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  • 1. Albert, Aurélie
    et al.
    Auffret, Alistair G.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Cosyns, Eric
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    D'hondt, Bram
    Eichberg, Carsten
    Eycott, Amy E.
    Heinken, Thilo
    Hoffmann, Maurice
    Jaroszewicz, Bogdan
    Malo, Juan E.
    Mårell, Anders
    Mouissie, Maarten
    Pakeman, Robin J.
    Picard, Mélanie
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Poschlod, Peter
    Provoost, Sam
    Schulze, Kiowa Alraune
    Baltzinger, Christophe
    Seed dispersal by ungulates as an ecological filter: a trait-based meta-analysis2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 9, p. 1109-1120Article in journal (Refereed)
    Abstract [en]

    Plant communities are often dispersal-limited and zoochory can be an efficient mechanism for plants to colonize new patches of potentially suitable habitat. We predicted that seed dispersal by ungulates acts as an ecological filter - which differentially affects individuals according to their characteristics and shapes species assemblages - and that the filter varies according to the dispersal mechanism (endozoochory, fur-epizoochory and hoof-epizoochory). We conducted two-step individual participant data meta-analyses of 52 studies on plant dispersal by ungulates in fragmented landscapes, comparing eight plant traits and two habitat indicators between dispersed and non-dispersed plants. We found that ungulates dispersed at least 44% of the available plant species. Moreover, some plant traits and habitat indicators increased the likelihood for plant of being dispersed. Persistent or nitrophilous plant species from open habitats or bearing dry or elongated diaspores were more likely to be dispersed by ungulates, whatever the dispersal mechanism. In addition, endozoochory was more likely for diaspores bearing elongated appendages whereas epizoochory was more likely for diaspores released relatively high in vegetation. Hoof-epizoochory was more likely for light diaspores without hooked appendages. Fur-epizoochory was more likely for diaspores with appendages, particularly elongated or hooked ones. We thus observed a gradient of filtering effect among the three dispersal mechanisms. Endozoochory had an effect of rather weak intensity (impacting six plant characteristics with variations between ungulate-dispersed and non-dispersed plant species mostly below 25%), whereas hoof-epizoochory had a stronger effect (eight characteristics included five ones with above 75% variation), and fur-epizoochory an even stronger one (nine characteristics included six ones with above 75% variation). Our results demonstrate that seed dispersal by ungulates is an ecological filter whose intensity varies according to the dispersal mechanism considered. Ungulates can thus play a key role in plant community dynamics and have implications for plant spatial distribution patterns at multiple scales.

  • 2. Albrectsen, B R
    et al.
    Gardfjell, H
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Orians, C M
    Murray, B
    FRitz, R S
    Slugs, willow seedlings and nutrient fertilization: intrinsic vigor inversely affects palatability2004In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 105, p. 268-278Article in journal (Refereed)
  • 3.
    Albrectsen, Benedicte R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ericson, Lars
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lundberg, Per
    Nutrient addition extends flowering display, which gets tracked by seed predators, but not by their parasitoids2008In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 117, p. 473-480Article in journal (Refereed)
    Abstract [en]

    Although phenological matching between two and three trophic interactions has received some attention, it has largely been disregarded in explaining the lack of strong cascade dynamics in terrestrial systems. We studied the response of the specialist seed predator, Paroxyna plantaginis (Tephritidae) and associated generalist parasitoids (Chalcidoidea) to controlled fertilisation of individuals of naturally growing Tripolium vulgare (Asteraceae) on four island populations (Skeppsvik Archipelago, Sweden). We consistently found evidence of nutrient limitation: fertilised plants increased their biomass, produced more capitula (the oviposition units for tephritid flies), were more at risk of attack by the tephritids, and puparia were heavier in fertilised plants. During some parts of the season tephritids became more heavily parasitized, supporting the presence of cascade dynamics, however net parasitism over season decreased in response to nutrient addition. We found no evidence that capitulum size complicated parasitoid access to the tephritids, however the extended bud production prolonged the flowering season. Thus, tephritids utilized the surplus production of capitula throughout the entire season, while parasitoids did not expand their oviposition time window accordingly. Implications for top down regulation and cascade dynamics in the system are discussed.

  • 4. Alpedrinha, João
    et al.
    Rodrigues, Leonor R.
    Stockholm University, Faculty of Science, Department of Zoology. University of Lisbon, Portugal.
    Magalhaes, Sara
    Abbott, Jessica
    The virtues and limitations of exploring the eco-evolutionary dynamics of sexually selected traits2019In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 128, no 10, p. 1381-1389Article in journal (Refereed)
    Abstract [en]

    Most studies on eco-evolutionary feedbacks concern the influence of abiotic factors, or predator-prey and host-parasite interactions, while studies involving sexual interactions are lagging behind. This is at odds with the potential of these interactions to engage in such processes. Indeed, there is now ample evidence that sexual selection is affected by ecological change and that sexually selected traits can evolve rapidly, which may modify the ecological context of populations, and thus the selection pressures they will be exposed to. Here we review evidence for such eco-evolutionary processes. We discuss examples of eco-evolutionary change in an attempt to understand the challenges related with identifying and characterizing such processes. In particular, we focus on the challenges associated with accurately identifying the components of the feedback as well as their causal relation. Finally, we evaluate scenarios where understanding eco-evolutionary feedbacks of sexual selection may help us appreciate the effects of sexual selection in shaping evolutionary processes.

  • 5.
    Andersson, Petter
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Löfstedt, Christer
    Hambäck, Peter A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    How insects sense olfactory patches: the spatial scaling of olfactory information2013In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 122, no 7, p. 1009-1016Article in journal (Refereed)
    Abstract [en]

    When searching for resources in heterogeneous environments, animals must rely on their abilities to detect the resources via their sensory systems. However, variation in the strength of the sensory cue may be mediated by the physical size of the resource patch. Patch detection of insects are often predicted by the scaling of sensory cues to patch size, where visual cues has been proposed to scale proportional to the diameter of the patch. The scaling properties of olfactory cues are, however, virtually unknown. Here, we investigated scaling rules for olfactory information in a gradient of numbers of odour sources, relevant to odour-mediated attraction under field conditions. We recorded moth antennal responses to sex pheromones downwind from pheromone patches and estimated the slope in the scaling relationship between the effective length of the odour plumes and the number of odour sources. These measurements showed that the effective plume length increased proportional to the square root of the number of odour sources. The scaling relationship, as estimated in the field experiment, was then evaluated against field data of the slope in the relationship between trap catch and release rate of chemical attractants for a wide range of insects. This meta-analysis revealed an average slope largely consistent with the estimated scaling relationship between the effective plume length and the number of odour sources. This study is the first to estimate the scaling properties of olfactory cues empirically and has implications for understanding and predicting the spatial distributions of insects searching by means of olfactory cues in heterogeneous environments.

