Helmut Hillebrand

Carl von Ossietzky Universität Oldenburg, Oldenburg, Lower Saxony, Germany

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Publications (143)800.68 Total impact

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    ABSTRACT: Biodiversity-ecosystem functioning (BEF) research has been a major topic in ecology for over 2 decades, and recent meta-analyses have confirmed biodiversity to be a driver of ecosystem processes and services. To date, the vast majority of BEF studies have been conducted experimentally, and it is unclear whether their outcomes can be transferred to natural communities and ecosystems. The major challenge faced in the analysis of observational data is to incorporate direct and indirect processes which influence the response variable of interest. Consequently, the statistical methods used to analyze such relationships must accommodate the multivariate nature of these data. One multivariate approach, viz. structural equation modeling, has already been applied to BEF research in terrestrial and freshwater ecosystems. In this study, we applied a structural equation model to monitoring data on marine phytoplankton communities, including data on environmental parameters, community structure, and measures of productivity. Our aim was to ascertain whether similar patterns and processes driving BEF relationships as described for other ecosystem types are evident in marine phytoplankton communities. We found that different aspects of biodiversity (richness, evenness) are significantly linked to ecosystem functions (productivity, resource use efficiency). These relationships are embedded in a multitude of direct and indirect links between environmental factors, community diversity, and productivity. Overall, our analysis confirms patterns observed in terrestrial and freshwater ecosystems and highlights the importance of incorporating multivariate methods for a better understanding of BEF processes in natural ecosystems.
    Marine Ecology Progress Series 03/2015; 523:31-40. DOI:10.3354/meps11153 · 2.64 Impact Factor
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    ABSTRACT: Biodiversity−ecosystem functioning (BEF) research has been a major topic in ecology for over 2 decades, and recent meta-analyses have confirmed biodiversity to be a driver of eco- system processes and services. To date, the vast majority of BEF studies have been conducted experimentally, and it is unclear whether their outcomes can be transferred to natural communi- ties and ecosystems. The major challenge faced in the analysis of observational data is to incorpo- rate direct and indirect processes which influence the response variable of interest. Consequently, the statistical methods used to analyze such relationships must accommodate the multivariate nature of these data. One multivariate approach, viz. structural equation modeling, has already been applied to BEF research in terrestrial and freshwater ecosystems. In this study, we applied a structural equation model to monitoring data on marine phytoplankton communities, including data on environmental parameters, community structure, and measures of productivity. Our aim was to ascertain whether similar patterns and processes driving BEF relationships as described for other ecosystem types are evident in marine phytoplankton communities. We found that differ- ent aspects of biodiversity (richness, evenness) are significantly linked to ecosystem functions (productivity, resource use efficiency). These relationships are embedded in a multitude of direct and indirect links between environmental factors, community diversity, and productivity. Overall, our analysis confirms patterns observed in terrestrial and freshwater ecosystems and highlights the importance of incorporating multivariate methods for a better understanding of BEF processes in natural ecosystems.
    Marine Ecology Progress Series 03/2015; 523:31 - 40. · 2.64 Impact Factor
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    ABSTRACT: Body size is related to an extensive number of species traits and ecological processes and has therefore been suggested as an effective metric to assess community changes and ecosystem’s state. However, the applicability of body size as an ecological indicator in benthic environments has been hindered by the poor knowledge of the factors influencing the size spectra of organisms. By applying biological trait analysis (BTA) and generalized linear models to a species dataset collected in the German Wadden Sea (53°41′14′′ N, 7°14′19′′ E) between 1999 and 2012, we show that the size structure of the macrobenthic community changes predictably along environmental gradients. Specifically, body size increases with increasing current-induced shear stress and sediment organic matter content. In addition, the presence of oyster–mussel reefs in one of the sampling stations enhanced the survival of species belonging to the smallest size categories in habitats with high hydrodynamic energy. This was probably due to the local sheltering effects, which together with biodeposition also increased organic matter in the sediment, likely favoring large deposit feeders as well. Our results suggest that body size can be a useful trait for estimating effects of anthropogenic stressors, such as organic enrichment or alteration of hydrodynamic regime and could therefore be effectively included in current monitoring programs of intertidal macrobenthic communities.
