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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.
    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.

  • 3.
    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

  • 4.
    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.

  • 5.
    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.

  • 6.
    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.

  • 7. 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.

  • 8.
    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.

  • 9. 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.

  • 10.
    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.

  • 11.
    Eklöf, Johan S.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Havenhand, Jonathan N.
    Alsterberg, Christian
    Gamfeldt, Lars
    Community-level effects of rapid experimental warming and consumer loss outweigh effects of rapid ocean acidification2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 8, p. 1040-1049Article in journal (Refereed)
    Abstract [en]

    Climate change and consumer loss simultaneously affect marine ecosystems, but we have limited understanding of the relative importance of these factors and the interactions between them. Moreover, effects of environmental change are mediated by organism traits or life histories, which determine their sensitivity. Yet, trait-based analyses have rarely been used to understand the effects of climate change, especially in the marine environment. Here we used a five-week mesocosm experiment to assess the single and interactive effects of 1) rapid ocean warming, 2) rapid ocean acidification, and 3) simulated consumer loss, on the diversity and composition of macrofauna communities in eelgrass Zostera marina beds. Experimental warming (ambient versus + 3.2 degrees C) and loss of a key consumer (the omnivorous crustacean, Gammarus locusta) both increased macrofauna richness and abundance, and altered overall species trait distributions and life history composition. Warming and consumer-loss favored poorly defended epifaunal crustaceans (tube-building amphipods), and species that brood their off spring. We suggest these organisms were favored because warming and consumer-loss caused increased metabolism, food supply and, potentially, settling substrate, and lowered predation pressure from the omnivorous G. locusta. Importantly, we found no single, or interactive, effects of the rapid ocean acidification (ambient versus -0.35 pH units). We suggest this result reflects natural variability in the native habitat and, potentially, the short duration of the experiment: organisms in these communities routinely experience rapid diurnal pH fluctuations that exceed the mean ocean acidification predicted for the coming century (and used in our experiments). In summary, our study indicates that macrofauna in shallow vegetated ecosystems will be significantly more affected by rapid warming and consumer diversity loss than by rapid ocean acidification.

  • 12.
    Elmhagen, B.odil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    The applicability of metapopulation theory to large mammals2001In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 94, no 1, p. 89-100Article in journal (Refereed)
    Abstract [en]

    Metapopulation theory has become a common framework in conservation biology and it is sometimes suggested that a metapopulation approach should be used for management of large mammals. However. it has also been suggested that metapopulation theory would not be applicable to species with long generations compared to those with short ones. In this paper, we review how and on what empirical ground metapopulation terminology liar, been applied to insects, small mammals and large mammals, The review showed that the metapopulation term sometimes was used for population networks which only fulfilled the broadest possible definition of a metapopulation, i.e. they were subpopulations connected by migrating individuals. We argue that the metapopulation concept should be reserved for networks that also show some kind of metapopulation dynamics. Otherwise it applies to almost all populations and loses its substance. We found much empirical support for metapopulation dynamics in both insects and small mammals, but not in large mammals. A me possible reason is the methods used to confirm the existence of metapopulation dynamics, For insects and small mammals, the common approach is to study population turnover through patch occupancy data. Such data is difficult to obtain for large mammals, since longer temporal scales need to be covered to record extinctions and colonizations. Still, many populations of large mammals are exposed to habitat fragmentation and the resulting subpopulations sometimes have high risks of extinction. If there is migration between the subpopulations, the metapopulation framework could provide valuable information on their population dynamics. We suggest that a metapopulation approach can be interesting for populations of large mammals. when there are discrete breeding subpopulations and when these subpopulations have different growth rates and demographic fates. Thus, a comparison of the subpopulations' demographic fates, rather than subpopulation turnover, can be a feasible alternative for studies of metapopulation dynamics in large mammals.

  • 13.
    Enfjäll, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Density-dependent dispersal in the Glanville fritillary, Melitaea cinxia2005In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 108, p. 465-472Article in journal (Refereed)
  • 14.
    Enfjäll, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    The evolution of dispersal - the importance of information about population density and habitat characteristics2009In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 118, p. 291-299Article in journal (Refereed)
    Abstract [en]

    The evolution of mobility patterns and dispersal strategies depend on different population, habitat and life history characteristics. The ability to perceive and make use of information about the surrounding environment for dispersal decisions will also differ between organisms. To investigate the evolutionary consequences of such differences, we have used a simulation model with nearest-neighbour dispersal in a metapopulation to study how variation in the ability to obtain and make use of information about habitat quality and conspecific density affects the evolution of dispersal strategies. We found a rather strong influence of variation in information on the overall rate of dispersal in a metapopulation. The highest emigration rate evolved in organisms with no information about either density or habitat quality and the lowest rate was found in organisms with information about both the natal and the neighbouring patches. For organisms that can make use of information about conspecific density, positively density-dependent dispersal evolved in the majority of cases, with the strongest density dependence occurring when an individual only has information about density in the natal patch. However, we also identified situations, involving strong local population fluctuations and frequent local extinctions, where negatively density-dependent dispersal evolved.

  • 15.
    Griffiths, Jennifer R.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hajdu, Susanna
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Downing, Andrea S.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Hjerne, Olle
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Larsson, Ulf
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Winder, Monika
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Phytoplankton community interactions and environmental sensitivity in coastal and offshore habitats2016In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 125, no 8, p. 1134-1143Article in journal (Refereed)
    Abstract [en]

    Assessing the relative importance of environmental conditions and community interactions is necessary for evaluating the sensitivity of biological communities to anthropogenic change. Phytoplankton communities have a central role in aquatic food webs and biogeochemical cycles, therefore, consequences of differing community sensitivities may have broad ecosystem effects. Using two long-term time series (28 and 20 years) from the Baltic Sea, we evaluated coastal and offshore major phytoplankton taxonomic group biovolume patterns over annual and monthly time-scales and assessed their response to environmental drivers and biotic interactions. Overall, coastal phytoplankton responded more strongly to environmental anomalies than offshore phytoplankton, although the specific environmental driver changed with time scale. A trend indicating a state shift in annual biovolume anomalies occurred at both sites and the shift's timing at the coastal site closely tracked other long-term Baltic Sea ecosystem shifts. Cyanobacteria and the autotrophic ciliate Mesodinium rubrum were more strongly related than other groups to this trend with opposing relationships that were consistent across sites. On a monthly scale, biotic interactions within communities were rare and did not overlap between the coastal and offshore sites. Annual scales may be better able to assess general patterns across habitat types in the Baltic Sea, but monthly community dynamics may differ at relatively small spatial scales and consequently respond differently to future change.