  • 6.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Gigantism in Island Populations of Wood Mice (Apodemus) in Europe1986In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 47, no 1, p. 47-56Article in journal (Refereed)
    Abstract [en]

    Many rodents have large body sizes on islands, and there are many hypotheses that try to explain this observed pattern. Using body size data on Apodemus in Europe as an example, I try to evaluate the main hypotheses. These can be divided in four different categories. 1) Hypotheses assuming climatic differences between islands and mainland: no trend in body size on islands in the Mediterranean, in Britain or in the Baltic area is observed. 2) Hypotheses based on island size: no trend is observed in the data analysed. 3) Hypotheses based on distance to mainland: no general effect is found, although there is an effect in the British material. 4) Hypotheses based on faunistic differences: consistent relationships are found in all areas. A. sylvaticus shows larger body size when lacking competition from A. flavicollis or Clethrionomys glareolus or when predation is absent. A. flavicollis is larger when predators are lacking, and smaller when no competitors are present. This is in agreement with character displacement theory

  • 7. Axelsson, Björn
    et al.
    Gärdefors, Dag
    Hytteborn, Håkan
    Lohm, Ulrik
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Persson, Tryggve
    Tenow, Olle
    Estimation of leaf number and leaf biomass of hazel (Corylus avellana L.) by two methods1972In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 23, p. 281-283Article in journal (Refereed)
  • 8. Axelsson, Björn
    et al.
    Gärdefors, Dag
    Lohm, Ulrik
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Persson, Tryggve
    Tenow, Olle
    Wallin, Lars
    Components of variance and the cost of a sampling programme concerning biomass of hazel (Corylus avellana L.) available to leaf-eating insects1970In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 21, p. 203-207Article in journal (Refereed)
  • 9.
    Backéus, Ingvar
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecological Botany.
    Bog vegetation re-Mapped after sixty years: Studies on Skagershultamossen, central Sweden1972In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 23, no 3, p. 384-393Article in journal (Refereed)
    Abstract [en]

    The author has re-mapped two areas on Skagershultamossen. The new maps have been compared with maps of the same areas from 1910, made by L. von Post. The vegetation changes are small. The open water surfaces have diminished in number and extent. The theory of cyclic succession on peat bogs finds no support from the maps. Plant communities have been delimited as to correspond to those on the old maps and defined through analysis of a number of sample plots

  • 10.
    Barthelemy, Hélène
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Dorrepaal, Ellen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Olofsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Defoliation of a grass is mediated by the positive effect of dung deposition, moss removal and enhanced soil nutrient contents: results from a reindeer grazing simulation experiment2019In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 128, no 10, p. 1515-1524Article in journal (Refereed)
    Abstract [en]

    Herbivory is one of the key drivers shaping plant community dynamics. Herbivores can strongly influence plant productivity directly through defoliation and the return of nutrients in the form of dung and urine, but also indirectly by reducing the abundance of neighbouring plants and inducing changes in soil processes. However, the relative importance of these processes is poorly understood. We, therefore, established a common garden experiment to study plant responses to defoliation, dung addition, moss cover, and the soil legacy of reindeer grazing. We used an arctic tundra grazed by reindeer as our study system, and Festuca ovina, a common grazing-tolerant grass species as the model species. The soil legacy of reindeer grazing had the strongest effect on plants, and resulted in higher growth in soils originating from previously heavily-grazed sites. Defoliation also had a strong effect and reduced shoot and root growth and nutrient uptake. Plants did not fully compensate for the tissue lost due to defoliation, even when nutrient availability was high. In contrast, defoliation enhanced plant nitrogen concentrations. Dung addition increased plant production, nitrogen concentrations and nutrient uptake, although the effect was fairly small. Mosses also had a positive effect on aboveground plant production as long as the plants were not defoliated. The presence of a thick moss layer reduced plant growth following defoliation. This study demonstrates that grasses, even though they suffer from defoliation, can tolerate high densities of herbivores when all aspects of herbivores on ecosystems are taken into account. Our results further show that the positive effect of herbivores on plant growth via changes in soil properties is essential for plants to cope with a high grazing pressure. The strong effect of the soil legacy of reindeer grazing reveals that herbivores can have long-lasting effects on plant productivity and ecosystem functioning after grazing has ceased.

  • 11.
    Bauerfeind, Stephanie S.
    et al.
    Univ Zurich, Dept Evolutionary Biol & Environm Studies, Zurich, Switzerland.
    Schaefer, Martin A.
    Univ Zurich, Dept Evolutionary Biol & Environm Studies, Zurich, Switzerland.
    Berger, David
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology. Univ Zurich, Dept Evolutionary Biol & Environm Studies, Zurich, Switzerland.
    Blanckenhorn, Wolf U.
    Univ Zurich, Dept Evolutionary Biol & Environm Studies, Zurich, Switzerland.
    Fox, Charles W.
    Univ Kentucky, Dept Entomol, S225 Ag Sci Ctr North, Lexington, KY 40546 USA.
    Replicated latitudinal clines in reproductive traits of European and North American yellow dung flies2018In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 127, no 11, p. 1619-1632Article in journal (Refereed)
    Abstract [en]

    Geographic variation in phenotypic traits is commonly correlated with spatial variation in the environment, e.g. seasonality and mean temperature, providing evidence that natural selection generates such patterns. In particular, both body size and egg size of ectothermic animals are commonly larger in northern climates, and temperature induces plastic responses in both traits. Size-independent egg quality can also vary with latitude, though this is rarely investigated. For the widespread yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae) we investigated whether there are latitudinal clines in reproductive traits (clutch size, egg size and egg composition), whether these clines are due to variation in body and/or egg size, and whether such clines replicate across independent experiments performed on different continents (North America and Europe). Egg size generally increased with latitude (especially in Europe), an effect largely explained by body size of the mother, while clutch size did not; overall reproductive effort thus increased with latitude. Both the absolute and relative (correcting for egg size) amount of egg protein increased with latitude, egg glycogen decreased with latitude, while latitudinal trends for egg lipids and total egg energy content were complex and non-linear. Altitude sometimes showed relationships analogous to those of latitude (egg proteins and glycogen) but occasionally opposite (egg size), possibly because latitude and altitude are negatively related among populations of this cold-adapted species. There was no evidence of a tradeoff between egg size and number across latitudinal populations; if anything, the relationship was positive. All traits, including body and egg size, varied with rearing temperature (12 degrees C, 18 degrees C, 24 degrees C), generally following the temperature-size rule. Clines based on common garden rearing, thus reflecting genetic differentiation, were qualitatively but not always quantitatively consistent between continents, and were similar across rearing temperatures, suggesting they evolved due to natural selection, although the concrete selective mechanisms involved require further study.

  • 12.
    Berg, Sofia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Christianou, Maria
    Linköping University, Department of Physics, Chemistry and Biology, Biotechnology . Linköping University, The Institute of Technology.
    Jonsson, Tomas
    Research centre for Systems Biology, Univ. of Skövde, Sweden.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Using sensitivity analysis to identify keystone species and keystone links in size-based food webs2011In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 120, no 4, p. 510-519Article in journal (Refereed)
    Abstract [en]

    Human-induced alterations in the birth and mortality rates of species and in the strength of interactions within and between species can lead to changes in the structure and resilience of ecological communities. Recent research points to the importance of considering the distribution of body sizes of species when exploring the response of communities to such perturbations. Here, we present a new size-based approach for assessing the sensitivity and elasticity of community structure (species equilibrium abundances) and resilience (rate of return to equilibrium) to changes in the intrinsic growth rate of species and in the strengths of species interactions. We apply this approach on two natural systems, the pelagic communities of the Baltic Sea and Lake Vättern, to illustrate how it can be used to identify potential keystone species and keystone links. We find that the keystone status of a species is closely linked to its body size. The analysis also suggests that communities are structurally and dynamically more sensitive to changes in the effects of prey on their consumers than in the effects of consumers on their prey. Moreover, we discuss how community sensitivity analysis can be used to study and compare the fragility of communities with different body size distributions by measuring the mean sensitivity or elasticity over all species or all interaction links in a community. We believe that the community sensitivity analysis developed here holds some promise for identifying species and links that are critical for the structural and dynamic robustness of ecological communities.

