TY - JOUR A1 - Kefi, Sonia A1 - Berlow, Eric L. A1 - Wieters, Evie A. A1 - Navarrete, Sergio A. A1 - Petchey, Owen L. A1 - Wood, Spencer A. A1 - Boit, Alice A1 - Joppa, Lucas N. A1 - Lafferty, Kevin D. A1 - Williams, Richard J. A1 - Martinez, Neo D. A1 - Menge, Bruce A. A1 - Blanchette, Carol A. A1 - Iles, Alison C. A1 - Brose, Ulrich T1 - More than a meal ... integrating non-feeding interactions into food webs JF - Ecology letters N2 - Organisms eating each other are only one of many types of well documented and important interactions among species. Other such types include habitat modification, predator interference and facilitation. However, ecological network research has been typically limited to either pure food webs or to networks of only a few (<3) interaction types. The great diversity of non-trophic interactions observed in nature has been poorly addressed by ecologists and largely excluded from network theory. Herein, we propose a conceptual framework that organises this diversity into three main functional classes defined by how they modify specific parameters in a dynamic food web model. This approach provides a path forward for incorporating non-trophic interactions in traditional food web models and offers a new perspective on tackling ecological complexity that should stimulate both theoretical and empirical approaches to understanding the patterns and dynamics of diverse species interactions in nature. KW - Ecological network KW - ecosystem engineering KW - facilitation KW - food web KW - interaction modification KW - non-trophic interactions KW - trophic interactions Y1 - 2012 U6 - https://doi.org/10.1111/j.1461-0248.2011.01732.x SN - 1461-023X VL - 15 IS - 4 SP - 291 EP - 300 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Metz, Johannes A1 - Tielboerger, Katja T1 - Spatial and temporal aridity gradients provide poor proxies for plant-plant interactions under climate change: a large-scale experiment JF - Functional ecology : an official journal of the British Ecological Society N2 - 1. Plant-plant interactions may critically modify the impact of climate change on plant communities. However, the magnitude and even direction of potential future interactions remains highly debated, especially for water-limited ecosystems. Predictions range from increasing facilitation to increasing competition with future aridification. 2. The different methodologies used for assessing plant-plant interactions under changing environmental conditions may affect the outcome but they are not equally represented in the literature. Mechanistic experimental manipulations are rare compared with correlative approaches that infer future patterns from current observations along spatial climatic gradients. 3. Here, we utilize a unique climatic gradient in combination with a large-scale, long-term experiment to test whether predictions about plant-plant interactions yield similar results when using experimental manipulations, spatial gradients or temporal variation. We assessed shrub-annual interactions in three different sites along a natural rainfall gradient (spatial) during 9 years of varying rainfall (temporal) and 8 years of dry and wet manipulations of ambient rainfall (experimental) that closely mimicked regional climate scenarios. 4. The results were fundamentally different among all three approaches. Experimental water manipulations hardly altered shrub effects on annual plant communities for the assessed fitness parameters biomass and survival. Along the spatial gradient, shrub effects shifted from clearly negative to mildly facilitative towards drier sites, whereas temporal variation showed the opposite trend: more negative shrub effects in drier years. 5. Based on our experimental approach, we conclude that shrub-annual interaction will remain similar under climate change. In contrast, the commonly applied space-for-time approach based on spatial gradients would have suggested increasing facilitative effects with climate change. We discuss potential mechanisms governing the differences among the three approaches. 6. Our study highlights the critical importance of long-term experimental manipulations for evaluating climate change impacts. Correlative approaches, for example along spatial or temporal gradients, may be misleading and overestimate the response of plant-plant interactions to climate change. KW - annual plant communities KW - climate manipulation KW - competition KW - facilitation KW - Mediterranean shrubland KW - nurse plant KW - rainfall gradient KW - Sarcopoterium spinosum KW - semi-arid KW - stress-gradient hypothesis Y1 - 2016 U6 - https://doi.org/10.1111/1365-2435.12599 SN - 0269-8463 SN - 1365-2435 VL - 30 SP - 20 EP - 29 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Lachmuth, Susanne A1 - Henrichmann, Colette A1 - Horn, Juliane A1 - Pagel, Jörn A1 - Schurr, Frank M. T1 - Neighbourhood effects on plant reproduction BT - an experimental-analytical framework and its application to the invasive Senecio inaequidens JF - The journal of ecology N2 - Density dependence is of fundamental importance for population and range dynamics. Density-dependent reproduction of plants arises from competitive and facilitative plant-plant interactions that can be pollination independent or pollination mediated. In small and sparse populations, conspecific density dependence often turns from negative to positive and causes Allee effects. Reproduction may also increase with heterospecific density (community-level Allee effect), but the underlying mechanisms are poorly understood and the consequences for community dynamics can be complex. Allee effects have crucial consequences for the conservation of declining species, but also the dynamics of