    Marine Biology 03/2015; 162(3). DOI:10.1007/s00227-015-2614-z · 2.39 Impact Factor
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    ABSTRACT: Aquatic and terrestrial ecosystems are tightly linked through the fluxes of organisms and matter. However, aquatic and terrestrial ecologists have mainly studied these ecosystems separately, a “splendid isolation” historically fostered by disciplinary boundaries between institutes and funding schemes. Here, we synthesize the progress made in joint aquatic and terrestrial research and suggest new approaches to meeting future research challenges in changing environments. Aquatic and terrestrial organisms use cross-system subsidies to a comparable extent and addressing reciprocal subsidies is therefore necessary in order to understand biodiversity and functioning of both aquatic and terrestrial ecosystems. We suggest that the metaecosystem framework could be expanded to explicitly consider cross-system fluxes of matter differing in magnitude and quality. We further advocate the inclusion of cross-system analyses at broader spatial extents, for which remote-sensing applications would be a useful tool in environmental research at the land-water interface. A cross-ecosystem approach would therefore be valuable for a more thorough understanding of ecosystem responses to various stressors in the face of rapid environmental change.
    BioScience 01/2015; DOI:10.1093/biosci/biu216 · 5.44 Impact Factor
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    ABSTRACT: In time of scarcity of fossil energies, microalgae are attracting interest as a potential source of renewable energy due to their high growth rates and potential high lipid contents. Additionally, cultivation may be an abatement measure to remove surplus nutrients from eutrophicated ecosystems. At present, microalgal cultivations for biomass production are run mainly in monocultures, which are easily contaminated with competing microalgae or grazers. Furthermore, hetero-trophic bacteria are highly abundant and may strongly reduce the yield in the target microalgae through competition for nutrients. In three laboratory experiments, we tested whether heterotrophic flagellates (Oxyrrhis marina and Cafeteria roenbergensis) can make nutrients bound in bacteria available for marine diatoms (Coscinodiscus granii and Odontella sinensis) and can shift the competition for inorganic nutrients towards the microalgae. Cultures were run with and without flagellates, under different conditions: without an external carbon source, in presence of organic matter (barley grains) or biogas wastewater. The presence of flagellates had a posi-tive effect on microalgal growth, but this was context and species specific. The presence of the flagellates affected the maximum algal growth rates (r) especially in Coscinodiscus granii. A maximal biomass increase (29.93±2.98 %) (mean ± standard deviation, n=3) was observed for Coscinodiscus granii in F/2 + Si medium. Furthermore, although the flagellates were attributed to the detrital fraction, their presence resulted in a significant reduc-tion of detritus. In conclusion, heterotrophic flagellates have the potential to increase nutrient use efficiency especially in algae bioreactors with slow-growing large phytoplankton taxa. This effect may be particularly relevant in organic polluted water.
    Journal of Applied Phycology 01/2015; 27(1):87-96. DOI:10.1007/s10811-014-0286-6 · 2.49 Impact Factor
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    ABSTRACT: Humans are modifying the availability of nutrients such as nitrogen (N) and phosphorus (P), and it is therefore important to understand how these nutrients, independently or in combination, influence the growth and nutrient content of primary producers. Using meta-analysis of 118 field and laboratory experiments in freshwater, marine and terrestrial ecosystems, we tested hypotheses about co-limitation of N and P by comparing the effects of adding N alone, P alone, and both N and P together on internal N (e.g. %N, C:N) and P (e.g. %P, C:P) concentrations in autotroph communities. In particular, we tested the following predictions. First, if only one nutrient was limiting, addition of that nutrient should decrease the concentration of the other nutrient, but addition of the non-limiting nutrient would have no effect on the internal concentration of the limiting nutrient. If community co-limitation was occurring then addition of either nutrient should result in a decrease in the internal concentration of the other nutrient. Community co-limitation could also result in no change – or even an increase – in N concentrations in response to P addition if P stimulated growth of N fixers. Finally, if biochemically dependent co-limitation was occurring, addition of a limiting nutrient would not decrease, and could even increase, the concentration of the other, co-limited nutrient. We found no general evidence for the decrease in the internal concentration of one nutrient due to addition of another nutrient. The one exception to this overall pattern was marine systems, where N addition decreased internal P concentrations. In contrast, P addition increased internal N concentrations across all experiments, consistent with co-limitation. These results have important implications for understanding the roles that N and P play in controlling producer growth and internal nutrient accumulation as well as for managing the effects of nutrient enrichment in ecosystems.