  • 13.
    Berg, Sofia
    et al.
    University of Skövde, School of Life Sciences. University of Skövde, The Systems Biology Research Centre. IFM Theory and Modelling, Div. of Theoretical Biology, Linköping Univ., Linköping, Sweden.
    Christianou, Maria
    IFM Theory and Modelling, Div. of Theoretical Biology, Linköping Univ., Linköping, Sweden.
    Jonsson, Tomas
    University of Skövde, School of Life Sciences. University of Skövde, The Systems Biology Research Centre.
    Ebenman, Bo
    IFM Theory and Modelling, Div. of Theoretical Biology, Linköping Univ., Linköping, Sweden.
    Using sensitivity analysis to identify keystone species and keystone links in size-based food webs2011In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 120, no 4, p. 510-519Article in journal (Refereed)
    Abstract [en]

    Human-induced alterations in the birth and mortality rates of species and in the strength of interactions within and between species can lead to changes in the structure and resilience of ecological communities. Recent research points to the importance of considering the distribution of body sizes of species when exploring the response of communities to such perturbations. Here, we present a new size-based approach for assessing the sensitivity and elasticity of community structure (species equilibrium abundances) and resilience (rate of return to equilibrium) to changes in the intrinsic growth rate of species and in the strengths of species interactions. We apply this approach on two natural systems, the pelagic communities of the Baltic Sea and Lake Vättern, to illustrate how it can be used to identify potential keystone species and keystone links. We find that the keystone status of a species is closely linked to its body size. The analysis also suggests that communities are structurally and dynamically more sensitive to changes in the effects of prey on their consumers than in the effects of consumers on their prey. Moreover, we discuss how community sensitivity analysis can be used to study and compare the fragility of communities with different body size distributions by measuring the mean sensitivity or elasticity over all species or all interaction links in a community. We believe that the community sensitivity analysis developed here holds some promise for identifying species and links that are critical for the structural and dynamic robustness of ecological communities.

  • 14.
    Berg, Sofia
    et al.
    University of Skövde, School of Bioscience. University of Skövde, The Systems Biology Research Centre. Dept of Physics, Chemistry and Biology, Div. of Theoretical Biology, Linköping Univ., Linköping, Sweden.
    Pimenov, Aexander
    Weierstrass Inst., Berlin, Germany / Environmental Research Inst., Univ. College Cork, Cork, Ireland.
    Palmer, Catherine
    Weierstrass Inst., Berlin, Germany.
    Emmerson, Mark
    School of Biological Sciences, Queen's Univ. Belfast, Belfast, United Kingdom.
    Jonsson, Tomas
    University of Skövde, School of Bioscience. University of Skövde, The Systems Biology Research Centre. Dept of Ecology, Swedish Univ. of Agricultural Sciences, Uppsala, Sweden.
    Ecological communities are vulnerable to realistic extinction sequences2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 4, p. 486-496Article in journal (Refereed)
  • 15.
    Berg, Sofia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology. University of Skovde, Sweden.
    Pimenov, Alexander
    Weierstrass Institute, Germany; National University of Ireland University of Coll Cork, Ireland.
    Palmer, Catherine
    Weierstrass Institute, Germany.
    Emmerson, Mark
    Queens University of Belfast, North Ireland.
    Jonsson, Tomas
    University of Skovde, Sweden; Swedish University of Agriculture Science, Sweden.
    Ecological communities are vulnerable to realistic extinction sequences2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 4, p. 486-496Article in journal (Refereed)
    Abstract [en]

    Loss of species will directly change the structure and potentially the dynamics of ecological communities, which in turn may lead to additional species loss (secondary extinctions) due to direct and/or indirect effects (e.g. loss of resources or altered population dynamics). Furthermore, the vulnerability of food webs to repeated species loss is expected to be affected by food web topology, species interactions, as well as the order in which species go extinct. Species traits such as body size, abundance and connectivity might determine a species vulnerability to extinction and, thus, the order in which species go primarily extinct. Yet, the sequence of primary extinctions, and their effects on the vulnerability of food webs to secondary extinctions, when species abundances are allowed to respond dynamically, has only recently become the focus of attention. Here, we analyse and compare topological and dynamical robustness to secondary extinctions of model food webs, in the face of 34 extinction sequences based on species traits. Although secondary extinctions are frequent in the dynamical approach and rare in the topological approach, topological and dynamical robustness tends to be correlated for many bottom-up directed, but not for top-down directed deletion sequences. Furthermore, removing species based on traits that are strongly positively correlated to the trophic position of species (such as large body size, low abundance, high net effect) is, under the dynamical approach, found to be as destructive as removing primary producers. Such top-down oriented removal of species are often considered to correspond to realistic extinction scenarios, but earlier studies, based on topological approaches, have found such extinction sequences to have only moderate effects on the remaining community. Thus, our result suggests that the structure of ecological communities, and therefore the integrity of important ecosystem processes could be more vulnerable to realistic extinction sequences than previously believed.

  • 16.
    Berglund, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Sex dimorphism and skewed sex-ratios in the prawn species Palaemon adspersus and P. squilla1981In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 36, no 2, p. 158-162Article in journal (Refereed)
  • 17.
    Berglund, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Rosenqvist, Gunilla
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Animal Ecology.
    Reproductive costs in the prawn Palaemon adspersus: effects on growth and predator vulnerability1986In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 46, no 3, p. 349-354Article in journal (Refereed)
  • 18.
    Berglund, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Rosenqvist, Gunilla
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Svensson, Ingrid
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Multiple matings and paternal brood care in the pipefish Syngnathus typhle1988In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 51, no 2, p. 184-188Article in journal (Refereed)
  • 19.
    Björklund, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Are comparative analyses always necessary?1997In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 80, p. 607-612Article in journal (Refereed)
  • 20.
    Björklund, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Bergek, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    On the relationship between population differentiation and sampling effort: is more always better?2009In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 118, no 8, p. 1127-1129Article in journal (Refereed)
    Abstract [en]

    Given the relative ease by which genotypic data now can be obtained, studies of population differentiation can attain high statistical power provided the number of individuals and loci scored are sufficiently high. This has led to a misunderstanding of the concept of power, and studies with a low number of individuals and loci are dismissed despite highly significant results. This raises statistical, biological and ethical concerns, which we discuss in this note. We suggest that authors should routinely report the number of additional non-significant loci as a measure of the robustness of the results.

  • 21.
    Boalt, Elin
    et al.
    Södertörn University, School of Life Sciences.
    Lehtilä, Kari
    Södertörn University, School of Life Sciences.
    Tolerance to apical and foliar damage: costs and mechanisms in Raphanus raphanistrum2007In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 116, no 12, p. 2071-2081Article in journal (Refereed)
    Abstract [en]

    To study mechanisms underlying plant tolerance to herbivore damage, we used apical and foliar damage as experimental treatments to study whether there are similar tolerance mechanisms to different types of damage. We also studied whether tolerance to different types of damage are associated, and whether there is a cost involved in plant tolerance to different types of herbivore damage. Our greenhouse experiment involved 480 plants from 30 full-sib families of an annual weed Raphanus raphanistrum, wild radish, which were subjected to control and two different simulated herbivore damage treatments, apex removal and foliar damage of 30% of leaf area. Apical damage significantly decreased seed production, whereas foliar damage had no effect. There was a significant genetic variation for tolerance to foliar, but not apical damage. No costs were observed in terms of negative correlation between tolerance to either damage type and fitness of undamaged plants. Tolerances to apical and foliar damage were not significantly correlated with each other. We observed a larger number of significant associations between tolerance and reproductive traits than between tolerance and vegetative traits. Plant height and leaf size of damaged plants interacted in their association to tolerance to foliar damage. Inflorescence number and pollen quantity per flower of damaged plants were positively associated with tolerance to apical damage. In late-flowering genotypes, petal size of undamaged plants and pollen quantity of damaged plants were positively associated with tolerance to foliar damage. In summary, traits involved in floral display and male fitness were associated with plant tolerance to herbivore damage.

