TY  - JOUR
A1  - Wright, Justin P.
A1  - Ames, Gregory M.
A1  - Mitchelll, Rachel M.
T1  - The more things change, the more they stay the same? When is trait variability important for stability of ecosystem function in a changing environment
JF  - Philosophical transactions of the Royal Society of London : B, Biological sciences
N2  - The importance of intraspecific trait variability for community dynamics and ecosystem functioning has been underappreciated. There are theoretical reasons for predicting that species that differ in intraspecific trait variability will also differ in their effects on ecosystem functioning, particularly in variable environments. We discuss whether species with greater trait variability are likely to exhibit greater temporal stability in their population dynamics, and under which conditions this might lead to stability in ecosystem functioning. Resolving this requires us to consider several questions. First, are species with high levels of variation for one trait equally variable in others? In particular, is variability in response and effects traits typically correlated? Second, what is the relative contribution of local adaptation and phenotypic plasticity to trait variability? If local adaptation dominates, then stability in function requires one of two conditions: (i) individuals of appropriate phenotypes present in the environment at high enough frequencies to allow for populations to respond rapidly to the changing environment, and (ii) high levels of dispersal and gene flow. While we currently lack sufficient information on the causes and distribution of variability in functional traits, filling in these key data gaps should increase our ability to predict how changing biodiversity will alter ecosystem functioning.
KW  - biodiversity
KW  - intraspecific variation
KW  - ecosystem function
KW  - functional traits
KW  - phenotypic plasticity
Y1  - 2016
U6  - https://doi.org/10.1098/rstb.2015.0272
SN  - 0962-8436
SN  - 1471-2970
VL  - 371
PB  - Royal Society
CY  - London
ER  - 
TY  - GEN
A1  - Wilske, Burkhard
A1  - Eccard, Jana
A1  - Zistl-Schlingmann, Marcus
A1  - Hohmann, Maximilian
A1  - Methler, Annabel
A1  - Herde, Antje
A1  - Liesenjohann, Thilo
A1  - Dannenmann, Michael
A1  - Butterbach-Bahl, Klaus
A1  - Breuer, Lutz
T1  - Effects of short term bioturbation by common voles on biogeochemical soil variables
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Bioturbation contributes to soil formation and ecosystem functioning. With respect to the active transport of matter by voles, bioturbation may be considered as a very dynamic process among those shaping soil formation and biogeochemistry. The present study aimed at characterizing and quantifying the effects of bioturbation by voles on soil water relations and carbon and nitrogen stocks. Bioturbation effects were examined based on a field set up in a luvic arenosol comprising of eight 50 x 50 m enclosures with greatly different numbers of common vole (Microtus arvalis L., ca. 35-150 individuals ha(-1) mth(-1)). Eleven key soil variables were analyzed: bulk density, infiltration rate, saturated hydraulic conductivity, water holding capacity, contents of soil organic carbon (SOC) and total nitrogen (N), CO2 emission potential, C/N ratio, the stable isotopic signatures of C-13 and N-15, and pH. The highest vole densities were hypothesized to cause significant changes in some variables within 21 months. Results showed that land history had still a major influence, as eight key variables displayed an additional or sole influence of topography. However, the delta N-15 at depths of 10-20 and 20-30 cm decreased and increased with increasing vole numbers, respectively. Also the CO2 emission potential from soil collected at a depth of 15-30 cm decreased and the C/N ratio at 5-10 cm depth narrowed with increasing vole numbers. These variables indicated the first influence of voles on the respective mineralization processes in some soil layers. Tendencies of vole activity homogenizing SOC and N contents across layers were not significant. The results of the other seven key variables did not confirm significant effects of voles. Thus overall, we found mainly a first response of variables that are indicative for changes in biogeochemical dynamics but not yet of those representing changes in pools.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 499 
KW  - small mammalian herbivores
KW  - Microtus agrestis
KW  - pocket gophers
KW  - field voles
KW  - ecosystem services
KW  - functional traits
KW  - organic-carbon
KW  - nitrogen
KW  - population
KW  - landscape
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-408375
SN  - 1866-8372
IS  - 499
ER  - 
TY  - JOUR
A1  - Wells, Konstans
A1  - O'Hara, R. B.
A1  - Boehm, S. M.
A1  - Gockel, Sonja
A1  - Hemp, Andreas
A1  - Renner, S. C.
A1  - Pfeiffer, S.
A1  - Boehning-Gaese, Katrin
A1  - Kalko, Elisabeth K. V.
T1  - Trait-dependent occupancy dynamics of birds in temperate forest landscapes fine-scale observations in a hierarchical multi-species framework
JF  - Animal conservation
N2  - Silvicultural practices lead to changes in forest composition and structure and may impact species diversity from the overall regional species pool to stand-level species occurrence. We explored to what extent fine-scale occupancy patterns in differently managed forest stands are driven by environment and ecological traits in three regions in Germany using a multi-species hierarchical model. We tested for the possible impact of environmental variables and ecological traits on occupancy dynamics in a joint modelling exercise while taking possible variation in coefficient estimates over years and plots into account. Bird species richness differed across regions and years, and trends in species richness across years were different in the three regions. On the species level, forest management affected occupancy of species in all regions, but only 35% of the total assemblage-level variation in occurrence probability was explained by either forest type and successional stage and <?1% by forest edge. On the assemblage level, bird occurrence decreased with body mass in all regions. Species with smaller breeding ranges had lower occurrence probabilities in one region, while later spring arrival decreased occurrence probabilities in the two other regions. Spatial variation in the effect size of trait covariates such as species phylogeny and breeding strata showed that variation in patch occupancy due to fine-scale differences in forest management is, to some extent, predictable from ecological traits. Our results show that environmental factors and ecological traits jointly predict variation in bird occupancy patterns and their response to forest management. Observations at the fine scale of forest stands, at which conservation efforts can be arranged along with forest management practices in heterogeneous environments, have been shown to provide meaningful insights despite the difficulties involved in monitoring mobile organisms such as birds at the plot level.
KW  - bird community
KW  - biodiversity conservation
KW  - forest management
KW  - functional traits
KW  - multi-species hierarchical modelling
KW  - patch occupancy
KW  - silviculture
Y1  - 2012
U6  - https://doi.org/10.1111/j.1469-1795.2012.00560.x
SN  - 1367-9430
VL  - 15
IS  - 6
SP  - 626
EP  - 637
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Weithoff, Guntram
A1  - Rocha, Marcia R.
A1  - Gaedke, Ursula
T1  - Comparing seasonal dynamics of functional and taxonomic diversity reveals the driving forces underlying phytoplankton community structure
JF  - Freshwater biology
N2  - In most biodiversity studies, taxonomic diversity is the measure for the multiplicity of species and is often considered to represent functional diversity. However, trends in taxonomic diversity and functional diversity may differ, for example, when many functionally similar but taxonomically different species co-occur in a community. The differences between these diversity measures are of particular interest in diversity research for understanding diversity patterns and their underlying mechanisms. We analysed a temporally highly resolved 20-year time series of lake phytoplankton to determine whether taxonomic diversity and functional diversity exhibit similar or contrasting seasonal patterns. We also calculated the functional mean of the community in n-dimensional trait space for each sampling day to gain further insights into the seasonal dynamics of the functional properties of the community. We found an overall weak positive relationship between taxonomic diversity and functional diversity with a distinct seasonal pattern. The two diversity measures showed synchronous behaviour from early spring to mid-summer and a more complex and diverging relationship from autumn to late winter. The functional mean of the community exhibited a recurrent annual pattern with the most prominent changes before and after the clear-water phase. From late autumn to winter, the functional mean of the community and functional diversity were relatively constant while taxonomic diversity declined, suggesting competitive exclusion during this period. A further decline in taxonomic diversity concomitant with increasing functional diversity in late winter to early spring is seen as a result of niche diversification together with competitive exclusion. Under these conditions, several different sets of traits are suitable to thrive, but within one set of functional traits only one, or very few, morphotypes can persist. Taxonomic diversity alone is a weak descriptor of trait diversity in phytoplankton. However, the combined analysis of taxonomic diversity and functional diversity, along with the functional mean of the community, allows for deeper insights into temporal patterns of community assembly and niche diversification.
