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  • 1.
    Andersson, Jens
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Claessen, D
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    De Roos, A. M.
    Stabilization of population fluctuations due to cannibalism promotes resource polymorphism in fish2007Ingår i: American Naturalist, Vol. 169, s. 820-829Artikel i tidskrift (Refereegranskat)
  • 2.
    Andersson, Jens
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Byström, Pär
    Department of Aquaculture, Swedish University of Agricultural Sciences, Sweden.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    De Roos, André M.
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Netherlands.
    Plastic reources polymorphism: effects or resource availability on Arctic char (Salvelinus alpinus) morphology2005Ingår i: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 85, nr 3, s. 341-351Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Resource polymorphism has been suggested to be a platform for speciation. In some cases resource polymorphism depends on phenotypic plasticity but in other cases on genetic differences between morphotypes, which in turn has been suggested to be the ongoing development of a species pair. Here we study environmentally induced morphological differences in two age classes of Arctic char (Salvelinus alpinus) influencing char performance and diet in relation to resource availability. We found that structurally complex habitats with relatively lower zooplankton densities gave rise to individuals with a deeper body, and a downward positioned tip of the snout compared with individuals from structurally simple habitats with relatively higher zooplankton densities for both age classes. Environment also had an effect on foraging efficiency on zooplankton, with fish from structurally simple habitats had a higher foraging rate than fish from structurally complex habitats. Diet analyses showed that resource use in char mainly depends on the relative abundance of different resources. Therefore, to gain further understanding of resource polymorphism we suggest that future studies must include population dynamic feedbacks by the resources on the consumers.

  • 3.
    Andersson, Jens
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Behavioural and morphological responses to cannibalism in Arctic charr (Salvelinus alpinus)2005Ingår i: Evolutionary Ecology Research, ISSN 1522-0613, E-ISSN 1937-3791, Vol. 7, nr 5, s. 767-778Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Question: Does cannibalism lead to resource polymorphism in young Arctic charr (Salvelinusalpinus, Pisces)?

    Hypothesis: Cannibals should evoke a low-activity morph that is well adapted to benthivorybut not planktivory, and which differs in morphology compared with a planktivorous morph.

    Methods: We reared young-of-the-year charr in laboratory aquaria with and without largercannibalistic charr present. Thereafter, we measured foraging efficiency on pelagic and benthicresources, swimming speed when foraging, and morphology of the young charr.

    Conclusions: Living among cannibals did not affect the morphology of the young charr. Italso did not affect the foraging efficiency of the young charr on the benthic resource. However,individuals from cannibal treatments swam closer and had lower foraging efficiency on thepelagic resource.

  • 4.
    Ask, Jenny
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ask, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Terrestrial organic matter and light penetration: Effects on bacterial and primary production in lakes2009Ingår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 54, nr 6, s. 2034-2040Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated productivity at the basal trophic level in 15 unproductive lakes in a gradient ranging from clear-water to brown-water (humic) lakes in northern Sweden. Primary production and bacterial production in benthic and pelagic habitats were measured to estimate the variation in energy mobilization from external energy sources (primary production plus bacterial production on allochthonous organic carbon) along the gradient. Clear-water lakes were dominated by autotrophic energy mobilization in the benthic habitat, whereas humic lakes were dominated by heterotrophic energy mobilization in the pelagic habitat. Whole-lake (benthic + pelagic) energy mobilization was negatively correlated to the light-extinction coefficient, which was determined by colored terrestrial organic matter in the lake water. Thus, variation in the concentration of terrestrial organic matter and its light-absorbing characteristics exerts strong control on the magnitude, as well as on the processes and pathways, of energy mobilization in unproductive lakes. We suggest that unproductive lakes in general are sensitive to input of terrestrial organic matter because of its effects on basal energy mobilization in both benthic and pelagic habitats.