  • 22.
    Bolmgren, Kjell
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Cowan, Peter D.
    Time – size tradeoffs: a phylogenetic comparative study of flowering time, plant height and seed mass in a north-temperate flora2008In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 117, no 3, p. 424-429Article in journal (Refereed)
    Abstract [en]

    Parents face a timing problem as to when they should begin devoting resources from their own growth and survival to mating and offspring development. Seed mass and number, as well as maternal survival via plant size, are dependent on time for development. The time available in the favorable season will also affect the size of the developing juveniles and their survival through the unfavorable season. Flowering time may thus represent the outcome of such a time partitioning problem. We analyzed correlations between flowering onset time, seed mass, and plant height in a north-temperate flora, using both cross-species comparisons and phylogenetic comparative methods. Among perennial herbs, flowering onset time was negatively correlated with seed mass (i.e. plants with larger seeds started flowering earlier) while flowering onset time was positively correlated with plant height. Neither of these correlations was found among woody plants. Among annual plants, flowering onset time was positively correlated with seed mass. Cross-species and phylogenetically informed analyses largely agreed, except that flowering onset time was also positively correlated with plant height among annuals in the cross-species analysis. The different signs of the correlations between flowering onset time and seed mass (compar. gee regression coefficient=−7.8) and flowering onset time and plant height (compar. gee regression coefficient=+30.5) for perennial herbs, indicate that the duration of the growth season may underlie a tradeoff between maternal size and offspring size in perennial herbs, and we discuss how the partitioning of the season between parents and offspring may explain the association between early flowering and larger seed mass among these plants.

  • 23.
    Bolmgren, Kjell
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. SLU Swedish University of Agricultural Sciences, Sweden.
    Eriksson, Ove
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Are mismatches the norm? Timing of flowering, fruiting, dispersal and germination and their fitness effects in Frangula alnus (Rhamnaceae)2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 5, p. 639-648Article in journal (Refereed)
    Abstract [en]

    The close morphological and temporal links between phases of plant growth and reproduction call for integrated studies incorporating several reproductive phases from flowering to recruitment, and associated plant-animal interactions. Phenological strategies, as well as plastic phenological response to climate change, incorporate complex interactions between developmental constraints, pollination and seed dispersal. Relationships between reproductive phenology and components of fitness were studied for two years in the north-temperate, self-incompatible, insect-pollinated, and bird-dispersed shrub Frangula alnus (Rhamnaceae). Fruit set, dispersal, germination and juvenile survival, as well as seed mass and juvenile size were measured in relation to flowering, fruiting and germination time. The results suggest that effects of flowering and fruiting time prevailed in subsequent phases, to some extent as far as to the juvenile phase, but effects of timing were complex and had partly opposing effects on different fitness components. Early flowers had higher fruit-set and experiments indicated that synchronous peak flowering increased fruit-set, but later flowers had higher seed mass. Peak fruiting was not associated with peak dispersal. Late fruits derived from late flowers promoted dispersal. Juvenile recruitment was enhanced by increasing seed size. We conclude that the phenology of flowering and fruiting in F. alnus comprises several features, each with different and sometimes counteracting effects on fitness components. From a general perspective, this result implies that we should not expect to find finely tuned matches in timing specifically between flowering and pollinators, and fruiting and seed dispersing birds.

  • 24.
    Bolmgren, Kjell
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Eriksson, Ove
    Seed mass and the evolution of fleshy fruits in angiosperms2010In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 119, no 4, p. 707-718Article, review/survey (Refereed)
    Abstract [en]

    Fleshy fruits, like drupes and berries, have evolved many times through angiosperm history. Two hypotheses suggest that fleshy fruit evolution is related to changes in the seed mass fitness landscape. The reduced dispersal capability following from an increase in seed mass may be counterbalanced by evolution of traits mediating seed dispersal by animals, such as fleshy fruits. Alternatively, increasing availability and capabilities of frugivores promote evolution of fleshy fruits and allow an increase in seed size. Both these hypotheses predict an association between evolution of fleshy fruits and increasing seed size. We investigated patterns of fruit and seed evolution by contrasting seed mass between fleshy and non-fleshy fruited sister clades. We found a consistent association between possession of fleshy fruits and heavier seeds. The direction of fruit type change did not alter this pattern; seed mass was higher in clades where fleshy fruits evolved and lower in clades where non-fleshy fruits evolved, as compared to their sister clades. These patterns are congruent with the predictions from the two hypotheses, but other evidence is needed to distinguish between them. We emphasize the need to integrate studies of seed disperser effectiveness, seed morphology, and plant recruitment success to better understand the frugivores' role in fleshy fruit evolution.

  • 25.
    Bolmgren, Kjell
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Ove, Eriksson
    Stockholm University, Faculty of Science, Department of Botany.
    Fleshy fruits – origins, niche shifts, and diversification.2005In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 109, no 2, p. 255-272Article in journal (Refereed)
    Abstract [en]

    We examined shifts in fruit type, fleshy vs non-fleshy, in relation to habitat-related niche shifts, species richness, and historical distribution, in 50 phylogenetically independent plant lineages. Each lineage consisted of a sister-group pair of fleshy vs non-fleshy taxa and their outgroup. Niche shifts were assessed based on plant community characteristics. Two niche dimensions assumed to reflect community dynamics were derived: spatial predictability of disturbances and canopy closure. Phylogenetically independent origins of fleshy fruit types (1) were correlated with changes to habitats characterized by more shaded and spatially more unpredictable disturbances, (2) had an opposite effect on species richness in woody and herbaceous clades, enhancing species richness in woody clades, and (3) were continuously distributed over a period covering the last 70 million years. These results support the hypothesis that fleshy fruit evolution is driven by vegetation dynamics, and suggest that the strength of frugivore mediated selection on fleshy fruits increases when recruitment sites are spatially unpredictable and/or characterized by low light conditions.

  • 26. Bourdeau, Paul E.
    et al.
    Johansson, Frank
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Population and Conservation Biology.
    Predator-induced morphological defences as by-products of prey behaviour: a review and prospectus2012In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 121, no 8, p. 1175-1190Article, review/survey (Refereed)
    Abstract [en]

    Predator-induced morphological defences (PIMDs) are ubiquitous. Many PIMDs may be mediated by prey behaviour rather than directly cued by predators. A survey of 92 studies indicated 40 that quantified prey behaviour, all of which document positive associations between defence production and activity reduction. Thus, PIMDs are associated with changes in prey activity, which could have caused the morphological change. We propose two possible mechanisms: 1) decreased activity reduces feeding rate, resulting in lower growth and morphological change; and 2) activity reduction conserves energy, which is reallocated for growth, subsequently changing morphology. Resource availability also causes similar morphological change to predator presence, suggesting confounding effects of resources and predators with current methodology. Future studies should estimate food ingestion, assimilation efficiency, and growth rate in the presence and absence of predators, crossing predator presence with resource levels. Not all PIMDs will be behaviourally-mediated, but consideration of causal linkages between prey behaviour and PIMDs is warranted.