KW  - algae
KW  - biodiversity
KW  - functional traits
KW  - seasonality
KW  - time series
Y1  - 2015
U6  - https://doi.org/10.1111/fwb.12527
SN  - 0046-5070
SN  - 1365-2427
VL  - 60
IS  - 4
SP  - 758
EP  - 767
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Weithoff, Guntram
A1  - Gaedke, Ursula
T1  - Mean functional traits of lake phytoplankton reflect seasonal and inter-annual changes in nutrients, climate and herbivory
JF  - Journal of plankton research
N2  - Trait-based approaches have become increasingly successful in community ecology. They assume that the distribution of functional traits within communities responds in a predictable way to alterations in environmental forcing and that strong forcing may accelerate such trait changes. We used high frequency measurements of phytoplankton to test these assumptions. We analyzed the seasonal and long-term dynamics of the community trait mean within a multi-dimensional trait space under alternating multifactorial environmental conditions. The community trait mean exhibited a distinct recurrent annual pattern that reflected minor changes in climate, herbivory and nutrients. Independent of early spring conditions, the community trait mean was repeatedly driven into a narrow confined area in the trait space under pronounced herbivory during the clear water phase. The speed of movement was highest at the onset and the relaxation of such strong unidirectional forcing. Thus, our data support the conceptual framework of trait-based ecology that alterations in environmental conditions are systematically tracked by adjustments in the dominant functional trait values and that the speed of trait changes depends on the kind and intensity of the selection pressure. Our approach provides a sensitive tool to detect small functional differences in the community related to subtle differences in forcing.
KW  - phytoplankton
KW  - temporal dynamics
KW  - climate
KW  - trait distribution
KW  - Lake Constance
KW  - functional traits
Y1  - 2017
U6  - https://doi.org/10.1093/plankt/fbw072
SN  - 0142-7873
SN  - 1464-3774
VL  - 39
SP  - 509
EP  - 517
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Weithoff, Guntram
A1  - Beisner, Beatrix E.
T1  - Measures and Approaches in Trait-Based Phytoplankton Community Ecology
BT  - From Freshwater to Marine Ecosystems
JF  - Frontiers in Marine Science
N2  - Trait-based approaches to investigate (short- and long-term) phytoplankton dynamics and community assembly have become increasingly popular in freshwater and marine science. Although the nature of the pelagic habitat and the main phytoplankton taxa and ecology are relatively similar in both marine and freshwater systems, the lines of research have evolved, at least in part, separately. We compare and contrast the approaches adopted in marine and freshwater ecosystems with respect to phytoplankton functional traits. We note differences in study goals relating to functional trait use that assess community assembly and those that relate to ecosystem processes and biogeochemical cycling that affect the type of characteristics assigned as traits to phytoplankton taxa. Specific phytoplankton traits relevant for ecological function are examined in relation to
herbivory, amplitude of environmental change and spatial and temporal scales of study. Major differences are identified, including the shorter time scale for regular environmental change in freshwater ecosystems compared to that in the open oceans as well as the
type of sampling done by researchers based on site-accessibility. Overall, we encourage researchers to better motivate why they apply trait-based analyses to their studies and to make use of process-driven approaches, which are more common in marine studies. We further propose fully comparative trait studies conducted along the habitat gradient spanning freshwater to brackish to marine systems, or along geographic gradients. Such studies will benefit from the combined strength of both fields.
KW  - algae
KW  - functional traits
KW  - ocean
KW  - lake
KW  - biogeochemistry
KW  - community assembly
Y1  - 2019
U6  - https://doi.org/10.3389/fmars.2019.00040
SN  - 2296-7745
VL  - 6
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - GEN
A1  - Weithoff, Guntram
A1  - Beisner, Beatrix E.
T1  - Measures and Approaches in Trait-Based Phytoplankton Community Ecology
BT  - From Freshwater to Marine Ecosystems
T2  - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
N2  - Trait-based approaches to investigate (short- and long-term) phytoplankton dynamics and community assembly have become increasingly popular in freshwater and marine science. Although the nature of the pelagic habitat and the main phytoplankton taxa and ecology are relatively similar in both marine and freshwater systems, the lines of research have evolved, at least in part, separately. We compare and contrast the approaches adopted in marine and freshwater ecosystems with respect to phytoplankton functional traits. We note differences in study goals relating to functional trait use that assess community assembly and those that relate to ecosystem processes and biogeochemical cycling that affect the type of characteristics assigned as traits to phytoplankton taxa. Specific phytoplankton traits relevant for ecological function are examined in relation to
herbivory, amplitude of environmental change and spatial and temporal scales of study. Major differences are identified, including the shorter time scale for regular environmental change in freshwater ecosystems compared to that in the open oceans as well as the
type of sampling done by researchers based on site-accessibility. Overall, we encourage researchers to better motivate why they apply trait-based analyses to their studies and to make use of process-driven approaches, which are more common in marine studies. We further propose fully comparative trait studies conducted along the habitat gradient spanning freshwater to brackish to marine systems, or along geographic gradients. Such studies will benefit from the combined strength of both fields.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 679 
KW  - algae
KW  - functional traits
KW  - ocean
KW  - lake
KW  - biogeochemistry
KW  - community assembly
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-425814
SN  - 1866-8372
IS  - 679
ER  - 
TY  - JOUR
A1  - Tanentzap, Andrew J.
A1  - Lee, William G.
A1  - Schulz, Katharina A. C.
T1  - Niches drive peaked and positive relationships between diversity and disturbance in natural ecosystems
JF  - Ecosphere : the magazine of the International Ecology University
N2  - A unified understanding of the relationship between disturbance and biodiversity is needed to predict biotic responses to global change. Recent advances have identified the need to deconstruct traditional models of disturbance into intensity and frequency to reconcile empirical studies that appear to generate contradictory associations between species diversity and disturbance. We integrate results from theoretical simulation modelling, field-based surveys of 5176 vegetation plots from 48 transects across 6 sites, and experimental pot-based manipulations of flooding to identify how disturbance drives species diversity within ephemeral wetlands in South Island, New Zealand. We find empirical, hump-shaped and positive relationships between species diversity and both disturbance intensity and frequency, mirroring patterns from a simulation model in which species differed in their demographic responses to disturbance. More generally, our simulations show that the relationships between diversity and disturbance shift from positive to hump-shaped to negative as species that are favored at low disturbance because of their resistance strategies, defined by low mortality and recruitment, decline within communities relative to resilient species. Resilient species with higher mortality and recruitment rates are instead favored as disturbance intensity and frequency intensify. Our theoretical findings suggest that sites must also have a third group of unique species with intermediate resilience and resistance. Analyses of community composition along our disturbance gradients support this prediction, emphasizing that shifts in community-level resistance and resilience drive empirical associations between diversity and disturbance. Overall, terrestrial plants may be unable to resist intense and frequent flooding, even with specialized traits. Only fast-growing species with high regeneration from seed may respond once flooding subsides and dominate community composition in these situations, especially on nutrient-rich soils. However, different strategies can co-occur at intermediate disturbance, ultimately increasing species richness. As disturbances become more pervasive globally, our results suggest that differences in the niches of species, rather than demographic stochasticity, drive biodiversity patterns. These niche-based processes may especially prevail, without accompanying losses in species richness, where sites are initially dominated by resistant taxa or life history strategies that balance resistance and resilience.
KW  - beta-diversity
KW  - coexistence
KW  - community structure
KW  - functional traits
KW  - intermediate disturbance hypothesis
KW  - neutral theory
KW  - trade-offs
Y1  - 2013
U6  - https://doi.org/10.1890/ES13-00102.1
SN  - 2150-8925
VL  - 4
IS  - 11
PB  - Wiley
CY  - Washington
ER  - 
TY  - GEN
A1  - Sonnemann, Ilja
A1  - Pfestorf, Hans
A1  - Jeltsch, Florian
A1  - Wurst, Susanne
T1  - Community- weighted mean plant traits predict small scale distribution of insect root herbivore abundance
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Small scale distribution of insect root herbivores may promote plant species diversity by creating patches of different herbivore pressure. However, determinants of small scale distribution of insect root herbivores, and impact of land use intensity on their small scale distribution are largely unknown. We sampled insect root herbivores and measured vegetation parameters and soil water content along transects in grasslands of different management intensity in three regions in Germany. We calculated community-weighted mean plant traits to test whether the functional plant community composition determines the small scale distribution of insect root herbivores. To analyze spatial patterns in plant species and trait composition and insect root herbivore abundance we computed Mantel correlograms. Insect root herbivores mainly comprised click beetle (Coleoptera, Elateridae) larvae (43%) in the investigated grasslands. Total insect root herbivore numbers were positively related to community-weighted mean traits indicating high plant growth rates and biomass (specific leaf area, reproductive-and vegetative plant height), and negatively related to plant traits indicating poor tissue quality (leaf C/N ratio). Generalist Elaterid larvae, when analyzed independently, were also positively related to high plant growth rates and furthermore to root dry mass, but were not related to tissue quality. Insect root herbivore numbers were not related to plant cover, plant species richness and soil water content. Plant species composition and to a lesser extent plant trait composition displayed spatial autocorrelation, which was not influenced by land use intensity. Insect root herbivore abundance was not spatially autocorrelated. We conclude that in semi-natural grasslands with a high share of generalist insect root herbivores, insect root herbivores affiliate with large, fast growing plants, presumably because of availability of high quantities of food. Affiliation of insect root herbivores with large, fast growing plants may counteract dominance of those species, thus promoting plant diversity.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 494 
KW  - Diabrotica Virgifera Virgifera
KW  - land-use intensity
KW  - functional traits
KW  - wireworms coloptera
KW  - spatial-distribution
KW  - Agriotes Ustulatus
KW  - population-dynamics
KW  - grassland diversity
KW  - european flora
KW  - arable land
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-408161
SN  - 1866-8372
IS  - 494
ER  - 
TY  - JOUR
A1  - Rocha, Marcia R.