  • 16.
    Hambäck, Peter
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Gilbert, James
    Schneider, Katie
    Martinson, Holly
    Kolb, Gundula
    Stockholm University, Faculty of Science, Department of Botany.
    Fagan, William
    Effects of body size, trophic mode and larval habitat on Diptera stoichiometry: a regional comparison2009In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 118, p. 615-623Article in journal (Refereed)
    Abstract [en]

    Ecological stoichiometry has emerged as a tool for exploring nutrient demand and evolutionary responses to nutrient limitation. Previous studies of insects have found predictable variability in stoichiometry, both in relation to body size and trophic mode, at ordinal levels or higher. Our study further examines the evolutionary and ecological lability in these traits by comparing the effects of body size, trophic mode (larval and adult) and larval habitat on the stoichiometry of insects within one order (Diptera). The study also expands on previous work by analyzing trophic mode both at coarse (detritivore, herbivore, predator) and fine (high- vs low- nutrient quality resources within trophic categories) scales and by comparing nutrient stoichiometry in two geographical regions, Sweden and Arizona. As predicted, adults feeding on nectar or pollen had the lowest body N content in the dataset. Additionally, for Diptera with predatory larvae, species low N diets had lower body N content than those with high N diets. However, body N content was not consistently lower for all species with low N resources, as species feeding on plant material were indistinguishable in stoichiometry from predators with high N diets. We suggest that these results emerge because larval resource exploitation is poorly understood in herbivorous Diptera species. Body P content for Swedish Diptera decreased with body size for all trophic modes, and the only difference among trophic modes was that blood feeders had higher P content than other groups. The regional comparison further showed that the allometry of body P content is a labile trait that may vary at regional scales, as there was no allometric scaling of body P content in the Arizona data set, in contrast to the Swedish data set. These results are not easily explained by existing theoretical frameworks, but instead point to a general context-dependence of P stoichiometry, which should now be a focus for future work.

  • 17.
    Henden, John-André
    et al.
    University of Tromsø, Norway.
    Ims, Rolf Anker
    University of Tromsø, Norway.
    Yoccoz, Nigel G
    University of Tromsø, Norway.
    Hellström, Peter
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Strength of asymmetric competition between predators in food webs ruled by fluctuating prey: the case of foxes in tundra2010In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 119, no 1, p. 27-34Article in journal (Refereed)
    Abstract [en]

    In food webs heavily influenced by multi-annual population fluctuations of key herbivores, predator species may differ in their functional and numerical responses as well as their competitive ability. Focusing on red and arctic fox in tundra with cyclic populations of rodents as key prey, we develop a model to predict how population dynamics of a dominant and versatile predator (red fox) impacted long-term growth rate of a subdominant and less versatile predator (arctic fox). We compare three realistic scenarios of red fox performance: (1) a numerical response scenario where red fox acted as a resident rodent specialist exhibiting population cycles lagging one year after the rodent cycle, (2) an aggregative response scenario where red fox shifted between tundra and a nearby ecosystem (i.e. boreal forest) so as to track rodent peaks in tundra without delay, and (3) a constant subsidy scenario in which the red fox population was stabilized at the same mean density as in the other two scenarios. For all three scenarios it is assumed that the arctic fox responded numerically as a rodent specialist and that the mechanisms of competition is of a interference type for space, in which the arctic fox is excluded from the most resource rich patches in tundra. Arctic fox is impacted most by the constant subsidy scenario and least by the numerical response scenario. The differential effects of the scenarios stemmed from cyclic phase-dependent sensitivity to competition mediated by changes in temporal mean and variance of available prey to the subdominant predator. A general implication from our result is that external resource subsidies (prey or habitats), monopolized by the dominant competitor, can significantly reduce the likelihood for co-existence within the predator guild. In terms of conservation of vulnerable arctic fox populations this means that the likelihood of extinction increases with increasing amount of subsidies (e.g. carcasses of large herbivores or marine resources) in tundra and nearby forest areas, since it will act to both increase and stabilize populations of red fox.

  • 18.
    Janz, Niklas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Bergström, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Sjögren, Anna
    The role of nectar sources for oviposition decisions of the common blue butterfly (Polyommatus icarus)2005In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 109, p. 535-538Article in journal (Refereed)
    Abstract [en]

    Neural limitations on information processing have been shown to play an important role for host plant specialization in herbivorous insects. The necessity of fast and accurate decisions favors the adoption of a few high-contrast signals, which selects against the use of multiple resources. Many species face a similar problem when searching for adult food sources and the simultaneous need to fulfill both search tasks can lead to a potential conflict. Some insects use the same host plant species for both adult and larval nutrition, which makes it possible to decrease the number of search images and thus potentially increase efficiency of the choices. The aim of this study was to investigate if there is a connection between choice of nectar sources and choice of oviposition host plant. In a laboratory experiment, females of Polyommatus icarus preferred to oviposit on Lotus corniculatus plants with flowers over those without flowers. Observations of behavioral sequences also revealed that oviposition often followed immediately after nectaring. The results suggest that nectar availability could play an important role in oviposition decisions of P. icarus and can provide one explanation to why some phytophagous insects not always choose the host plant that gives the best offspring performance.

  • 19. Kratina, Pavel
    et al.
    Winder, Monika
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of California, USA.
    Biotic invasions can alter nutritional composition of zooplankton communities2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 10, p. 1337-1345Article in journal (Refereed)
    Abstract [en]

    Ecologists and ecosystem managers often base their understanding of trophic dynamics on consumer and resource biomass. However, the factors that alter the relative nutritional value of resources are often poorly understood, despite their potential to decouple trophic interactions. Recent population declines in pelagic fishes of the upper San Francisco Estuary were not accompanied by an equivalent decrease in zooplankton biomass, which are the main resource for the fish and their larvae. It was hypothesized that changes in zooplankton nutritional conditions following the establishment of invasive species caused food-quality related limitations for these higher-order consumers. Using stable isotopes, elemental stoichiometry and fatty acid analyses for all dominant invasive and native zooplankton taxa and seston, we characterized the plankton community structure in the estuary and demonstrated taxon-specific differences in their nutritional value. We then quantified the temporal dynamics in meso-zooplankton proportions of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), polyunsaturated fatty acids (PUFA), and ratio of n3: n6 fatty acids. We found temporal increase in the community-level DHA, n3 to n6 fatty acid ratio, decrease in the community-level EPA and PUFA in the brackish water region, but no change in the bulk PUFA proportions in the freshwater region of the estuary. These changes were caused mainly by declines of native cladocerans that are rich in EPA and by an increase in the dominance of invasive taxa with high DHA concentrations, similar to that of native taxa. Although we showed temporal shifts in individual fatty acid classes, the proportion of the essential fatty acids remained relatively high, suggesting that nutritional prey availability for fish remained unchanged with the shift in species composition. We argue that the nutritional content of resource communities should be considered when analyzing the long-term trophic dynamics and designing effective management and restoration strategies.

