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  • 51. Sebastian, Patrizia
    et al.
    Stibor, Herwig
    Berger, Stella
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Effects of water temperature and mixed layer depth on zooplankton body size2012Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 159, nr 11, s. 2431-2440Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ecological consequences of global warming include shifts of species ranges toward higher altitudes and latitudes as well as temporal shifts in phenology and life-cycle events. Evidence is accumulating that increasing temperature is also linked to reduced body size of ectotherms. While temperature can act directly on body size, it may also act indirectly by affecting the timing of life-cycle events and the resulting population age and size structure, especially in seasonal environments. Population structure may, in turn, be influenced by temperature-driven changes in resource availability. In a field mesocosm experiment, we investigated how water temperature and mixed surface layer depth (a temperature-dependent determinant of light availability to phytoplankton) affected population dynamics, population age and size structure, and individual size at stage (size at first reproduction) of Daphnia hyalina during and after a phytoplankton spring bloom. Mixed layer depth was inversely related to the magnitudes of the phytoplankton spring bloom and the subsequent Daphnia peak, but had no effect on the body size of Daphnia. Conversely, temperature had no effects on abundance peaks but strongly affected the timing of these events. This resulted in at times positive, at other times negative, transient effects of temperature on mean body size, caused by asynchronous changes in population size structure in cold versus warm treatments. In contrast to mean body size, individual size at stage consistently decreased with increasing temperature. We suggest that size at stage could be used as an unbiased response parameter to temperature that is unaffected by transient, demographically driven changes in population size structure.

  • 52. Stibor, H.
    et al.
    Vadstein, O.
    Diehl, S.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Gelzleichter, A.
    Hansen, T.
    Hantzsche, F.
    Katechakis, A.
    Lippert, B.
    Loseth, K.
    Peters, C.
    Roederer, W.
    Sandow, M.
    Sundt-Hansen, L.
    Olsen, Y.
    Copepods act as a switch between alternative trophic cascades in marine pelagic food webs2004Ingår i: Ecology Letters, Vol. 7, nr 4, s. 321-328Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A recent meta-analysis indicates that trophic cascades (indirect effects of predators on plants via herbivores) are weak in marine plankton in striking contrast to freshwater plankton (Shurin et al. 2002 , Ecol. Lett., 5, 785-791). Here we show that in a marine plankton community consisting of jellyfish, calanoid copepods and algae, jellyfish predation consistently reduced copepods but produced two distinct, opposite responses of algal biomass. Calanoid copepods act as a switch between alternative trophic cascades along food chains of different length and with counteracting effects on algal biomass. Copepods reduced large algae but simultaneously promoted small algae by feeding on ciliates. The net effect of jellyfish on total algal biomass was positive when large algae were initially abundant in the phytoplankton, negative when small algae were dominant, but zero when experiments were analysed in combination. In contrast to marine systems, major pathways of energy flow in Daphnia-dominated freshwater systems are of similar chain length. Thus, differences in the length of alternative, parallel food chains may explain the apparent discrepancy in trophic cascade strength between freshwater and marine planktonic systems.

  • 53. Striebel, M.
    et al.
    Bartholme, S.
    Zernecke, R.
    Steinlein, C.
    Haupt, F.
    Diehl, S.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Stibor, H.
    Carbon sequestration and stoichiometry of motile and nonmotile green algae2009Ingår i: Limnology and Oceanography, Vol. 54, nr 5, s. 1746-1752Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Actively motile, flagellated phytoplankton taxa often exploit vertical gradients in the availability of light and nutrients. The ability to move actively usually goes along with low investment in structural carbon components and should entail costs in terms of increased energy expenditure. This should be reflected in higher metabolic rates and higher light requirements for growth and, consequently, in lower light-dependent specific production rates, carrying capacities, and carbon-to-phosphorus (C : P) ratios (during phosphorus limitation) of flagellated compared to nonmotile taxa. Laboratory experiments with four flagellated and five nonmotile species of green algae, performed over a light gradient, corroborated these expectations. Parameter fits to short-term production-irradiance measurements suggest that flagellated taxa had higher respiration rates and higher light requirements for growth than nonmotile taxa. Accordingly, both short-term photosynthetic rates and longer-term (14 d) biomass accrual were lower for flagellated than for nonmotile taxa. While most of the variance in algal C : P ratios was explained by species-specific effects, there was also a tendency for algal C : P ratios to be lower in flagellated that in nonmotile taxa. Collectively, these results point at significant costs of motility, which may explain why flagellated taxa are often outcompeted by nonmotile taxa in turbulently mixed environments, where active motility is of little use.