    Oikos 10/2014; 124(2). DOI:10.1111/oik.01215 · 3.56 Impact Factor
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    ABSTRACT: Loss of plant diversity influences essential ecosystem processes as aboveground productivity, and can have cascading effects on the arthropod communities in adjacent trophic levels. However, few studies have examined how those changes in arthropod communities can have additional impacts on ecosystem processes caused by them (e.g. pollination, bioturbation, predation, decomposition, herbivory). Therefore, including arthropod effects in predictions of the impact of plant diversity loss on such ecosystem processes is an important but little studied piece of information. In a grassland biodiversity experiment, we addressed this gap by assessing aboveground decomposer and herbivore communities and linking their abundance and diversity to rates of decomposition and herbivory. Path analyses showed that increasing plant diversity led to higher abundance and diversity of decomposing arthropods through higher plant biomass. Higher species richness of decomposers, in turn, enhanced decomposition. Similarly, species-rich plant communities hosted a higher abundance and diversity of herbivores through elevated plant biomass and C:N ratio, leading to higher herbivory rates. Integrating trophic interactions into the study of biodiversity effects is required to understand the multiple pathways by which biodiversity affects ecosystem functioning.
    PLoS ONE 09/2014; 9(9):e106529. DOI:10.1371/journal.pone.0106529 · 3.53 Impact Factor
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    ABSTRACT: Background/Question/Methods Can diversity simultaneously affect a wide variety of different ecosystem functions? Despite first studies analyzing effects of diversity on multiple ecosystem functions having revealed stronger diversity effects than studies looking at single functions this questions remains little studied. As an often used approach, the number of species contributing to functioning has been shown to increases with the number of studies, years, or functions considered. Yet, conclusions based on the number of contributing species have been criticized and recent methodological advances have proposed alternatives. Here we used multivariate statistics to investigate the relationship between plant diversity and multifunctionality. We based our analysis on more than 100 functions measured along an experimental gradient of grassland plant diversity ranging from 1 to 60 species. The set of ecosystem functions included various above- and below-ground processes, e.g. cover, LAI, plant biomass, soil nutrients, and abundance data of plant-associated invertebrates such as earthworms, pollinators and herbivores. Using principle component analysis based on the value of each function in each plot we investigated (1) correlations and trade-offs between functions, (2) the functional fingerprint and (3) the overall level of expressed functioning of each plot and (4) the relationships of all these parameters to plant species richness. Results/Conclusions Relationships between the investigated functions spanned the whole spectrum from strong positive correlation (association) to almost perfect negative correlation (trade-off). Intermediate between these extremes, a large number of functions were independent from each other, thus showed correlations around zero. Consequently, a large number of axes (23) was needed to explain at least 75% of the variation observed in the multifunctional space. Plant diversity correlated strongly with the first principle component axis (r=0.67, p<<0.001) while axes of higher order did not show any relationships with plant diversity. This indicates that especially the functions associated with the first principal component axis change along the plant diversity gradient. To calculate an index of multifunctionality, we extendend the “averaging approach” from single functions to a multivariate measure by summing scores for the first 30 principle component axes. The resulting multifunctionality index increased highly significantly with plant diversity from predominantly negative values at low diversity to positive values at high diversity (F1,76=8.26; p=0.005). Thus, plots of high diversity supported more functions at above average levels than low diversity plots. Results from our multivariate approach are compared to other proposed approaches to measure multifunctionality.
    99th ESA Annual Convention 2014; 08/2014
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    ABSTRACT: Trichocyst-enriched fractions were isolated from the marine dinophyte Prorocentrum micans. Transmission electron microscopy revealed that most of the trichocysts were discharged and had elongated to long filaments. Some trichocysts were still condensed. Fragments of discharged trichocysts measured up to 20 μm in length and 260 nm in width, those still condensed measured up to 1 μm in width and 16 μm in length. A distinct banding pattern with a transversal periodicity of approximately 16-18 nm and a periodic longitudinal striation of 3-4 nm could be measured along the trichocyst filaments. At higher magnifications, a fragile, alveolated, net-like organisation became obvious which resembled the one shown for the trichocysts of ciliates. When trichocyst-enriched fractions were treated with sodium dodecyl sulfate and centrifuged subsequently, no trichocysts were registered any longer in the sodium dodecyl sulfate-insoluble fraction by electron microscopy. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of trichocyst-enriched fractions and of the SDS-soluble fractions revealed a protein banding pattern which was dominated by polypeptides of 50-30, 12.5, and approximately 8.5 kDa. The polypeptide banding pattern deviated significantly from those registered for ejectisomes of cryptophytes and of the prasinophyte Pyramimonas grossii, for the Reb polypeptides which constitute the R-bodies of Caedibacter taeniospiralis, and also from the banding pattern of trichocysts of Paramecium. An antiserum directed against trichocysts of Paramecium did not cross-react with the polypeptides present in the trichocyst-enriched fraction of Prorocentrum micans.
