiency, production, stability, and resilience of entire food webs. KW - early-warning signals KW - top-down control KW - community ecology KW - regime shifts KW - food webs KW - compensatory dynamics KW - consumer diversity KW - metabolic theory KW - rapid evolution KW - stable states Y1 - 2019 U6 - https://doi.org/10.1038/s41598-019-43974-1 SN - 2045-2322 VL - 9 PB - Macmillan Publishers Limited CY - London ER - TY - JOUR A1 - Guill, Christian A1 - Hülsemann, Janne A1 - Klauschies, Toni T1 - Self-organised pattern formation increases local diversity in metacommunities JF - Ecology letters N2 - Self-organised formation of spatial patterns is known from a variety of different ecosystems, yet little is known about how these patterns affect the diversity of communities. Here, we use a food chain model in which autotroph diversity is described by a continuous distribution of a trait that affects both growth and defence against heterotrophs. On isolated patches, diversity is always lost over time due to stabilising selection, and the local communities settle on one of two alternative stable community states that are characterised by a dominance of either defended or undefended species. In a metacommunity context, dispersal can destabilise these states and complex spatio-temporal patterns in the species' abundances emerge. The resulting biomass-trait feedback increases local diversity by an order of magnitude compared to scenarios without self-organised pattern formation, thereby maintaining the ability of communities to adapt to potential future changes in biotic or abiotic environmental conditions. KW - biomass-trait feedback KW - fitness gradient KW - food chain KW - functional KW - diversity KW - metacommunity KW - self-organisation KW - source-sink dynamics KW - spatio-temporal pattern KW - trait-based aggregate model KW - Turing instability Y1 - 2021 U6 - https://doi.org/10.1111/ele.13880 SN - 1461-023X SN - 1461-0248 VL - 24 IS - 12 SP - 2624 EP - 2634 PB - Wiley-Blackwell CY - Oxford ER - TY - JOUR A1 - Velzen, Ellen van A1 - Gaedke, Ursula A1 - Klauschies, Toni T1 - Quantifying the capacity for contemporary trait changes to drive intermittent predator-prey cycles JF - Ecological monographs : a publication of the Ecological Society of America N2 - A large and growing body of theory has demonstrated how the presence of trait variation in prey or predator populations may affect the amplitude and phase of predator-prey cycles. Less attention has been given to so-called intermittent cycles, in which predator-prey oscillations recurrently disappear and re-appear, despite such dynamics being observed in empirical systems and modeling studies. A comprehensive understanding of the conditions under which trait changes may drive intermittent predator-prey dynamics, as well as their potential ecological implications, is therefore missing. Here we provide a first systematic analysis of the eco-evolutionary conditions that may give rise to intermittent predator-prey cycles, investigating 16 models that incorporate different types of trait variation within prey, predators, or both. Our results show that intermittent dynamics often arise through predator-prey coevolution, but only very rarely when only one trophic level can adapt. Additionally, the frequency of intermittent cycles depends on the source of trait variation (genetic variation or phenotypic plasticity) and the genetic architecture (Mendelian or quantitative traits), with intermittency occurring most commonly through Mendelian evolution, and very rarely through phenotypic plasticity. Further analysis identified three necessary conditions for when trait variation can drive intermittent cycles. First, the intrinsic stability of the predator-prey system must depend on the traits of prey, predators, or both. Second, there must be a mechanism causing the recurrent alternation between stable and unstable states, leading to a "trait" cycle superimposed on the population dynamics. Finally, these trait dynamics must be significantly slower than the predator-prey cycles. We show how these conditions explain all the abovementioned patterns. We further show an important unexpected consequence of these necessary conditions: they are most easily met when intraspecific trait variation is at high risk of being lost. As trait diversity is positively associated with ecosystem functioning, this can have potentially severe negative consequences. This novel result highlights the importance of identifying and understanding intermittent cycles in theoretical studies and natural systems. The new approach for detecting and quantifying