A1  - Gaedke, Ursula
A1  - Vasseur, David A.
T1  - Functionally similar species have similar dynamics
JF  - The journal of ecology
N2  - 1. Improving the mechanistic basis of biodiversity-ecosystem function relationships requires a better understanding of how functional traits drive the dynamics of populations. For example, environmental disturbances or grazing may increase synchronization of functionally similar species, whereas functionally different species may show independent dynamics, because of different responses to the environment. Competition for resources, on the other hand, may yield a wide range of dynamic patterns among competitors and lead functionally similar and different species to display synchronized to compensatory dynamics. The mixed effect of these forces will influence the temporal fluctuations of populations and, thus, the variability of aggregate community properties.
 2. To search for a relationship between functional and dynamics similarity, we studied the relationship between functional trait similarity and temporal dynamics similarity for 36 morphotypes of phytoplankton using long-term high-frequency measurements.
 3. Our results show that functionally similar morphotypes exhibit dynamics that are more synchronized than those of functionally dissimilar ones. Functionally dissimilar morphotypes predominantly display independent temporal dynamics. This pattern is especially strong when short time-scales are considered.
 4. Negative correlations are present among both functionally similar and dissimilar phytoplankton morphotypes, but are rarer and weaker than positive ones over all temporal scales.
 5. Synthesis. We demonstrate that diversity in functional traits decreases community variability and ecosystem-level properties by decoupling the dynamics of individual morphotypes.
KW  - compensatory dynamics
KW  - competition
KW  - environmental forcing
KW  - functional diversity
KW  - functional traits
KW  - grazing
KW  - phytoplankton
KW  - plant population and community dynamics
KW  - synchrony
KW  - temporal dynamics
Y1  - 2011
U6  - https://doi.org/10.1111/j.1365-2745.2011.01893.x
SN  - 0022-0477
VL  - 99
IS  - 6
SP  - 1453
EP  - 1459
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Reeg, Jette
A1  - Strigl, Lea
A1  - Jeltsch, Florian
T1  - Agricultural buffer zone thresholds to safeguard functional bee diversity
BT  - Insights from a community modeling approach
JF  - Ecology and Evolution
N2  - Wild bee species are important pollinators in agricultural landscapes. However, population decline was reported over the last decades and is still ongoing. While agricultural intensification is a major driver of the rapid loss of pollinating species, transition zones between arable fields and forest or grassland patches, i.e., agricultural buffer zones, are frequently mentioned as suitable mitigation measures to support wild bee populations and other pollinator species. Despite the reported general positive effect, it remains unclear which amount of buffer zones is needed to ensure a sustainable and permanent impact for enhancing bee diversity and abundance. To address this question at a pollinator community level, we implemented a process-based, spatially explicit simulation model of functional bee diversity dynamics in an agricultural landscape. More specifically, we introduced a variable amount of agricultural buffer zones (ABZs) at the transition of arable to grassland, or arable to forest patches to analyze the impact on bee functional diversity and functional richness. We focused our study on solitary bees in a typical agricultural area in the Northeast of Germany. Our results showed positive effects with at least 25% of virtually implemented agricultural buffer zones. However, higher amounts of ABZs of at least 75% should be considered to ensure a sufficient increase in Shannon diversity and decrease in quasi-extinction risks. These high amounts of ABZs represent effective conservation measures to safeguard the stability of pollination services provided by solitary bee species. As the model structure can be easily adapted to other mobile species in agricultural landscapes, our community approach offers the chance to compare the effectiveness of conservation measures also for other pollinator communities in future.
KW  - agricultural landscape
KW  - buffer zones
KW  - community model
KW  - functional traits
KW  - solitary bees
KW  - spatially explicit
Y1  - 2022
U6  - https://doi.org/10.1002/ece3.8748
SN  - 2045-7758
VL  - 12
SP  - 1
EP  - 17
PB  - Wiley Online Library
CY  - Hoboken, New Jersey, USA
ET  - 3
ER  - 
TY  - GEN
A1  - Reeg, Jette
A1  - Strigl, Lea
A1  - Jeltsch, Florian
T1  - Agricultural buffer zone thresholds to safeguard functional bee diversity: Insights from a community modeling approach
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Wild bee species are important pollinators in agricultural landscapes. However, population decline was reported over the last decades and is still ongoing. While agricultural intensification is a major driver of the rapid loss of pollinating species, transition zones between arable fields and forest or grassland patches, i.e., agricultural buffer zones, are frequently mentioned as suitable mitigation measures to support wild bee populations and other pollinator species. Despite the reported general positive effect, it remains unclear which amount of buffer zones is needed to ensure a sustainable and permanent impact for enhancing bee diversity and abundance. To address this question at a pollinator community level, we implemented a process-based, spatially explicit simulation model of functional bee diversity dynamics in an agricultural landscape. More specifically, we introduced a variable amount of agricultural buffer zones (ABZs) at the transition of arable to grassland, or arable to forest patches to analyze the impact on bee functional diversity and functional richness. We focused our study on solitary bees in a typical agricultural area in the Northeast of Germany. Our results showed positive effects with at least 25% of virtually implemented agricultural buffer zones. However, higher amounts of ABZs of at least 75% should be considered to ensure a sufficient increase in Shannon diversity and decrease in quasi-extinction risks. These high amounts of ABZs represent effective conservation measures to safeguard the stability of pollination services provided by solitary bee species. As the model structure can be easily adapted to other mobile species in agricultural landscapes, our community approach offers the chance to compare the effectiveness of conservation measures also for other pollinator communities in future.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1281 
KW  - agricultural landscape
KW  - buffer zones
KW  - community model
KW  - functional traits
KW  - solitary bees
KW  - spatially explicit
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-570800
SN  - 1866-8372
IS  - 1281
ER  - 
TY  - GEN
A1  - Mendes Ferreira, Clara
A1  - Dammhahn, Melanie
A1  - Eccard, Jana
T1  - Forager-mediated cascading effects on food resource species diversity
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Perceived predation risk varies in space and time. Foraging in this landscape of fear alters forager-resource interactions via cascading nonconsumptive effects. Estimating these indirect effects is difficult in natural systems. Here, we applied a novel measure to quantify the diversity at giving-up density that allows to test how spatial variation in perceived predation risk modifies the diversity of multispecies resources at local and regional spatial levels. Furthermore, we evaluated whether the nonconsumptive effects on resource species diversity can be explained by the preferences of foragers for specific functional traits and by the forager species richness. We exposed rodents of a natural community to artificial food patches, each containing an initial multispecies resource community of eight species (10 items each) mixed in sand. We sampled 35 landscapes, each containing seven patches in a spatial array, to disentangle effects at local (patch) and landscape levels. We used vegetation height as a proxy for perceived predation risk. After a period of three nights, we counted how many and which resource species were left in each patch to measure giving-up density and resource diversity at the local level (alpha diversity) and the regional level (gamma diversity and beta diversity). Furthermore, we used wildlife cameras to identify foragers and assess their species richness. With increasing vegetation height, i.e., decreasing perceived predation risk, giving-up density, and local alpha and regional gamma diversity decreased, and patches became less similar within a landscape (beta diversity increased). Foragers consumed more of the bigger and most caloric resources. The higher the forager species richness, the lower the giving-up density, and alpha and gamma diversity. Overall, spatial variation of perceived predation risk of foragers had measurable cascading effects on local and regional resource species biodiversity, independent of the forager species. Thus, nonconsumptive predation effects modify forager-resource interactions and might act as an equalizing mechanism for species coexistence.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1312 
KW  - coexistence
KW  - functional traits
KW  - giving-up density
KW  - landscape of fear
KW  - perceived predation risk
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-585092
SN  - 1866-8372
IS  - 1312
ER  - 
TY  - JOUR
A1  - Mendes Ferreira, Clara
A1  - Dammhahn, Melanie
A1  - Eccard, Jana
T1  - Forager-mediated cascading effects on food resource species diversity
JF  - Ecology and Evolution
N2  - Perceived predation risk varies in space and time. Foraging in this landscape of fear alters forager-resource interactions via cascading nonconsumptive effects. Estimating these indirect effects is difficult in natural systems. Here, we applied a novel measure to quantify the diversity at giving-up density that allows to test how spatial variation in perceived predation risk modifies the diversity of multispecies resources at local and regional spatial levels. Furthermore, we evaluated whether the nonconsumptive effects on resource species diversity can be explained by the preferences of foragers for specific functional traits and by the forager species richness. We exposed rodents of a natural community to artificial food patches, each containing an initial multispecies resource community of eight species (10 items each) mixed in sand. We sampled 35 landscapes, each containing seven patches in a spatial array, to disentangle effects at local (patch) and landscape levels. We used vegetation height as a proxy for perceived predation risk. After a period of three nights, we counted how many and which resource species were left in each patch to measure giving-up density and resource diversity at the local level (alpha diversity) and the regional level (gamma diversity and beta diversity). Furthermore, we used wildlife cameras to identify foragers and assess their species richness. With increasing vegetation height, i.e., decreasing perceived predation risk, giving-up density, and local alpha and regional gamma diversity decreased, and patches became less similar within a landscape (beta diversity increased). Foragers consumed more of the bigger and most caloric resources. The higher the forager species richness, the lower the giving-up density, and alpha and gamma diversity. Overall, spatial variation of perceived predation risk of foragers had measurable cascading effects on local and regional resource species biodiversity, independent of the forager species. Thus, nonconsumptive predation effects modify forager-resource interactions and might act as an equalizing mechanism for species coexistence.