  • 54. Striebel, M.
    et al.
    Behl, S.
    Diehl, S.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Stibor, H.
    Spectral Niche Complementarity and Carbon Dynamics in Pelagic Ecosystems2009Ingår i: American Naturalist, Vol. 174, nr 1, s. 141-147Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Positive effects of biodiversity on ecosystem function are described from an increasing number of systems, but the underlying mechanisms frequently remain elusive. A truly predictive understanding of biodiversity-ecosystem function relationships requires the a priori identification of traits conferring specific ( and possibly complementary) functions to individual species. Although planktonic organisms are responsible for approximately half of the world's primary production, few studies have reported on the relationship between phytoplankton biodiversity and planktonic primary production. We argue that taxon-specific differential equipment with photosynthetically active pigments provides a biochemical mechanism of resource use complementarity among phototrophic microorganisms, enabling more diverse communities to more completely harvest the light spectrum. In line with this, more diverse phytoplankton communities showed higher pigment diversity, higher biomass-specific light absorbance, and higher rates of primary production and biomass accrual.

  • 55.
    Thomsson, Gustaf
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Kahlert, Maria
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Liess, Antonia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Inverse relationship of benthic algae and pelagic phosphorus in unproductive lakes: roles of N2 fixers and lightManuskript (preprint) (Övrigt vetenskapligt)
  • 56.
    Uszko, Wojciech
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Temperature dependence of the type III functional response in DaphniaManuskript (preprint) (Övrigt vetenskapligt)
  • 57.
    Uszko, Wojciech
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Englund, Göran
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Amarasekare, Priyanga
    Effects of warming on predator-prey interactions - a resource-based approach and a theoretical synthesis2017Ingår i: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 20, nr 4, s. 513-523Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We theoretically explore consequences of warming for predator-prey dynamics, broadening previous approaches in three ways: we include beyond-optimal temperatures, predators may have a type III functional response, and prey carrying capacity depends on explicitly modelled resources. Several robust patterns arise. The relationship between prey carrying capacity and temperature can range from near-independence to monotonically declining/increasing to hump-shaped. Predators persist in a U-shaped region in resource supply (=enrichment)-temperature space. Type II responses yield stable persistence in a U-shaped band inside this region, giving way to limit cycles with enrichment at all temperatures. In contrast, type III responses convey stability at intermediate temperatures and confine cycles to low and high temperatures. Warming-induced state shifts can be predicted from system trajectories crossing stability and persistence boundaries in enrichment-temperature space. Results of earlier studies with more restricted assumptions map onto this graph as special cases. Our approach thus provides a unifying framework for understanding warming effects on trophic dynamics.

  • 58.
    Uszko, Wojciech
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Englund, Göran
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Amarasekare, Priyanga
    Effects of warming on predator-prey interactions: a resource-based approach and a theoretical synthesisManuskript (preprint) (Övrigt vetenskapligt)
  • 59.
    Uszko, Wojciech
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department Biologie II, Ludwig-Maximilians-Universität, München.
    Pitsch, Nadine
    Department Biologie II, Ludwig-Maximilians-Universita¨t Mu¨nchen, Grosshaderner Str. 2, D-82152 Planegg-Martinsried, Germany.
    Lengfellner, Kathrin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Müller, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    When is a type III functional response stabilizing?: theory and practice of predicting plankton dynamics under enrichment2015Ingår i: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 96, nr 12, s. 3243-3256Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The curvature of generalized Holling type functional response curves is controlled by a shape parameter b yielding hyperbolic type II (b = 1) to increasingly sigmoid type III (b > 1) responses. Empirical estimates of b vary considerably across taxa. Larger consumer-resource body mass ratios have been suggested to generate more pronounced type III responses and therefore to promote dynamic stability. The dependence of consumer-resource stability on b has, however, not been systematically explored, and the accurate empirical determination of b is challenging. Specifically, the shape of the functional response of the pelagic grazer Daphnia feeding on phytoplankton, and its consequences for stability, remain controversial. We derive a novel analytical condition relating b to local stability of consumer-resource interactions and use it to predict stability of empirically parameterized models of Daphnia and phytoplankton under enrichment. Functional response parameters were experimentally derived for two species of Daphnia feeding separately on single cultures of two different phytoplankton species. All experimentally studied Daphnia-algae systems exhibited type III responses. Parameterized type III responses are predicted to stabilize the modeled Daphnia-phytoplankton dynamics in some species pairs but not in others. Remarkably, stability predictions differ depending on whether functional response parameters are derived from clearance vs. ingestion rates. Accurate parameter estimation may therefore require fitting to both rates. In addition, our estimates of b for filter-feeding Daphnia are much smaller than predicted for actively hunting predators at similar consumer-resource body mass ratios. This suggests that the relationship between functional response shape and body mass ratios may vary with predation mode.