  • 5.
    Ask, Jenny
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ask, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Whole-lake estimates of carbon flux through algae and bacteria in benthic and pelagic habitats of clear-water lakes2009Ingår i: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 90, nr 7, s. 1923-1932Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study quantified new biomass production of algae and bacteria in both benthic and pelagic habitats of clear-water lakes to contrast how carbon from the atmosphere and terrestrial sources regulates whole-lake metabolism. We studied four small unproductive lakes in subarctic northern Sweden during one summer season. The production of new biomass in both benthic and pelagic habitats was calculated as the sum of autotrophic production by algae and heterotrophic production by bacteria using allochthonous organic carbon (OC). Whole-lake production of new biomass was dominated by the benthic habitat (86% +/- 4% [mean +/- SD]) and by primary production (77% +/- 9%). Still, heterotrophic bacteria fueled by allochthonous OC constituted a significant portion of the new biomass production in both benthic (19% +/- 11%) and pelagic habitats (51% +/- 24%). In addition, overall net production (primary production minus respiration) was close to zero in the benthic habitats but highly negative (-163 +/- 81 mg C.m(-2).d(-1)) in pelagic regions of all lakes. We conclude (1) that allochthonous OC supported a significant part of total production of new biomass in both pelagic and benthic habitats, (2) that benthic habitats dominated the whole-lake production of new biomass, and (3) that respiration and net CO2 production dominated the carbon flux of the pelagic habitats and biomass production dominated the benthic carbon flux. Taken together, these findings suggest that previous investigations have greatly underestimated the productivity of clear-water lakes when benthic autotrophic production and metabolism of allochthonous OC have not been measured.

  • 6.
    Ask, Per
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ask, Jenny
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Competition mediated coexistence of invading intermediate consumer, ninespine stickleback, and a resident omnivorous top predator, Arctic charManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Climate change results in changes in the geographical distribution of species. Species invasion success into a new area is dependent both on the dispersal ability of species as well as the strength and identity of biotic interactions between resident and invading species. Coexistence in intraguild predation (IGP) systems depends on the relative strength of predation and competition interactions which in turn are temperature dependent. We investigated the effects of introducing an intermediate consumer, ninespine stickleback (Pungitius pungitius), into allopatric populations of the omnivorous top predator Arctic char (Salvelinus alpinus). Introductions were performed in lakes with different climate regimes, two tundra lakes and two forest lakes that differed in average summer temperatures with 1.4 ± 0.5 ºC (average ± 1SD). We found that sticklebacks were able to invade and increase in density in both tundra and forest lakes. Sticklebacks had strong negative effects on resource densities which also was reflected in a decreased growth of small char. Increasing stickleback density had a positive effect on growth of large adults and on the maximum size of char. We conclude that stickleback presence is not limited by biological interactions in these systems but rather by dispersion ability. We suggest that the size dependency in the response of char to the invasion of sticklebacks is fundamental for the successful invasion of sticklebacks, and that size dependent interactions including cannibalism play important roles for coexistence in natural IGP-systems.

  • 7.
    Ask, Per
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ask, Jenny
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Temperature mediated effects on top consumer populations in subarctic lakesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The effects of temperature on top consumer populations in subarctic lake communities were studied by contrasting two lake pairs in different climate regimes: one pair on the low alpine tundra and one pair in the subalpine birch forest. We measured zooplankton and macroinvertebrate biomasses over the season and estimated population density and size structure of the top consumer Arctic char (Salvelinus alpinus). Furthermore, we modelled char growth using literature data on temperature dependent search rate, handling time and metabolic demands. The forest lakes were warmer than the tundra lakes. Char in the forest lakes were larger and had a higher individual growth compared to char in the tundra lakes, while population density and biomasses of char were not different between the forest and the tundra lakes. There were no differences in macroinvertebrate and zooplankton resource levels available for char between lake pairs. Our modeling of char growth revealed that higher temperature increased growth of char at the observed resource densities, suggesting that the higher temperature in the forest lakes was primarily the cause of the higher growth of char in these lakes. We suggest that cannibalism in char may regulate char recruitment and thereby population density and biomass of char leading to effects of increasing temperature on consumer biomass and consumer individual growth different from what is expected in pure consumer-resource systems. Our results emphasize the importance of feedbacks within ecosystems when addressing effects of climate change and increasing temperature on lake communities.