KW  - coexistence
KW  - functional traits
KW  - giving-up density
KW  - landscape of fear
KW  - perceived predation risk
Y1  - 2022
U6  - https://doi.org/10.1002/ece3.9523
SN  - 2045-7758
VL  - 12
IS  - 11
PB  - John Wiley & Sons
ER  - 
TY  - THES
A1  - Mendes Ferreira, Clara
T1  - Indirect, tri-trophic effects of fear on biodiversity
N2  - Predator-forager interactions are a major factor in evolutionary adaptation of many species, as predators need to gain energy by consuming prey species, and foragers needs to avoid the worst fate of mortality while still consuming resources for energetic gains. In this evolutionary arms race, the foragers have constantly evolved anti-predator behaviours (e.g. foraging activity changes). To describe all these complex changes, researchers developed the framework of the landscape of fear, that is, the spatio-temporal variation of perceived predation risk. This concept simplifies all the involved ecological processes into one framework, by integrating animal biology and distribution with habitat characteristics. Researchers can then evaluate the perception of predation risk in prey species, what are the behavioural responses of the prey and, therefore, understand the cascading effects of landscapes of fear at the resource levels (tri-trophic effects). Although tri-trophic effects are well studied at the predator-prey interaction level, little is known on how the forager-resource interactions are part of the overall cascading effects of landscapes of fear, despite the changes of forager feeding behaviour - that occur with perceived predation risk - affecting directly the level of the resources.
This thesis aimed to evaluate the cascading effects of the landscape of fear on biodiversity of resources, and how the feeding behaviour and movement of foragers shaped the final resource species composition (potential coexistence mechanisms). We studied the changes caused by landscapes of fear on wild and captive rodent communities and evaluated: the cascading effects of different landscapes of fear on a tri-trophic system (I), the effects of fear on a forager’s movement patterns and dietary preferences (II) and cascading effects of different types of predation risk (terrestrial versus avian, III).
In Chapter I, we applied a novel measure to evaluate the cascading effects of fear at the level of resources, by quantifying the diversity of resources left after the foragers gave-up on foraging (diversity at the giving-up density). We tested the measure at different spatial levels (local and regional) and observed that with decreased perceived predation risk, the density and biodiversity of resources also decreased. Foragers left a very dissimilar community of resources based on perceived risk and resources functional traits, and therefore acted as an equalising mechanism.
In Chapter II, we wanted to understand further the decision-making processes of rodents in different landscapes of fear, namely, in which resource species rodents decided to forage on (based on three functional traits: size, nutrients and shape) and how they moved depending on perceived predation risk. In safe landscapes, individuals increased their feeding activity and movements and despite the increased costs, they visited more often patches that were further away from their central-place. Despite a preference for the bigger resources regardless of risk, when perceived predation risk was low, individuals changed their preference to fat-rich resources.
In Chapter III, we evaluated the cascading effects of two different types of predation risk in rodents: terrestrial (raccoon) versus avian predation risk. Raccoon presence or absence did not alter the rodents feeding behaviour in different landscapes of fear. Rodent’s showed risk avoidance behaviours towards avian predators (spatial risk avoidance), but not towards raccoons (lack of temporal risk avoidance).
By analysing the effects of fear in tri-trophic systems, we were able to deepen the knowledge of how non-consumptive effects of predators affect the behaviour of foragers, and quantitatively measure the cascading effects at the level of resources with a novel measure. Foragers are at the core of the ecological processes and responses to the landscape of fear, acting as variable coexistence agents for resource species depending on perceived predation risk. This newly found measures and knowledge can be applied to more trophic chains, and inform researchers on biodiversity patterns originating from landscapes of fear.
N2  - Die Wechselwirkungen zwischen Raubtier und Beute sind ein wichtiger Faktor in der Evolution der Tierwelt, da sich die Raubtiere anpassen müssen, um ihre Beute besser jagen zu können und die Beutetiere vermeiden müssen, gefressen zu werden, während sie immer noch genügend Ressourcen für ihre täglichen Bedürfnisse verbrauchen. In diesem ständigen Kampf müssen die Beutetiere ihr Verhalten ständig ändern, da sie die Anwesenheit von Raubtieren fürchten. Die Landschaft der Angst ist ein Rahmen, der alle ökologischen Prozesse beschreibt, die ablaufen, wenn die Tiere das Raubtierrisiko auf unterschiedliche Weise wahrnehmen. In Angstlandschaften reichen die indirekten Auswirkungen der Angst vor einem Raubtier aus, um eine Vielzahl von Reaktionen bei den Beutetieren hervorzurufen und folglich die Art und Weise zu beeinflussen, in der die Beutetiere Naturgutstype fressen (tritrophe Effekte).
Während die Interaktionen zwischen Raubtieren und Beutetieren gut erforscht sind, fehlt es an Wissen darüber, wie die Landschaft der Angst die Interaktionen zwischen Beutetieren und Naturgutstype beeinflussen kann (z. B. Pflanzenfresser, die Pflanzen fressen). In dieser Arbeit untersuchten wir die Kaskadeneffekte (d.h. Domino Effekte), die Beutetiere auf Naturgutstype haben, wenn sie verschiedene Prädationsrisiken wahrnehmen. Insbesondere wollten wir untersuchen, wie die Beutetiere entscheiden, was sie fressen und wohin sie sich bewegen, wie sich diese Veränderungen auf die biologische Vielfalt der Ressourcen auswirken können und welche Folgen dies für die Evolution der Ressourcenarten hat.
Für alle unsere Studien haben wir Nagetiere als Modellarten verwendet. Wir entwickelten ein neues Maß zur Quantifizierung der Auswirkungen von Angst auf die biologische Vielfalt von Ressourcen und testeten es erfolgreich an wilden Nagetierpopulationen. Wir konnten beobachten, dass die Nagetiere unterschiedliche Samenarten und -mengen fressen, je nachdem, wie sie das Raubtierrisiko einschätzen und abhängig von den Eigenschaften der Samen und der Art der vorhandenen Raubtiere (terrestrische oder aviäre Fleischfresser). Wir konnten diese Veränderungen quantifizieren und Vorhersagen darüber machen, wie sich der Wettbewerb zwischen den Samen um das Wachstum verändern würde (Koexistenzmechanismen). Mit diesem Wissen haben wir den Rahmen der Angstlandschaft um die komplexen Wechselwirkungen zwischen Beute und Ressourcen erweitert und können unsere Erkenntnisse auch dazu nutzen, um zu verstehen, wie weitere Tierarten die biologische Vielfalt anderer Arten verändern, indem wir einfach verstehen, wie ängstlich sie sind.
KW  - landscape of fear
KW  - functional traits
KW  - foraging behaviour
KW  - biodiversity
KW  - giving-up density
KW  - cascading effects
KW  - Biodiversität
KW  - Kaskadeneffekte
KW  - Futtersuchverhalten
KW  - funktionale Merkmale
KW  - Landschaft der Angst
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-611020
ER  - 
TY  - JOUR
A1  - Marcisz, Katarzyna
A1  - Jassey, Vincent E. J.
A1  - Kosakyan, Anush
A1  - Krashevska, Valentyna
A1  - Lahr, Daniel J. G.
A1  - Lara, Enrique
A1  - Lamentowicz, Lukasz
A1  - Lamentowicz, Mariusz
A1  - Macumber, Andrew
A1  - Mazei, Yuri
A1  - Mitchell, Edward A. D.
A1  - Nasser, Nawaf A.
A1  - Patterson, R. Timothy
A1  - Roe, Helen M.
A1  - Singer, David
A1  - Tsyganov, Andrey N.