    Protoplasma 07/2014; 252(1). DOI:10.1007/s00709-014-0675-3 · 3.17 Impact Factor
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    Nils Guelzow, Merten Dirks, Helmut Hillebrand
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    ABSTRACT: Disentangling the mechanisms that maintain the stability of communities and ecosystem properties has become a major research focus in ecology in the face of anthropogenic environmental change. Dispersal plays a pivotal role in maintaining diversity in spatially subdivided communities, but only a few experiments have simultaneously investigated how dispersal and environmental fluctuation affect community dynamics and ecosystem stability. We performed an experimental study using marine phytoplankton species as model organisms to test these mechanisms in a metacommunity context. We established three levels of dispersal and exposed the phytoplankton to fluctuating light levels, where fluctuations were either spatially asynchronous or synchronous across patches of the metacommunity. Dispersal had no effect on diversity and ecosystem function (biomass), while light fluctuations affected both evenness and community biomass. The temporal variability of community biomass was reduced by fluctuating light and temporal beta diversity was influenced interactively by dispersal and fluctuation, whereas spatial variability in community biomass and beta diversity were barely affected by treatments. Along the establishing gradient of species richness and dominance, community biomass increased but temporal variability of biomass decreased, thus highest stability was associated with species-rich but highly uneven communities and less influenced by compensatory dynamics. In conclusion, both specific traits (dominance) and diversity (richness) affected the stability of metacommunities under fluctuating conditions.
    Oecologia 07/2014; 176(2). DOI:10.1007/s00442-014-3015-6 · 3.25 Impact Factor
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    ABSTRACT: Chemostats and their common alternative, semicontinuous cultures, play a pivotal role as model systems in aquatic ecology. Despite the theoretical and conceptual advantages chemostat systems offer, they can be challenging to set up and operate. One such challenge is to obtain a representative sample volume without changing the dilution rate, another is to ensure that the outflow constitutes an unbiased loss of the chemostat contents. Here, we present a specific system, the exponentially fed-batch culture (EFB), as an economic, simply operable albeit reliable alternative to conventional chemostats. The EFB is well-known in biotechnological research and in industrial bioengineering. Like a conventional chemostat, the EFB culture is a continuous culture method. In contrast to a conventional chemostat, there is no outflow. To ensure a constant dilution rate and therefore steady state, fresh medium is continuously supplied proportional to the current culture volume. Hence culture volume and medium supply rate both increase exponentially with time until sampling, when the volume is set back to the initial state. This allows taking large sample volumes without disturbing the steady state of the experimental unit. Here we compare the performance of the exponentially fed-batch culture with a conventional chemostat and a semicontinuous system by growing a green algae until steady state is reached. Most pronounced differences were found between semicontinuous system and the two continuous methods. Results from the EFB and chemostat were very similar. However, a bias in the sampling of the chemostat resulted in accumulation of biomass relative to the EFB.
    Limnology and oceanography, methods 07/2014; 12(7). DOI:10.4319/lom.2014.12.432 · 1.68 Impact Factor
  • Silke Ammermann, Helmut Hillebrand, Erhard Rhiel
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    ABSTRACT: Ejectisome fragments were isolated from the prasinophyte Pyramimonas grossii and subjected to different treatments, i.e. Percoll density gradient centrifugation, incubation at pH 2.5 or at pH 10.8, or incubation in 6 M guanidine hydrochloride. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that Percoll density gradient centrifugation did not improve the purity of the ejectisome fragment-enriched fractions. The ejectisome fragments withstood pH 2.5 and pH 10.8 treatment, and no loosely bound polypeptides became detached. The disintegration of ejectisome fragments was achieved in 6 M guanidine hydrochloride, and reassembly into filamentous, ejectisome-like structures occurred after dialysis against distilled water. Fractions enriched either in ejectisome fragments or in reconstituted ejectisome-like structures were dominated by three polypeptides with relative molecular weights of approximately 12.5-19 kDa and two additional polypeptides of 23 and 26 kDa. A polyclonal antiserum directed against an ejectisome fragment-enriched fraction weakly cross-reacted with these polypeptides, and no significant immuno-labelling of ejectisome fragments was registered. A positive immuno-label was achieved using immunoglobulin (IgG) fractions which were gained by selectively incubating nitrocellulose stripes of these polypeptides with the antiserum.
