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  • 1.
    Andersson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Berga, Mercè
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    The spatial structure of bacterial communities is influenced by historical environmental conditions2014In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 95, no 5, p. 1134-1140Article in journal (Refereed)
    Abstract [en]

    The spatial structure of ecological communities, including that of bacteria, is often influenced by species sorting by contemporary environmental conditions. Moreover, historical processes, i.e., ecological and evolutionary events that have occurred at some point in the past, such as dispersal limitation, drift, priority effects, or selection by past environmental conditions, can be important, but are generally investigated much less. Here, we conducted a field study using 16 rock pools, where we specifically compared the importance of past vs. contemporary environmental conditions for bacterial community structure by correlating present differences in bacterial community composition among pools to environmental conditions measured on the same day, as well as to those measured 2, 4, 6, and 8 d earlier. The results prove that selection by past environmental conditions exists, since we were able to show that bacterial communities are, to a greater extent, an imprint of past compared to contemporary environmental conditions. We suggest that this is the result of a combination of different mechanisms, including priority effects that cause rapid adaptation to new environmental conditions of taxa that have been initially selected by past environmental conditions, and slower rates of turnover in community composition compared to environmental conditions.

  • 2. Araújo, M.S.
    et al.
    Guimarães, P.R.
    Svanbäck, R.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Pinheiro, A.
    Guimarães, P.
    Dos Reis, S.F.
    Bolnick, D.I.
    Network analysis reveals contrasting effects of intraspecific competition on individual versus population diets2008In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 89, no 7, p. 1981-1993Article in journal (Refereed)
    Abstract [en]

    Optimal foraging theory predicts that individuals should become more opportunistic when intraspecific competition is high and preferred resources are scarce. This density-dependent diet shift should result in increased diet breadth for individuals as they add previously unused prey to their repertoire. As a result, the niche breadth of the population as a whole should increase. In a recent study, R. Svanback and D. I. Bolnick confirmed that intraspecific competition led to increased population diet breadth in threespine stickleback (Gasterosteus aculeatus). However, individual diet breadth did not expand as resource levels declined. Here, we present a new method based on complex network theory that moves beyond a simple measure of diet breadth, and we use the method to reexamine the stickleback experiment. This method reveals that the population as a whole added new types of prey as stickleback density was increased. However, whereas foraging theory predicts that niche expansion is achieved by individuals accepting new prey in addition to previously preferred prey, we found that a subset of individuals ceased to use their previously preferred prey, even though other members of their population continued to specialize on the original prey types. As a result, populations were subdivided into groups of ecologically similar individuals, with diet variation among groups reflecting phenotype-dependent changes in foraging behavior as prey density declined. These results are consistent with foraging theory if we assume that quantitative trait variation among consumers affects prey preferences, and if cognitive constraints prevent individuals from continuing to use their formerly preferred prey while adding new prey.

  • 3.
    Arnqvist, Göran
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Johansson, F
    Ontogenetic reaction norms of predator-induced defensive morphology in dragonfly larvae1998In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 79, no 6, p. 1847-1858Article in journal (Refereed)
  • 4.
    Bartels, Pia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Cucherousset, Julien
    Steger, Kristin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Eklöv, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Hillebrand, Helmut
    Reciprocal subsidies between freshwater and terrestrial ecosystems structure consumer-resource dynamics2012In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 93, no 5, p. 1173-1182Article in journal (Refereed)
    Abstract [en]

    Cross-ecosystem movements of material and energy, particularly reciprocal resource fluxes across the freshwater-land interface, have received major attention. Freshwater ecosystems may receive higher amounts of subsidies (i.e., resources produced outside the focal ecosystem) than terrestrial ecosystems, potentially leading to increased secondary production in freshwaters. Here we used a meta-analytic approach to quantify the magnitude and direction of subsidy inputs across the freshwater-land interface and to determine subsequent responses in recipient animals. Terrestrial and freshwater ecosystems differed in the magnitude of subsidies they received, with aquatic ecosystems generally receiving higher subsidies than terrestrial ecosystems. Surprisingly, and despite the large discrepancy in magnitude, the contribution of these subsidies to animal carbon inferred from stable isotope composition did not differ between freshwater and terrestrial ecosystems, likely due to the differences in subsidy quality. The contribution of allochthonous subsidies was highest to primary consumers and predators, suggesting that bottom-up and top-down effects may be affected considerably by the input of allochthonous resources. Future work on subsidies will profit from a food web dynamic approach including indirect trophic interactions and propagating effects.

  • 5. Beisner, Beatrix E.
    et al.
    Peres-Neto, Pedro R.
    Lindström, Eva S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Barnett, Alain
    Longhi, Maria Lorena
    The role of environmental and spatial processes in structuring lake communities from bacteria to fish2006In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 87, no 12, p. 2985-2991Article in journal (Refereed)
    Abstract [en]

    We assessed the relative roles of local environmental conditions and dispersal on community structure in a landscape of lakes for the major trophic groups. We use taxonomic presence–absence and abundance data for bacteria, phytoplankton, zooplankton, and fish from 18 lakes in southern Quebec, Canada. The question of interest was whether communities composed of organisms with more limited dispersal abilities, because of size and life history (zooplankton and fish) would show a different effect of lake distribution than communities composed of good dispersers (bacteria and phytoplankton). We examine the variation in structure attributable to local environmental (i.e., lake chemical and physical variables) vs. dispersal predictors (i.e., overland and watercourse distances between lakes) using variation partitioning techniques. Overall, we show that less motile species (crustacean zooplankton and fish) are better predicted by spatial factors than by local environmental ones. Furthermore, we show that for zooplankton abundances, both overland and watercourse dispersal pathways are equally strong, though they may select for different components of the community, while for fish, only watercourses are relevant dispersal pathways. These results suggest that crustacean zooplankton and fish are more constrained by dispersal and therefore more likely to operate as a metacommunity than are bacteria and phytoplankton within this studied landscape.

  • 6.
    Berglund, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Sex-change by a polychaete: effects of social and reproductive costs1986In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 67, no 4, p. 837-845Article in journal (Refereed)
  • 7.
    Carreira, B. M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology. Univ Lisbon, cE3c Ctr Ecol Evolut & Environm Changes, Fac Ciencias, Bloco C2, P-1749016 Lisbon, Portugal.
    Segurado, P.
    Univ Lisbon, Inst Super Agron, Ctr Estudos Florestais, P-1349017 Lisbon, Portugal..
    Orizaola, German
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Goncalves, N.
    Univ Lisbon, cE3c Ctr Ecol Evolut & Environm Changes, Fac Ciencias, Bloco C2, P-1749016 Lisbon, Portugal..
    Pinto, V.
    Univ Lisbon, cE3c Ctr Ecol Evolut & Environm Changes, Fac Ciencias, Bloco C2, P-1749016 Lisbon, Portugal..
    Laurila, Anssi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Rebelo, R.
    Univ Lisbon, cE3c Ctr Ecol Evolut & Environm Changes, Fac Ciencias, Bloco C2, P-1749016 Lisbon, Portugal..
    Warm vegetarians?: Heat waves and diet shifts in tadpoles2016In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 97, no 11, p. 2964-2974Article in journal (Refereed)
    Abstract [en]

    Temperature can play an important role in determining the feeding preferences of ectotherms. In light of the warmer temperatures arising with the current climatic changes, omnivorous ectotherms may perform diet shifts toward higher herbivory to optimize energetic intake. Such diet shifts may also occur during heat waves, which are projected to become more frequent, intense, and longer lasting in the future. Here, we investigated how heat waves of different duration affect feeding preferences in omnivorous anuran tadpoles and how these choices affect larval life history. In laboratory experiments, we fed tadpoles of three species on animal, plant, or mixed diet and exposed them to short heat waves (similar to the heat waves these species experience currently) or long heat waves (predicted to increase under climate change). We estimated the dietary choices of tadpoles fed on the mixed diet using stable isotopes and recorded tadpole survival and growth, larval period, and mass at metamorphosis. Tadpole feeding preferences were associated with their thermal background, with herbivory increasing with breeding temperature in nature. Patterns in survival, growth, and development generally support decreased efficiency of carnivorous diets and increased efficiency or higher relative quality of herbivorous diets at higher temperatures. All three species increased herbivory in at least one of the heat wave treatments, but the responses varied among species. Diet shifts toward higher herbivory were maladaptive in one species, but beneficial in the other two. Higher herbivory in omnivorous ectotherms under warmer temperatures may impact species differently and further contribute to changes in the structure and function of freshwater environments.

  • 8.
    Dahlgren, Johan P.
    et al.
    Univ Southern Denmark, Max Planck Odense Ctr Biodemog Aging, Dept Biol, Campusvej 55, DK-5230 Odense M, Denmark..
    Bengtsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ehrlen, Johan
    Stockholm Univ, Dept Ecol Environm & Plant Sci, SE-10691 Stockholm, Sweden..
    The demography of climate-driven and density-regulated population dynamics in a perennial plant2016In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 97, no 4, p. 899-907Article in journal (Refereed)
    Abstract [en]

    Identifying the internal and external drivers of population dynamics is a key objective in ecology, currently accentuated by the need to forecast the effects of climate change on species distributions and abundances. The interplay between environmental and density effects is one particularly important aspect of such forecasts. We examined the simultaneous impact of climate and intraspecific density on vital rates of the dwarf shrub Fumana procumbens over 20 yr, using generalized additive mixed models. We then analyzed effects on population dynamics using integral projection models. The population projection models accurately captured observed fluctuations in population size. Our analyses suggested the population was intrinsically regulated but with annual fluctuations in response to variation in weather. Simulations showed that implicitly assuming variation in demographic rates to be driven solely by the environment can overestimate extinction risks if there is density dependence. We conclude that density regulation can dampen effects of climate change on Fumana population size, and discuss the need to quantify density dependence in predictions of population responses to environmental changes.