  • 60.
    Vasconcelos, Francisco Rivera
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Rodriguez, Patricia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Austral Centre for Scientific Research (CADIC-CONICET), 9410 Ushuaia, Tierra del Fuego, Argentina.
    Hedström, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Asymmetrical competition between aquatic primary producers in a warmer and browner world2016Ingår i: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 97, nr 10, s. 2580-2592Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In shallow lakes, pelagic and benthic producers engage in spatially asymmetrical resource competition. Pelagic producers intercept the flux of light to the benthic habitat and benthic producers intercept the flux of sediment-derived nutrients to the pelagic habitat. In boreal and subarctic regions, climate change is affecting this interaction both directly through warming and indirectly through increased loading with colored dissolved organic matter (cDOM) from the catchment (brownification). We use a dynamical ecosystem model to explore the consequences of these changing environmental conditions for lake primary production and compare model predictions with the results of an experiment in which we manipulated water temperature and cDOM supply in a 2x2 factorial design. The experiment was performed in field mesocosms large enough to harbor reproducing fish populations and was run over an entire growing season. In agreement with model predictions, benthic algal production and biomass declined and pelagic algal production and biomass increased with browning. Pelagic nutrient concentrations diverged over time between low and high cDOM treatments, suggesting that browning alleviated pelagic algal nutrient limitation by shading benthic competitors and preventing them from intercepting the release of nutrients from the sediment. Warming considerably reduced benthic and pelagic algal production as well as pelagic algalbiomass and total phosphorus. The warming results are only in partial accordance with model expectations, but can be explained by an indirectly inferred, positive response of macrophyte production (which was not included in the model) to warming. Our study suggests that lake ecosystem responses to climate change are mediated by cross-habitat feedbacks between benthic and pelagic producers.

  • 61.
    Vasconcelos, Francisco Rivera
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Integrated Science Lab - IceLab, Umeå University, Umeå, Sweden.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Integrated Science Lab - IceLab, Umeå University, Umeå, Sweden.
    Rodríguez, Patricia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Austral Centre for Scientific Research (CADIC‐CONICET), Ushuaia, Tierra del Fuego, Argentina.
    Hedström, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Bottom-up and top-down effects of browning and warming on shallow lake food webs2019Ingår i: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 25, s. 504-521Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The productivity and trophic structure of aquatic ecosystems is the result of an interplay between bottom-up and top-down forces that operate both within and across the benthic and pelagic compartments of lake food webs. Contemporary and projected climate changes urge the question how this interplay will be affected by increasing inputs of terrestrial derived, dissolved organic matter (‘browning’) and warming. We addressed this issue by exploring how browning and warming affect the behavior of a relatively simple, conceptual model of a shallow lake food web that is compartmentalized into, dynamically coupled, benthic and pelagic components (abiotic resources, primary producers, grazers, and carnivores). We compared model expectations with the results of a factorial manipulation of browning and warming in a replicated, large-scale field experiment. Both the model and the experiment suggest that browning affects the food web from the bottom-up by reducing light supply to the benthic habitat and increasing nutrient supply to the pelagic habitat, with concomitant decreases of benthic and increases of pelagic primary and secondary production. The model also predicts that warming effects should primarily operate via relaxed top-down control by top consumers in the more productive of the two habitats. The latter was only partially supported by the experimental data, possibly because the model still lacks one or two important trophic links, such as the one from pelagic producers to benthic deposit feeders. We propose that our coupled benthic-pelagic food web model provides a useful conceptual starting point for future theoretical and empirical studies of the impacts of environmental changes on shallow lakes.