  • 27.
    Bourdeau, Paul E.
    et al.
    Michigan State Univ, Dept Fisheries & Wildlife, E Lansing, MI 48824 USA.
    Johansson, Frank
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Predator-induced morphological defences as by-products of prey behaviour: a review and prospectus2012In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 121, no 8, p. 1175-1190Article, review/survey (Refereed)
    Abstract [en]

    Predator-induced morphological defences (PIMDs) are ubiquitous. Many PIMDs may be mediated by prey behaviour rather than directly cued by predators. A survey of 92 studies indicated 40 that quantified prey behaviour, all of which document positive associations between defence production and activity reduction. Thus, PIMDs are associated with changes in prey activity, which could have caused the morphological change. We propose two possible mechanisms: 1) decreased activity reduces feeding rate, resulting in lower growth and morphological change; and 2) activity reduction conserves energy, which is reallocated for growth, subsequently changing morphology. Resource availability also causes similar morphological change to predator presence, suggesting confounding effects of resources and predators with current methodology. Future studies should estimate food ingestion, assimilation efficiency, and growth rate in the presence and absence of predators, crossing predator presence with resource levels. Not all PIMDs will be behaviourally-mediated, but consideration of causal linkages between prey behaviour and PIMDs is warranted.

  • 28.
    Brodersen, Jakob
    et al.
    Lunds universitet.
    Nicolle, Alice
    Lunds universitet.
    Nilsson, P. Anders
    Lunds universitet.
    Skov, Christian
    Tech Univ Denmark, Natl Inst Aquat Resources DTU Aqua, Sect Freshwater Fisheries Ecol, DK-8600 Silkeborg, Denmark.
    Brönmark, C
    Lunds universitet.
    Hansson, Lars-Anders
    Lunds universitet.
    Interplay between temperature, fish partial migration and trophic dynamics2011In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 120, p. 1838-1846Article in journal (Refereed)
  • 29. Bååth, Erland
    et al.
    Lohm, Ulrik
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Lundgren, Björn
    Rosswall, Thomas
    Söderström, Bengt
    Sohlenius, Björn
    Impact of microbial-feeding animals on total soil activity and nitrogen dynamics: a microcosm experiment1981In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 37, p. 257-264Article in journal (Refereed)
    Abstract [en]

      

  • 30. Bååth, Erland
    et al.
    Lohm, Ulrik
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Lundgren, Björn
    Rosswall, Tomas
    Söderström, Bengt
    Sohlenius, Björn
    Wirén, Anders
    The effect of nitrigen and carbon supply on the development of soil organism populations and pine seedlings: a microcosm experiment1978In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 31, p. 153-163Article in journal (Refereed)
  • 31.
    Candolin, Ulrika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Engström-Öst, Jonna
    Salesto, Tiina
    Human-induced eutrophication enhances reproductive success through effects on parenting ability in sticklebacks2008In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 117, no 3, p. 459-465Article in journal (Refereed)
    Abstract [en]

    Human-induced processes are altering habitats at an unprecedented rate and scale. This has changed the biodiversity and biomass in many areas, but also led to phenotypic and genetic alterations of populations. Here we investigated the effects of the ongoing eutrophication in the Baltic Sea on the reproductive success of threespine stickleback males Gasterosteus aculeatus, through effects on reproductive behaviour and parenting ability. We allowed males to complete breeding cycles in a competitive setting under increased macro algae cover or increased turbidity caused by phytoplankton growth. Both environmental factors improved the parenting ability of the males and enhanced reproductive output. Increased alga growth and turbidity reduced aggressive interactions between males during the parental phase, probably due to reduced visibility, which slowed down a deterioration of condition. This increased the reproductive lifespan of the males and enabled them to complete more breeding cycles, as found when males were allowed to complete as many breeding cycles as they could under increased algae cover. In addition, increased turbidity improved oxygen conditions, which enhanced hatching success and reduced the need for vigorous fanning behaviour. Increased turbidity, however, relaxed selection on male size. Together with earlier results on relaxed sexual selection under changed environmental conditions, this suggests that the effect of eutrophication on stickleback populations is complex. It increases the reproductive output of populations, since more individuals are spawning within eutrophicated areas and their hatching success is increased, but it relaxes sexual and natural selection at the reproductive stage. Whether this will shift selection and population regulation to other life stages, such as the juvenile stage, deserves further investigations.

  • 32.
    Carlsson-Granér, Ulla
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Thrall, Peter H
    The spatial distribution of plant populations, disease dynamics and evolution of resistance2002In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 97, no 1, p. 97-110Article in journal (Refereed)
    Abstract [en]

    Empirical studies of the interaction between the anther smut fungus Microbotryum violaceum and its host plant Lychnis alpina were combined with modelling approaches to investigate how variation in the spatial distribution of host populations influences disease dynamics and variation in resistance. Patterns of disease incidence and prevalence were surveyed in three contrasting systems of natural L. alpina populations where there is substantial variation in spatial structure, ranging from large continuous populations through to small isolated patches. Disease incidence (fraction of populations where disease was present) was highest in the continuous situation, and lowest in the most isolated populations. The reverse was true for prevalence (fraction of individuals diseased). To better understand the long-term ecological and evolutionary consequences of differences in among population spatial structure, we developed a two-dimensional spatially explicit simulation model in which host-population spacing was modelled by varying the percentage of sites suitable for the host. The general patterns of disease incidence and prevalence generated in the simulations corresponded well with the patterns observed in natural populations of L. alpina and M. violaceum; i.e. the fraction of sites with disease increased while the average disease prevalence in diseased populations decreased when host populations became more connected. One likely explanation for the differences in disease incidence and prevalence seen in natural populations is that the evolution of host resistance varies as a function of the degree of fragmentation. This is supported by simulation results that were qualitatively similar to the survey data when resistance was allowed to vary, but not when hosts were assumed to be uniformly susceptible. In the former, the frequency of resistance increased markedly as host populations became more connected.

  • 33. Cease, Arianne J.
    et al.
    Capps, Krista A.
    Gates, Kiza K.
    McCrackin, Michelle L.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Nidzgorski, Daniel A.
    Consumer-driven nutrient dynamics in urban environments: the stoichiometry of human diets and waste management2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 7, p. 931-948Article in journal (Refereed)
    Abstract [en]

    Studies in both terrestrial and aquatic ecosystems have documented the potential importance of consumers on ecosystem-level nutrient dynamics. This is especially true when aggregations of organisms create biogeochemical hotspots through nutrient consumption, assimilation, and remineralization via excretion and egestion. Here, we focused on aggregations of humans in cities to examine how diet and waste management interact to drive nitrogen-(N) and phosphorus-(P) fluxes into nutrient pollution, inert forms, and nutrient recycling. We constructed six diet patterns (five US-based and one developing nation) to examine N-and P-consumption and excretion, and explored their implications for human health. Next, we constructed six waste-management patterns (three US and three for developing nations) to model how decisions at household and city scales determine the eventual fates of N and P. When compared to the US Recommended Daily Intake, all US diet patterns exceeded N and P requirements. Other than the enriched CO2 environment scenario diet, the typical US omnivore had the greatest excess (37% N and 62% P). Notably, P from food additives could account for all of the excess P found in US omnivore and vegetarian diets. Across all waste-management approaches, a greater proportion of P was stored or recycled (0 to > 100% more P than N) and a greater proportion of N was released as effluent (20 to > 100% more N than P) resulting in pollution enriched with N and a recycling stream enriched with P. In developing nations, 60% of N and 50% of P from excreta entered the environment as pollution because of a lack of sanitation infrastructure. Our study demonstrates a novel addition to modeling sustainable scenarios for urban N-and P-budgets by linking human diets and waste management through socio-ecological systems.