  • 20.
    Leimar, Olof
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Norberg, Ulf
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Metapopulation extinction and genetic variation in dispersal-related traits1997In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 80, p. 448-458Article in journal (Refereed)
  • 21.
    Lindgren, Åsa
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Klint, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    Moen, Jon
    Defense mechanisms against grazing: a study of trypsin inhibitor responses to simulated grazing by the sedge Carex bigelowii2007In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 116, no 9, p. 1540-1546Article in journal (Refereed)
    Abstract [en]

    Trypsin inhibitors have been suggested to constitute an inducible defense in the sedge Carex bigelowii, and some former studies suggest that this might be a cause for the cyclic population dynamics in many alpine and arctic small mammals, for example lemmings (Lemmus lemmus). We investigated this further by using a method of simulated grazing (clipping) at different intensities, in three different habitats with varying resource availability, with different harvest times (hours after clipping), and two different stages of ramets (reproductive/vegetative) in a study from the Swedish mountain range. Our results do not indicate that C. bigelowii has an inducible defense constituted by an increase in trypsin inhibitor activity (TIA), but rather that the amount of soluble plant proteins (SPP) is lowered in wounded plants. The responses were somewhat different in the three habitats, with ramets growing in the marsh showing the highest ratio of TIA to SPP, due to low amounts of SPP. We did not find any significant effects of harvest time, or of the stage of the ramet that could support the hypothesis of an inducible defense. To conclude, we could not find any evidence for an inducible defense consisting of trypsin inhibitors in Carex bigelowii ramets, but we did find variations in the amount of SPP that may have nutritional consequences for herbivores.

  • 22.
    Lönnberg, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Eriksson, Ove
    Stockholm University, Faculty of Science, Department of Botany.
    Rules of the seed size game: contests between large-seeded and small-seeded species2013In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 122, no 7, p. 1080-1084Article in journal (Refereed)
    Abstract [en]

    The coexistence of multiple seed size strategies within plant communities have been considered puzzling, based on a theoretical expectation of the existence of an optimal seed size under each set of specific environmental conditions. A model aimed at explaining the coexistence of different seed sizes has been suggested, where a seed size – seed number trade-off is connected to a trade-off between competition and colonization, leading to a competitive advantage in larger-seeded species and a colonization advantage in smaller-seeded species. Recently an alternative model has been suggested, based on a trade-off between stress tolerance and fecundity, associated with the variation from large to small seeds. Here, we examine the role of seed size for recruitment in two-species contests subjected to various treatments. In a garden experiment seeds of 14 plant species were combined pair-wise into seven pairs, each with one larger-seeded species and one smaller-seeded species. Each species-pair was sown with sparse and dense seed densities and subjected to different treatments of shading and litter. Recruitment was recorded during two years. Our results showed a general advantage of larger-seeded species over smaller-seeded species. This seed size advantage increased in treatments with litter, whereas there were minor effects of shade, and no effect of seed density was found. We thus found little support for a density dependent seed size game as assumed in models of a competition-colonization trade-off, whereas our results fit well with a model based on a trade-off between stress tolerance and fecundity. Our experiment provides novel empirical data to theoretical models on co-existence between multiple seed size strategies.

  • 23. Lönnell, Niklas
    et al.
    Norros, Veera
    Sundberg, Sebastian
    Rannik, Üllar
    Johansson, Victor
    Ovaskainen, Otso
    Hylander, Kristoffer
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Testing a mechanistic dispersal model against a dispersal experiment with a wind-dispersed moss2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 9, p. 1232-1240Article in journal (Refereed)
    Abstract [en]

    Wind is the main dispersal agent for a wide array of species and for these species the environmental conditions under which diaspores are released can potentially modify the dispersal kernel substantially. Little is known about how bryophytes regulate spore release, but conditions affecting peristome movements and vibration of the seta may be important. We modelled airborne spore dispersal of the bryophyte species Discelium nudum (spore diameter 25 m), in four different release scenarios, using a Lagrangian stochastic dispersion model and meteorological data. We tested the model predictions against experimental data on colonization success at five distances (5, 10, 30, 50 and 100 m) and eight directions from a translocated point source during seven two-day periods. The model predictions were generally successful in describing the observed colonization patterns, especially beyond 10 m. In the laboratory we established spore release thresholds; horizontal wind speed sd > 0.25 m s(-1) induced the seta to vibrate and in relative humidity < 75% the peristome was open. Our dispersal model predicts that the proportion of spores dispersing beyond 100 m is almost twice as large if the spores are released under turbulent conditions than under more stable conditions. However, including release thresholds improved the fit of the model to the colonization data only minimally, with roughly the same amount of variation explained by the most constrained scenario (assuming both vibration of the seta and an open peristome) and the scenario assuming random release. Model predictions under realised experimental conditions suggest that we had a low statistical power to rank the release scenarios due to the lack of measurements of the absolute rate of spore release. Our results hint at the importance of release conditions, but also highlight the challenges in dispersal experiments intended for validating mechanistic dispersal models.

  • 24. Moksnes, Per-Olav
    et al.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Tryman, Kentaroo
    Baden, Susanne
    Trophic cascades in a temperate seagrass community2008In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 117, no 5, p. 763-777Article in journal (Refereed)
    Abstract [en]

    We assessed the relative importance of bottom-up and top-down processes in structuring an eelgrass community in Sweden, a system impacted both by eutrophication and overfishing. Using artificial seagrass as substrate, we manipulated nutrient levels and predator abundance in a full-factorial cage-experiment.