    European Journal of Protistology 06/2014; DOI:10.1016/j.ejop.2014.02.001 · 2.34 Impact Factor
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    ABSTRACT: Ökologische Stöchiometrie (ecological stoichiometry, ES) hat sich in den letzten beiden Jahrzehnten zu einer der grundlegenden Theorien der Umweltwissenschaften und der Biologie entwickelt. Durch den Vergleich von elementarer Zusammensetzung von Organismen und ihren Ressourcenansprüchen mit der relativen Verfügbarkeit der Ressourcen sagt ES Prozesse auf allen Organisationsebenen von subzellulären Strukturen bis hin zu Ökosystemen voraus. Allerdings wurde ES bisher selten angewandt um den Zusammenhang zwischen Biodiversität und Ökosystemfunktion zu verstehen, obwohl ES ideal dazu geeignet wäre, da es sowohl Vorhersagen zu Prozessen macht, die Biodiversität beeinflussen, als auch zu Materieflüssen und–transformationen, auf denen wichtige Ökosystemfunktionen basieren. In diesem Artikel untersuchen wir den Zusammenhang dieser beiden Forschungsfelder und zeigen zukünftige Forschungsfelder anhand von drei Themen auf: i) die stöchiometrische Aspekte der Treiber des Biodiversitätswandels, ii) stöchiometrische Grundlagen des Zusammenhangs zwischen Biodiversität und Produktivität, iii) potentielle Interaktionen zwischen Biodiversität und Stöchiometrie im Nahrungsnetzkontext.
    Basic and Applied Ecology 06/2014; 15(6). DOI:10.1016/j.baae.2014.06.003 · 2.39 Impact Factor
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    ABSTRACT: Landscape connectivity can increase the capacity of communities to maintain their function when environments change by promoting the immigration of species or populations with adapted traits. However, high immigration may also restrict fine tuning of species compositions to local environmental conditions by homogenizing the community. Here we demonstrate that dispersal generates such a tradeoff between maximizing local biomass and the capacity of model periphyton metacommunities to recover after a simulated heat wave. In non-disturbed metacommunities, dispersal decreased the total biomass by preventing differentiation in species composition between the local patches making up the metacommunity. On the contrary, in metacommunities exposed to a realistic summer heat wave, dispersal promoted recovery by increasing the biomass of heat tolerant species in all local patches. Thus, the heat wave reorganized the species composition of the metacommunities and after an initial decrease in total biomass by 38.7%, dispersal fueled a full recovery of biomass in the restructured metacommunities. Although dispersal may decrease equilibrium biomass, our results highlight that connectivity is a key requirement for the response diversity that allows ecological communities to adapt to climate change through species sorting.
    Oikos 06/2014; 123(6). DOI:10.1111/j.1600-0706.2013.00927.x · 3.56 Impact Factor
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    ABSTRACT: Es wird angenommen, dass funktionelle Pflanzenmerkmale verantwortlich sind für beobachtete Effekte von Pflanzendiversität auf Ökosystemfunktionen, wodurch sich der Fokus der Biodiversitätsforschung von der Betrachtung der Effekte von Pflanzenartenzahlen hin zu der Betrachtung von Pflanzenmerkmalen in einer Gemeinschaft erweitert hat. Die Berücksichtigung von funktionellen Pflanzenmerkmalen hilft möglichweise zu verstehen, wie der Verlust von Arten Ökosystemprozesse beeinflusst. Unseres Wissens wurde jedoch die funktionelle Ähnlichkeit verschiedener Pflanzenarten zueinander noch nie als Grundlage für ein Grasland-Biodiversitätsexperiment genutzt. Wir präsentieren den theoretischen Hintergrund, das experimentelle Design und erste Ergebnisse eines sogenannten ‚Trait-Based Biodiversity Experiments’ (TBE), welches 2010 im Rahmen des Jena Experimentes etabliert wurde und bei welchem direkt die funktionelle Diversität von Pflanzeneigenschaften manipuliert wurde. Mithilfe einer Hauptkomponentenanalyse wurden sechs Pflanzenmerkmale von 60 Graslandarten analysiert, die bedeutend für Ressourcenaufnahme und -nutzung sind. Dabei bildeten die Pflanzenarten, die entlang zweier unabhängiger Achsen angeordnet waren, Gradienten in ihrer funktionellen Ähnlichkeit, die als Basis für das Design des TBE dienten. Auf neu angelegten Versuchsflächen etablierten wir Pflanzengemeinschaften mit unterschiedlicher Pflanzenartenzahl, die sich in ihrer räumlichen und zeitlichen funktionellen Komplementarität unterscheiden. Das neuartige Design des TBE erlaubt es uns in Zukunft den relativen Einfluss von Selektions- und Komplementaritätseffekten auf Ökosystemprozesse zu bestimmen und ermöglicht die mechanistische Erforschung der Konsequenzen von vereinfachten Lebensgemeinschaften.