A1  - Fournier, Bertrand
T1  - Testate amoeba functional traits and their use in paleoecology
JF  - Frontiers in Ecology and Evolution
N2  - This review provides a synthesis of current knowledge on the morphological and functional traits of testate amoebae, a polyphyletic group of protists commonly used as proxies of past hydrological changes in paleoecological investigations from peatland, lake sediment and soil archives. A trait-based approach to understanding testate amoebae ecology and paleoecology has gained in popularity in recent years, with research showing that morphological characteristics provide complementary information to the commonly used environmental inferences based on testate amoeba (morpho-)species data. We provide a broad overview of testate amoeba morphological and functional traits and trait-environment relationships in the context of ecology, evolution, genetics, biogeography, and paleoecology. As examples we report upon previous ecological and paleoecological studies that used trait-based approaches, and describe key testate amoebae traits that can be used to improve the interpretation of environmental studies. We also highlight knowledge gaps and speculate on potential future directions for the application of trait-based approaches in testate amoeba research.
KW  - protists
KW  - functional traits
KW  - morphological traits
KW  - ecology
KW  - peatlands
KW  - lakes
KW  - soils
KW  - trait-based approaches
Y1  - 2020
U6  - https://doi.org/10.3389/fevo.2020.575966
SN  - 2296-701X
VL  - 8
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Krause, Sascha
A1  - Le Roux, Xavier
A1  - Niklaus, Pascal A.
A1  - Van Bodegom, Peter M.
A1  - Lennon, Jay T.
A1  - Bertilsson, Stefan
A1  - Grossart, Hans-Peter
A1  - Philippot, Laurent
A1  - Bodelier, Paul L. E.
T1  - Trait-based approaches for understanding microbial biodiversity and ecosystem functioning
JF  - Frontiers in microbiology
N2  - In ecology, biodiversity-ecosystem functioning (BEE) research has seen a shift in perspective from taxonomy to function in the last two decades, with successful application of trait-based approaches. This shift offers opportunities for a deeper mechanistic understanding of the role of biodiversity in maintaining multiple ecosystem processes and services. In this paper, we highlight studies that have focused on BEE of microbial communities with an emphasis on integrating trait-based approaches to microbial ecology. In doing so, we explore some of the inherent challenges and opportunities of understanding BEE using microbial systems. For example, microbial biologists characterize communities using gene phylogenies that are often unable to resolve functional traits. Additionally, experimental designs of existing microbial BEE studies are often inadequate to unravel BEE relationships. We argue that combining eco-physiological studies with contemporary molecular tools in a trait-based framework can reinforce our ability to link microbial diversity to ecosystem processes. We conclude that such trait-based approaches are a promising framework to increase the understanding of microbial BEE relationships and thus generating systematic principles in microbial ecology and more generally ecology.
KW  - functional traits
KW  - ecosystem function
KW  - ecological theory
KW  - study designs
KW  - microbial diversity
Y1  - 2014
U6  - https://doi.org/10.3389/fmicb.2014.00251
SN  - 1664-302X
VL  - 5
PB  - Frontiers Research Foundation
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Kernecker, Maria
A1  - Fienitz, Meike
A1  - Nendel, Claas
A1  - Paetzig, Marlene
A1  - Walzl, Karin Pirhofer
A1  - Raatz, Larissa
A1  - Schmidt, Martin
A1  - Wulf, Monika
A1  - Zscheischler, Jana
T1  - Transition zones across agricultural field boundaries for integrated landscape research and management of biodiversity and yields
JF  - Ecological solutions and evidence
N2  - Biodiversity conservation and agricultural production have been largely framed as separate goals for landscapes in the discourse on land use. Although there is an increasing tendency to move away from this dichotomy in theory, the tendency is perpetuated by the spatially explicit approaches used in research and management practice. Transition zones (TZ) have previously been defined as areas where two adjacent fields or patches interact, and so they occur abundantly throughout agricultural landscapes. Biodiversity patterns in TZ have been extensively studied, but their relationship to yield patterns and social-ecological dimensions has been largely neglected. Focusing on European, temperate agricultural landscapes, we outline three areas of research and management that together demonstrate how TZ might be used to facilitate an integrated landscape approach: (i) plant and animal species' use and response to boundaries and the resulting effects on yield, for a deeper understanding of how landscape structure shapes quantity and quality of TZ; (ii) local knowledge on field or patch-level management and its interactions with biodiversity and yield in TZ, and (iii) conflict prevention and collaborative management across land-use boundaries.
KW  - ecotones
KW  - field boundaries
KW  - functional traits
KW  - landscape complexity;
KW  - land-use conflicts
KW  - local knowledge
KW  - spillovers
Y1  - 2022
U6  - https://doi.org/10.1002/2688-8319.12122
SN  - 2688-8319
VL  - 3
IS  - 1
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - THES
A1  - Kath, Nadja Jeanette
T1  - Functional traits determine biomass dynamics, coexistence and energetics in plankton food webs
N2  - Plankton food webs are the basis of marine and limnetic ecosystems. Especially aquatic ecosystems of high biodiversity provide important ecosystem services for humankind as providers of food, coastal protection, climate regulation, and tourism. Understanding the dynamics of biomass and coexistence in these food webs is a first step to understanding the ecosystems. It also lays the foundation for the development of management strategies for the maintenance of the marine and freshwater biodiversity despite anthropogenic influences.
Natural food webs are highly complex, and thus often equally complex methods are needed to analyse and understand them well. Models can help to do so as they depict simplified parts of reality. In the attempt to get a broader understanding of the complex food webs, diverse methods are used to investigate different questions.
In my first project, we compared the energetics of a food chain in two versions of an allometric trophic network model. In particular, we solved the problem of unrealistically high trophic transfer efficiencies (up to 70%) by accounting for both basal respiration and activity respiration, which decreased the trophic transfer efficiency to realistic values of ≤30%. Next in my second project I turned to plankton food webs and especially phytoplankton traits. Investigating a long-term data set from Lake Constance we found evidence for a trade-off between defence and growth rate in this natural phytoplankton community. I continued working with this data set in my third project focusing on ciliates, the main grazer of phytoplankton in spring. Boosted regression trees revealed that temperature and predators have the highest influence on net growth rates of ciliates. We finally investigated in my fourth project a food web model inspired by ciliates to explore the coexistence of plastic competitors and to study the new concept of maladaptive switching, which revealed some drawbacks of plasticity: faster adaptation led to higher maladaptive switching towards undefended phenotypes which reduced autotroph biomass and coexistence and increased consumer biomass.
It became obvious that even well-established models should be critically questioned as it is important not to forget reality on the way to a simplistic model. The results showed furthermore that long-term data sets are necessary as they can help to disentangle complex natural processes. Last, one should keep in mind that the interplay between models and experiments/ field data can deliver fruitful insights about our complex world.
N2  - Plankton-Nahrungsnetze sind die Grundlage mariner und limnischer Ökosysteme. Besonders die aquatischen Ökosysteme mit hoher Biodiversität erbringen wichtige Ökosystemdienstleistungen für uns Menschen wie beispielsweise die Bereitstellung von Nahrung, Küstenschutz, Klimaregulation sowie Tourismus. Die Dynamiken und die Koexistenz der Arten in diesen Ökosystemen zu verstehen, ist ein erster Schritt für die Entwicklung von Möglichkeiten zum Schutz ihrer Biodiversität.
Aufgrund der hohen Komplexität natürlicher Nahrungsnetze braucht es oft ebenso komplexe Methoden um sie zu analysieren und zu verstehen. Modelle können dabei unterstützen, da sie Teile der Realität vereinfacht abbilden. In meiner Dissertation arbeitete ich mit verschiedenen Nahrungsnetzmodellen, um die Dynamiken in Nahrungsnetzen zu verstehen.
In meinem ersten Projekt haben wir die Energieflüsse einer Nahrungskette in zwei Versionen eines allometrisch skalierten Nahrungsnetzmodells untersucht. Wenn nur die klassische basale Respiration einbezogen wird, steigt die trophische Transfereffizienz auf bis zu unrealistische 70 %. Durch die Einbeziehung der aktivitätsbezogenen Respiration sank die trophische Transfereffizienz auf realistische Werte von maximal 30 %. Danach wandte ich mich in meinem zweiten Projekt Plankton-Nahrungsnetzen und den Eigenschaften des Phytoplanktons zu. Bei der Untersuchung eines Langzeitdatensatzes von 21 Jahren aus dem Bodensee fanden wir einen Beweis für einen Trade-off zwischen Verteidigung und Wachstumsrate in einer natürlichen Phytoplankton-gemeinschaft. In diesem Datensatz konzentrierte ich mich anschließend in meinem dritten Projket auf Ciliaten, welche die wichtigsten Fraßfeinde von Phytoplankton im Frühjahr darstellen. Die Methode der boosted regression trees zeigte, dass Temperatur und Räuber den größten Einfluss auf die Nettowachstumsraten der Ciliaten haben. Schließlich nutzten wir in meinem vierten Projekt ein von Ciliaten inspiriertes Nahrungsnetzmodell, um die Koexistenz von Konkurrenten mit veränderlichen Eigenschaften und das neue Konzept des maladaptive switching zu untersuchen, welches Nachteile der Plastizität zeigt: höhere Wechselraten zwischen den Phänotypen führten zu höherem maladaptive switching in Richtung der unverteidigten Phänotypen, was die Biomasse und Koexistenz der Autotrophen reduziert und die Biomasse des Konsumenten erhöht.