  • 9.
    de Kroon, Hans
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    van Groenendael, Jan M.
    Ehrlén, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Elasticities: a review of methods and model limitations2000In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 81, no 3, p. 607-618Article in journal (Refereed)
    Abstract [en]

    Elasticity is a perturbation measure in matrix projection models that quantifiesthe proportional change in population growth rate as a function of a proportionalchange in a demographic transition (growth, survival, reproduction, etc.). Elasticities thusindicate the relative "importance" of life cycle transitions for population growth and maintenance.In this paper, we discuss the applications of elasticity analysis, and its extension,loop analysis, in life history studies and conservation. Elasticity can be interpreted as therelative contribution of a demographic parameter to population growth rate. Loop analysisreveals the underlying pathway structure of the life cycle graph. The different kinds ofresults of the two analyses in studies of life histories are emphasized. Because elasticitiesquantify the relative importance of life cycle transitions to population growth rate, it isgenerally inferred that management should focus on the transitions with the largest elasticities.Such predictions based on elasticities seem robust, but we do identify three situationswhere problems may arise. The mathematical properties and biological constraints thatunderlie these pitfalls are explained. Examples illustrate the additional information thatneeds to be taken into account for a sensible use of elasticities in population management.We conclude by indicating topics that are in need of research.

  • 10.
    Diehl, Sebastian
    et al.
    Umeå University, Department of Animal Ecology.
    Eklöv, Peter
    Umeå University, Department of Animal Ecology.
    EFFECTS OF PISCIVORE-MEDIATED HABITAT USE ON RESOURCES, DIET, AND GROWTH OF PERCH1995In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 76, no 6, p. 1712-1726Article in journal (Refereed)
    Abstract [en]

    We investigated experimentally how presence or absence of different piscivores influenced habitat use, diet, and individual growth of two size classes of juvenile perch (Perca fluviatilis) and abundances of juvenile perch resources in different habitats. Pond enclosures encompassed 3 X 6 m of dense vegetation and 9 X 6 m of open habitat, and were stocked with 75 young-of-year and 30 1-yr-old perch and with either three piscivorous perch, three northern pike (Esox lucius), or no piscivores. Northern pike were both larger and possessed a larger gape than piscivorous perch. To isolate behavioral responses of juvenile perch to piscivores, we replaced consumed young-of-year perch. Prey fish mortality was lowest without piscivores and highest with northern pike. Young-of-year perch increased their use of vegetation in the presence of both piscivores, whereas 1-yr-old perch increased their use of vegetation only with northern pike. For both age classes of prey fish, increased use of the vegetation led to reduced individual growth, owing to two complementary mechanisms. First, the physical complexity of submerged macrophytes likely interfered with the benthic feeding of perch, Second, increased use of the (relatively small) vegetated habitat increased the mean density experienced by prey fish. Piscivore-induced changes of prey fish densities in the two habitats had substantial effects on the biomass of prey fish resources in the open habitat, but only minor effects in the vegetation. Sialis lutaria, the major predatory macroinvertebrate (approximate to 50% of total macroinvertebrate biomass in the open habitat), and total predatory macroinvertebrates were positively affected by piscivores in the open habitat, but not in the vegetation. Chironomids (<3% of total macroinvertebrate biomass in the vegetation) and the sizes of nonpredatory macroinvertebrates were negatively affected by piscivores in the vegetation, but not in the open habitat. Biomass of nonpredatory macroinvertebrates, Cladocera, and Copepoda did not differ among treatments in either habitat. From our review of field experiments, vulnerable prey fish always change their habitat use in the presence of piscivores. Behaviorally mediated indirect effects of piscivores on individual growth rates and prey fish resources were just as frequently observed as direct effects of piscivores on prey fish survival.

  • 11.
    Edelfeldt, Stina
    et al.
    Univ Southern Denmark, Dept Biol, Campusvej 55, DK-5230 Odense M, Denmark;Univ Southern Denmark, Interdisciplinary Ctr Populat Dynam, Campusvej 55, DK-5230 Odense M, Denmark.
    Bengtsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Dahlgren, Johan P.
    Univ Southern Denmark, Dept Biol, Campusvej 55, DK-5230 Odense M, Denmark;Univ Southern Denmark, Interdisciplinary Ctr Populat Dynam, Campusvej 55, DK-5230 Odense M, Denmark.
    Demographic senescence and effects on population dynamics of a perennial plant2019In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 100, no 8, article id e02742Article in journal (Refereed)
    Abstract [en]

    Demographic rates in plants are usually assumed to be more stage or size dependent than age dependent, and aging is therefore not considered in demographic models. However, little is known about the effect of age on demographic rates, as there still are few studies based on long-term individual-based plant population data that consider both individual age and size. In addition, little is known about how aging of individuals may affect population dynamics. We present analyses of demographic data for three populations of Fumana procumbens collected 1985-2013, on individuals with known year of germination. We modeled age- and size-dependence of the vital rates of survival, growth, fruiting probability, and fruit number using thin plate spline regressions, and constructed an age x size integral projection model (IPM) to project population-level effects of aging. We found strong correlations between age and vital rates in solely age-based vital rate models, where vital rates initially increased with age, after which they stabilized and, in some cases, eventually declined. In survival models with both age and size, the effects of age were statistically significant, whereas size effects were insignificant at two of the sites. For other vital rates, most of the effect of age could be explained by size alone. In addition, including the age effects on survival in the IPM led to lower population growth rates compared to predictions of a size-only IPM. These results illustrate that demographic senescence does occur in perennial plants, which has only been demonstrated clearly in a few recent detailed studies. Moreover, we show that population projections may be overly optimistic if they do not consider plant age. We conclude that the possibility of demographic senescence should be considered in demographic population models, such as those used in viability analyses of threatened species.

  • 12.
    Ehrlén, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    The dynamics of plant populations: does the history of individuals matter?2000In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 81, no 6, p. 1675-1684Article in journal (Refereed)
    Abstract [en]

    Historical events have been used to explain a wide range of phenomenaincluding geographical distributions of species, community diversity, and population structure.At the level of individuals, historical effects in which past conditions influence futureperformance are particularly likely to occur in long-lived organisms that store resourcesbetween seasons and that form organs months or years before their elaboration. Such carryovermechanisms have been documented in several perennial plant species, but the implicationsfor population processes are poorly known. In this study, I examine how the historyof individuals influences their future performance, population dynamics, and life cycle,structure in the long-lived herb Lathyrus vernus. Overall effects of plant history on populationdynamics, in terms of growth rate, reproductive values, stable stage distribution,and elasticities, are examined by comparing an ordinary first-order matrix model with asecond-order matrix model. In the latter, not only the present state of individuals, but alsotheir past state is allowed to influence future fate.The results demonstrate that the history of individuals is sometimes important in modelsof population dynamics. Plant size change over a one-year period was negatively correlatedamong time intervals. Addition of the previous year's stage in population models shiftedthe growth rate from positive (X = 1.010) to negative (X = 0.986) and increased theproportion of small established individuals in the stable stage distribution. If historicaleffects are due to a capacity to buffer environmental variation and regain size or state, asin L. vernus, then recruitment contributes less and stasis more to population growth thansuggested by ahistorical models. The presence of historical effects at the level of individuals,in any form, may have important consequences for population development and should beincluded in any interpretation of the life-cycle structure.

  • 13.
    Ehrlén, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Eriksson, O
    Dispersal limitation and patch occupancy in forest herbs2000In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 81, p. 1667-1674Article in journal (Refereed)
    Abstract [en]

    The distribution of species depends on the availability of suitable habitats, the capacity to disperse to these habitats, and the capacity of populations to persist after establishment. Dispersal limitation implies that not all suitable habitat patches will be occupied by a species. However, the extent to which dispersal limits local distribution is poorly known. In this study, we transplanted seeds, bulbils, and juvenile plants to examine patterns of dispersal limitation and patch occupancy in seven temperate-forest herbs. Recruitment was recorded during four years in 48 patches. The investigated species varied considerably in their natural abundance in the patches. Patterns of seedling emergence and establishment among patches were not related to any of nine investigated abiotic factors. In contrast, the availability of seeds or bulbils was found to limit recruitment in six of the investigated species. Establishment was also successful in many patches where the species did not occur naturally. Estimated patch occupancy in the investigated species ranged from 17.2% to 94.6%. Seed size was positively correlated with the probability of successful establishment of seeds and negatively correlated with patch occupancy. The results suggest that dispersal limitation is an important structuring factor in temperate-forest herb communities. The distribution of species can be perceived as the result of processes operating both among and within patches. Seed size is a key trait in these processes.