  • 34.
    Cherif, Mehdi
    et al.
    Department of Biology, McGill University.
    Loreau, Michel
    Department of Biology, McGill University.
    Towards a more biologically realistic use of Droop's equations to model growth under multiple nutrient limitation2010In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 119, no 6, p. 897-907Article in journal (Refereed)
    Abstract [en]

    Droop's model was originally designed to describe the growth of unicellular phytoplankton species in chemostats but it is now commonly used for a variety of organisms in models of trophic interactions, ecosystem functioning, and evolution. Despite its ubiquitous use, Droop's model is still limited by several simplifying assumptions. For example, the assumption of equal theoretical maximum growth rates for all nutrients is commonly used to describe growth limited by multiple nutrients. This assumption, however, is both biologically unrealistic and potentially misleading. We propose the alternative hypothesis of equal realized maximum growth rates for all nutrients. We support our hypothesis with empirical and theoretical arguments and discuss how it may improve our understanding of the biology of growth, while avoiding some of the pitfalls of the previous assumption.

  • 35. Cichon, M
    et al.
    Merilä, Juha
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Population Biology.
    Hillström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Animal Ecology.
    Wiggins, David
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Animal Ecology.
    Mass-dependent mass loss in breeding birds: getting the null hypothesis right1999In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 87, no 1, p. 191-194Article in journal (Refereed)
    Abstract [en]

    An assumption central to many tests of statistical association between two variables is the null expectation of zero association. Here, we draw attention to the fact that in many published tests of mass-dependent mass loss in breeding birds, this assumption has been violated. We show that a correct null hypothesis can be derived by using resampling methods, and analyse three data sets (two previously published) from passerine birds to illustrate the approach. Our results show, that under a correct null hypothesis, the biological interpretation of the previously published results is reversed-initially heavy birds do actually lose less mass (relative to their weight) than the initially light birds.

  • 36.
    Cirtwill, Alyssa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. Univ Canterbury, New Zealand.
    Roslin, Tomas
    Swedish Univ Agr Sci, Sweden; Univ Helsinki, Finland.
    Rasmussen, Claus
    Aarhus Univ, Denmark.
    Olesen, Jens Mogens
    Aarhus Univ, Denmark.
    Stouffer, Daniel B.
    Univ Canterbury, New Zealand.
    Between-year changes in community composition shape species' roles in an Arctic plant-pollinator network2018In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 127, no 8, p. 1163-1176Article in journal (Refereed)
    Abstract [en]

    Inter-annual turnover in community composition can affect the richness and functioning of ecological communities. If incoming and outgoing species do not interact with the same partners, ecological functions such as pollination may be disrupted. Here, we explore the extent to which turnover affects species' roles - as defined based on their participation in different motifs positions - in a series of temporally replicated plant-pollinator networks from high-Arctic Zackenberg, Greenland. We observed substantial turnover in the plant and pollinator assemblages, combined with significant variation in species' roles between networks. Variation in the roles of plants and pollinators tended to increase with the amount of community turnover, although a negative interaction between turnover in the plant and pollinator assemblages complicated this trend for the roles of pollinators. This suggests that increasing turnover in the future will result in changes to the roles of plants and likely those of pollinators. These changing roles may in turn affect the functioning or stability of this pollination network.

  • 37.
    Dahlgren, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Ehrlen, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    Incorporating environmental change over succession in an integral projection model of population dynamics of a forest herb2011In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 120, no 8, p. 1183-1190Article in journal (Refereed)
    Abstract [en]

    Despite seemingly obvious effects of environmental drivers, mechanisms behind long-term changes in plant population sizes over time are often poorly known. We investigated how soil potassium concentration and seed predation are likely to change over time as a result of succession from deciduous forest to spruce forest, and how this affects population trajectories of Actaea spicata. Observations and addition experiments showed that high soil potassium concentration increased individual growth rates. Among-site comparisons showed that soil potassium concentration was lower where proportion spruce was higher. Incorporation of a gradual increase in spruce over time in an integral projection model where individual growth depended on potassium suggested a net decrease in A. spicata population sizes over forest succession. This result suggests that small changes in factors with small effects on individual performance can influence patterns of species occupancy along successional gradients. We incorporated also density independent and density dependent effects of pre-dispersal seed predation over succession into the same model. Seed predation influenced the tree composition at which A. spicata population growth was positive. However, significant effects of A. spicata population size on seed predation intensity did not translate into important feedback effects on population growth trajectories over succession. Our results illustrate how demographic models can be used to gain understanding of the mechanisms behind effects of environmental change on species abundances and distributions by the simultaneous inclusion of changing abiotic and biotic factors.

  • 38. de Boer, M. Karin
    et al.
    Moor, Helen
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Matthiessen, Birte
    Hillebrand, Helmut
    Eriksson, Britas Klemens
    Dispersal restricts local biomass but promotes the recovery of metacommunities after temperature stress2014In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 123, no 6, p. 762-768Article in journal (Refereed)
    Abstract [en]

    Landscape connectivity can increase the capacity of communities to maintain their function when environments change by promoting the immigration of species or populations with adapted traits. However, high immigration may also restrict fine tuning of species compositions to local environmental conditions by homogenizing the community. Here we demonstrate that dispersal generates such a tradeoff between maximizing local biomass and the capacity of model periphyton metacommunities to recover after a simulated heat wave. In non-disturbed metacommunities, dispersal decreased the total biomass by preventing differentiation in species composition between the local patches making up the metacommunity. On the contrary, in metacommunities exposed to a realistic summer heat wave, dispersal promoted recovery by increasing the biomass of heat tolerant species in all local patches. Thus, the heat wave reorganized the species composition of the metacommunities and after an initial decrease in total biomass by 38.7%, dispersal fueled a full recovery of biomass in the restructured metacommunities. Although dispersal may decrease equilibrium biomass, our results highlight that connectivity is a key requirement for the response diversity that allows ecological communities to adapt to climate change through species sorting.

  • 39. De Long, Jonathan R.
    et al.
    Kardol, Paul
    Sundqvist, Maja K.
    Veen, G. F. (Ciska)
    Wardle, David A.
    Plant growth response to direct and indirect temperature effects varies by vegetation type and elevation in a subarctic tundra2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 6, p. 772-783Article in journal (Refereed)
    Abstract [en]

    There has been growing recent use of elevational gradients as tools for assessing effects of temperature changes on vegetation properties, because these gradients enable temperature effects to be considered over larger spatial and temporal scales than is possible through conventional experiments. While many studies have explored the direct effects of temperature, the indirect effects of temperature through its long-term influence on soil abiotic or biotic properties remain essentially unexplored. We performed two climate chamber experiments using soils from a subarctic elevational gradient in Abisko, Sweden to investigate the direct effects of temperature, and indirect effects of temperature via soil legacies, on growth of two grass species. The soils were collected from each of two vegetation types (heath, dominated by dwarf shrubs, and meadow, dominated by graminoids and herbs) at each of three elevations. We found that plants responded to both the direct effect of temperature and its indirect effect via soil legacies, and that direct and indirect effects were largely decoupled. Vegetation type was a major determinant of plant responses to both the direct and indirect effects of temperature; responses to soils from increasing elevation were stronger and showed a more linear decline for meadow than for heath soils. The influence of soil biota on plant growth was independent of elevation, with a positive influence across all elevations regardless of soil origin for meadow soils but not for heath soils. Taken together, this means that responses of plant growth to soil legacy effects of temperature across the elevational gradient were driven primarily by soil abiotic, and not biotic, factors. These findings emphasize that vegetation type is a strong determinant of how temperature variation across elevational gradients impacts on plant growth, and highlight the need for considering both direct and indirect effects of temperature on plant responses to future climate change.