  • 62.
    Vasconcelos, Francisco Rivera
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Rodríguez, Patricia
    Austral Centre for Scientific Research, Argentina.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Terrestrial organic matter reverses competition between aquatic primary producers by altering within-lake, cross-habitat resource fluxesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Flows of energy and matter across habitat boundaries can be major determinants of the functioning of recipient ecosystems. It is currently debated whether terrestrial dissolved organic matter (tDOM) is a resource subsidy or a resource subtraction in recipient lakes. In a long-term field experiment, pelagic phosphorus concentration and aquatic primary production increased with increasing tDOM input, suggesting that tDOM acted primarily as a direct nutrient subsidy. Piecewise structural equation modeling supports, however, an approximately equally important role for a second mechanism: colored tDOM acted also as a resource subtraction by shading benthic algae, preventing them from intercepting nutrients released across the sediment-water interface. Inhibition of benthic algae by colored tDOM thus indirectly promoted pelagic algae and whole-ecosystem primary production. We conclude that cross-ecosystem terrestrial DOM inputs can modify light and nutrient flows between aquatic habitats and alter the outcome of resource competition between benthic and pelagic producers. These results are particularly relevant for shallow northern lakes, which are facing increased tDOM runoff with climate change.

  • 63.
    Vasconcelos, Rivera Francisco
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Rodríguez, Patricia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Austral Centre for Scientific Research (CADIC-CONICET), Ushuaia, Tierra del Fuego, Argentina.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Effects of Terrestrial Organic Matter on Aquatic Primary Production as Mediated by Pelagic-Benthic Resource Fluxes2018Ingår i: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 21, nr 6, s. 1255-1268Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Flows of energy and matter across habitat boundaries can be major determinants of the functioning of recipient ecosystems. It is currently debated whether terrestrial dissolved organic matter (tDOM) is a resource subsidy or a resource subtraction in recipient lakes. We present data from a long-term field experiment in which pelagic phosphorus concentration and whole-ecosystem primary production increased with increasing tDOM input, suggesting that tDOM acted primarily as a direct nutrient subsidy. Piecewise structural equation modeling supports, however, a substantial contribution of a second mechanism: colored tDOM acted also as a resource subtraction by shading benthic algae, preventing them from intercepting nutrients released across the sediment-water interface. Inhibition of benthic algae by colored tDOM thus indirectly promoted pelagic algae and whole-ecosystem primary production. We conclude that cross-ecosystem terrestrial DOM inputs can modify light and nutrient flows between aquatic habitats and alter the relative contributions of benthic and pelagic habitats to total primary production. These results are particularly relevant for shallow northern lakes, which are projected to receive increased tDOM runoff.

  • 64. Wahlstrom, E.
    et al.
    Persson, L.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Diehl, S.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Bystrom, P.
    Size-dependent foraging efficiency, cannibalism and zooplankton community structure2000Ingår i: Oecologia, Vol. 123, nr 1, s. 138-148Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To examine size-dependent food web interactions in systems with cannibalism, we compared the abundances of zooplankton and phytoplankton over 2 years in four lakes with cannibalistic perch (Perca fluviatilis ) of which two also supported the top predator pike (Esox lucius). The abundance of perch 2 years and older was lower in lakes with pike than in lakes with only perch. In contrast, the abundance of small perch (young-of-the-year and I-year old) was lower in lakes with only perch suggesting that intense cannibalism reduced these size classes to low levels in lakes lacking pike. Functional response experiments with differently sized perch and zooplankton showed that the attack rate of small perch susceptible to cannibalism was much higher than that of large cannibalising perch. The optimal body size of perch with respect to attack rate was also lower for small zooplankton prey than for large zooplankton. The zooplankton communities in lakes with only perch were dominated by the relatively small species Ceriodaphnia quadrangula and Bosmina spp. and total zooplankton biomass was higher in these lakes than in lakes with both pike and perch. In contrast, the mean size of cladoceran zooplankton was largest in lakes with both pike and perch owing to a dominance of the large zooplankton species Holopedium gibberum in these lakes. We relate these patterns to (1) the low foraging efficiency of large perch on small zooplankton and (2) the low abundance of small zooplanktivorous perch (due to cannibalism) in lakes with only perch. The differences in zooplankton community structure also resulted in different seasonal dynamics of phytoplankton between lakes. Cannibalism introduces a vertical heterogeneity to food webs that causes consumer-resource dynamics that are not predictable from linear food chain models.