  • 14. Emerson, Brent C.
    et al.
    Kolm, Niclas
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Species diversity can drive speciation: reply2007In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 88, no 8, p. 2135-2138Article in journal (Refereed)
  • 15.
    Granath, Gustaf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Strengbom, Joachim
    Rydin, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Rapid ecosystem shifts in peatlands: Linking plant physiology and succession2010In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 91, no 10, p. 3047-3056Article in journal (Refereed)
    Abstract [en]

    Stratigraphic records from peatlands suggest that the shift from a rich fen (calcareous fen) to an ombrotrophic bog can occur rapidly. This shift constitutes a switch from a species-rich ecosystem to a species-poor one with greater carbon storage. In this process, the invasion and expansion of acidifying bog species of Sphagnum (peat mosses) play a key role. To test under what conditions an acidifying bog species could invade a rich fen, we conducted three experiments, contrasting the bog species S. fucsum with the rich-fen species S. warnstorfii and S. teres. We first tested the effect of calcareous water by growing the three species at different constant height above the water table (HWT; 2, 7, and 14 cm) in a rich-fen pool and measured maximum photosynthetic rate and production and difference in length growth as an indicator of competition. In none of the species was the photosynthetic capacity negatively affected when placed at low HWT, but S. fuscum was a weaker competitor at low HWT. In our second experiment we transplanted the three species into microhabitats with different and naturally varying HWT in a rich fen. Here, S. fuscum nearly ceased to photosynthesize when transplanted to low HWT (brown moss carpet), while it performed similarly to the two rich-fen species at the intermediate level (S. warnstorfii hummock level). In contrast to S. fuscum, the rich-fen sphagna performed equally well in both habitats. The brown moss carpet was seasonally flooded, and in our third experiment we found that S. fuscum, but not S. teres, was severely damaged when submerged in rich-fen water. Our results suggest two thresholds in HWT affecting the ecosystem switch: one level that reduces the risk of submergence and a higher one that makes bog sphagna competitive against the rich-fen species.

  • 16. Hambäck, PA
    et al.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Plant Ecology.
    Ericson, L
    Associational resistance: insect damage to purple loosestrife reduced in thickets of sweet gale2000In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 81, no 7, p. 1784-1794Article in journal (Refereed)
    Abstract [en]

    Associational resistance occurs when herbivore damage to a focal plant is reduced by the presence of other plant species. Neighboring plants can reduce herbivore damage (1) by their effects on the predator community, (2) by reducing the ability of herbivores to find their host plants, and (3) by reducing the time herbivores remain on their host plants. We examined how the presence of the aromatic low shrub Myrica gale and of predatory lady beetles affected herbivore damage and reproductive output in a population of the perennial herb Lythrum salicaria in northern Sweden. An observational study showed that L. salicaria growing in Myrica thickets were less damaged by herbivores, had a lower abundance of the monophagous, leaf-feeding, chrysomelid beetle Galerucella calmariensis, and had higher flower and seed production than L. salicaria outside Myrica thickets. To test whether these differences could be explained by (a) differences in some aspect of plant quality, or (b) differences in predator abundance, we placed potted L. salicaria within and outside Myrica thickets. To determine whether differences in the abundance of G. calmariensis were primarily the result of different rates of colonization or emigration, we marked adult beetles and placed them on a second set of potted plants in the two micro-habitats. The results show that differences in herbivore abundance, plant damage, and reproductive output between potted L. salicaria placed within and outside Myrica thickets were in the same direction and of the same magnitude as those observed for naturally occurring plants, indicating that the observed patterns were not an effect of differences in the chemical composition of the host plant. Moreover, we found no support for the hypothesis that a higher abundance of insect predators could explain the lower abundance of G. calmariensis on L. salicaria in Myrica thickets. On the contrary, lady beetles (Coccinella quinqempunctata and Coccinella septempunctata) were observed on a greater proportion of the plants placed outside the Myrica thickets. The monitoring of marked beetles indicated that differences in the abundance of G. calmariensis were the result of a markedly higher colonization rate and a somewhat lower emigration rate from L. salicaria outside Myrica thickets. Outside the Myrica thickets, the survival of G. calmariensis and the magnitude of herbivore damage were lower, and fruit and seed output were higher on plants with observations of lady beetles than on plants without lady beetles. The results indicate that the abundance of the specialist herbivore G. calmariensis, and the herbivore damage and reproductive output of its host plant, L. salicaria, are affected both by the presence of the nonhost Myrica and by predation from lady beetles. We suggest that the most likely mechanism causing decreased feeding on L. salicaria growing in Myrica thickets is that Myrica affects the ability of G. calmariensis to find its host, either through visual or olfactory interference.

  • 17.
    Hedwall, Per-Ola
    et al.
    Swedish Univ Agr Sci, Southern Swedish Forest Res Ctr, Sundsvagen 3, SE-23053 Alnarp, Sweden..
    Brunet, Jörg
    Swedish Univ Agr Sci, Southern Swedish Forest Res Ctr, Sundsvagen 3, SE-23053 Alnarp, Sweden..
    Rydin, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Peatland plant communities under global change: negative feedback loops counteract shifts in species composition2017In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 98, no 1, p. 150-161Article in journal (Refereed)
    Abstract [en]

    Mires (bogs and fens) are nutrient-limited peatland ecosystems, the vegetation of which is especially sensitive to nitrogen deposition and climate change. The role of mires in the global carbon cycle, and the delivery of different ecosystem services can be considerably altered by changes in the vegetation, which has a strong impact on peat-formation and hydrology. Mire ecosystems are commonly open with limited canopy cover but both nitrogen deposition and increased temperatures may increase the woody vegetation component. It has been predicted that such an increase in tree cover and the associated effects on light and water regimes would cause a positive feed-back loop with respect to the ground vegetation. None of these effects, however, have so far been confirmed in large-scale spatiotemporal studies. Here we analyzed data pertaining to mire vegetation from the Swedish National Forest Inventory collected from permanent sample plots over a period of 20 yr along a latitudinal gradient covering 14 degrees. We hypothesized that the changes would be larger in the southern parts as a result of higher nitrogen deposition and warmer climate. Our results showed an increase in woody vegetation with increases in most ericaceous dwarf-shrubs and in the basal area of trees. These changes were, in contrast to our expectations, evenly distributed over most of the latitudinal gradient. While nitrogen deposition is elevated in the south, the increase in temperatures during recent decades has been larger in the north. Hence, we suggest that different processes in the north and south have produced similar vegetation changes along the latitudinal gradient. There was, however, a sharp increase in compositional change at high deposition, indicating a threshold effect in the response. Instead of a positive feed-back loop caused by the tree layer, an increase in canopy cover reduced the changes in composition of the ground vegetation, whereas a decrease in canopy cover lead to larger changes. Increased natural disturbances of the tree layer due to, for example, pathogens or climate is a predicted outcome of climate change. Hence, these results may have important implications for predictions of long-term effects of increased temperature on peatland vegetation.

  • 18. Johnson, Steven D.
    et al.
    Peter, Craig I.
    Nilsson, L. Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Pollination success in a deceptive orchid is enhanced by co-ocurring rewarding magnet plants2003In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 84, no 11, p. 2919-2927Article in journal (Refereed)
    Abstract [en]

    It has been debated whether pollination success in nonrewarding plants that flower in association with nectar-producing plants will be diminished by competition for pollinator visits or, alternatively, enhanced through increased local abundance of pollinators (the magnet species effect). We experimentally evaluated these effects using the nonrewarding bumblebee-pollinated orchid Anacamptis morio and associated nectar-producing plants at a site in Sweden. Pollination success (estimated as pollen receipt and pollen removal) in A. morio was significantly greater for individuals translocated to patches of nectar-producing plants (Geum rivale and Allium schoenoprasum) than for individuals placed outside (20 m away) such patches. These results provide support for the existence of a facilitative magnet species effect in the interaction between certain nectar plants and A. morio. To determine the spatial scale of these interactions, we correlated the visitation rate to flowers of A. morio with the density of sympatric nectar plants in 1-m2 and 100-m2 plots centered around groups of translocated plants, and at the level of whole meadows (0.5–2 ha). Visitation rate to flowers of A. morio was not correlated with the 1-m2 patch density of G. rivale and A. schoenoprasum, but showed a significant positive relationship with density of these nectar plants in 100-m2 plots. In addition, visitation to flowers of A. morio was strongly and positively related to the density of A. schoenoprasum at the level of the meadow. Choice experiments showed that bees foraging on the purple flowers of A. schoenoprasum (a particularly effective magnet species) visit the purple flowers of A. morio more readily (47.6% of choices) than bees foraging on the yellow flowers of Lotus corniculatus (17% of choices). Overall similarity in flower color and shape may increase the probability that a pollinator will temporarily shift from a nectar-producing “magnet” plant to a nonrewarding plant. We discuss the possibility of a mimicry continuum between those orchids that exploit instinctive food-seeking behavior of pollinators and those that show an adaptive resemblance to nectar-producing plants.

  • 19. Kivela, Sami M.
    et al.
    Seppanen, Janne-Tuomas
    Ovaskainen, Otso
    Doligez, Blandine
    Gustafsson, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Monkkonen, Mikko
    Forsman, Jukka T.
    The past and the present in decision-making: the use of conspecific and heterospecific cues in nest site selection2014In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 95, no 12, p. 3428-3439Article in journal (Refereed)
    Abstract [en]

    Nest site selection significantly affects fitness, so adaptations for assessment of the qualities of available sites are expected. The assessment may be based on personal or social information, the latter referring to the observed location and performance of both conspecific and heterospecific individuals. Contrary to large-scale breeding habitat selection, small-scale nest site selection within habitat patches is insufficiently understood. We analyzed nest site selection in the migratory Collared Flycatcher Ficedula albicollis in relation to present and past cues provided by conspecifics and by resident tits within habitat patches by using long-term data. Collared Flycatchers preferred nest boxes that were occupied by conspecifics in the previous year. This preference was strongest in breeding pairs where both individuals bred in the same forest patch in the previous year. The results also suggest preference for nest boxes close to boxes where conspecifics had a high breeding success in the previous year, and for nest boxes which are presently surrounded by a high number of breeding Great Tits Parus major. The results indicate social information use in nest site selection at a small spatial scale, where Collared Flycatchers use conspecific cues with a time lag of one year and heterospecific cues instantly.