Es wurde offensichtlich, dass auch etablierte Modelle kritisch hinterfragt werden müssen, da es wichtig ist, die Realität auf dem Weg zu einem einfachen Modell nicht zu vergessen. Meine Ergebnisse zeigten des Weiteren, wie wichtig Langzeitdatensätze sind, da sie helfen können, komplexe natürliche Prozesse zu beleuchten. Dieses Wechselspiel zwischen Modellen und Daten aus Experimenten oder Felduntersuchungen kann fruchtbare Ergebnisse liefern und zu einem größeren Verständnis unserer komplexen Welt beitragen.
KW  - functional traits
KW  - plankton food web
KW  - coexistence
KW  - modelling
KW  - Modellierung
KW  - Planktonnahrungsnetz
KW  - Koexistenz
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-551239
ER  - 
TY  - THES
A1  - Guislain, Alexis
T1  - Eco-physiological consequences of  fluctuating light on phytoplankton
T1  - Ökophysiologische Konsequenzen von fluktuierendem Licht auf das Phytoplankton
N2  - Phytoplankton growth depends not only on the mean intensity but also on the dynamics of the light supply. The nonlinear light-dependency of growth is characterized by a small number of basic parameters: the compensation light intensity PARcompμ, where production and losses are balanced, the growth efficiency at sub-saturating light αµ, and the maximum growth rate at saturating light µmax. In surface mixed layers, phytoplankton may rapidly move between high light intensities and almost darkness. Because of the different frequency distribution of light and/or acclimation processes, the light-dependency of growth may differ between constant and fluctuating light. Very few studies measured growth under fluctuating light at a sufficient number of mean light intensities to estimate the parameters of the growth-irradiance relationship. Hence, the influence of light dynamics on µmax, αµ and PARcompμ are still largely unknown. By extension, accurate modelling predictions of phytoplankton development under fluctuating light exposure remain difficult to make. This PhD thesis does not intend to directly extrapolate few experimental results to aquatic systems – but rather improving the mechanistic understanding of the variation of the light-dependency of growth under light fluctuations and effects on phytoplankton development. 
In Lake TaiHu and at the Three Gorges Reservoir (China), we incubated phytoplankton communities in bottles placed either at fixed depths or moved vertically through the water column to mimic vertical mixing. Phytoplankton at fixed depths received only the diurnal changes in light (defined as constant light regime), while phytoplankton received rapidly fluctuating light by superimposing the vertical light gradient on the natural sinusoidal diurnal sunlight. The vertically moved samples followed a circular movement with 20 min per revolution, replicating to some extent the full overturn of typical Langmuir cells. Growth, photosynthesis, oxygen production and respiration of communities (at Lake TaiHu) were  
measured. To complete these investigations, a physiological experiment was performed in the laboratory on a toxic strain of Microcystis aeruginosa (FACBH 1322) incubated under 20 min period fluctuating light. Here, we measured electron transport rates and net oxygen production at a much higher time resolution (single minute timescale).
The present PhD thesis provides evidence for substantial effects of fluctuating light on the eco-physiology of phytoplankton. Both experiments performed under semi-natural conditions in Lake TaiHu and at the Three Gorges Reservoir gave similar results. The significant decline in community growth efficiencies αµ under fluctuating light was caused for a great share by different frequency distribution of light intensities that shortened the effective daylength for production. The remaining gap in community αµ was attributed to species-specific photoacclimation mechanisms and to light-dependent respiratory losses. In contrast, community maximal growth rates µmax were similar between incubations at constant and fluctuating light. At daily growth saturating light supply, differences in losses for biosynthesis between the two light regimes were observed. Phytoplankton experiencing constant light suffered photo-inhibition - leading to photosynthesis foregone and additional respiratory costs for photosystems repair.  On the contrary, intermittent exposure to low and high light intensities prevented photo-inhibition of mixed algae but forced them to develop alternative light strategy. They better harvested and exploited surface irradiance by enhancing their photosynthesis. In the laboratory, we showed that Microcystis aeruginosa increased its oxygen consumption by dark respiration in the light few minutes only after exposure to increasing light intensities. More, we proved that within a simulated Langmuir cell, the net production at saturating light and the compensation light intensity for production at limiting light are positively related. These results are best explained by an accumulation of photosynthetic products at increasing irradiance and mobilization of these fresh resources by rapid enhancement of dark respiration for maintenance and biosynthesis at decreasing irradiance. At the daily timescale, we showed that the enhancement of photosynthesis at high irradiance for biosynthesis of species increased their maintenance respiratory costs at limiting light. Species-specific growth at saturating light µmax and compensation light intensity for growth PARcompμ of species incubated in Lake TaiHu were positively related. Because of this species-specific physiological tradeoff, species displayed different light affinities to limiting and saturating light - thereby exhibiting a gleaner-opportunist tradeoff. In Lake TaiHu, we showed that inter-specific differences in light acquisition traits (µmax and PARcompμ) allowed coexis¬tence of species on a gradient of constant  
light while avoiding competitive exclusion. More interestingly we demonstrated for the first time that vertical mixing (inducing fluctuating light supply for phytoplankton) may alter or even reverse the light utilization strategies of species within couple of days. The intra-specific variation in traits under fluctuating light increased the niche space for acclimated species, precluding competitive exclusion. 
Overall, this PhD thesis contributes to a better understanding of phytoplankton eco-physiology under fluctuating light supply. This work could enhance the quality of predictions of phytoplankton development under certain weather conditions or climate change scenarios.
N2  - Das Wachstum von Phytoplankton hängt ab nicht nur von der mittleren Intensität, sondern auch von der Dynamik des verfügbaren Lichts. Die nicht-lineare Lichtabhängigkeit des Wachstums kann durch drei Parameter beschrieben werden: die Kompensationslichtintensität PARcompµ, bei der Bruttoproduktion und Verluste gleich sind, die Wachstumseffizienz bei Lichtlimitation αµ und die maximale Wachstumsrate bei sättigendem Licht µmax. In durchmischten Schichten nahe der Gewässeroberfläche kann das Phytoplankton innerhalb weniger Minuten zwischen Starklicht und nahezu völliger Dunkelheit bewegt werden. Durch die unterschiedliche Häufigkeitsverteilung der Lichtintensitäten und/oder unterschiedliche Anpassungen kann die Lichtabhängigkeit des Wachstums sich bei fluktuierendem Licht von dem bei konstantem Licht unterscheiden. Bislang wurde die Lichtabhängigkeit des Wachstums bei fluktuierendem Licht nur in sehr wenigen Studien für genügend viele Lichtintensitäten gemessen, um die genannten Parameter bestimmen zu können. Entsprechend ist der Einfluss der Lichtdynamik auf die Parameter der Wachstums-Licht-Beziehung noch weitgehend unbekannt. Dies beeinträchtigt auch die Zuverlässigkeit von Modellaussagen zur Phytoplanktondynamik unter Durchmischungsbedingungen. In dieser Dissertation sollen die experimentell gewonnenen Ergebnisse nicht auf ganze Ökosysteme extrapoliert werden; Ziel ist vielmehr ein verbessertes Verständnis der Prozesse, die die Lichtabhängigkeit des Phytoplanktonwachstums unter dynamischen Lichtbedingungen steuern.
Hierzu wurden im Tai-See und im Dreischluchten-Stausee (China) Experimente mit Phytoplanktongemeinschaften durchgeführt. Es wurden Proben entweder in konstanten Tiefen exponiert oder mit Liften vertikal zwischen Wasseroberfläche und verschiedenen Tiefen bewegt. Während das Lichtangebot in konstanten Tiefen nur dem Tagesgang der  
Globalstrahlung folgte (hier als konstantes Licht bezeichnet), war das Phytoplankton in den bewegten Proben zusätzlich raschen Lichtfluktuationen ausgesetzt. Mit der Liftbewegung wurden mittlere Bedingungen in den Außenbahnen von Langmuir-Zellen simuliert, wobei eine Umlaufzeit von 20 Minuten gewählt wurde. Es wurden Wachstum, Photosynthese und (im Tai-See) Respiration gemessen. Zusätzlich wurde in Laborversuchen mit einem toxischen Stamm des Cyanobakteriums Microcystis aeruginosa (FACBH 1322) unter fluktuierendem und konstantem Licht Elektronentransportraten sowie Produktion und Verbrauch von Sauerstoff mit höherer zeitlicher Auflösung (1 min) gemessen. 