  • 65.
    Wickman, Jonas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Blasius, Bernd
    Klausmeier, Christopher A.
    Ryabov, Alexey B.
    Brännström, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Determining Selection across Heterogeneous Landscapes: A Perturbation-Based Method and Its Application to Modeling Evolution in Space2017Ingår i: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 189, nr 4, s. 381-395Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Spatial structure can decisively influence the way evolutionary processes unfold. To date, several methods have been used to study evolution in spatial systems, including population genetics, quantitative genetics, moment-closure approximations, and individual-based models. Here we extend the study of spatial evolutionary dynamics to eco-evolutionary models based on reaction-diffusion equations and adaptive dynamics. Specifically, we derive expressions for the strength of directional and stabilizing/disruptive selection that apply both in continuous space and to metacommunities with symmetrical dispersal between patches. For directional selection on a quantitative trait, this yields a way to integrate local directional selection across space and determine whether the trait value will increase or decrease. The robustness of this prediction is validated against quantitative genetics. For stabilizing/disruptive selection, we show that spatial heterogeneity always contributes to disruptive selection and hence always promotes evolutionary branching. The expression for directional selection is numerically very efficient and hence lends itself to simulation studies of evolutionary community assembly. We illustrate the application and utility of the expressions for this purpose with two examples of the evolution of resource utilization. Finally, we outline the domain of applicability of reaction-diffusion equations as a modeling framework and discuss their limitations.

  • 66.
    Wickman, Jonas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Brännström, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik. Evolution and Ecology Program, International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Evolution of resource specialisation in competitive metacommunities2019Ingår i: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 22, nr 11, s. 1746-1756Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Spatial environmental heterogeneity coupled with dispersal can promote ecological persistence of diverse metacommunities. Does this premise hold when metacommunities evolve? Using a two-resource competition model, we studied the evolution of resource-uptake specialisation as a function of resource type (substitutable to essential) and shape of the trade-off between resource uptake affinities (generalist- to specialist-favouring). In spatially homogeneous environments, evolutionarily stable coexistence of consumers is only possible for sufficiently substitutable resources and specialist-favouring trade-offs. Remarkably, these same conditions yield comparatively low diversity in heterogeneous environments, because they promote sympatric evolution of two opposite resource specialists that, together, monopolise the two resources everywhere. Consumer diversity is instead maximised for intermediate trade-offs and clearly substitutable or clearly essential resources, where evolved metacommunities are characterised by contrasting selection regimes. Taken together, our results present new insights into resource-competition-mediated evolutionarily stable diversity in homogeneous and heterogeneous environments, which should be applicable to a wide range of systems.

  • 67.
    Wickman, Jonas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Brännström, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Patterns of diversity in evolved metacommunities of resource competitorsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Spatial heterogeneity in environmental conditions coupled with moderate dispersal can promote ecological persistence of diverse metacommunities. We explored whether this premise holds when metacommunities can evolve. Using a model of competition for two resources, we studied the evolution of resource-uptake specialization as a function of resource type (substitutable to essential) and the shape of the trade-off in resource uptake affinities (generalist- to specialist-favoring). In homogeneous environments, evolutionarily stable coexistence of consumers is only possible for sufficiently substitutable resources and specialist-favoring trade-offs. Remarkably, these same conditions yield comparatively low diversity in heterogeneous environments, where consumer diversity is instead maximized for clearly substitutable or clearly essential resources and intermediate trade-offs. When resources are weakly interactively essential, at most two consumers persist evolutionarily in spite of high spatial variance in resource supply ratios. We explain these patterns based on analytical results for the limiting case of a spatially homogeneous system.

  • 68. Winder, Monika
    et al.
    Berger, Stella A
    Lewandowska, Aleksandra
    Aberle, Nicole
    Lengfellner, Kathrin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sommer, Ulrich
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Spring phenological responses of marine and freshwater plankton to changing temperature and light conditions2012Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 159, nr 11, s. 2491-2501Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Shifts in the timing and magnitude of the spring plankton bloom in response to climate change have been observed across a wide range of aquatic systems. We used meta-analysis to investigate phenological responses of marine and freshwater plankton communities in mesocosms subjected to experimental manipulations of temperature and light intensity. Systems differed with respect to the dominant mesozooplankton (copepods in seawater and daphnids in freshwater). Higher water temperatures advanced the bloom timing of most functional plankton groups in both marine and freshwater systems. In contrast to timing, responses of bloom magnitudes were more variable among taxa and systems and were influenced by light intensity and trophic interactions. Increased light levels increased the magnitude of the spring peaks of most phytoplankton taxa and of total phytoplankton biomass. Intensified size-selective grazing of copepods in warming scenarios affected phytoplankton size structure and lowered intermediate (20-200 mu m)-sized phytoplankton in marine systems. In contrast, plankton peak magnitudes in freshwater systems were unaffected by temperature, but decreased at lower light intensities, suggesting that filter feeding daphnids are sensitive to changes in algal carrying capacity as mediated by light supply. Our analysis confirms the general shift toward earlier blooms at increased temperature in both marine and freshwater systems and supports predictions that effects of climate change on plankton production will vary among sites, depending on resource limitation and species composition.