    The results revealed a seagrass community dominated by strong top-down processes controlling the aggregate biomass of mesograzers and macroalgae. In the absence of predators the large amphipod Gammarus locusta became very abundant resulting in a leaf community with low biomass of algae and smaller mobile fauna. One enclosed gobid fish predator reduced the abundance of adult G. locusta by > 90%, causing a three to six times increase in the biomass of algae, smaller mesograzers and meiofauna. Numerous small predators in uncaged habitats reduced the biomass of G. locusta and other mesograzers by > 95% in comparison to the fish treatment, further increasing the biomass of epiphytic algae and meiofauna. Although water column nutrient enrichment caused a temporal bloom of the filamentous macroalgae Ulva spp., no significant nutrient-effects were found on the algal community at the end of the experiment. The only lasting nutrient-effect was a significant increase in the biomass of G. locusta, but only in the absence of ambient predators.

    These results demonstrate that mesograzers can respond to enhanced food supply, increase their biomass and control the algal growth when predation rates are low. However, in the assessed system, high predation rates appear to make mesograzers functionally extinct, causing a community-wide trophic cascade that promotes the growth of ephemeral algae. This top-down effect could penetrate down, despite a complex food-web because the interaction strength in the community was strongly skewed towards two functionally dominant algal and grazer species that were vulnerable to consumption. These results indicate that overexploitation of gadoid fish may be linked to increased macroalgal blooms and loss of eelgrass in the area through a trophic cascade affecting the abundance of mesograzers.

  • 25. Nash, Kirsty L.
    et al.
    Allen, Craig R.
    Barichievy, Chris
    Nyström, Magnus
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Sundström, Shana
    Graham, Nicholas A. J.
    Habitat structure and body size distributions: cross-ecosystem comparison for taxa with determinate and indeterminate growth2014In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 123, no 8, p. 971-983Article in journal (Refereed)
    Abstract [en]

    Habitat structure across multiple spatial and temporal scales has been proposed as a key driver of body size distributions for associated communities. Thus, understanding the relationship between habitat and body size is fundamental to developing predictions regarding the influence of habitat change on animal communities. Much of the work assessing the relationship between habitat structure and body size distributions has focused on terrestrial taxa with determinate growth, and has primarily analysed discontinuities (gaps) in the distribution of species mean sizes (species size relationships or SSRs). The suitability of this approach for taxa with indeterminate growth has yet to be determined. We provide a cross-ecosystem comparison of bird (determinate growth) and fish (indeterminate growth) body mass distributions using four independent data sets. We evaluate three size distribution indices: SSRs, species size-density relationships (SSDRs) and individual size-density relationships (ISDRs), and two types of analysis: looking for either discontinuities or abundance patterns and multi-modality in the distributions. To assess the respective suitability of these three indices and two analytical approaches for understanding habitat-size relationships in different ecosystems, we compare their ability to differentiate bird or fish communities found within contrasting habitat conditions. All three indices of body size distribution are useful for examining the relationship between cross-scale patterns of habitat structure and size for species with determinate growth, such as birds. In contrast, for species with indeterminate growth such as fish, the relationship between habitat structure and body size may be masked when using mean summary metrics, and thus individual-level data (ISDRs) are more useful. Furthermore, ISDRs, which have traditionally been used to study aquatic systems, present a potentially useful common currency for comparing body size distributions across terrestrial and aquatic ecosystems.

  • 26.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Carmichael, Lindsey
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Hersteinsson, Páll
    Samelius, Gustaf
    Fuglei, Eva
    Kapel, Christian M. O.
    Menyushina, Irina
    Strobeck, Curtis
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Arctic fox Vulpes lagopus population structure: circumpolar patterns and processes2011In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 120, no 6, p. 873-885Article in journal (Refereed)
    Abstract [en]

    Movement is a prominent process shaping genetic population structure. In many northern mammal species, population structure is formed by geographic distance, geographical barriers and various ecological factors that influence movement over the landscape. The Arctic fox Vulpes lagopus is a highly mobile, opportunistic carnivore of the Arctic that occurs in two main ecotypes with different ecological adaptations. We assembled microsatellite data in 7 loci for 1834 Arctic foxes sampled across their entire distribution to describe the circumpolar population structure and test the impact of (1) geographic distance, (2) geographical barriers and (3) ecotype designation on the population structure. Both Structure and Geneland demonstrated distinctiveness of Iceland and Scandinavia whereas low differentiation was observed between North America-northern Greenland, Svalbard and Siberia. Genetic differentiation was significantly correlated to presence of sea ice on a global scale, but not to geographical distance or ecotype designation. However, among areas connected by sea ice, we recorded a pattern of isolation by distance. The maximum likelihood approach in Migrate suggested that connectivity across North America-northern Greenland and Svalbard was particularly high. Our results demonstrate the importance of sea ice for maintaining connectivity between Arctic fox populations and we therefore predict that climate change will increase genetic divergence among populations in the future.

  • 27.
    Nyström, Veronica
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Genetic consequences of a demographic bottleneck in the Scandinavian arctic fox2006In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 114, no 1, p. 84-94Article in journal (Refereed)
    Abstract [en]

    Demographic bottlenecks can result in a loss of genetic variation due to the bottleneck effect and subsequent genetic drift. The arctic fox population in Scandinavia went through a severe demographic bottleneck in the early 20th century, and is today classified as critically endangered. In this study, we investigated the pre-bottleneck genetic variation in Scandinavia and compared it to modern samples from Scandinavia and North Russia. Variation in the mtDNA control region and five microsatellite loci was examined through ancient DNA analysis on museum specimens. The microsatellite data from the museum specimens was further used to simulate the expected effect of the bottleneck. The arctic foxes in Scandinavia have lost approximately 25% of the microsatellite alleles and four out of seven mtDNA haplotypes. The results also suggest that the genetic differentiation between North Russia and Scandinavia has doubled over the last 100 years. However, the level of heterozygosity was significantly higher than expected from the simulations. This highlights both the advantage of using museum specimens and the importance of generating specific predictions in conservation genetics.