Die Ergebnisse der vorliegenden Dissertation demonstrieren bedeutsame Effekte von Lichtfluktuationen auf die Ökophysiologie von Phytoplankton. Die Experimente unter halb-natürlichen Bedingungen im Tai-See und im Dreischluchten-Stausee zeigten ähnliche Muster. Die Wachstumseffizienz der Gemeinschaften nahm durch fluktuierendes Licht deutlich ab, überwiegend durch die veränderte Häufigkeitsverteilung der Lichtintensitäten, die zu verkürzten effektiven Taglängen führte. Zudem verringerten artspezifische Anpassungsmechanismen und lichtabhängige Verluste durch Respiration die Wachstumseffizienz bei fluktuierendem Licht. Die maximalen Wachstumsraten der Gemeinschaft unterschieden sich hingegen nicht zwischen den Ansätzen mit konstantem und fluktuierendem Licht. Bei Lichtsättigung des Wachstums unterschieden sich die Aufwendungen für die Biosynthese zwischen den beiden Lichtregimen. Unter konstantem Starklicht wurden die Photosynthese gehemmt und die Respiration zur Reparatur der Photosysteme erhöht. Fluktuierendes Licht hingegen vermied Lichthemmung, zwang die vertikal bewegten Algen aber zu alternativen Strategien der Lichtnutzung. Durch eine erhöhte Photosynthesekapazität konnten sie Starklicht nahe der Wasseroberfläche besser nutzen. Microcystis aeruginosa verbrauchte im Labor mehr Sauerstoff durch Respiration bei abnehmenden Lichtintensitäten kurz nach Starklicht. Innerhalb eines Lichtzyklus von 20 min stieg die Kompensationslichtintensität mit steigender Nettoproduktion bei Lichtsättigung. Diese Beobachtungen sind am besten durch eine Anreicherung von Photosyntheseprodukten bei ansteigender Lichtintensität und deren sofortige verstärkte Respiration für Erhaltungsumsatz und Biosynthese bei abnehmender Lichtintensität erklärbar. Im Tagesmittel führte eine verstärkte Photosynthese bei Lichtsättigung zu erhöhter Respiration bei Schwachlicht. Die Kompensationslichtintensitäten dominanter Arten im Tai-See stiegen mit deren artspezifischen maximalen Wachstumsraten. Durch diesen artspezifischen physiologischen Kompromiss unterschieden sich die dominanten Arten im See bezüglich ihrer  
Lichtoptima. Unterschiedliche Strategien der Lichtnutzung (höhere maximale Wachstumsraten oder niedrigere Lichtansprüche) ermöglichten die Koexistenz verschiedener Arten entlang eines Gradienten der Intensität konstanten Lichts im Tai-See. Durch vertikale Durchmischung änderten sich die Strategien der Lichtnutzung innerhalb weniger Tage komplett. Die unterschiedlichen Anpassungsstrategien an fluktuierendes Licht  vergrößerten die  ökologischen Nischen der dominanten Arten und verhinderten ihre gegenseitige Verdrängung.
Insgesamt trägt diese Dissertation zum besseren Verständnis der Ökophysiologie von Phytoplankton unter Durchmischungsbedingungen bei. Dadurch werden verlässlichere Prognosen der Phytoplanktonentwicklung möglich, kurzzeitig in Kombination mit Wettervorhersagen und über lange Zeiträume durch Kopplung mit Klimaszenarien.
KW  - Lake TaiHu
KW  - Three Gorges reservoir
KW  - functional traits
KW  - tradeoff
KW  - fluctuating light
KW  - pPhytoplankton photoacclimation
KW  - effective daylength
KW  - photosynthesis
KW  - respiration
KW  - niche partitioning
KW  - non-equilibrium coexistence
KW  - TaiHu
KW  - Dreischluchten-Stausee
KW  - funktionelle Eigenschaften
KW  - Zielkonflikte
KW  - fluktuierendes Licht
KW  - Lichtanpassung
KW  - Photosynthese
KW  - Respiration
KW  - Nischen-Aufteilung
KW  - Koexistenz unter wechselnden Bedingungen
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-469272
ER  - 
TY  - JOUR
A1  - Ehrlich, Elias
A1  - Kath, Nadja Jeanette
A1  - Gaedke, Ursula
T1  - The shape of a defense-growth trade-off governs seasonal trait dynamics in natural phytoplankton
JF  - The ISME journal
N2  - Theory predicts that trade-offs, quantifying costs of functional trait adjustments, crucially affect community trait adaptation to altered environmental conditions, but empirical verification is scarce. We evaluated trait dynamics (antipredator defense, maximum growth rate, and phosphate affinity) of a lake phytoplankton community in a seasonally changing environment, using literature trait data and 21 years of species-resolved high-frequency biomass measurements. The trait data indicated a concave defense-growth trade-off, promoting fast-growing species with intermediate defense. With seasonally increasing grazing pressure, the community shifted toward higher defense levels at the cost of lower growth rates along the trade-off curve, while phosphate affinity explained some deviations from it. We discuss how low fitness differences of species, inferred from model simulations, in concert with stabilizing mechanisms, e.g., arising from further trait dimensions, may lead to the observed phytoplankton diversity. In conclusion, quantifying trade-offs is key for predictions of community trait adaptation and biodiversity under environmental change.
KW  - coexistence
KW  - community ecology
KW  - diversity
KW  - evolution
KW  - fitness
KW  - functional traits
KW  - lake
KW  - maintenance
KW  - mechanisms
KW  - plankton
Y1  - 2020
U6  - https://doi.org/10.1038/s41396-020-0619-1
SN  - 1751-7362
SN  - 1751-7370
VL  - 14
IS  - 6
SP  - 1451
EP  - 1462
PB  - Nature Publishing Group
CY  - London
ER  - 
TY  - GEN
A1  - Ehrlich, Elias
A1  - Kath, Nadja Jeanette
A1  - Gaedke, Ursula
T1  - The shape of a defense-growth trade-off governs seasonal trait dynamics in natural phytoplankton
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Theory predicts that trade-offs, quantifying costs of functional trait adjustments, crucially affect community trait adaptation to altered environmental conditions, but empirical verification is scarce. We evaluated trait dynamics (antipredator defense, maximum growth rate, and phosphate affinity) of a lake phytoplankton community in a seasonally changing environment, using literature trait data and 21 years of species-resolved high-frequency biomass measurements. The trait data indicated a concave defense-growth trade-off, promoting fast-growing species with intermediate defense. With seasonally increasing grazing pressure, the community shifted toward higher defense levels at the cost of lower growth rates along the trade-off curve, while phosphate affinity explained some deviations from it. We discuss how low fitness differences of species, inferred from model simulations, in concert with stabilizing mechanisms, e.g., arising from further trait dimensions, may lead to the observed phytoplankton diversity. In conclusion, quantifying trade-offs is key for predictions of community trait adaptation and biodiversity under environmental change.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1390 
KW  - functional traits
KW  - community ecology
KW  - evolution
KW  - lake
KW  - mechanisms
KW  - diversity
KW  - plankton
KW  - fitness
KW  - maintenance
KW  - coexistence
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-513956
SN  - 1866-8372
IS  - 6
ER  - 
TY  - JOUR
A1  - Ehrlich, Elias
A1  - Gaedke, Ursula
T1  - Coupled changes in traits and biomasses cascading through a tritrophic plankton food web
JF  - Limnology and oceanography
N2  - Trait-based approaches have broadened our understanding of how the composition of ecological communities responds to environmental drivers. This research has mainly focussed on abiotic factors and competition determining the community trait distribution, while effects of trophic interactions on trait dynamics, if considered at all, have been studied for two trophic levels at maximum. However, natural food webs are typically at least tritrophic. This enables indirect interactions of traits and biomasses among multiple trophic levels leading to underexplored effects on food web dynamics. Here, we demonstrate the occurrence of mutual trait adjustment among three trophic levels in a natural plankton food web (Lake Constance) and in a corresponding mathematical model. We found highly recurrent seasonal biomass and trait dynamics, where herbivorous zooplankton increased its size, and thus its ability to counter phytoplankton defense, before phytoplankton defense actually increased. This is contrary to predictions from bitrophic systems where counter-defense of the consumer is a reaction to prey defense. In contrast, counter-defense of carnivores by size adjustment followed the defense of herbivores as expected. By combining observations and model simulations, we show how the reversed trait dynamics at the two lower trophic levels result from a "trophic biomass-trait cascade" driven by the carnivores. Trait adjustment between two trophic levels can therefore be altered by biomass or trait changes of adjacent trophic levels. Hence, analyses of only pairwise trait adjustment can be misleading in natural food webs, while multitrophic trait-based approaches capture indirect biomass-trait interactions among multiple trophic levels.