  • 69. Wollrab, Sabine
    et al.
    de Roos, Andre M.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ontogenetic diet shifts promote predator-mediated coexistence2013Ingår i: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 94, nr 12, s. 2886-2897Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is widely believed that predation moderates interspecific competition and promotes prey diversity. Still, in models of two prey sharing a resource and a predator, predator-mediated coexistence occurs only over narrow ranges of resource productivity. These models have so far ignored the widespread feature of ontogenetic diet shifts in predators. Here, we theoretically explore the consequences of a diet shift from juvenile to adult predator stages for coexistence of two competing prey. We find that only very minor deviations from perfectly identical diets in juveniles and adults destroy the traditional mechanism of predator-mediated coexistence, which requires an intrinsic trade-off between prey defendedness and competitive ability. Instead, predator population structure can create an emergent competition-predation trade-off between prey, where a bottleneck in one predator stage enhances predation on the superior competitor and relaxes predation on the inferior competitor, irrespective of the latter's intrinsic defendedness. Pronounced diet shifts therefore greatly enlarge the range of prey coexistence along a resource gradient. With diet shifts, however, coexistence usually occurs as one of two alternative states and, once lost, may not be easily restored.

  • 70. Wollrab, Sabine
    et al.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Univ Munich, Dept Biol 2, Planegg Martinsried, Germany.
    Bottom-up responses of the lower oceanic food web are sensitive to copepod mortality and feeding behavior2015Ingår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 60, nr 2, s. 641-656Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The functional response, describing consumption rate as a function of food abundance, critically links consumer-resource dynamics. Yet, little is known about how its shape affects communities of multiple, dynamically linked species. We theoretically investigated how the functional response of copepods (saturating type 2 vs. sigmoidal type 3, both of which have been observed) mediates bottom-up and top-down influences on the lower oceanic food web as described by five compartments (pentagon web): a shared limiting nutrient, small and large algae, ciliates feeding on small algae, and copepods feeding on ciliates and large algae. We compare system dynamics in response to nutrient enrichment and copepod mortality, the latter being varied first directly and then indirectly through inclusion of planktivores (fish or jellyfish). Regardless of functional response type, when planktivores are absent, equilibrium densities of all members of the even food chain (nutrients-small algae-ciliates-copepods) typically increase with nutrient enrichment whereas large algae decrease. In contrast, and congruent with conventional wisdom, large algae increase with nutrient enrichment when copepods are controlled by planktivores. A type 2 response in copepods strongly destabilizes the pentagon web, whereas stable equilibria are possible when copepods have a type 3 response. High copepod mortality (e.g., caused by increasing planktivore pressure under nutrient enrichment) destabilizes such systems, however. Moreover, because community feedbacks produce a negative correlation between the copepod's alternative prey, type 3 switching behavior is amplified in the pentagon web. This prevents extinctions but can give rise to an alternative state with small algal dominance at high enrichment.

  • 71. Wollrab, Sabine
    et al.
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    De Roos, Andre M.
    Simple rules describe bottom-up and top-down control in food webs with alternative energy pathways2012Ingår i: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 15, nr 9, s. 935-946Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many human influences on the world's ecosystems have their largest direct impacts at either the top or the bottom of the food web. To predict their ecosystem-wide consequences we must understand how these impacts propagate. A long-standing, but so far elusive, problem in this endeavour is how to reduce food web complexity to a mathematically tractable, but empirically relevant system. Simplification to main energy channels linking primary producers to top consumers has been recently advocated. Following this approach, we propose a general framework for the analysis of bottom-up and top-down forcing of ecosystems by reducing food webs to two energy pathways originating from a limiting resource shared by competing guilds of primary producers (e.g. edible vs. defended plants). Exploring dynamical models of such webs we find that their equilibrium responses to nutrient enrichment and top consumer harvesting are determined by only two easily measurable topological properties: the lengths of the component food chains (oddodd, oddeven, or eveneven) and presence vs. absence of a generalist top consumer reconnecting the two pathways (yielding looped vs. branched webs). Many results generalise to other looped or branched web structures and the model can be easily adapted to include a detrital pathway.

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