range edge populations. In invasive species, Allee effects may slow or stop range expansion. Observational studies in natural plant communities cannot distinguish whether reproduction is limited by pollination-mediated interactions among plants or by other neighbourhood effects (e.g. competition for abiotic resources). Even experimental pollen supply cannot distinguish whether variation in reproduction is caused by direct density effects or by plant traits correlated with density. Finally, it is unknown over which spatial scales pollination-mediated interactions occur. To circumvent these problems, we introduce a comprehensive experimental and analytical framework which simultaneously (1) manipulates pollen availability and quality by hand pollination and pollinator exclusion, (2) manipulates neighbourhoods by transplanting target plants, and (3) analyses the effects of con- and heterospecific neighbourhoods on reproduction with spatially explicit trait-based neighbourhood models. Synthesis. By manipulating both pollen availability and target plant locations within neighbourhoods, we can comprehensively analyse spatially explicit density dependence of plant reproduction. This experimental approach enhances our ability to understand the dynamics of sparse populations and of species geographical ranges. KW - Allee effect KW - biological invasion KW - competition KW - density dependence KW - facilitation KW - plant-plant interactions KW - pollination KW - reproductive success KW - spatially explicit model KW - trait-based neighbourhood model Y1 - 2017 U6 - https://doi.org/10.1111/1365-2745.12816 SN - 0022-0477 SN - 1365-2745 VL - 106 IS - 2 SP - 761 EP - 773 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Heger, Tina A1 - Nikles, Gabriele A1 - Jacobs, Brooke S. T1 - Differentiation in native as well as introduced ranges BT - germination reflects mean and variance in cover of surrounding vegetation JF - AoB PLANTS N2 - Germination, a crucial phase in the life cycle of a plant, can be significantly influenced by competition and facilitation. The aim of this study was to test whether differences in cover of surrounding vegetation can lead to population differentiation in germination behaviour of an annual grassland species, and if so, whether such a differentiation can be found in the native as well as in the introduced range. We used maternal progeny of Erodium cicutarium previously propagated under uniform conditions that had been collected in multiple populations in the native and two introduced ranges, in populations representing extremes in terms of mean and variability of the cover of surrounding vegetation. In the first experiment, we tested the effect of germination temperature and mean cover at the source site on germination, and found interlinked effects of these factors. In seeds from one of the introduced ranges (California), we found indication for a 2-fold dormancy, hindering germination at high temperatures even if physical dormancy was broken and water was available. This behaviour was less strong in high cover populations, indicating cross-generational facilitating effects of dense vegetation. In the second experiment, we tested whether spatial variation in cover of surrounding vegetation has an effect on the proportion of dormant seeds. Contrary to our expectations, we found that across source regions, high variance in cover was associated with higher proportions of seeds germinating directly after storage. In all three regions, germination seemed to match the local environment in terms of climate and vegetation cover. We suggest that this is due to a combined effect of introduction of preadapted genotypes and local evolutionary processes. KW - Bet-hedging KW - competition KW - eco-evolutionary experience KW - facilitation KW - genetic adaptation KW - physical and physiological dormancy KW - preadaptation Y1 - 2018 U6 - https://doi.org/10.1093/aobpla/ply009 SN - 2041-2851 VL - 10 IS - 1 PB - Oxford Univ. Press CY - Oxford ER - TY - GEN A1 - Heger, Tina A1 - Nikles, Gabriele A1 - Jacobs, Brooke S. T1 - Differentiation in native as well as introduced ranges BT - germination reflects mean and variance in cover of surrounding vegetation T2 - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe N2 - Germination, a crucial phase in the life cycle of a plant, can be significantly influenced by competition and facilitation. The aim of this study was to test whether differences in cover of surrounding vegetation can lead to population differentiation in germination behaviour of an annual grassland species, and if so, whether such a differentiation can be found in the native as well as in the introduced range. We used maternal progeny of Erodium cicutarium previously propagated under uniform conditions that had been collected in multiple populations in the native and two introduced ranges, in populations representing extremes in terms of mean and variability of the cover of surrounding vegetation. In the first experiment, we tested the effect of germination temperature and mean cover at the source site on germination, and found interlinked effects of these factors. In seeds from one of the introduced ranges (California), we found indication for a 2-fold dormancy, hindering germination at high temperatures even if physical dormancy was broken and water was available. This behaviour was less strong in high cover populations, indicating cross-generational facilitating effects of dense vegetation. In the second experiment, we tested whether spatial variation in cover of surrounding vegetation has an effect on the proportion of dormant seeds. Contrary to our expectations, we found that across source regions, high variance in cover was associated with higher proportions of seeds germinating directly after storage. In all three regions, germination seemed to match the local environment in terms of climate and vegetation cover. We suggest that this is due to a combined effect of introduction of preadapted genotypes and local evolutionary processes. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 650 KW - bet-hedging KW - competition KW - eco-evolutionary experience KW - facilitation KW - genetic adaptation KW - physical and physiological dormancy KW - preadaptation Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-424642 SN - 1866-8372 IS - 650 ER - TY - THES A1 - Molinengo, Giulia T1 - The micropolitics of collaborative governance T1 - Die Mikropolitik von „collaborative governance“ BT - a power-sensitive and process-oriented perspective BT - eine machtsensitive und prozessorientierte Perspektive N2 - Why do exercises in collaborative governance often witness more impasse than advantage? This cumulative dissertation undertakes a micro-level analysis of collaborative governance to tackle this research puzzle. It situates micropolitics at the very center of analysis: a wide range of activities, interventions, and tactics used by actors – be they conveners, facilitators, or participants – to shape the collaborative exercise. It is by focusing on these daily minutiae, and on the consequences that they bring along, the study argues, that we can better understand why and how collaboration can become stuck or unproductive. To do so, the foundational part of this dissertation (Article 1) uses power as a sensitizing concept to investigate the micro-dynamics that shape collaboration. It develops an analytical approach to advance the study of collaborative governance at the empirical level under a power-sensitive and process-oriented perspective. The subsequent articles follow the dissertation's red thread of investigating the micropolitics of collaborative governance by showing facilitation artefacts' interrelatedness and contribution to the potential success or failure of collaborative arrangements (Article 2); and by examining the specialized knowledge, skills and practices mobilized when designing a collaborative process (Article 3). The work is based on an abductive research approach, tacking back and forth between empirical data and theory, and offers a repertoire of concepts – from analytical terms (designed and emerging interaction orders, flows of power, arenas for power), to facilitation practices (scripting, situating, and supervising) and types of knowledge (process expertise) – to illustrate and study the detailed and constant work (and rework) that surrounds collaborative arrangements. These concepts sharpen the way researchers can look at, observe, and understand collaborative processes at a micro level. The thesis thereby elucidates the subtleties of power, which may be overlooked if we focus only on outcomes rather than the processes that engender them, and supports efforts to identify potential sources of impasse. N2 - Warum führen Prozesse der collaborative governance oft eher in die Sackgasse als zum Erfolg? Die vorliegende kumulative Dissertation geht dieses Problem an, indem sie die Mikroebene von collaborative governance analysiert. Untersuchungsgegenstand ist die Mikropolitik, verstanden als weites Spektrum an Aktivitäten, Interventionen und Taktiken, mit denen beteiligte Akteure – seien es VeranstalterInnen, ModeratorInnen oder TeilnehmerInnen – kollaborative Prozesse gestalten. Es ist dieser Fokus auf alltägliche Handlungen und ihre Auswirkungen, so argumentiert die Arbeit, der ein besseres Verständnis ermöglicht, wann und warum kollaborative Prozesse unproduktiv werden. Um dies zu erreichen, verwendet der grundlegende Teil der Dissertation (Artikel 1) Macht als sensibilisierenden Begriff, um die Mikrodynamiken zu untersuchen, welche collaborative governance prägen. Der Artikel entwickelt ein Analysemodell, um die empirische Untersuchung der collaborative governance aus einer machtsensiblen und prozessorientierten Perspektive zu ermöglichen. Die weiteren Artikel folgen dem roten Faden der Dissertation und untersuchen die Mikropolitik der collaborative governance, indem sie die Wechselwirkungen und den Beitrag von Moderationsgegenständen zum potenziellen Erfolg oder Misserfolg kollaborativer Prozesse aufzeigen (Artikel 2), sowie die speziellen Kenntnisse, Fähigkeiten und Praktiken untersuchen, die bei der Gestaltung eines Beteiligungsprozesses mobilisiert werden (Artikel 3). Die Arbeit basiert auf einem abduktiven Forschungsansatz, bewegt sich zwischen empirischen Daten und Theorie hin und her, und entwickelt ein Repertoire an Begriffen und Konzepten - von analytischen Begriffen (designed and emerging interaction orders, flows of power, arenas for power) bis hin zu Moderationspraktiken (scripting, situating, und supervising) und Wissensarten (Prozessexpertise) - um die minutiösen und kontinuierlichen Gestaltungen (und Umgestaltungen) von kollaborativen Prozessen zu veranschaulichen und untersuchen. Diese Begriffe und Konzepte erlauben ForscherInnen, ihren Blick auf die Mikroebene von kollaborativen Prozessen zu schärfen. Die Dissertation verdeutlicht damit die Feinheiten von Macht, welche bei einem Fokus auf Ergebnisse statt auf die ihnen vorgelagerten Prozesse oft übersehen werden, und unterstützt die Bemühungen, potenzielle Quellen von collaborative impasse zu identifizieren. KW - collaborative governance KW - micropolitics KW - facilitation KW - power KW - process design KW - artefacts KW - process expertise KW - Artefakte KW - Moderation KW - Mikropolitik KW - Macht KW - Prozessgestaltung KW - Prozessexpertise Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-577123 ER -