    Basic and Applied Ecology 05/2014; 15(3). DOI:10.1016/j.baae.2014.02.003 · 2.39 Impact Factor
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    ABSTRACT: Ecosystem functioning is affected by horizontal (within trophic groups) and vertical (across trophic levels) biodiversity. Theory predicts that the effects of vertical biodiversity depend on consumer specialization. In a microcosm experiment, we investigated ciliate consumer diversity and specialization effects on algal prey biovolume, evenness and composition, and on ciliate biovolume production. The experimental data was complemented by a process-based model further analyzing the ecological mechanisms behind the observed diversity effects. Overall, increasing consumer diversity had no significant effect on prey biovolume or evenness. However, consumer specialization affected the prey community. Specialist consumers showed a stronger negative impact on prey biovolume and evenness than generalists. The model confirmed that this pattern was mainly driven by a single specialist with a high per capita grazing rate, consuming the two most productive prey species. When these were suppressed, the prey assemblage became dominated by a less productive species, consequently decreasing prey biovolume and evenness. Consumer diversity increased consumer biovolume, which was stronger for generalists than for specialists and highest in mixed combinations, indicating that consumer functional diversity, i.e. more diverse feeding strategies, increased resource use efficiency. Overall, our results indicate that consumer diversity effects on prey and consumers strongly depend on species-specific growth and grazing rates, which may be at least equally important as consumer specialization in driving consumer diversity effects across trophic levels.
    Oikos 03/2014; 123(8). DOI:10.1111/oik.01219 · 3.56 Impact Factor
  • Helmut Hillebrand, Jessica Gurevitch
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    ABSTRACT: A recurrent question in meta-analyses is the validity of including both field and laboratory studies in a single analysis, given the differences in characteristics such as the duration or size of these experiments. In particular, are field studies consistently more variable, longer in duration, or do they differ from laboratory studies in other important ways? We examined these questions using an unusually large and comprehensive data set on grazing effects on benthic microalgae, consisting of 865 experiments including both field and lab studies and using marine, lotic or lentic communities of small benthic primary producers. We found there was greater variation in field than laboratory studies, but that this difference explained only 0.5% of the variance in the coefficient of variation. Field studies were longer, on average, than laboratory studies, but experiments in the two systems did not differ consistently in other ecological or design parameters. Thus, the common assumption that field studies have higher variances than laboratory studies, while true, explained only a tiny proportion of the heterogeneity in variation. Therefore, perhaps surprisingly, any conclusions from research syntheses would be unlikely to be affected by consistent differences in variance (or other parameters we examined) between the laboratory and field studies.
    Oikos 03/2014; 123(7). DOI:10.1111/oik.01288 · 3.56 Impact Factor
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    ABSTRACT: Changes in plant diversity have consequences for higher trophic levels, e.g., higher plant diversity can enhance the reproduction and fitness of plant-associated insects. This response of higher trophic levels potentially depends on diversity-related changes in both resource quantity (abundance) and quality (nutritional content). The availability of elemental nutrients in plant resources is one aspect of nutritional quality, but has rarely been addressed as a pathway relating plant diversity to associated insects. Using the experimental plant diversity gradient of a large biodiversity grassland project, the Jena-Experiment, we analyzed the %C, %N and %P and the molar ratios of those elements (C:N, C:P and N:P) in a pollinating bee, Chelostoma distinctum, and an herbivorous grasshopper, Chorthippus parallelus, reared on plots of different plant diversity. Insects showed higher content of C, N and P (% dry mass), and lower C:N and C:P ratios than plants. C:N ratios were significantly higher in grasshoppers than in bees and higher in females than in males of both species. Increasing plant species richness increased the C:N ratio of male bees and female grasshoppers. In both groups, stoichiometry was positively related to plant stoichiometry (male bees: C:P and N:P; grasshoppers: C:N and N:P). Path analysis revealed that diversity-driven changes in plant elemental composition can have consequences for abundance and chemical composition of higher trophic levels, with different responses of the two functional groups.