  • 28.
    Plue, Jan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Södertörn University, Stockholm.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Seed dispersal in both space and time is necessary for plant diversity maintenance in fragmented landscapes2018In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 127, no 6, p. 780-791Article in journal (Refereed)
    Abstract [en]

    Metacommunity theory emphasizes that seed dispersal not only limits but equally maintains plant diversity, though the latter receives little empirical attention. Discerning the temporal and spatial components of seed dispersal and understanding how their interaction shapes fragmented communities and maintains their diversity may be pivotal to further our ecological understanding of spatial and temporal seed dispersal and its implications for landscape-scale conservation management. To investigate the relative importance of spatial and temporal seed dispersal and their roles in maintaining plant diversity, the herb layer and seed bank of grassland communities were inventoried in 77 sites across abandoned and intact rotational grazing networks in a 100 km(2) fragmented grassland landscape in the Stockholm archipelago (Baltic Sea, Sweden). Besides analysing alpha- and beta-diversity patterns, nestedness analyses connect deterministic community changes and diversity losses with dispersal-related life-history traits and habitat specialization to identify the mechanism driving community changes and maintaining local diversity. The loss of rotational grazing networks caused community diversity declines via non-random extinctions of spatially and temporally poor dispersers, particularly among grassland specialists. Temporal seed dispersal halted further community disassembly, maintaining diversity in the abandoned grazing networks. Spatial dispersal within the intact grazing networks was found to be an overriding, homogenizing agent conserving diversity in both the herb layer and seed bank. This empirical evidence establishes how spatial and temporal seed dispersal interact to maintain diversity in fragmented landscapes. Poorly connected grasslands appear limited by spatial dispersal, yet are maintained by temporal seed dispersal. In fragmented landscapes where grazing networks are rarely present, temporal rather than spatial seed dispersal may be more important in maintaining species diversity, since effective spatial dispersal may be significantly diminished. The grazing network's efficacy at boosting spatial dispersal and upholding community diversity presents a powerful management tool to conserve local and regional species diversity.

  • 29. Ruesink, Jennifer L.
    et al.
    Stachowicz, John J.
    Reynolds, Pamela L.
    Boström, Christoffer
    Cusson, Mathieu
    Douglass, James
    Eklöf, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Engelen, Aschwin H.
    Hori, Masakazu
    Hovel, Kevin
    Iken, Katrin
    Moksnes, Per-Olav
    Nakaoka, Masahiro
    O'Connor, Mary I.
    Olsen, Jeanine L.
    Sotka, Erik E.
    Whalen, Matthew A.
    Duffy, J. Emmett
    Form-function relationships in a marine foundation species depend on scale: a shoot to global perspective from a distributed ecological experiment2018In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 127, no 3, p. 364-374Article in journal (Refereed)
    Abstract [en]

    Form-function relationships in plants underlie their ecosystem roles in supporting higher trophic levels through primary production, detrital pathways, and habitat provision. For widespread, phenotypically-variable plants, productivity may differ not only across abiotic conditions, but also from distinct morphological or demographic traits. A single foundation species, eelgrass Zostera marina, typically dominates north temperate seagrass meadows, which we studied across 14 sites spanning 32-61 degrees N latitude and two ocean basins. Body size varied by nearly two orders of magnitude through this range, and was largest at mid-latitudes and in the Pacific Ocean. At the global scale, neither latitude, site-level environmental conditions, nor body size helped predict productivity (relative growth rate 1-2% day(-1) at most sites), suggesting a remarkable capacity of Z. marina to achieve similar productivity in summer. Furthermore, among a suite of stressors applied within sites, only ambient leaf damage reduced productivity; grazer reduction and nutrient addition had no effect on eelgrass size or growth. Scale-dependence was evident in different allometric relationships within and across sites for productivity and for modules (leaf count) relative to size. Zostera marina provides a range of ecosystem functions related to both body size (habitat provision, water flow) and growth rates (food, carbon dynamics). Our observed decoupling of body size and maximum production suggests that geographic variation in these ecosystem functions may be independent, with a future need to resolve how local adaptation or plasticity of body size might actually enable more consistent peak productivity across disparate environmental conditions.

  • 30.
    Salo, Tiina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Swiss Federal Institute of Aquatic Science and Technology, Switzerland.
    Räsänen, Katja
    Stamm, Christian
    Burdon, Francis J.
    Seppälä, Otto
    Simultaneous exposure to a pulsed and a prolonged anthropogenic stressor can alter consumer multifunctionality2018In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 127, no 10, p. 1437-1448Article in journal (Refereed)
    Abstract [en]

    Ecosystems face multiple anthropogenic threats globally, and the effects of these environmental stressors range from individual-level organismal responses to altered system functioning. Understanding the combined effects of stressors on process rates mediated by individuals in ecosystems would greatly improve our ability to predict organismal multifunctionality (e.g. multiple consumer-mediated functions). We conducted a laboratory experiment to test direct and indirect, as well as immediate and delayed effects of a heat wave (pulsed stress) and micropollutants (MPs) (prolonged stress) on individual consumers (the great pond snail Lymnaea stagnalis) and their multifunctionality (i.e. consumption of basal resources, growth, reproduction, nutrient excretion and organic-matter cycling). We found that stressful conditions increased the process rates of multiple functions mediated by individual consumers. Specifically, the artificial heat wave increased process rates in the majority of the quantified functions (either directly or indirectly), whereas exposure to MPs increased consumption of basal resources which led to increases in the release of nutrients and fine particulate organic matter. Moreover, snails exposed to a heat wave showed decreased reproduction and nutrient excretion after the heat-wave, indicating the potential for ecologically relevant delayed effects. Our study indicates that the immediate and delayed effects of stressors on individual organisms may directly and indirectly impact multiple ecosystem functions. In particular, delayed effects of environmental stress on individual consumers may cumulatively impede recovery due to decreased functioning following a perturbation. Reconciling these results with studies incorporating responses at higher levels of biological complexity will enhance our ability to forecast how individual responses upscale to ecosystem multifunctionality.

  • 31.
    Stutz, Rebecca S.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of Sydney, Australia.
    Croak, Benjamin M.
    Proschogo, Nicholas
    Banks, Peter B.
    McArthur, Clare
    Olfactory and visual plant cues as drivers of selective herbivory2017In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 126, no 2, p. 259-268Article in journal (Refereed)
    Abstract [en]

    Food quality is an important consideration in the foraging strategy of all animals, including herbivores. Those that can detect and assess the nutritional value of plants from afar, using senses such as smell and sight, can forage more efficiently than those that must assess food quality by taste alone. Selective foraging not only affects herbivore fitness but can influence the structure and composition of plant communities, yet little is known about how olfactory and visual cues help herbivores to find preferred plants. We tested the ability of a free-ranging, generalist mammalian browser, the swamp wallaby Wallabia bicolor, to use olfactory and visual plant cues to find and/or browse differentially on Eucalyptus pilularis seedlings grown under different nutrient conditions. Low-nutrient seedlings differed from high-nutrient seedlings, having lighter coloured leaves, red stems and lower biomass and nitrogen content. In the absence of visual cues, wallabies used odour to differentiate vials containing cut seedlings. They visited and investigated patches with high-nutrient seedling odour most, followed by patches with low-nutrient seedling odour, and patches with no added odour least. However, when visual and olfactory cues of seedlings were present, wallabies reversed their foraging response and were more likely to browse low- than high-nutrient seedlings. This browsing difference, in turn, disappeared when long-range visual cues were reduced by pinning seedlings horizontal to the ground. We suggest that visual cues overrode the effects of olfactory cues on browsing patterns of intact seedlings. Our study shows that herbivores can respond to odours of higher nutrient plants but in ecologically realistic scenarios they use a variety of visual and olfactory cues, with a context-dependent outcome that is not always selection of high nutrient food. Our results demonstrate the importance of testing the sensory abilities of herbivores in realistic multi-sensory settings to understand their function in selective foraging.