intermittency we develop here will be instrumental in enabling future study. KW - eco-evolutionary feedbacks KW - ecosystem functioning KW - intraspecific trait KW - variation KW - population cycles KW - predator-prey dynamics KW - trait dynamics Y1 - 2022 U6 - https://doi.org/10.1002/ecm.1505 SN - 1557-7015 SN - 0012-9615 VL - 92 IS - 2 PB - Wiley CY - New York ER - TY - JOUR A1 - Flöder, Sabine A1 - Yong, Joanne A1 - Klauschies, Toni A1 - Gaedke, Ursula A1 - Poprick, Tobias A1 - Brinkhoff, Thorsten A1 - Moorthi, Stefanie T1 - Intraspecific trait variation alters the outcome of competition in freshwater ciliates JF - Ecology and evolution N2 - Trait variation among heterospecific and conspecific organisms may substantially affect community and food web dynamics. While the relevance of competition and feeding traits have been widely studied for different consumer species, studies on intraspecific differences are more scarce, partly owing to difficulties in distinguishing different clones of the same species. Here, we investigate how intraspecific trait variation affects the competition between the freshwater ciliates Euplotes octocarinatus and Coleps hirtus in a nitrogen-limited chemostat system. The ciliates competed for the microalgae Cryptomonas sp. (Cry) and Navicula pelliculosa (Nav), and the bacteria present in the cultures over a period of 33 days. We used monoclonal Euplotes and three different Coleps clones (Col 1, Col 2, and Col 3) in the experiment that could be distinguished by a newly developed rDNA-based molecular assay based on the internal transcribed spacer (ITS) regions. While Euplotes feeds on Cry and on bacteria, the Coleps clones cannot survive on bacteria alone but feed on both Cry and Nav with clone-specific rates. Experimental treatments comprised two-species mixtures of Euplotes and one or all of the three different Coleps clones, respectively. We found intraspecific variation in the traits "selectivity" and "maximum ingestion rate" for the different algae to significantly affect the competitive outcome between the two ciliate species. As Nav quickly escaped top-down control and likely reached a state of low food quality, ciliate competition was strongly determined by the preference of different Coleps clones for Cry as opposed to feeding on Nav. In addition, the ability of Euplotes to use bacteria as an alternative food source strengthened its persistence once Cry was depleted. Hence, trait variation at both trophic levels codetermined the population dynamics and the outcome of species competition. KW - ciliate predators KW - intraspecific trait variation KW - microalgal resource KW - predator trait variation KW - predator-prey systems KW - resource competition Y1 - 2021 U6 - https://doi.org/10.1002/ece3.7828 SN - 2045-7758 VL - 11 IS - 15 SP - 10225 EP - 10243 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Bauer, Barbara A1 - Vos, Matthijs A1 - Klauschies, Toni A1 - Gaedke, Ursula T1 - Diversity, functional similarity, and top-down control drive synchronization and the reliability of ecosystem function JF - The American naturalist : a bi-monthly journal devoted to the advancement and correlation of the biological sciences N2 - The concept that diversity promotes reliability of ecosystem function depends on the pattern that community-level biomass shows lower temporal variability than species-level biomasses. However, this pattern is not universal, as it relies on compensatory or independent species dynamics. When in contrast within--trophic level synchronization occurs, variability of community biomass will approach population-level variability. Current knowledge fails to integrate how species richness, functional distance between species, and the relative importance of predation and competition combine to drive synchronization at different trophic levels. Here we clarify these mechanisms. Intense competition promotes compensatory dynamics in prey, but predators may at the same time increasingly synchronize, under increasing species richness and functional similarity. In contrast, predators and prey both show perfect synchronization under strong top-down control, which is promoted by a combination of low functional distance and high net growth potential of predators. Under such conditions, community-level biomass variability peaks, with major negative consequences for reliability of ecosystem function. KW - biodiversity KW - ecosystem services KW - population dynamics KW - predator-prey system KW - species richness KW - synchrony Y1 - 2014 U6 - https://doi.org/10.1086/674906 SN - 0003-0147 SN - 1537-5323 VL - 183 IS - 3 SP - 394 EP - 409 PB - Univ. of Chicago Press CY - Chicago ER - TY - JOUR A1 - Klauschies, Toni A1 - Bauer, Barbara A1 - Aberle-Malzahn, Nicole A1 - Sommer, Ulrich A1 - Gaedke, Ursula T1 - Climate change effects on phytoplankton depend on cell size and food web structure JF - Marine biology : international journal on life in oceans and coastal waters N2 - We investigated the effects of warming on a natural phytoplankton community from the Baltic Sea, based on six mesocosm experiments conducted 2005-2009. We focused on differences in the dynamics of three phytoplankton size groups which are grazed to a variable extent by different zooplankton groups. While small-sized algae were mostly grazer-controlled, light and nutrient availability largely determined the growth of medium- and large-sized algae. Thus, the latter groups dominated at increased light levels. Warming increased mesozooplankton grazing on medium-sized algae, reducing their biomass. The biomass of small-sized algae was not affected by temperature, probably due to an interplay between indirect effects spreading through the food web. Thus, under the higher temperature and lower light levels anticipated for the next decades in the southern Baltic Sea, a higher share of smaller phytoplankton is expected. We conclude that considering the size structure of the phytoplankton community strongly improves the reliability of projections of climate change effects. Y1 - 2012 U6 - https://doi.org/10.1007/s00227-012-1904-y SN - 0025-3162 VL - 159 IS - 11 SP - 2455 EP - 2478 PB - Springer CY - New York ER - TY - JOUR A1 - Coutinho, Renato Mendes A1 - Klauschies, Toni A1 - Gaedke, Ursula T1 - Bimodal trait distributions with large variances question the reliability of trait-based aggregate models JF - Theoretical ecology N2 - Functionally diverse communities can adjust their species composition to altered environmental conditions, which may influence food web dynamics. Trait-based aggregate models cope with this complexity by ignoring details about species identities and focusing on their functional characteristics (traits). They describe the temporal changes of the aggregate properties of entire communities, including their total biomasses, mean trait values, and trait variances. The applicability of aggregate models depends on the validity of their underlying assumptions that trait distributions are normal and exhibit small variances. We investigated to what extent this can be expected to work by comparing an innovative model that accounts for the full trait distributions of predator and prey communities to a corresponding aggregate model. We used a food web structure with well-established trade-offs among traits promoting mutual adjustments between prey edibility and predator selectivity in response to selection. We altered the shape of the trade-offs to compare the outcome of the two models under different selection regimes, leading to trait distributions increasingly deviating from normality. Their biomass and trait dynamics agreed very well for stabilizing selection and reasonably well for directional selection, under which different trait values are favored at different times. However, for disruptive selection, the results of the aggregate model strongly deviated from the full trait distribution model that showed bimodal trait distributions with large variances. Hence, the outcome of aggregate models is reliable under ideal conditions but has to be questioned when confronted with more complex selection regimes and trait distributions, which are commonly observed in nature. KW - Fitness gradient KW - Communities as complex adaptive systems KW - Moment closure for trait-based aggregate model approaches KW - Multimodal trait distributions KW - Lumpiness in pattern formation and self-organization KW - Shape of trade-offs and stabilizing and disruptive selection Y1 - 2016 U6 - https://doi.org/10.1007/s12080-016-0297-9 SN - 1874-1738 SN - 1874-1746 VL - 9 SP - 389 EP - 408 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Gaedke, Ursula A1 - Klauschies, Toni T1 - Analyzing the shape of observed trait distributions enables a data-based moment closure of aggregate models JF - Limnology and Oceanography: Methods N2 - The shape of trait distributions may inform about the selective forces that structure ecological communities. Here, we present a new moment-based approach to classify the shape of observed biomass-weighted trait distributions into normal, peaked, skewed, or bimodal that facilitates spatio-temporal and cross-system comparisons. Our observed phytoplankton trait distributions exhibited substantial variance