  • 20.
    Langenheder, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Ragnarsson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    The role of environmental and spatial factors for the composition of aquatic bacterial communities2007In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 88, no 9, p. 2154-2161Article in journal (Refereed)
    Abstract [en]

    This study investigates the importance of local vs. spatial factors on bacterial community composition of 35 rock pools at the Baltic Sea coast. The pools were located in five distinct spatial clusters over a total scale of <500 m and differed widely in terms of water chemistry. To determine the fractions of the variance in bacterial community composition (BCC) between rock pools that are explained by local environmental vs. spatial factors, a variance partitioning procedure using partial canonical correspondence analysis was performed. Three environmental variables (salinity, chlorophyll a concentration, and water color) had a significant effect on BCC, irrespective of the spatial location of the pools. Vice versa, there was a significant effect of spatial factors on BCC irrespective of any of the environmental factors included in this study. Hence, the patchy spatial distribution of the pools was partly reflected in the composition of the bacterial communities in the pools, which might be caused by congruent colonization events of adjacent pools, such as simultaneous sea-spray inputs or direct exchange of bacteria via connecting rivulets. This study shows that the composition of planktonic bacteria can show provincialism at small spatial scales, which is likely to be caused by -environmental conditions as well as historical events.

  • 21. Lasky, Jesse R.
    et al.
    Bachelot, Bénédicte
    Muscarella, Robert
    Schwartz, Naomi B.
    Forero-Montaña, Jimena
    Nytch, Christopher J.
    Swenson, Nathan Garrick
    Thompson, Jill
    Zimmerman, Jess K.
    Uriarte, María
    Ontogenetic shifts in trait-mediated mechanisms of plant community assembly2015In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 96Article in journal (Refereed)
    Abstract [en]

    Identifying the processes that maintain highly diverse plant communities remains a central goal in ecology. Species variation in growth and survival rates across ontogeny, represented by tree size classes, and life history stage-specific niche partitioning, are potentially important mechanisms for promoting forest diversity. However, the role of ontogeny in mediating competitive dynamics and promoting functional diversity is not well understood, particular in high-diversity systems such as tropical forests. The interaction between interspecific functional trait variation and ontogenetic shifts in competitive dynamics may yield insights into the ecophysiological mechanisms promoting community diversity. We investigated how functional trait (seed size, maximum height, SLA, leaf N and wood density) associations with growth and survival and response to competing neighbors, differ among seedlings and two size classes of trees in a subtropical rainforest in Puerto Rico. We used a hierarchical Bayes model of diameter growth and survival to infer trait relationships with ontogenetic change in competitive dynamics. Traits were more strongly associated with average growth and survival than with neighborhood interactions, and were highly consistent across ontogeny for most traits. The associations between trait values and tree responses to crowding by neighbors showed significant shifts as trees grew. Large trees exhibited greater growth as the difference in species trait values among neighbors increased, suggesting trait-associated niche partitioning was important for the largest size class. Our results identify potential axes of niche partitioning and performance-equalizing functional tradeoffs across ontogeny, promoting species coexistence in this diverse forest community.

  • 22.
    Laurila, Anssi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Lindgren, Beatrice
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Laugen, Ane Timenes
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
    Antipredator defenses along a latitudinal gradient in Rana temporaria2008In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 89, no 5, p. 1399-1413Article in journal (Refereed)
    Abstract [en]

    Antipredator defenses are expected to decrease toward higher latitudes because predation rates are predicted to decrease with latitude. However, latitudinal variation in predator avoidance and defense mechanisms has seldom been studied. We studied tadpole antipredator defenses in seven Rana temporaria populations collected along a 1500-km latitudinal gradient across Sweden, along which previous studies have found increasing tadpole growth and development rates. In a laboratory common garden experiment, we measured behavioral and morphological defenses by raising tadpoles in the presence and absence of a predator (Aeshna dragonfly larva) in two temperature treatments. We also estimated tadpole survival in the presence of free-ranging predators and compared predator densities between R. temporaria breeding ponds situated at low and high latitudes. Activity and foraging were generally positively correlated with latitude in the common garden experiment. While all populations responded to predator presence by decreasing activity and foraging, high-latitude populations maintained higher activity levels in the presence of the predator. All populations exhibited defensive morphology in body and tail shape. However, whereas tail depth tended to increase with latitude in the presence of predator, it did not change with latitude in the absence of the predator. Predator presence generally increased larval period and decreased growth rate. In the southern populations, predator presence tended to have a negative effect on metamorphic size, whereas in the northern populations predators had little or a positive effect on size. Latitude of origin had a strong effect on survival in the presence of a free-ranging predator, with high-latitude tadpoles experiencing higher mortality than those from the low latitudes. In the wild, predator densities were significantly lower in high-latitude than in mid-latitude breeding ponds. Although the higher activity level in the northern populations seems to confer a significant survival disadvantage under predation risk, it is probably needed to maintain the high growth and development rates. However, the occurrence of R. temporaria at high latitudes may be facilitated by the lower predator densities in the north.

  • 23.
    Lindström, Eva S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Eiler, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Drakare, Stina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Ragnarsson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Does ecosystem size determine aquatic bacterial richness? Comment2007In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 88, no 1, p. 252-253Article in journal (Refereed)
  • 24.
    Mehner, Thomas
    et al.
    Leibniz‐Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany.
    Lischke, Betty
    Leibniz‐Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany.
    Scharnweber, Kristin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Leibniz‐Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany.
    Attermeyer, Katrin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Leibniz‐Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany.
    Brothers, Soren
    Leibniz‐Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany;Department of Watershed Sciences and Ecology Center, Utah State University, Logan, Utah, USA.
    Gaedke, Ursula
    Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany.
    Hilt, Sabine
    Leibniz‐Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany.
    Brucet, Sandra
    Aquatic Ecology Group, University of Vic – Central University of Catalonia, Vic, Barcelona, Catalonia, Spain;Catalan Institution for Research and Advanced Studies ICREA, Barcelona, Catalonia, Spain.
    Empirical correspondence between trophic transfer efficiency in freshwater food webs and the slope of their size spectra2018In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 99, no 6, p. 1463-1472Article in journal (Refereed)
    Abstract [en]

    The density of organisms declines with size, because larger organisms need more energy than smaller ones and energetic losses occur when larger organisms feed on smaller ones. A potential expression of density-size distributions are Normalized Biomass Size Spectra (NBSS), which plot the logarithm of biomass independent of taxonomy within bins of logarithmic organismal size, divided by the bin width. Theoretically, the NBSS slope of multi-trophic communities is exactly - 1.0 if the trophic transfer efficiency (TTE, ratio of production rates between adjacent trophic levels) is 10% and the predator-prey mass ratio (PPMR) is fixed at 10(4). Here we provide evidence from four multi-trophic lake food webs that empirically estimated TTEs correspond to empirically estimated slopes of the respective community NBSS. Each of the NBSS considered pelagic and benthic organisms spanning size ranges from bacteria to fish, all sampled over three seasons in 1 yr. The four NBSS slopes were significantly steeper than -1.0 (range -1.14 to -1.19, with 95% CIs excluding -1). The corresponding average TTEs were substantially lower than 10% in each of the four food webs (range 1.0% to 3.6%, mean 1.85%). The overall slope merging all biomass-size data pairs from the four systems (-1.17) was almost identical to the slope predicted from the arithmetic mean TTE of the four food webs (-1.18) assuming a constant PPMR of 10(4). Accordingly, our empirical data confirm the theoretically predicted quantitative relationship between TTE and the slope of the biomass-size distribution. Furthermore, we show that benthic and pelagic organisms can be merged into a community NBSS, but future studies have yet to explore potential differences in habitat-specific TTEs and PPMRs. We suggest that community NBSS may provide valuable information on the structure of food webs and their energetic pathways, and can result in improved accuracy of TTE-estimates.

  • 25. Muscarella, Robert
    et al.
    Lohbeck, Madelon
    Martínez-Ramos, Miguel
    Poorter, Lourens
    Rodríguez-Velázquez, Jorge Enrique
    van Breugel, Michiel
    Bongers, Frans
    Demographic drivers of functional composition dynamics2017In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 98, no 11Article in journal (Refereed)
    Abstract [en]

    Abstract Mechanisms of community assembly and ecosystem function are often analyzed using community-weighted mean trait values (CWMs). We present a novel conceptual framework to quantify the contribution of demographic processes (i.e., growth, recruitment, and mortality) to temporal changes in CWMs. We used this framework to analyze mechanisms of secondary succession in wet tropical forests in Mexico. Seed size increased over time, reflecting a trade-off between colonization by small seeds early in succession, to establishment by large seeds later in succession. Specific leaf area (SLA) and leaf phosphorus content decreased over time, reflecting a trade-off between fast growth early in succession vs. high survival late in succession. On average, CWM shifts were driven mainly (70%) by growth of surviving trees that comprise the bulk of standing biomass, then mortality (25%), and weakly by recruitment (5%). Trait shifts of growing and recruiting trees mirrored the CWM trait shifts, and traits of dying trees did not change during succession, indicating that these traits are important for recruitment and growth, but not for mortality, during the first 30 yr of succession. Identifying the demographic drivers of functional composition change links population dynamics to community change, and enhances insights into mechanisms of succession.