    Basic and Applied Ecology 03/2014; 15(2). DOI:10.1016/j.baae.2014.02.001 · 2.39 Impact Factor
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    ABSTRACT: Studies of experimental grassland communities have demonstrated that plant diversity can stabilize productivity through species asynchrony, in which decreases in the biomass of some species are compensated for by increases in others. However, it remains unknown whether these findings are relevant to natural ecosystems, especially those for which species diversity is threatened by anthropogenic global change. Here we analyse diversity-stability relationships from 41 grasslands on five continents and examine how these relationships are affected by chronic fertilization, one of the strongest drivers of species loss globally. Unmanipulated communities with more species had greater species asynchrony, resulting in more stable biomass production, generalizing a result from biodiversity experiments to real-world grasslands. However, fertilization weakened the positive effect of diversity on stability. Contrary to expectations, this was not due to species loss after eutrophication but rather to an increase in the temporal variation of productivity in combination with a decrease in species asynchrony in diverse communities. Our results demonstrate separate and synergistic effects of diversity and eutrophication on stability, emphasizing the need to understand how drivers of global change interactively affect the reliable provisioning of ecosystem services in real-world systems.
    Nature 02/2014; DOI:10.1038/nature13014 · 42.35 Impact Factor
  • Dorothee Hodapp, Dietmar Kraft, Helmut Hillebrand
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    ABSTRACT: One of the most controversially discussed topics in current biodiversity-ecosystem function research is the transfer of results from experimental and theoretical studies to natural ecosystems. At the same time, monitoring data on biodiversity are requested as key indicators for the state of an ecosystem in most environmental evaluation frameworks. We analyse two monitoring data sets comprising information on abundance and biomass of macrozoobenthos communities in the German Wadden Sea in order to evaluate how much information monitoring data on biodiversity provide concerning ecosystem functioning and what implications this information (or the lack thereof) has for future monitoring programmes. Our results show a positive correlation between number of species of macrozoobenthos and its standing stock. Despite differences in overall biomass and individual size in different functional groups, this correlation remained consistent for different feeding guilds and therefore is likely to be independent of certain species traits. Moreover, functional turnover analyses indicate that increasing species richness is needed to maintain biomass levels over increasing periods of time. Whereas our data thus corroborate predictions from theory, we could not determine any causal relationships, because monitoring data commonly include only vague proxies for very few functional parameters, in our case standing biomass as a proxy for production. As to the use of diversity as an indicator for ecosystem functioning, we advise that management decisions are to be based on verified causal relationships and therefore strongly suggest the general incorporation of unambiguous proxies for functional parameters in the measuring campaigns of monitoring programmes.
    Biodiversity and Conservation 02/2014; 23(2). DOI:10.1007/s10531-013-0609-y · 2.07 Impact Factor

Publication Stats

7k Citations
800.68 Total Impact Points

Institutions

  • 2008–2015
    • Carl von Ossietzky Universität Oldenburg
      • Department of Chemistry and Biology of the Marine Environment (ICBM)
      Oldenburg, Lower Saxony, Germany
  • 2012
    • Cary Institute of Ecosystem Studies
      Millbrook, New York, United States
  • 2004–2012
    • University of Cologne
      • Botanical Institute
      Köln, North Rhine-Westphalia, Germany
    • Christian-Albrechts-Universität zu Kiel
      Kiel, Schleswig-Holstein, Germany
  • 2011
    • Utah State University
      Logan, Ohio, United States
  • 2006
    • University of California, Santa Barbara
      Santa Barbara, California, United States
  • 2000–2006
    • Uppsala University
      • Department of Ecology and Genetics
      Uppsala, Uppsala, Sweden
  • 2002
    • Dalhousie University
      • Department of Biology
      Halifax, Nova Scotia, Canada