  • 32.
    Svensson, Filip
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Swedish University of Agricultural Sciences, Sweden.
    Karlsson, Erik
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Institute of Coastal Research, Sweden.
    Gårdmark, Anna
    Olsson, Jens
    Adill, Anders
    Zie, Jenny
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Snoeijs-Leijonmalm, Pauline
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Eklöf, Johan S.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    In situ warming strengthens trophic cascades in a coastal food web2017In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 126, no 8, p. 1150-1161Article in journal (Refereed)
    Abstract [en]

    Global warming may affect most organisms and their interactions. Theory and simple mesocosm experiments suggest that consumer top-down control over primary producer biomass should strengthen with warming, since consumer respiration increases faster with warming than plant photosynthesis. However, these predictions have so far not been tested on natural communities that have experienced warming over many generations. Natural systems display a higher diversity, heterogeneity and complexity than mesocosms, which could alter predicted effects of warming. Here we used an artificially heated part of the northern Baltic Sea (the Forsmark Biotest basin) to test how warming influences trophic interactions in a shallow coastal food web with four trophic levels: omnivorous fish, invertivorous fish, herbivorous invertebrates, and filamentous macroalgae. Monitoring of fish assemblages over six years showed that small invertivorous fish (gobiids, sticklebacks and minnows) were much less abundant in the heated basin than in unheated references areas. Stomach content analyses of the dominating omnivorous fish - Eurasian perch Perca fluviatilis - revealed a strikingly different diet within and outside the Biotest basin; gammarid crustaceans were the dominating prey at heated sites, whereas invertivorous fish (e.g. gobiids) dominated at unheated sites. A 45-day cage experiment showed that fish exclusion did not affect the biomass of algal herbivores (gastropods and gammarids), but reduced algal biomass in heated sites (but not unheated). This suggests that warming induced a trophic cascade from fish to algae, and that this effect was mediated by predator-induced changes in herbivore behavior, rather than number. Overall, our study suggests that warming has effectively compressed the food chain from four to three trophic levels (algae, gammarids and perch), which have benefitted the primary producers by reducing grazing pressure. Consequently, warming appears to have restructured this coastal food web through a combination of direct (physiological) and indirect (species interactions) effects.

  • 33.
    Tannerfeldt, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Fluctuating resources and the evolution of litter size in the arctic fox1998In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 83, no 3, p. 545-559Article in journal (Refereed)
    Abstract [en]

    Fluctuations in essential resources cause a strong selection pressure on the ability to adjust parental investment accordingly. In the dog family, Canidae, variance in female prebirth investment is adjusted by litter size. The arctic fox, Alopex lagopus, is a small canid living on the northern tundras of the world. It has the largest known litter size in the order Carnivora. up to 18 young, and litter size is highly variable. We have analysed data From arctic fox populations throughout the species circumpolar range. In some areas, arctic foxes feed on strongly fluctuating populations of small rodents. In contrast, they have more stable food resources at bird cliffs and along coast lines. Food availability determines arctic fos litter and population sizes. A comparison between fluctuating and stable arctic fox populations showed that fluctuations are associated with large litter sizes. There were significant differences in litter size means, maxima and variances, as well as in placental scar count means. We have discussed five hypotheses on the determination of variation in litter size: one energetic, one genetic (based on density variation), one diet-determined, one based on reproductive allocation and one based on differences in reaction norms. Our findings suggest that litter size in the arctic fox is determined by the combined effect of immediate resource levels and the degree of resource predictability. We describe reaction norms that suggest how litter sizes result from adaptive plasticity within each of two genetic strategies where, according to the jackpot hypothesis, populations with unpredictable food resources generally have larger litter sizes. Within each genetic strategy, or reaction norm, litter sizes are adjusted through a number of plastic trails. These traits are influenced by nutritional limitations and include reduced ovulation rates, prenatal losses, and litter size reduction during the lactation period.

  • 34.
    Tegelaar, Karolina
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hagman, Mattias
    Stockholm University, Faculty of Science, Department of Zoology.
    Glinwood, Robert
    Petterson, Jan
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology. Wissenschaftskolleg zu Berlin, Germany.
    Ant-aphid mutualism: the influence of ants on the aphid summer cycle2012In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 121, no 1, p. 61-66Article in journal (Refereed)
    Abstract [en]

    There are few longtime studies on the effects on aphids of being tended by ants. The aim of this study is to investigate how the presence of ants influences settling decisions by colonizing aphids and the post-settlement growth and survival of aphid colonies. We conducted a field experiment using the facultative myrmecophile Aphis fabae and the ant Lasius niger. The experiment relied on natural aphid colonization of potted plants of scentless mayweed Tripleurospermum perforatum placed outdoors. Ants occurred naturally at the field site and had access to half of the pots and were prevented from accessing the remainder. The presence of winged, dispersing aphids, the growth and survival of establishing aphid colonies, and the presence of parasitoids were measured in relation to presence or absence of ants, over a period of five weeks. The presence of ants did not significantly influence the pattern of initial host plant colonization or the initial colony growth, but ant-tended aphids were subject to higher parasitism by hymenopteran parasitoids. The net result over the experimental period was that the presence of ants decreased aphid colony productivity, measured as the number of winged summer migrants produced from the colonized host plants. This implies that aphids do not always benefit from the presence of ants, but under some conditions rather pay a cost in the form of reduced dispersal.