  • 26. Muscarella, Robert
    et al.
    Messier, Julie
    Condit, Richard
    Hubbell, Stephen P.
    Svenning, Jens-Christian
    Effects of biotic interactions on tropical tree performance depend on abiotic conditions2018In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 99, no 12Article in journal (Refereed)
    Abstract [en]

    Abstract Predicting biotic responses to environmental change requires understanding the joint effects of abiotic conditions and biotic interactions on community dynamics. One major challenge is to separate the potentially confounding effects of abiotic environmental variation and local biotic interactions on individual performance. The stress gradient hypothesis (SGH) addresses this issue directly by predicting that the effects of biotic interactions on performance become more positive as the abiotic environment becomes more stressful. It is unclear, however, how the predictions of the SGH apply to plants of differing functional strategies in diverse communities. We asked (1) how the effect of crowding on performance (growth and survival) of trees varies across a precipitation gradient, and (2) how functional strategies (as measured by two key traits: wood density and leaf mass per area, LMA) mediate average demographic rates and responses to crowding across the gradient. We built trait-based neighborhood models of growth and survival across a regional precipitation gradient where increasing precipitation is associated with reduced abiotic stress. In total, our dataset comprised ~170,000 individual trees belonging to 252 species. The effect of crowding on tree performance varied across the gradient; crowding negatively affected growth across plots and positively affected survival in the wettest plot. Functional traits mediated average demographic rates across the gradient, but we did not find clear evidence that the strength of these responses depends on species? traits. Our study lends support to the SGH and demonstrates how a trait-based perspective can advance these concepts by linking the diversity of species interactions with functional variation across abiotic gradients.

  • 27. Nilsson-Ortman, Viktor
    et al.
    Stoks, Robby
    De Block, Marjan
    Johansson, Frank
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Population and Conservation Biology.
    Generalists and specialists along a latitudinal transect: patterns of thermal adaptation in six species of damselflies2012In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 93, no 6, p. 1340-1352Article in journal (Refereed)
    Abstract [en]

    Tropical organisms colonizing temperate environments face reduced average temperatures and dramatic thermal fluctuations. Theoretical models postulate that thermal specialization should be favored either when little environmental variation is experienced within generations or when among-generation variation is small relative to within-generation variation. To test these predictions, we studied six temperate species of damselflies differing in latitudinal distribution. We developed a computer model simulating how organisms experience environmental variation (accounting for diapause and voltinism) and performed a laboratory experiment assaying thermal sensitivities of growth rates. The computer model showed opposing latitudinal trends in among-and within-generation thermal variability: within-generation thermal variability decreased toward higher latitudes, whereas relative levels of among-generation thermal variability peaked at midlatitudes (where a shift in voltinism occurred). The growth experiment showed that low-latitude species were more thermally generalized than mid- and high-latitude species, supporting the prediction that generalists are favored under high levels of within-generation variation. Northern species had steeper, near-exponential reaction norms suggestive of thermal specialization. However, they had strikingly high thermal optima and grew very slowly over most of the thermal range they are expected to experience in the field. This observation is at present difficult to explain. These results highlight the importance of considering interactions between life history and environmental variation when deriving expectations of thermal adaptation.

  • 28. Nilsson-Ortman, Viktor
    et al.
    Stoks, Robby
    Johansson, Frank
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Competitive interactions modify the temperature dependence of damselfly growth rates2014In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 95, no 5, p. 1394-1406Article in journal (Refereed)
    Abstract [en]

    Individual growth rates and survival are major determinants of individual fitness, population size structure, and community dynamics. The relationships between growth rate, survival, and temperature may thus be important for predicting biological responses to climate change. Although it is well known that growth rates and survival are affected by competition and predation in addition to temperature, the combined effect of these factors on growth rates, survival, and size structure has rarely been investigated simultaneously in the same ecological system. To address this question, we conducted experiments on the larvae of two species of damselflies and determined the temperature dependence of growth rate, survival, and cohort size structure under three scenarios of increasing ecological complexity: no competition, intraspecific competition, and interspecific competition. In one species, the relationship between growth rate and temperature became steeper in the presence of competitors, whereas that of survival remained unchanged. In the other species, the relationship between growth rate and temperature was unaffected by competitive interactions, but survival was greatly reduced at high temperatures in the presence of interspecific competitors. The combined effect of competitive interactions and temperature on cohort size structure differed from the effects of these factors in isolation. Together, these findings suggest that it will be challenging to scale up information from single-species laboratory studies to the population and community level.

  • 29.
    Nunes, Ana L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Orizaola, German
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Laurila, Anssi
    Rebelo, Rui
    Rapid evolution of constitutive and inducible defenses against an invasive predator2014In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 95, no 6, p. 1520-1530Article in journal (Refereed)
    Abstract [en]

    Invasive alien predators can impose strong selection on native prey populations and induce rapid evolutionary change in the invaded communities. However, studies on evolutionary responses to invasive predators are often complicated by the lack of replicate populations differing in coexistence time with the predator, which would allow the determination of how prey traits change during the invasion. The red swamp crayfish Procambarus clarkii has invaded many freshwater areas worldwide, with negative impacts for native fauna. Here, we examined how coexistence time shapes antipredator responses of the Iberian waterfrog (Pelophylax perezi) to the invasive crayfish by raising tadpoles from five populations differing in historical exposure to P. clarkii (30 years, 20 years, or no coexistence). Tadpoles from non-invaded populations responded to the presence of P. clarkii with behavioral plasticity (reduced activity), whereas long-term invaded populations showed canalized antipredator behavior (constant low activity level). Tadpoles from one of the long-term invaded populations responded to the crayfish with inducible morphological defenses (deeper tails), reflecting the use of both constitutive and inducible antipredator defenses against the exotic predator by this population. Our results suggest that, while naive P. perezi populations responded behaviorally to P. clarkii, the strong predation pressure imposed by the crayfish has induced the evolution of qualitatively different antipredator defenses in populations with longer coexistence time. These responses suggest that strong selection by invasive predators may drive rapid evolutionary change in invaded communities. Examining responses of prey species to biological invasions using multiple populations will help us better forecast the impact of invasive predators in natural communities.

  • 30.
    Orizaola, German
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Richter-Boix, Alex
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Laurila, Anssi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Transgenerational effects and impact of compensatory responses to changes in breeding phenology on antipredator defenses2016In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 97, no 9, p. 2470-2478Article in journal (Refereed)
    Abstract [en]

    As organisms living in temperate environments often have only a short time window for growth and reproduction, their life-history strategies are expected to be influenced by these time constraints. Parents may alter the pace of offspring life-history as a response to changes in breeding phenology. However, the responses to changes in time constraints must be balanced with those against other stressors, such as predation, one of the strongest and more ubiquitous selective factors in nature. Here, after experimentally modifying the timing of breeding and hatching in the moor frog (Rana arvalis), we studied how compensatory responses to delayed breeding and hatching affect antipredator strategies in amphibian larvae. We examined the activity patterns, morphology and life-history responses in tadpoles exposed to different combinations of breeding and hatching delays in the presence and absence of predators. We found clear evidence of adaptive transgenerational effects since tadpoles from delayed breeding treatments increased growth and development independently of predation risk. The presence of predators reduced tadpole activity, tadpoles from delayed breeding treatments maintaining lower activity than non-delayed ones also in the absence of predators. Tadpoles reared with predators developed deeper tails and bodies, however, tadpoles from breeding delay treatments had reduced morphological defenses as compared to non-delayed individuals. No significant effects of hatching delay were detected in this study. Our study reveals that amphibian larvae exposed to breeding delay develop compensatory life-history responses even under predation risk, but these responses trade-off with the development of morphological antipredator defenses. These results suggest that under strong time constraints organisms are selected to develop fast growth and development responses, and rely on lower activity rates as their main antipredator defense. Examining how responses to changes in phenology affect species interactions is highly relevant for better understanding ecological responses to climate change.

  • 31.
    Persson, L
    et al.
    Umeå University, Department of Animal Ecology.
    Andersson, J
    Umeå University, Department of Animal Ecology.
    Wahlstrom, E
    Umeå University, Department of Animal Ecology.
    Eklöv, Peter
    Umeå University, Department of Animal Ecology.
    Size-specific interactions in lake systems: Predator gape limitation and prey growth rate and mortality1996In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 77, no 3, p. 900-911Article in journal (Refereed)
    Abstract [en]

    To study the effects of different predators on the behavior and dynamics of their prey, we compared the performance of perch (Perca fluviatilis) and the abundance of their prey resource in four lakes with two different types of piscivory. In two of the lakes, perch were the only fish species present and piscivory was restricted to cannibalism. In the other two lakes, perch co-occurred with piscivorous pike (Esox lucius). Pike grow to larger sizes and can capture larger prey than piscivorous perch. Therefore, perch reach a size refuge earlier in the lakes without pike. Perch in the lakes lacking pike used both the epilimnion and hypolimnion habitats of the lakes, and a high proportion of the perch occurred below the thermocline. In contrast, perch in the lakes with pike were mainly captured along the littoral zone and were never captured below the thermocline. This difference in habitat use was reflected in different diets of perch in the different lakes. Perch in the lakes with pike were also less abundant than those in the lakes lacking pike and the growth rates of individual perch and the densities of predator-sensitive prey (pelagic and littoral) were higher, indicating that the presence of pike resulted in decreased intraspecific competition in perch. Evidence for a behavioral response to predation risk was found in 1+ (1 yr old) perch, which was suggested to be due to predation risk from both larger perch and pike. It is hypothesized that the use of the cold-water hypolimnion habitat by perch in the lakes lacking pike was a response of perch to reduce metabolic demands under conditions of severe resource limitation. Differences in gape limitation between predators species are suggested to have major effects on size-dependent mortalities and growth rates in prey and thereby on overall community dynamics. Evidence for this latter effect was observed in differences in zooplankton size structure between the lakes with and without pike.