KW  - community ecology
KW  - cyclops vicinus
KW  - dynamics
KW  - functional traits
KW  - lake
KW  - life-cycle
KW  - natural rotifer
KW  - phytoplankton
KW  - trophic cascades
KW  - zooplankton
Y1  - 2020
U6  - https://doi.org/10.1002/lno.11466
SN  - 0024-3590
SN  - 1939-5590
VL  - 65
IS  - 10
SP  - 2502
EP  - 2514
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Ehrlich, Elias
A1  - Becks, Lutz
A1  - Gaedke, Ursula
T1  - Trait-fitness relationships determine how trade-off shapes affect species coexistence
JF  - Ecology : a publication of the Ecological Society of America
N2  - Trade-offs between functional traits are ubiquitous in nature and can promote species coexistence depending on their shape. Classic theory predicts that convex trade-offs facilitate coexistence of specialized species with extreme trait values (extreme species) while concave trade-offs promote species with intermediate trait values (intermediate species). We show here that this prediction becomes insufficient when the traits translate non-linearly into fitness which frequently occurs in nature, e.g., an increasing length of spines reduces grazing losses only up to a certain threshold resulting in a saturating or sigmoid trait-fitness function. We present a novel, general approach to evaluate the effect of different trade-off shapes on species coexistence. We compare the trade-off curve to the invasion boundary of an intermediate species invading the two extreme species. At this boundary, the invasion fitness is zero. Thus, it separates trait combinations where invasion is or is not possible. The invasion boundary is calculated based on measurable trait-fitness relationships. If at least one of these relationships is not linear, the invasion boundary becomes non-linear, implying that convex and concave trade-offs not necessarily lead to different coexistence patterns. Therefore, we suggest a new ecological classification of trade-offs into extreme-favoring and intermediate-favoring which differs from a purely mathematical description of their shape. We apply our approach to a well-established model of an empirical predator-prey system with competing prey types facing a trade-off between edibility and half-saturation constant for nutrient uptake. We show that the survival of the intermediate prey depends on the convexity of the trade-off. Overall, our approach provides a general tool to make a priori predictions on the outcome of competition among species facing a common trade-off in dependence of the shape of the trade-off and the shape of the trait-fitness relationships.
KW  - coexistence
KW  - competition
KW  - fitness
KW  - functional traits
KW  - invasion boundary
KW  - neutrality
KW  - predator-prey model
KW  - shape
KW  - trade-offs
Y1  - 2017
U6  - https://doi.org/10.1002/ecy.2047
SN  - 0012-9658
SN  - 1939-9170
VL  - 98
SP  - 3188
EP  - 3198
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Eccard, Jana
A1  - Mendes Ferreira, Clara
A1  - Peredo Arce, Andres
A1  - Dammhahn, Melanie
T1  - Top-down effects of foraging decisions on local, landscape and regional biodiversity of resources (DivGUD)
JF  - Ecology letters
N2  - Foraging by consumers acts as a biotic filtering mechanism for biodiversity at the trophic level of resources. Variation in foraging behaviour has cascading effects on abundance, diversity, and functional trait composition of the community of resource species. Here we propose diversity at giving-up density (DivGUD), i.e. when foragers quit exploiting a patch, as a novel concept and simple measure quantifying cascading effects at multiple spatial scales. In experimental landscapes with an assemblage of plant seeds, patch residency of wild rodents decreased local alpha-DivGUD (via elevated mortality of species with large seeds) and regional gamma-DivGUD, while dissimilarity among patches in a landscape (beta-DivGUD) increased. By linking theories of adaptive foraging behaviour with community ecology, DivGUD allows to investigate cascading indirect predation effects, e.g. the ecology-of-fear framework, feedbacks between functional trait composition of resource species and consumer communities, and effects of inter-individual differences among foragers on the biodiversity of resource communities.
KW  - biodiversity
KW  - cascading effects
KW  - foraging behaviour
KW  - functional traits
KW  - giving-up density
KW  - landscape of fear
KW  - optimal foraging
KW  - patch use
Y1  - 2022
U6  - https://doi.org/10.1111/ele.13901
SN  - 1461-0248
VL  - 25
IS  - 1
SP  - 3
EP  - 16
PB  - Wiley-Blackwell
CY  - Oxford [u.a.]
ER  - 
TY  - JOUR
A1  - De Frenne, Pieter
A1  - Baeten, Lander
A1  - Graae, Bente J.
A1  - Brunet, Jorg
A1  - Wulf, Monika
A1  - Orczewska, Anna
A1  - Kolb, Annette
A1  - Jansen, Ivy
A1  - Jamoneau, Aurelien
A1  - Jacquemyn, Hans
A1  - Hermy, Martin
A1  - Diekmann, Martin
A1  - De Schrijver, An
A1  - De Sanctis, Michele
A1  - Decocq, Guillaume
A1  - Cousins, Sara A. O.
A1  - Verheyen, Kris
T1  - Interregional variation in the floristic recovery of post-agricultural forests
JF  - The journal of ecology
N2  - 1. Worldwide, the floristic composition of temperate forests bears the imprint of past land use for decades to centuries as forests regrow on agricultural land. Many species, however, display significant interregional variation in their ability to (re)colonize post-agricultural forests. This variation in colonization across regions and the underlying factors remain largely unexplored.
 2. We compiled data on 90 species and 812 species x study combinations from 18 studies across Europe that determined species' distribution patterns in ancient (i.e. continuously forested since the first available land use maps) and post-agricultural forests. The recovery rate (RR) of species in each landscape was quantified as the log-response ratio of the percentage occurrence in post-agricultural over ancient forest and related to the species-specific life-history traits and local (soil characteristics and light availability) and regional factors (landscape properties as habitat availability, time available for colonization, and climate).
 3. For the herb species, we demonstrate a strong (interactive) effect of species' life-history traits and forest habitat availability on the RR of post-agricultural forest. In graminoids, however, none of the investigated variables were significantly related to the RR.
 4. The better colonizing species that mainly belonged to the short-lived herbs group showed the largest interregional variability. Their recovery significantly increased with the amount of forest habitat within the landscape, whereas, surprisingly, the time available for colonization, climate, soil characteristics and light availability had no effect.
 5. Synthesis. By analysing 18 independent studies across Europe, we clearly showed for the first time on a continental scale that the recovery of short-lived forest herbs increased with the forest habitat availability in the landscape. Small perennial forest herbs, however, were generally unsuccessful in colonizing post-agricultural forest even in relatively densely forested landscapes. Hence, our results stress the need to avoid ancient forest clearance to preserve the typical woodland flora.
KW  - ancient forest
KW  - colonization capacity
KW  - forest herbs
KW  - functional traits
KW  - habitat fragmentation
KW  - habitat loss
KW  - life-history traits
KW  - meta-analysis
KW  - plant population and community dynamics
KW  - secondary succession
Y1  - 2011
U6  - https://doi.org/10.1111/j.1365-2745.2010.01768.x
SN  - 0022-0477
VL  - 99
IS  - 2
SP  - 600
EP  - 609
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Bolius, Sarah
A1  - Wiedner, Claudia
A1  - Weithoff, Guntram
T1  - High local trait variability in a globally invasive cyanobacterium
JF  - Freshwater biology
N2  - 1. During the last couple of decades, invasive species have become a worldwide problem in many freshwater systems. Besides higher plants and animals, microbes, in particular the potentially toxic cyanobacterium Cylindrospermopsis raciborskii, has attracted increasing attention, due to its spread towards temperate zones of the northern and southern hemisphere. A number of advantageous functional traits and a high intraspecific plasticity have been suggested to explain its invasion success. 2. The aim of this study was to examine intraspecific functional trait variability in 12 different isolates of C.raciborskii originating from different lakes in an invaded region in Northeast Germany. We measured growth rate, C:N:P ratios, chlorophyll-a content and the abundance of heterocysts under nutrient-replete and phosphorus-limited conditions. Moreover, the isolate-specific morphology and grazing losses by an herbivorous rotifer, as a top-down force, were studied. 3. DNA fingerprinting revealed that all isolates were genetically different. C.raciborskii exhibited a large variability in all measured traits among isolates. The C:P, N:P and Chl-a:C ratios differed by a factor of two or more. The trait variability among isolates was higher under nutrient-replete conditions, except for the C:P ratio, which varied most during phosphorus limitation. The susceptibility to grazing, calculated as maximum ingestion rates of the rotifer Brachionus calyciflorus on C.raciborskii, varied most among isolates, but was not related to any of the measured physiological or morphological traits, i.e. no trade-off was found. 4. Ecological and genetic clustering did not match, indicating that the genetic relationship based on DNA fingerprinting did not cover ecological differences. 5. Our results show a high trait variability within locally occurring and partly co-occurring C.raciborskii isolates. No overall trade-offs between the measured functional traits were found. This demonstrates the ecological relevance of linking multiple traits, e.g. competitive and consumptive. Furthermore, this study emphasises the importance of analysing more than one strain of a species, as different strains show different trait values potentially relevant for their invasibility and the field of general trait-based ecology.
KW  - Cylindrospermopsis raciborskii
KW  - functional traits
KW  - genotypes
KW  - invasion
KW  - stoichiometry
Y1  - 2017
U6  - https://doi.org/10.1111/fwb.13028
SN  - 0046-5070
SN  - 1365-2427
VL  - 62
SP  - 1879
EP  - 1890
PB  - Wiley
CY  - Hoboken
ER  -