  • 40. De Long, Jonathan R.
    et al.
    Kardol, Paul
    Sundqvist, Maja K.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Dept of Forest Ecology and Management, Swedish Univ. of Agricultural Sciences, Umeå, Sweden.
    Veen, G. F. (Ciska)
    Wardle, David A.
    Plant growth response to direct and indirect temperature effects varies by vegetation type and elevation in a subarctic tundra2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 6, p. 772-783Article in journal (Refereed)
    Abstract [en]

    There has been growing recent use of elevational gradients as tools for assessing effects of temperature changes on vegetation properties, because these gradients enable temperature effects to be considered over larger spatial and temporal scales than is possible through conventional experiments. While many studies have explored the direct effects of temperature, the indirect effects of temperature through its long-term influence on soil abiotic or biotic properties remain essentially unexplored. We performed two climate chamber experiments using soils from a subarctic elevational gradient in Abisko, Sweden to investigate the direct effects of temperature, and indirect effects of temperature via soil legacies, on growth of two grass species. The soils were collected from each of two vegetation types (heath, dominated by dwarf shrubs, and meadow, dominated by graminoids and herbs) at each of three elevations. We found that plants responded to both the direct effect of temperature and its indirect effect via soil legacies, and that direct and indirect effects were largely decoupled. Vegetation type was a major determinant of plant responses to both the direct and indirect effects of temperature; responses to soils from increasing elevation were stronger and showed a more linear decline for meadow than for heath soils. The influence of soil biota on plant growth was independent of elevation, with a positive influence across all elevations regardless of soil origin for meadow soils but not for heath soils. Taken together, this means that responses of plant growth to soil legacy effects of temperature across the elevational gradient were driven primarily by soil abiotic, and not biotic, factors. These findings emphasize that vegetation type is a strong determinant of how temperature variation across elevational gradients impacts on plant growth, and highlight the need for considering both direct and indirect effects of temperature on plant responses to future climate change.

  • 41.
    Diehl, Sebastian
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Effects of habitat structure on resource availability, diet and growth of benthivorous perch, perca-fluviatilis1993In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 67, no 3, p. 403-414Article in journal (Refereed)
    Abstract [en]

    I experimentally evaluated the impact of habitat structural complexity on the interactions between a generalist predator and a benthic macroinvertebrate prey assemblage in a freshwater pond. Benthivorous perch (Perca fluviatilis) were stocked over a range of natural densities (no fish, low, and high densities) into enclosures with or without dense submerged vegetation. The biomass of macroinvertebrate prey decreased over time in the presence of perch and was always higher in enclosures with vegetation present than in enclosures lacking vegetation. The increase in mass of perch was positively related to the abundance of macroinvertebrate prey and negatively related to perch density and the density of vegetation. In the treatments lacking vegetation, the proportion of zooplankton in the diet of perch increased, and the growth rate of perch decreased over time. In the vegetation treatments, the proportion of zooplankton in the diet was low throughout the experiment and the growth rate of perch was constant over time. As a consequence, initial increase in mass was considerably higher in the treatments lacking vegetation than in the vegetation treatments, whereas no such pattern was observed in the second half of the experiment. In the absence of vegetation, perch are apparently able to forage efficiently, but this may reduce the availability of macroinvertebrate prey to the extent that perch are forced to include less profitable zooplankton prey into their diet. In vegetated habitats, the foraging efficiency of perch is reduced, which possibly prevents over-exploitation of macroinvertebrate prey and consequently may allow for a moderate, but relatively constant, consumption of macroinvertebrates by perch. The density-dependence of growth rates in both vegetated and unvegetated habitats can only partly be explained by resource competition, which suggests the presence of an additional mechanism of density-dependence. In natural lake communities, efficient predation from benthivorous fish should keep the biomass of macroinvertebrate prey in structurally simple habitats below the high levels initially present in my experiment. In these communities, submerged vegetation may be an equally profitable habitat for juvenile perch as are open areas. Through its effects on the feeding efficiencies of juvenile perch and other benthivorous fish, submerged vegetation may affect individual growth rates and the size structure of perch populations, which may contribute to explain differences in fish community structure among lakes differing in submerged vegetation cover.

  • 42.
    Diehl, Sebastian
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Relative consumer sizes and the strengths of direct and indirect interactions in omnivorous feeding relationships1993In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 68, no 1, p. 151-157Article in journal (Refereed)
    Abstract [en]

    Omnivory (the consumption of resources from more than one trophic level) is widespread in nature and has the potential to produce a richness of indirect effects. Nevertheless, its effects on population dynamics have received very little attention. In its simplest case, omnivory involves a top consumer, an intermediate consumer, and a resource that is common to both consumers. Simple models predict that the intermediate consumer can only coexist with the top consumer if the former is more efficient in exploiting the common resource, which would imply a net positive effect of the top consumer on the equilibrium density of resources (compared to the situation where only the intermediate consumer is present). Among 22 experimental manipulations of omnivorous top consumers I found only 2 studies in which top consumers had significant positive effects on resources. This discrepancy between experimental results and model predictions is, at least partly, related to deviations of the experimental systems from model assumptions. However, considerations of relative body sizes of intermediate and top consumers suggest, that top consumers having negative net effects on the basic resource should be common in nature. I argue that in systems where intermediate consumers and basic resources are relatively similar in size, but both are much smaller than omnivorous top consumers (e.g. vertebrate omnivores feeding on benthos, soil invertebrates, terrestrial insects etc.), the direct negative effect of top consumers on basic resources should not be outweighed by indirect positive effects, and that other mechanisms (e.g. prey refuges) must be invoked to explain the persistence of intermediate consumers in many natural systems. I further argue that a better knowledge of the population dynamical consequences of omnivory and the role of relative consumer sizes is necessary to improve our understanding of the-trophic dynamics of different kinds of communities.

  • 43.
    Digel, Christoph
    et al.
    University of Gottingen, Germany.
    Curtsdotter, Alva
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Riede, Jens
    Deutsch Wetterdienst, Germany.
    Klarner, Bernhard
    University of Gottingen, Germany.
    Brose, Ulrich
    University of Gottingen, Germany.
    Unravelling the complex structure of forest soil food webs: higher omnivory and more trophic levels2014In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 123, no 10, p. 1157-1172Article in journal (Refereed)
    Abstract [en]

    Food web topologies depict the community structure as distributions of feeding interactions across populations. Although the soil ecosystem provides important functions for aboveground ecosystems, data on complex soil food webs is notoriously scarce, most likely due to the difficulty of sampling and characterizing the system. To fill this gap we assembled the complex food webs of 48 forest soil communities. The food webs comprise 89 to 168 taxa and 729 to 3344 feeding interactions. The feeding links were established by combining several molecular methods (stable isotope, fatty acid and molecular gut content analyses) with feeding trials and literature data. First, we addressed whether soil food webs (n = 48) differ significantly from those of other ecosystem types (aquatic and terrestrial aboveground, n = 77) by comparing 22 food web parameters. We found that our soil food webs are characterized by many omnivorous and cannibalistic species, more trophic chains and intraguild-predation motifs than other food webs and high average and maximum trophic levels. Despite this, we also found that soil food webs have a similar connectance as other ecosystems, but interestingly a higher link density and clustering coefficient. These differences in network structure to other ecosystem types may be a result of ecosystem specific constraints on hunting and feeding characteristics of the species that emerge as network parameters at the food-web level. In a second analysis of land-use effects, we found significant but only small differences of soil food web structure between different beech and coniferous forest types, which may be explained by generally strong selection effects of the soil that are independent of human land use. Overall, our study has unravelled some systematic structures of soil food-webs, which extends our mechanistic understanding how environmental characteristics of the soil ecosystem determine patterns at the community level.