  • 32.
    Persson, Lennart
    et al.
    Umeå University, Department of Animal Ecology.
    Eklöv, Peter
    Umeå University, Department of Animal Ecology.
    PREY REFUGES AFFECTING INTERACTIONS BETWEEN PISCIVOROUS PERCH AND JUVENILE PERCH AND ROACH1995In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 76, no 1, p. 70-81Article in journal (Refereed)
    Abstract [en]

    In size-structured populations, interactions are strongly dependent on size-specific foraging and anti-predator capacities of the organism. Conflicting size-specific selection pressures over the ontogeny often have different effects on different species leading to asymmetries in competitive and predator-prey interactions. Habitat complexity is likely to affect such asymmetric interactions due to species/size-specific competitive abilities in different habitats and due to the fact that habitat structural complexity may act differently as a prey refuge for different species. We experimentally analyzed the impact of a piscivorous predator (adult perch, Perca fluviatilis) on performance of juvenile perch and roach (rutilus rutilus) at different levels of structural complexity (no structure, structure forming a partial refuge, and structure forming a complete refuge) in enclosures in an experimental pond. We measured predator diet and growth, prey fish habitat use, survival, diet and growth, and prey resource levels in different habitats. Prey fish (perch and roach) were found in the diet of piscivorous perch in no refuge and partial refuge treatments. Growth rate of the piscivorous perch decreased with increased refuge efficiency. Juvenile perch increased their proportional use of the structurally complex refuges in the presence of piscivorous perch and the survival increased with increased refuge efficiency (from partial to complete refuge). The diet of juvenile perch changed from predominantly cyclopoid copepods in the absence of predators to predominantly macroinvertebrates in the presence of predators. There was no effect of predator-induced habitat restriction on growth of juvenile perch. Roach survival also increased with increased refuge efficiency in the presence of predators, and roach survival in the refuge treatments did not differ from each other or from the treatments with predators absent. Predator-induced habitat restriction in roach was associated with a decreased growth of roach. Our results suggest that, compared to juvenile roach, juvenile perch may compensate more for lost foraging opportunity in the open water via increased exploitation of structure-associated prey in refuges. As a result, predator-induced habitat shifts by juvenile perch and roach may alter competitive interactions between the species. On the other hand, structural complexity may form an almost complete refuge for juvenile roach from predators and thereby affect the predator-prey relationships between piscivorous perch and juvenile perch and roach to the advantage of juvenile roach. The demonstrated effects of structural complexity on competitive and predator-prey interactions between perch and roach can be related to the two species' distributions in lakes with different degrees of structural complexity.

  • 33. Pfeifer-Meister, Laurel
    et al.
    Bridgham, Scott D.
    Little, Chelsea J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Reynolds, Lorien L.
    Goklany, Maya E.
    Johnson, Bart R.
    Pushing the limit: experimental evidence of climate effects on plant range distributions2013In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 94, no 10, p. 2131-2137Article in journal (Refereed)
    Abstract [en]

    Whether species will be extirpated in their current geographic ranges due to rapidly changing climate, and if so, whether they can avoid extinction by shifting their distributions are pressing questions for biodiversity conservation. However, forecasts of climate change impacts on species' geographic distributions rarely incorporate a demographic understanding of species' responses to climate. Because many biotic and abiotic factors at multiple scales control species' range limits, experimentation is essential to establish underlying mechanisms. We used a manipulative climate change experiment embedded within a natural climate gradient to examine demographic responses of 12 prairie species with northern range limits within the Pacific Northwest, USA. During the first year, warming decreased recruitment of species even at the coolest edge of their current ranges, but this effect disappeared when they were moved poleward beyond their current ranges. This response was largely driven by differences in germination rates. Other vital rates responded in unique and sometimes opposing ways (survivorship vs. fitness) to species' current ranges and climate change, and were mediated by indirect effects of climate on competition and nutrient availability. Our results demonstrate the importance of using regional-scale climate manipulations and the need for longer-term experiments on the demographic responses that control species' distributions.

  • 34.
    Quevedo, Mario
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Svanbäck, Richard
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Eklöv, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Intrapopulation niche partitioning in a generalist predator limits food web connectivity2009In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 90, no 8, p. 2263-2274Article in journal (Refereed)
    Abstract [en]

    Predators are increasingly recognized as key elements in food webs because of their ability to link the fluxes of nutrients and energy between spatially separated food chains. However, in the context of food web connectivity, predator populations have been mainly treated as homogeneous units, despite compelling evidence of individual specialization in resource use. It is conceivable that individuals of a predatory species use different resources associated with spatially separated food chains, thereby decoupling cross-habitat linkages. We tested whether intrapopulation differences in habitat use in the generalist freshwater predator Eurasian perch (Perca fluviatilis) led to long-term niche partitioning and affected the degree of ecological habitat coupling. We evaluated trophic niche variability at successively larger timescales by analyzing gut contents and stable isotopes (δ13C and δ15N) in liver and muscle, tissues that provide successively longer integration of trophic activity. We found that the use of distinct habitats in perch led to intrapopulation niche partitioning between pelagic and littoral subpopulations, consistent through the various timescales. Pelagic fish showed a narrower niche, lower individual specialization, and more stable trophic behavior than littoral fish, as could be expected from inhabiting a relatively less diverse environment. This result indicated that substantial niche reduction could occur in a generalist predator at the subpopulation level, consistent with the use of a habitat that provides fewer chances of individual specialization. We showed that intrapopulation niche partitioning limits the ability of individual predators to link spatially separated food chains. In addition, we suggest a quantitative, standardized approach based on stable isotopes to measure the degree of habitat coupling mediated by a top predator.

  • 35.
    Qvarnström, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Wiley, Chris
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Svedin, Nina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Vallin, Niclas
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Life-history divergence facilitates regional coexistence of competing Ficedula flycatchers2009In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 90, no 7, p. 1948-1957Article in journal (Refereed)
    Abstract [en]

    Regional coexistence of ecologically similar species is facilitated when fluctuations in environmental conditions favor different species at different times or places. However, why species with similar ecology should vary in their response to environmental change is unclear. In this study, we explore the role of a life-history divergence in causing changes in relative fitness across environmental conditions experienced by populations of two closely related Ficedula flycatchers on the Baltic island of Oland, Sweden. We compared patterns of nestling survival between Pied (Ficedula hypoleuca) and Collared (F. albicollis) Flycatchers in relation to two factors known to influence the environment experienced by nestlings: natural variation in their parents' onset of breeding and artificial manipulation of the brood size. Possible differences in the location of the nests (i.e., microhabitat differences) or in habitat use (i.e., feeding patterns) by the adult birds were controlled for by partial cross-fostering of young between the two species. We found that nestling mortality was relatively higher among Collared Flycatchers and that this difference increased with later breeding. Mass gain, which predicted survival probability, of nestling Collared Flycatchers did not respond to the seasonal decline in environmental conditions when they were raised in nests with reduced brood size (i.e., where sibling competition was experimentally reduced). This latter result suggests that the smaller clutch size of Collared Flycatchers reflects an adaptive adjustment to their offspring's higher sensitivity to environmental change. We discuss the possibility that the divergence in life-history traits between the two species represents adaptation to different environments experienced during their recent evolutionary history. We conclude that the survival of nestling Collared Flycatchers is more sensitive to harsh environment and that this is likely to limit where and when the more aggressive Collared Flycatchers are able to displace Pied Flycatchers. Our results provide support for models of species coexistence that emphasize the importance of spatial or temporal heterogeneity in relative fitness or life-history divergence. More precisely, our results demonstrate that variation in life-history adaptations may result in changes in relative fitness of species across environments despite their use of similar resources.

  • 36.
    Richter-Boix, Alex
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Orizaola, German
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Laurila, Anssi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Transgenerational phenotypic plasticity links breeding phenology with offspring life-history2014In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 95, no 10, p. 2715-2722Article in journal (Refereed)
    Abstract [en]

    The timing of seasonal life-history events is assumed to evolve to synchronize life cycles with the availability of resources. Temporal variation in breeding time can have severe fitness consequences for the offspring, but the interplay between adult reproductive decisions and offspring phenotypes remains poorly understood. Transgenerational plasticity (TGP) is a potential mechanism allowing rapid responses to environmental change. Here, we investigated if experimentally delayed breeding induces TGP in larval life-history traits in the moor frog (Rana arvalis). We found clear evidence of TGP in response to changes in breeding phenology: delayed breeding increased offspring development and growth rates in the absence of external cues. This constitutes the first unequivocal evidence for TGP in response to changes in breeding phenology in vertebrates. TGP can play an important role in adjusting offspring life-history strategies to the environment they are most likely to encounter, and may constitute an important mechanism for coping with climate change.

  • 37.
    Roger, Fabian
    et al.
    Univ Gothenburg, Dept Marine Sci, Box 461, SE-40530 Gothenburg, Sweden.
    Bertilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Langenheder, Silke
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Osman, Omneya
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Gamfeldt, Lars
    Univ Gothenburg, Dept Marine Sci, Box 461, SE-40530 Gothenburg, Sweden.
    Effects of multiple dimensions of bacterial diversity on functioning, stability and multifunctionality2016In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 97, no 10, p. 2716-2728Article in journal (Refereed)
    Abstract [en]

    Bacteria are essential for many ecosystem services but our understanding of factors controlling their functioning is incomplete. While biodiversity has been identified as an important driver of ecosystem processes in macrobiotic communities, we know much less about bacterial communities. Due to the high diversity of bacterial communities, high functional redundancy is commonly proposed as explanation for a lack of clear effects of diversity. The generality of this claim has, however, been questioned. We present the results of an outdoor dilution-to-extinction experiment with four lake bacterial communities. The consequences of changes in bacterial diversity in terms of effective number of species, phylogenetic diversity, and functional diversity were studied for (1) bacterial abundance, (2) temporal stability of abundance, (3) nitrogen concentration, and (4) multifunctionality. We observed a richness gradient ranging from 15 to 280 operational taxonomic units (OTUs). Individual relationships between diversity and functioning ranged from negative to positive depending on lake, diversity dimension, and aspect of functioning. Only between phylogenetic diversity and abundance did we find a statistically consistent positive relationship across lakes. A literature review of 24 peer-reviewed studies that used dilution-to-extinction to manipulate bacterial diversity corroborated our findings: about 25% found positive relationships. Combined, these results suggest that bacteria-driven community functioning is relatively resistant to reductions in diversity.

