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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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