  • 35.
    Toftegaard, Tenna
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Posledovich, Diana
    Stockholm University, Faculty of Science, Department of Zoology.
    Navarro-Cano, José A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Desertification Research Centre (CSIC-UV-GV), Spain.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Variation in plant thermal reaction norms along a latitudinal gradient - more than adaptation to season length2016In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 125, no 5, p. 622-628Article in journal (Refereed)
    Abstract [en]

    Little is known about the extent to which observed phenological responses to changes in climate are the result of phenotypic plasticity or genetic changes. We also know little about how plasticity, in terms of thermal reaction norms, vary spatially. We investigated if the thermal reaction norms for flower development of five crucifer species (Brassicaceae) differed among three regions along a south-north latitudinal gradient in replicated experiments. The mean response (elevation) of thermal reaction norms of flowering differed among regions in all study species, while sensitivity of flower development to temperature (slope) differed in only one of the species. Differences in mean responses corresponded to cogradient patterns in some species, but countergradient patterns in other. This suggests that differences among regions were not solely the result of adaptation to differences in the length of the growing season, but that other factors, such as herbivory, play an important role. Differences in development rate within species were mainly explained by variation in early phases of bud formation in some species but by variation in later phases of bud formation in other species. The differences in latitudinal patterns of thermal reaction norms among species observed in this study are important, both to identify agents of selection and to predict short- and long-term responses to a warming climate.

  • 36.
    Valdés, Alicia
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Direct and plant trait-mediated effects of the local environmental context on butterfly oviposition patterns2018In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 127, no 6, p. 825-833Article in journal (Refereed)
    Abstract [en]

    Variation in the intensity of plant-animal interactions over different spatial scales is widespread and might strongly influence fitness and trait selection in plants. Differences in traits among plant individuals have been shown to influence variation in interaction intensities within populations, while differences in environmental factors and community composition are shown to be important for variation over larger scales. However, little is still known about the relative importance of the local environmental context vs. plant traits for the outcome of interactions within plant populations. We investigated how oviposition by the seed-predator butterfly Phengaris alcon on its host plant Gentiana pneumonanthe was related to host plant traits and to local environmental variation, as well as how oviposition patterns translated into effects on host plant fruit set. We considered the local environmental context in terms of height of the surrounding vegetation and abundance of the butterfly's second host, Myrmica ants. The probability of oviposition was higher in plants that were surrounded by lower vegetation, and both the probability of oviposition and the number of eggs increased in early-flowering and tall plants with many flowers in the three study populations. Flowering phenology, shoot height and flower production were, in turn, related to higher surrounding vegetation. Myrmica abundance was correlated with vegetation height, but had no effect on oviposition patterns. Oviposition and subsequent seed predation by the caterpillars strongly reduced host plant fruit set. Our results show that plant-animal interactions are context-dependent not only because the context influences the abundance or the behavior of the animal interactor, but also because it influences the expression of plant traits that affect the outcome of the interaction. The results also demonstrate that heterogeneity in environmental conditions at a very local scale can be important for the outcomes of interactions.

  • 37. Van Dyck, Hans
    et al.
    Bonte, Dries
    Puls, Rik
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Maes, Dirk
    The lost generation hypothesis: could climate change drive ectotherms into a developmental trap?2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 1, p. 54-61Article in journal (Refereed)
    Abstract [en]

    Climate warming affects the rate and timing of the development in ectothermic organisms. Short-living, ectothermic organisms (including many insects) showing thermal plasticity in life-cycle regulation could, for example, increase the number of generations per year under warmer conditions. However, changed phenology may challenge the way organisms in temperate climates deal with the available thermal time window at the end of summer. Although adaptive plasticity is widely assumed in multivoltine organisms, rapid environmental change could distort the quality of information given by environmental cues that organisms use to make developmental decisions. Developmental traps are scenarios in which rapid environmental change triggers organisms to pursue maladaptive developmental pathways. This occurs because organisms must rely upon current environmental cues to predict future environmental conditions and corresponds to a novel case of ecological or evolutionary traps. Examples of introduced, invasive species are congruent with this hypothesis. Based on preliminary experiments, we argue that the dramatic declines of the wall brown Lasiommata megera in northwestern Europe may be an example of a developmental trap. This formerly widespread, bivoltine (or even multivoltine) butterfly has become a conundrum to conservationist biologists. A split-brood field experiment with L. megera indeed suggests issues with life-cycle regulation decisions at the end of summer. In areas where the species went extinct recently, 100% of the individuals developed directly into a third generation without larval diapause, whereas only 42.5% did so in the areas where the species still occurs. Under unfavourable autumn conditions, the attempted third generation will result in high mortality and eventually a lost or suicidal' third generation in this insect with non-overlapping, discrete generations. We discuss the idea of a developmental trap within an integrated framework for assessing the vulnerability of species to climate change.

  • 38. Vandvik, Vigdis
    et al.
    Klanderud, Kari
    Meineri, Eric
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Bergen, Norway.
    Måren, Inger E.
    Töpper, Joachim
    Seed banks are biodiversity reservoirs: species-area relationships above versus below ground2016In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 125, no 2, p. 218-228Article in journal (Refereed)
    Abstract [en]

    Soil seed banks offer plants the possibility to disperse through time. This has implications for population and community dynamics, as recognised by ecological and evolutionary theory. In contrast, the conservation and restoration literature often find seed banks to be depauperate, weedy and without much conservation value or restoration potential. One explanation for these contrasting views might lie in a systematic bias in the sampling of seed banks versus established plant communities. We use the species-area relationship as a tool to assess and compare the per-area species richness and spatial structuring of the diversity of the established plant community versus soil seed banks. To allow this direct comparison we extensively survey the species-area relationship of the vegetation and underlying seed bank of a grassland community across twelve sites spanning regional bioclimatic gradients. We also compile a global dataset of established vegetation and seed banks from published sources. We find that seed banks have consistently higher intercepts and slopes of the relationship, and hence higher diversity at any given spatial scale, than the vegetation both in the field and literature study. This is consistent across habitat types, climate gradients, and biomes. Similarity indices are commonly used to compare vegetation and seed bank, and we find that sampling effort (% of the vegetation area sampled for seed bank) was the strongest predictor of vegetation-seed bank similarity for both the SOrensen (R-2 = 0.70) and the Raup-Crick (R-2 = 0.25) index. Our study suggests that the perception that seed banks are intrinsically less diverse than established plant communities has been based more on inadequate sampling than on biological reality. Across a range of ecosystems and climatic settings, we find high diversity in seed banks relative to the established community, suggesting potentially important roles of seed banks in population dynamics and diversity maintenance.