  • 38. Romaní, Anna Maria
    et al.
    Fischer, Helmut
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Mille-Lindblom, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Interactions of bacteria and fungi on decomposing litter: Differential extracellular enzyme activities2006In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 87, no 10, p. 2559-2569Article in journal (Refereed)
    Abstract [en]

    Fungi and bacteria are key agents in plant litter decomposition in freshwater ecosystems. However, the specific roles of these two groups and their interactions during the decomposition process are unclear. We compared the growth and patterns of degradative enzymes expressed by communities of bacteria and fungi grown separately and in coexistence on Phragmites leaves. The two groups displayed both synergistic and antagonistic interactions. Bacteria grew better together with fungi than alone. In addition, there was a negative effect of bacteria on fungi, which appeared to be caused by suppression of fungal growth and biomass accrual rather than specifically affecting enzyme activity. Fungi growing alone had a high capacity for the decomposition of plant polymers such as lignin, cellulose, and hemicellulose. In contrast, enzyme activities were in general low when bacteria grew alone, and the activity of key enzymes in the degradation of lignin and cellulose (phenol oxidase and cellobiohydrolase) was undetectable in the bacteria-only treatment. Still, biomass-specific activities of most enzymes were higher in bacteria than in fungi. The low total activity and growth of bacteria in the absence of fungi in spite of apparent high enzymatic efficiency during the degradation of many substrates suggest that fungi provide the bacteria with resources that the bacteria were not able to acquire on their own, most probably intermediate decomposition products released by fungi that could be used by bacteria.

  • 39.
    Räsänen, Katja
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Population and Conservation Biology.
    Söderman, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Population and Conservation Biology.
    Laurila, Anssi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Population and Conservation Biology.
    Merila, Juha
    Geographic variation in maternal investment: Acidity affects egg size and fecundity in Rana arvalis2008In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 89, no 9, p. 2553-2562Article in journal (Refereed)
    Abstract [en]

    Environmental-stress-mediated geographic variation in reproductive parameters has been little studied in natural vertebrate populations outside the context of climatic variation. Based on life-history theory, an increase in the degree of environmental stress experienced by a population should lead to (1) a shift in reproductive allocation from fecundity to offspring quality, (2) stronger trade-offs between reproductive parameters, and (3) changes in the relationship between female phenotype and maternal investment. To test these predictions, we investigated geographic variation in maternal investment of moor frogs (Rana arvalis) in relation to breeding site acidity (pH 4-8). We found that mean egg size increased and clutch size and total reproductive output (TRO) decreased with increasing acidity among 19 Swedish moor frog populations. Tests for variation and co-variation in maternal investment and female size and age in 233 females from a subset of four acid origin (AO) and four neutral origin (NO) populations revealed that clutch size and TRO increased with female size in both acid and neutral environments. However, in AO populations, egg size also increased with female size, and clutch size and TRO with female age, whereas in NO populations, egg size increased with female age. The strength of the egg-size-clutch-size trade-off tended to be stronger in AO than in NO females as expected if the former experience stronger environmental constraints. All in all, these results suggest that environmental acidfication selects for investment in larger eggs at a cost to fecundity, imposes negative effects on reproductive output, and alters the relationship between female phenotype and maternal investment.

  • 40.
    Scharnweber, Kristin
    et al.
    Leibniz-Institute of Freshwater Biology and Inland Fisheries, Berlin.
    Syväranta, Jari
    Hilt, Sabine
    Brauns, Mario
    Vanni, M.J.
    Brothers, Soren
    Köhler, Jan
    Knežević-Jarić, Jelena
    Mehner, Thomas
    Whole-lake experiments reveal the fate of terrestrial particulate organic carbon in benthic food webs of shallow lakes2013In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 95, no 6, p. 1496-1505Article in journal (Refereed)
    Abstract [en]

    Lake ecosystems are strongly linked to their terrestrial surroundings by material and energy fluxes across ecosystem boundaries. However, the contribution of terrestrial particulate organic carbon (tPOC) from annual leaf fall to lake food webs has not yet been adequately traced and quantified. In this study, we conducted whole-lake experiments to trace artificially added tPOC through the food webs of two shallow lakes of similar eutrophic status, but featuring alternative stable regimes (macrophyte rich vs. phytoplankton dominated). Lakes were divided with a curtain, and maize (Zea mays) leaves were added, as an isotopically distinct tPOC source, into one half of each lake. To estimate the balance between autochthonous carbon fixation and allochthonous carbon input, primary production and tPOC and tDOC (terrestrial dissolved organic carbon) influx were calculated for the treatment sides. We measured the stable isotope ratios of carbon (δ13C) of about 800 samples from all trophic consumer levels and compared them between lake sides, lakes, and three seasons. Leaf litter bag experiments showed that added maize leaves were processed at rates similar to those observed for leaves from shoreline plants, supporting the suitability of maize leaves as a tracer. The lake-wide carbon influx estimates confirmed that autochthonous carbon fixation by primary production was the dominant carbon source for consumers in the lakes. Nevertheless, carbon isotope values of benthic macroinvertebrates were significantly higher with maize additions compared to the reference side of each lake. Carbon isotope values of omnivorous and piscivorous fish were significantly affected by maize additions only in the macrophyte-dominated lake and δ13C of zooplankton and planktivorous fish remained unaffected in both lakes. In summary, our results experimentally demonstrate that tPOC in form of autumnal litterfall is rapidly processed during the subsequent months in the food web of shallow lakes and is channeled to secondary and tertiary consumers predominantly via the benthic pathways. A more intense processing of tPOC seems to be connected to a higher structural complexity in littoral zones, and hence may differ between shallow lakes of alternative stable states.

  • 41. Seppänen, J.T.
    et al.
    Forsman, Jukka T.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Mönkkönen, M.
    Thompson, R.L.
    Social information use is a process across time, space, and ecology, reaching heterospecifics2007In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 88, no 7, p. 1622-1633Article in journal (Refereed)
    Abstract [en]

    Decision making can be facilitated by observing other individuals faced with the same or similar problem, and recent research suggests that this social information use is a widespread phenomenon. Implications of this are diverse and profound: for example, social information use may trigger cultural evolution, affect distribution and dispersal of populations, and involve intriguing cognitive traits. We emphasize here that social information use is a process consisting of the scenes of(1) event, (2) observation, (3) decision, and (4) consequence, where the initial event is a scene in such a process of another individual. This helps to construct a sound conceptual framework for measuring and studying social information use. Importantly, the potential value of social information is affected by the distance in time, space, and ecology between the initial observation and eventual consequence of a decision. Because negative interactions between individuals (such as direct and apparent competition) also depend on the distance between individuals along these dimensions, the potential value of information and the negative interactions may form a trade-off situation. Optimal solutions to this trade-off can result in adaptively extended social information use, where using information gathered some time ago, some distance away, and from ecologically different individuals is preferred. Conceivably, using information gathered from a heterospecific individual might often be optimal. Many recent studies demonstrate that social information use does occur between species, and the first review of published cases is provided here. Such interaction between species, especially in habitat selection, has important consequences for community ecology and conservation. Adaptively extended social information use may also be an important evolutionary force in guild formation. Complex coevolutionary patterns may result depending on the effect of information use on the provider of information.

  • 42.
    Sletvold, Nina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Grindeland, John Magne
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Vegetation context influences the strength and targets of pollinator-mediated selection in a deceptive orchid2013In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 94, no 6, p. 1236-1242Article in journal (Refereed)
    Abstract [en]

    Clarifying the relationship between environmental context and the adaptive significance of floral traits is fundamental for an understanding of spatial and temporal variation in pollinator-mediated selection. We manipulated vegetation height and pollination regime of the orchid Dactylorhiza lapponica in a factorial design to test whether pollinator-mediated selection on floral traits is stronger in tall than in short vegetation, and whether this difference is larger for visual traits affecting pollinator attraction than for traits affecting pollination efficiency. In tall vegetation, pollinators mediated strong selection for taller plants (change in selection gradient for pollination, Delta beta(poll) = 0.33), more flowers (Delta beta(poll) = 0.34), and longer spurs (Delta beta(poll) = 0.42). In short vegetation, there was no significant selection on plant height, and pollinator-mediated selection on number of flowers and spur length was reduced by 52% and 25%, respectively. The results demonstrate experimentally that vegetation context can markedly influence the strength of pollinator-mediated selection on visual display traits, and indicate that this effect is weaker for traits affecting pollination efficiency. The study illustrates how crossed manipulations of environmental factors can reveal the causal links between ecological context and selection on floral traits.

  • 43.
    Sletvold, Nina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Moritz, Kim K.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Additive effects of pollinators and herbivores result in both conflicting and reinforcing selection on floral traits2015In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 96, no 1, p. 214-221Article in journal (Refereed)
    Abstract [en]

    Mutualists and antagonists are known to respond to similar floral cues, and may thus cause opposing selection on floral traits. However, we lack a quantitative understanding of their independent and interactive effects. In a population of the orchid Gymnadenia conopsea, we manipulated the intensity of pollination and herbivory in a factorial design to examine whether both interactions influence selection on flowering phenology, floral display, and morphology. Supplemental hand-pollination increased female fitness by 31% and one-quarter of all plants were damaged by herbivores. Both interactions contributed to selection. Pollinators mediated selection for later flowering and herbivores for earlier flowering, while both selected for longer spurs. The strength of selection was similar for both agents, and their effects were additive. As a consequence, there was no net selection on phenology, whereas selection on spur length was strong. The experimental results demonstrate that both pollinators and herbivores can markedly influence the strength of selection on flowering phenology and floral morphology, and cause both conflicting and reinforcing selection. They also indicate that the direction of selection on phenology will vary with the relative intensity of the mutualistic and antagonistic interaction, potentially resulting in both temporal and among-population variation in optimal flowering time.