  • 8. Bartels, Pia
    et al.
    Cucherousset, Julien
    Gudasz, Cristian
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Karlsson, Jan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Premke, Katrin
    Rubach, Anja
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Steger, Kristin
    Tranvik, Lars J.
    Eklov, Peter
    Terrestrial subsidies to lake food webs: an experimental approach2012Ingår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 168, nr 3, s. 807-818Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cross-ecosystem movements of material and energy are ubiquitous. Aquatic ecosystems typically receive material that also includes organic matter from the surrounding catchment. Terrestrial-derived (allochthonous) organic matter can enter aquatic ecosystems in dissolved or particulate form. Several studies have highlighted the importance of dissolved organic carbon to aquatic consumers, but less is known about allochthonous particulate organic carbon (POC). Similarly, most studies showing the effects of allochthonous organic carbon (OC) on aquatic consumers have investigated pelagic habitats; the effects of allochthonous OC on benthic communities are less well studied. Allochthonous inputs might further decrease primary production through light reduction, thereby potentially affecting autotrophic resource availability to consumers. Here, an enclosure experiment was carried out to test the importance of POC input and light availability on the resource use in a benthic food web of a clear-water lake. Corn starch (a C-4 plant) was used as a POC source due to its insoluble nature and its distinct carbon stable isotope value (delta C-13). The starch carbon was closely dispersed over the bottom of the enclosures to study the fate of a POC source exclusively available to sediment biota. The addition of starch carbon resulted in a clear shift in the isotopic signature of surface-dwelling herbivorous and predatory invertebrates. Although the starch carbon was added solely to the sediment surface, the carbon originating from the starch reached zooplankton. We suggest that allochthonous POC can subsidize benthic food webs directly and can be further transferred to pelagic systems, thereby highlighting the importance of benthic pathways for pelagic habitats.

  • 9.
    Bernes, Claes
    et al.
    1 Mistra Council for Evidence-Based Environmental Management, Royal Swedish Academy of Sciences.
    Carpenter, Stephen
    University of Wisconsin, USA.
    Gårdmark, Anna
    Swedish University of Agricultural Sciences.
    Larsson, Per
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Skov, Christian
    Technical University of Denmark, Denmark.
    Speed, James
    Norwegian University of Science and Technology, Norway.
    Van Donk, Ellen
    Netherlands Institute of Ecology, The Netherlands.
    What is the influence of a reduction of planktivorous and benthivorous fish on water quality in temperate eutrophic lakes?: A systematic review2015Ingår i: Environmental Evidence, ISSN 2047-2382, E-ISSN 2047-2382, Vol. 4, nr 1, artikel-id 7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background

    In recent decades, many attempts have been made to restore eutrophic lakes through biomanipulation. Reducing the populations of planktivorous and benthivorous fish (either directly or through stocking of piscivorous fish) may induce ecosystem changes that increase water transparency and decrease the risk of algal blooms and fish kills, at least in the short term. However, the generality of biomanipulation effects on water quality across lake types and geographical regions is not known. Therefore, we have undertaken a systematic review of such effects in eutrophic lakes in temperate regions throughout the world.

    Methods

    Searches for literature were made using online publication databases, search engines, specialist websites and bibliographies of literature reviews. Search terms were developed in English, Danish, Dutch and Swedish. Identified articles were screened for relevance using inclusion criteria set out in an a priori protocol. To reduce the risk of bias, we then critically appraised the combined evidence found on each biomanipulation. Data were extracted on outcomes such as Secchi depth and chlorophyll a concentration before, during and/or after manipulation, and on effect modifiers such as lake properties and amounts of fish removed or stocked.