  • 44.
    Dinnétz, Patrik
    et al.
    Stockholm university.
    Jerling, Lenn
    Stockholm university.
    Spatial distribution of male sterility in Plantago maritima1998In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 81, p. 255-265Article in journal (Refereed)
    Abstract [en]

    Sexual polymorphism in angiosperms can be explained both by the functional responses of male and female function to autogamy and geitonogamy, and by the conflict between the nuclear and cytoplasmic genomes. In predominantly hermaphrodite species, cytoplasmically determined male sterility may persist in a population because of maternal inheritance, i.e, the loss of male function does not change the fitness of the cytoplasmic genome. However, in populations with cytoplasmic male sterility, male fertility is often restored by nuclear genes. Therefore, in populations with genetical substructure, the frequencies of the different sex-morphs will fluctuate depending on the presence of both the male sterile cytoplasms, and of their specific nuclear restorer genes. In Plantagomaritima, we showed that the frequencies of male sterility were highest in regions with the highest population turnover rates and that male sterile individuals were more frequently found in the lower, less dense parts of the meadows. This indicates that male sterile cytoplasms have their highest probabilities to escape their nuclear restorer genes during recolonisation in disturbed regions within populations. We also found that male sterile individuals dispersed their seeds a little bit further than did the hermaphrodites. This can be interpreted as an adaptive response to the local occurrence of nuclear restorer genes.

  • 45.
    Doi, Hideyuki
    et al.
    Institute for Chemistry and Biology of the Marine Environment, Carl-von-Ossietzky University Oldenburg.
    Cherif, Mehdi
    Department of Biology, McGill University.
    Iwabuchi, Tsubasa
    Graduate School of Life Science, Tohoku University.
    Katano, Izumi
    Institute for Chemistry and Biology of the Marine Environment, Carl-von-Ossietzky University Oldenburg.
    Stegen, James C.
    Dept of Biology, University of North Carolina.
    Striebel, Maren
    WasserCluster Lunz, University for Natural Resources and Applied Life Sciences.
    Integrating elements and energy through the metabolic dependencies of gross growth efficiency and the threshold elemental ratio2010In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 119, no 5, p. 752-765Article in journal (Refereed)
    Abstract [en]

    Metabolic theory proposes that individual growth is governed through the mass- and temperature-dependence of metabolism, and ecological stoichiometry posits that growth is maximized at consumer-specific optima of resource elemental composition. A given consumer's optimum, the threshold elemental ratio (TER), is proportional to the ratio of its maximum elemental gross growth efficiencies (GGEs). GGE is defined by the ratio of metabolism-dependent processes such that GGEs should be independent of body mass and temperature. Understanding the metabolic-dependencies of GGEs and TERs may open the path towards a theoretical framework integrating the flow of energy and chemical elements through ecosystems. However, the mass and temperature scaling of GGEs and TERs have not been broadly evaluated. Here, we use data from 95 published studies to evaluate these metabolic-dependencies for C, N and P from unicells to vertebrates. We show that maximum GGEs commonly decline as power functions of asymptotic body mass and exponential functions of temperature. The rates of change in maximum GGEs with mass and temperature are relatively slow, however, suggesting that metabolism may not causally influence maximum GGEs. We additionally derived the theoretical expectation that the TER for C:P should not vary with body mass and this was supported empirically. A strong linear relationship between carbon and nitrogen GGEs further suggests that variation in the TER for C:N should be due to variation in consumer C:N. In general we show that GGEs may scale with metabolic rate, but it is unclear if there is a causal link between metabolism and GGEs. Further integrating stoichiometry and metabolism will provide better understanding of the processes governing the flow of energy and elements from organisms to ecosystems.

  • 46.
    DUNBERG, A
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Why Beech and Oak Trees Retain Leaves Until Spring: A Comment on the Contribution by Otto and Nilsson1982In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 39, no 2, p. 275-277Article in journal (Other academic)
  • 47.
    Eckstein, Rolf Lutz
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences. Uppsala University.
    Karlsson, P S
    Uppsala University.
    Above-ground growth and nutrient use by plants in a subarctic environment: Effects of habitat, life-form and species1997In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 79, no 2, p. 311-324Article in journal (Refereed)
  • 48.
    Eckstein, Rolf Lutz
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences. Uppsala University.
    Karlsson, P S
    Uppsala University.
    Weih, M
    Uppsala University.
    The significance of resorption of leaf resources for shoot growth in evergreen and deciduous woody plants from a subarctic environment1998In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 81, no 3, p. 567-575Article in journal (Refereed)
  • 49.
    Edman, Mattias
    et al.
    Dept of Ecology and Environmental Science, Umeå University.
    Gustafsson, Mårten
    Dept of Forest Mycology and Pathology, SLU, Uppsala.
    Stenlid, Jan
    Dept of Forest Mycology and Pathology, SLU, Uppsala.
    Ericson, Lars
    Dept of Ecology and Environmental Science, Umeå University.
    Abundance and viability of fungal spores along a forestry gradient: responses to habitat loss and isolation?2004In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 104, no 1, p. 35-42Article in journal (Refereed)
    Abstract [en]

    Regional variation in spore deposition and viability was studied for two fungi, Fomitopsis rosea (Alb. & Schwein.: Fr.) P. Karst. and Phlebia centrifuga P. Karst., both confined to old-growth spruce forests in the boreal zone. Seven regions in Sweden were studied along a north-south transect in which the historical impact from forestry increases and the amount old forests decreases towards the south. The two southernmost regions were located outside the distribution border of the species. Spore deposition was measured species specifically as heterokaryotisation of homokaryotic mycelia growing on wood discs. There was a significant decline in spore deposition towards the south for both species. F. rosea deposited an average amount of 111 spores m-2 24 h-1 in the northernmost region compared to less than 1 spore in the four southernmost regions. The corresponding values for P. centrifuga were 27 spores m-2 24 h-1 in the north compared to less than 2 spores in the 4 southernmost regions. No deposition was found south of the distribution borders. The viability of spores from local populations within each region was measured as germination success on nutrient media. Individual fruiting bodies from large populations in the north generally produced spores with higher germinability than fruiting bodies from geographically isolated populations in the central and southern regions. However, there was a high variation among the southern populations. Our data suggest that some populations in mid- and south Sweden may suffer from negative genetic effects, possibly associated with fragmentation and loss of habitat. Thus, the combination of low spore deposition and low germinability of spores may be a threat to the long-term persistence of F. rosea and P. centrifuga in southern Sweden. Several other species may experience the same situation, especially when considering the severe decline of dead wood in Swedish forests.

  • 50.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Selection on flowering time in a life-cycle context2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 1, p. 92-101Article in journal (Refereed)
    Abstract [en]

    The main way in which plants can exert control over their local environment is by the timing of different events within their life cycles. Regarding timing of flowering as an integrated part of both the annual cycle and of the whole life cycle, rather than as an isolated event, has important implications for how we assess selection on timing of reproduction and interpret existing phenological patterns in perennial plants. I argue that: 1) we have little unequivocal evidence of pollinator-mediated selection on flowering time, but perhaps more evidence of antagonist-mediated selection; 2) much of selection on flowering time might occur before flowers have developed and after reproduction; 3) vital rates of non-flowering individuals can influence the strength and direction of selection on flowering time, and 4) differences in the direction of selection on flowering date between years might well correspond to consistent selection on the mechanisms determining flowering time. Overall, a life cycle perspective on timing of flowering is likely to facilitate the identification of selective agents and the understanding of the complex mechanisms underlying spatial and temporal variation in selection as well as to enable more accurate predictions of responses to environmental change.

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