  • 44.
    Sletvold, Nina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Trunschke, Judith
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Wimmergren, Carolina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Separating selection by diurnal and nocturnal pollinators on floral display and spur length in Gymnadenia conopsea2012In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 93, no 8, p. 1880-1891Article in journal (Refereed)
    Abstract [en]

    Most plants attract multiple flower visitors that may vary widely in their effectiveness as pollinators. Floral evolution is expected to reflect interactions with the most important pollinators, but few studies have quantified the contribution of different pollinators to current selection on floral traits. To compare selection mediated by diurnal and nocturnal pollinators on floral display and spur length in the rewarding orchid Gymnadenia conopsea, we manipulated the environment by conducting supplemental hand-pollinations and selective pollinator exclusions in two populations in central Norway. In both populations, the exclusion of diurnal pollinators significantly reduced seed production compared to open pollination, whereas the exclusion of nocturnal pollinators did not. There was significant selection on traits expected to influence pollinator attraction and pollination efficiency in both the diurnal and nocturnal pollination treatment. The relative strength of selection among plants exposed to diurnal and nocturnal visitors varied among traits and populations, but the direction of selection was consistent. The results suggest that diurnal pollinators are more important than nocturnal pollinators for seed production in the study populations, but that both categories contribute to selection on floral morphology. The study illustrates how experimental manipulations can link specific categories of pollinators to observed selection on floral traits, and thus improve our understanding of how species interactions shape patterns of selection.

  • 45.
    Sletvold, Nina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Experimental reduction in interaction intensity strongly affects biotic selection2016In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 97, no 11, p. 3091-3098Article in journal (Refereed)
    Abstract [en]

    The link between biotic interaction intensity and strength of selection is of fundamental interest for understanding biotically driven diversification and predicting the consequences of environmental change. The strength of selection resulting from biotic interactions is determined by the strength of the interaction and by the covariance between fitness and the trait under selection. When the relationship between trait and absolute fitness is constant, selection strength should be a direct function of mean population interaction intensity. To test this prediction, we excluded pollinators for intervals of different length to induce five levels of pollination intensity within a single plant population. Pollen limitation (PL) increased from 0 to 0.77 across treatments, accompanied by a fivefold increase in the opportunity for selection. Trait-fitness covariance declined with PL for number of flowers, but varied little for other traits. Pollinator-mediated selection on plant height, corolla size, and spur length increased by 91%, 34%, and 330%, respectively, in the most severely pollen-limited treatment compared to open-pollinated plants. The results indicate that realized biotic selection can be predicted from mean population interaction intensity when variation in trait-fitness covariance is limited, and that declines in pollination intensity will strongly increase selection on traits involved in the interaction.

  • 46.
    Sletvold, Nina
    et al.
    Norwegian University of Science and Technology, Museum of Natural History and Archaeology.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Nonadditive effects of floral display and spur length on reproductive success in a deceptive orchid2011In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 92, no 12, p. 2167-2174Article in journal (Refereed)
    Abstract [en]

    Pollinators may mediate selection on traits affecting pollinator attraction and effectiveness, and while nonadditive effects of traits influencing the two components of pollination success are expected when seed production is pollen limited, they have been little studied. In a factorial design, we manipulated one putative attraction trait (number of flowers) and one putative efficiency trait (spur length) previously shown to be subject to pollinator-mediated selection in the deceptive orchid Dactylorhiza lapponica. Removal of half of the flowers reduced pollen removal, proportion of flowers receiving pollen, fruit set, and fruit mass compared to unmanipulated plants, while spur-tip removal increased fruit set and fruit mass but did not affect pollen removal or proportion of flowers receiving pollen. The effect of spur-tip removal on fruit mass was stronger among plants with intact number of flowers compared to plants with experimentally reduced number of flowers. The results demonstrate that number of flowers and spur length are direct targets of selection and may affect female fitness nonadditively. More generally, they show that the adaptive value of a given trait can depend on floral context and illustrate how experimental approaches can advance our understanding of the evolution of trait combinations.

  • 47.
    Teplitsky, Céline
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Population and Conservation Biology.
    Laurila, Anssi
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Population and Conservation Biology.
    Flexible defense strategies: competition modifies investment in behavioral vs. morphological defenses2007In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 88, no 7, p. 1641-1646Article in journal (Refereed)
    Abstract [en]

    Competition is predicted to affect the expression of inducible defenses, but because costs of behavioral and morphological antipredator defenses differ along resource gradients, its effects on defenses may depend on the traits considered. We tested the predictions from different defense models in tadpoles of the common frog Rana temporaria, which exhibit both types of defenses. In an outdoor experiment, we exposed the tadpoles to nonlethal predators (Aeshna dragonfly larvae) and to a gradient of intraspecific competition. Morphological responses did not follow any of the expected patterns, since investment in defense was not affected by resource level. Instead, tail depth decreased in the absence of predators. Behavioral defenses followed a state-dependent model. Overall, the defense strategy of the tadpoles revealed a shift from morphological and behavioral defenses at low tadpole density to morphological defense only at high density. This difference probably reflects the different efficiency of the defenses. Hiding is an effective means of defense, but it is unsustainable when resources are scarce. Morphological responses become more important with increasing density to compensate for the increase in behavioral risk-taking. Our results indicate that competition can strongly affect reaction norms of inducible defenses and highlight the importance of integrating ecological parameters that affect the cost–benefit balance of phenotypic plasticity.

  • 48.
    Thomann, Michel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Ehrlen, Johan
    Stockholm Univ, Dept Ecol Environm & Plant Sci, SE-10691 Stockholm, Sweden.
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
    Grazers affect selection on inflorescence height both directly and indirectly and effects change over time2018In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 99, no 10, p. 2167-2175Article in journal (Refereed)
    Abstract [en]

    Selection mediated by one biotic agent will often be modified by the presence of other biotic interactions, and the importance of such indirect effects might change over time. We conducted an 11-yr field experiment to test the prediction that large grazers affect selection on floral display of the dimorphic herb Primula farinosa not only directly through differential grazing damage, but also indirectly by affecting vegetation height and thereby selection mediated by pollinators and seed predators. Exclusion of large grazers increased vegetation height and the strength of pollinator-mediated selection for tall inflorescences and seed-predator-mediated selection for short inflorescences. The direct effect of grazers on selection resulting from differential grazing damage to the two scape morphs showed no temporal trend. By contrast, the increase in vegetation height in exclosures over time was associated with an increase in selection mediated by pollinators and seed predators. In the early years of the experiment, the indirect effects of grazers on selection mediated by pollinators and seed predators were weak, whereas at the end of the experiment, the indirect effects were of similar magnitude as the direct effect due to differential grazing damage. The results demonstrate that the indirect effects of a selective agent can be as strong as its direct effects, and that the relative importance of direct vs. indirect effects on selection can change over time. A full understanding of the ecological processes governing variation in selection thus requires that both direct and indirect effects of biotic interactions are assessed.

  • 49.
    Toräng, Per
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ehrlén, Johan
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Facilitation in an insect pollinated herb with a floral display dimorphism2006In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 87, no 8, p. 2113-2117Article in journal (Refereed)
    Abstract [en]

    Population context should influence pollination success and selection on. oral display in animal-pollinated plants because attraction of pollinators depends not only on the characteristics of individual plants, but also on the attractiveness of co-occurring conspecifics. The insect-pollinated herb Primula farinosa is polymorphic for inflorescence height. Natural populations may include both long-scaped plants, which present their flowers well above the soil surface, and short-scaped plants, with their flowers positioned close to the ground. We experimentally tested whether seed production in short-scaped P. farinosa varied with local morph frequency and surrounding vegetation height. In tall vegetation, short-scaped plants in polymorphic populations produced more fruit and tended to produce more seeds than short-scaped plants did in monomorphic populations. In low vegetation, population composition did not significantly affect fruit and seed output of short-scaped plants. The results suggest that long-scaped plants facilitate short-scaped plants in terms of pollinator attraction and that the facilitation effect is contingent on the height of the surrounding vegetation. The documented facilitation should contribute to the maintenance of the scape length polymorphism in ungrazed areas where litter accumulates and vegetation grows tall.

  • 50.
    Toräng, Per
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Ehrlén, Johan
    Ågren, Jon
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Mutualists and antagonists mediate frequency-dependent selection on floral display2008In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 89, no 6, p. 1564-1572Article in journal (Refereed)
    Abstract [en]

    Theory predicts that, with conflicting selection pressures mediated by mutualists and antagonists, alternative reproductive strategies can be maintained by negative frequency-dependent selection if it results in rare-morph advantage. We combined field experiments and surveys of natural populations to determine whether selection on. oral display is frequency dependent in the self-incompatible herb Primula farinosa, which is polymorphic for inflorescence height and occurs in a short-scaped and a long-scaped morph. Among short-scaped plants, both pollination success, quantified as initiation of fruits and seeds, and seed predation were positively correlated with the relative frequency of the long-scaped morph. The relative strength of these effects and the direction of the resulting frequency-dependent selection on scape morph varied among years and populations. The results suggest that both mutualists and antagonists may mediate frequency-dependent selection and that frequency dependence may vary from positive to negative with rare-morph advantage, depending on the relative strength of these interactions.

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