and were mostly skewed or bimodal rather than normal. Additionally, mean, variance, skewness und kurtosis were strongly correlated. This is in conflict with trait-based aggregate models that often assume normally distributed trait values and small variances. Given these discrepancies between our data and general model assumptions we used the observed trait distributions to test how well different aggregate models with first- or second-order approximations and different types of moment closure predict the biomass, mean trait, and trait variance dynamics using weakly or moderately nonlinear fitness functions. For weakly non-linear fitness functions aggregate models with a second-order approximation and a data-based moment closure that relied on the observed correlations between skewness and mean, and kurtosis and variance predicted biomass and often also mean trait changes fairly well and better than models with first-order approximations or a normal-based moment closure. In contrast, none of the models reflected the changes of the trait variances reliably. Aggregate model performance was often also poor for moderately nonlinear fitness functions. This questions a general applicability of the normal-based approach, in particular for predicting variance dynamics determining the speed of trait changes and maintenance of biodiversity. We evaluate in detail how and why better approximations can be obtained. Y1 - 2018 U6 - https://doi.org/10.1002/lom3.10218 SN - 1541-5856 VL - 15 SP - 979 EP - 994 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Klauschies, Toni A1 - Coutinho, Renato Mendes A1 - Gaedke, Ursula T1 - A beta distribution-based moment closure enhances the reliability of trait-based aggregate models for natural populations and communities JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - Ecological communities are complex adaptive systems that exhibit remarkable feedbacks between their biomass and trait dynamics. Trait-based aggregate models cope with this complexity by focusing on the temporal development of the community’s aggregate properties such as its total biomass, mean trait and trait variance. They are based on particular assumptions about the shape of the underlying trait distribution, which is commonly assumed to be normal. However, ecologically important traits are usually restricted to a finite range, and empirical trait distributions are often skewed or multimodal. As a result, normal distribution-based aggregate models may fail to adequately represent the biomass and trait dynamics of natural communities. We resolve this mismatch by developing a new moment closure approach assuming the trait values to be beta-distributed. We show that the beta distribution captures important shape properties of both observed and simulated trait distributions, which cannot be captured by a Gaussian. We further demonstrate that a beta distribution-based moment closure can strongly enhance the reliability of trait-based aggregate models. We compare the biomass, mean trait and variance dynamics of a full trait distribution (FD) model to the ones of beta (BA) and normal (NA) distribution-based aggregate models, under different selection regimes. This way, we demonstrate under which general conditions (stabilizing, fluctuating or disruptive selection) different aggregate models are reliable tools. All three models predicted very similar biomass and trait dynamics under stabilizing selection yielding unimodal trait distributions with small standing trait variation. We also obtained an almost perfect match between the results of the FD and BA models under fluctuating selection, promoting skewed trait distributions and ongoing oscillations in the biomass and trait dynamics. In contrast, the NA model showed unrealistic trait dynamics and exhibited different alternative stable states, and thus a high sensitivity to initial conditions under fluctuating selection. Under disruptive selection, both aggregate models failed to reproduce the results of the FD model with the mean trait values remaining within their ecologically feasible ranges in the BA model but not in the NA model. Overall, a beta distribution-based moment closure strongly improved the realism of trait-based aggregate models. KW - Moment closure KW - Normal and beta distribution KW - Skewed and peaked trait distributions KW - Fitness landscape and frequency-dependent selection KW - Eco-evolutionary dynamics KW - Modelling functional diversity Y1 - 2018 U6 - https://doi.org/10.1016/j.ecolmodel.2018.02.001 SN - 0304-3800 SN - 1872-7026 VL - 381 SP - 46 EP - 77 PB - Elsevier CY - Amsterdam ER -