  • 39.
    Verschut, Thomas A.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hambäck, Peter A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Anderson, Peter
    Mating affects resource selection and modulates associational effects between neighbouring resourcesIn: Oikos, ISSN 0030-1299, E-ISSN 1600-0706Article in journal (Refereed)
  • 40.
    Verschut, Thomas A.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hambäck, Peter A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Anderson, Peter
    Mating affects resource selection and modulates associational effects between neighbouring resources2017In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 126, no 12, p. 1708-1716Article in journal (Refereed)
    Abstract [en]

    Associational effects occur when the attack rate on a resource depends on neighbouring resources in the environment. These effects are predicted to result from mismatches experienced by the consumer organism in resource selection along hierarchical search levels. As resource selection depends on sensory information used during search behaviour, we expected that different physiological states of an insect might modulate the outcome of associational effects due to differences in resource selection. We used Drosophila melanogaster, as a model organism for olfactory-guided behaviour in insects, to study the effects of mating induced behavioural changes on associational effects between two alternative resources. We found that mating has no effect on the ability of D. melanogaster to locate resource patches, but rather affects the perception of the resources within the patch. Consequently, we only found associational effects in the experiments with unmated females and not in the experiments with mated females. Our results suggest that the lack of associational effects for mated females resulted from changes in the use of short-range olfactory cues, leading to random selection among the resources. In conclusion, our results suggest that the physiological state of an insect modulates associational effects by affecting resource selection rates within the patch.

  • 41.
    von Euler, Tove
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Ågren, Jon
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    Floral display and habitat quality affect cost of reproduction in Primula farinosa2012In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 121, no 9, p. 1400-1407Article in journal (Refereed)
    Abstract [en]

    Costs of reproduction should depend on resource availability and on reproductive effort, which in turn may depend on traits influencing reproductive success. Therefore, variation in both habitat quality and reproductive traits should be considered when assessing reproductive costs. We investigated the effect of habitat quality and floral display on the costs of reproduction in the perennial herb Primula farinosa. In the study area, P. farinosa occurs in habitats that differ in water availability, which strongly influences plant performance. Furthermore, it displays a scape length dimorphism, with two distinct scape morphs differing in attractiveness to pollinators and reproductive success. To test the hypothesis that the cost of fruit production is higher in the long-scaped than in the short-scaped morph, and depends on water availability, we manipulated reproductive investment in eight P. farinosa populations along a gradient of soil moisture. Fruit set was higher in long-scaped individuals, and prevention of fruit set increased flower production in the following year among long-scaped, but not among short-scaped plants. Furthermore, costs of fruit production were evident at low and high moisture levels but not at intermediate levels. The results demonstrate an association between a genetically determined difference in floral display and cost of reproduction, and suggest that costs of reproduction are non-linearly related to water availability. They thus indicate links between the evolution of plant reproductive traits and plant life histories, and between habitat quality and optimal life history.

  • 42. Weigel, Benjamin
    et al.
    Blenckner, Thorsten
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Bonsdorff, Erik
    Maintained functional diversity in benthic communities in spite of diverging functional identities2016In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 125, no 10, p. 1421-1433Article in journal (Refereed)
    Abstract [en]

    Ecological studies based on time-series often investigate community changes centered on species abundance or biomass but rarely expose the consequential functional aspects underlying such changes. Functional diversity measures have proven to be more accurate predictors for ecosystem functioning than traditional taxonomic approaches and hence gained much attention. There are only limited studies available that analyse the functional implications behind decadal changes of entire communities. We studied zoobenthic communities of two habitats, sheltered and exposed, of a coastal system subject to contrasting changes in community composition over the past four decades. Besides eutrophication and climate-related impacts, the system has been invaded by a non-native polycheate Marenzelleria spp., adding altered functional properties to the communities. The functional dispersion (FDis) metric was used as a measure for comparing the functional diversity of the contrasting habitats, with special focus on the role of Marenzelleria for the entire communities. We highlight changes in the functional identity of the communities, expressed as community-weighted means of trait expression (CWM), using multivariate techniques, and investigate the relationship between taxonomic and functional changes. Despite contrasting community developments in the two habitats, with characteristics traditionally suggesting different environmental quality, we found that the FDis in both habitats remained similar and increased with the introduction of Marenzelleria. Although showing maintained functional diversity across time and space, the functional identity (CWM) of communities changed irrespective of taxonomical differences. Examples include inter alia alterations in palatability proxies, feeding position and sediment transportation types, indicating changed functionality of zoobenthos in coastal systems. We show, when focussing on qualitative functional changes of communities, it is important to evaluate the underlying functional identity, and not only rely on measures of the diversity of functions per se, as the quality indication of expressed functional traits can be concealed when using multi-functionality approaches.

  • 43. Xi, Xinqiang
    et al.
    Wu, Xinwei
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Sun, Shucun
    Body size response to warming: time of the season matters in a tephritid fly2016In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 125, no 3, p. 386-394Article in journal (Refereed)
    Abstract [en]

    Whether shrinking body size is a universal response to climate change remains controversial. Moreover, the mechanisms underlying body size shifts are poorly understood. Here, assuming that life history traits evolve to maximize fitness according to life history plasticity theory, we hypothesized that under global warming temperate multivoltine insects should emerge earlier with a smaller body mass in the early growing season, but emerge later with a larger body mass in the late season. We tested this hypothesis by conducting two field artificial warming experiments in an alpine meadow: 1) with one pre-dispersal seed predator species (tephritid flies, Tephritis femoralis) and its two host-plant species flowering in early and late growing seasons, respectively, and 2) with the tephritid flies and one host species with a flowering season that occupies parts of both the early and late growing seasons. These experiments were complemented by a microcosm chamber warming experiment, in which increasing and decreasing temperature trends were set to simulate temperature variation pattern in early and late growing seasons, respectively, but photoperiod was held constant. Warming generally advanced the adult emergence and decreased the body size (adult body mass) in the early season but delayed the emergence and increased the size in the late season in both field experiments, indicating that the seasonally different effects of warming on the fly body size was constant regardless of host-plant identity. The chamber warming resulted in consistent responses of emerging timing and body size to the simulated seasonal warming, demonstrating that the temperature increase per se and its interaction with direction of temperature change, but not other correlated effects, should be primarily responsible for the observed contrasting shifts of body size at different times of the season. Our results indicate that taking into account temperate seasonal patterns of temperature variation could be of general importance for predicting animal body size changes in the warmed future.

  • 44.
    Östergård, Hannah
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Hambäck, Peter
    Stockholm University, Faculty of Science, Department of Botany.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    Responses of a specialist and a generalist seed predator to variation in their common resource2009In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 118, p. 1471-1476Article in journal (Refereed)
1 - 44 of 44
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