    Results

    Our searches identified more than 14,500 articles. After screening for relevance, 233 of them remained. After exclusions based on critical appraisal, our evidence base included useful data on 128 biomanipulations in 123 lakes. Of these interventions, 85% had been made in Europe and 15% in North America. Meta-analysis showed that removal of planktivores and benthivores (with or without piscivore stocking) leads to increased Secchi depth and decreased chlorophyll a concentration during intervention and the first three years afterwards. Piscivore stocking alone has no significant effect. The response of chlorophyll a levels to biomanipulation is stronger in lakes where fish removal is intense, and in lakes which are small and/or have high pre-manipulation concentrations of total phosphorus.

    Conclusions

    Our review improves on previous reviews of biomanipulation in that we identified a large number of case studies from many parts of the world and used a consistent, repeatable process to screen them for relevance and susceptibility to bias. Our results indicate that removal of planktivorous and benthivorous fish is a useful means of improving water quality in eutrophic lakes. Biomanipulation tends to be particularly successful in relatively small lakes with short retention times and high phosphorus levels. More thorough fish removal increases the efficacy of biomanipulation. Nonetheless successes and failures have occurred across a wide range of conditions.

  • 10. Bolnick, Daniel I
    et al.
    Svanbäck, Richard
    Araújo, Márcio S.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Comparative support for the niche variation hypothesis that more generalized populations also are more heterogeneous2007Ingår i: Proceedings of the National Academy of Sciences, Vol. 104, nr 24, s. 10075-10079Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is extensive evidence that some species of ecological generalists, which use a wide diversity of resources, are in fact heterogeneous collections of relatively specialized individuals. This within-population variation, or "individual specialization," is a key requirement for frequency-dependent interactions that may drive a variety of types of evolutionary diversification and may influence the population dynamics and ecological interactions of species. Consequently, it is important to understand when individual specialization is likely to be strong or weak. The niche variation hypothesis (NVH) suggests that populations tend to become more generalized when they are released from interspecific competition. This niche expansion was proposed to arise via increased variation among individuals rather than increased individual niche breadth. Consequently, we expect ecological generalists to exhibit stronger individual specialization, but this correlation has been repeatedly rejected by empiricists. The drawback with previous empirical tests of the NVH is that they use morphological variation as a proxy for niche variation, ignoring the role of behavior and complex phenotype–function relationships. Here, we used diet data to directly estimate niche variation among individuals. Consistent with the NVH, we show that more generalized populations also exhibit more niche variation. This trend is quite general, appearing in all five case studies examined: three-spine stickleback, Eurasian perch, Anolis lizards, intertidal gastropods, and a community of neotropical frogs. Our results suggest that generalist populations may tend to be more ecologically variable. Whether this translates into greater genetic variation, evolvability, or ecological stability remains to be determined.

  • 11.
    Byström, P
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Andersson, J
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Persson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    De Roos, A M
    Size-dependent resource limitation and foraging-predation risk trade-offs: growth and habitat use in young arctic char2004Ingår i: Oikos, Vol. 104, s. 109-121Artikel i tidskrift (Refereegranskat)
  • 12.
    Byström, Pär
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ask, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Andersson, Jens
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Preference for cannibalism and ontogenetic constraints in competitive ability of piscivorous top predators2013Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, nr 7, s. e70404-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We experimentally show that the piscivorous top predator Arctic char (Salvelinus alpinus) have higher attack rates on cannibal prey compared to the interspecific prey species ninespine stickleback (Pungitius pungitius), and that sticklebacks are more efficient competitiors for zooplankton resources compared to juvenile char. We also conducted a literature survey that together with our experiments showed that piscivorous top consumers selected cannibal prey over interspecific prey in 9 out of 10 cases. Our literature survey also showed that specialist prey species are competitively superior compared to juvenile piscivorous species within the zooplankton niche. We discuss our results in relation to omnivory in fish communities and we suggest that the observed general preference for cannibal prey over interspecific prey in piscivores and the competitive advantage of prey species over juvenile piscivores may be major mechanisms for coexistence in fish communities.

  • 13.
    Byström, Pär
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Huss, Magnus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ontogenetic constraints and diet shifts in Perch (Perca fluviatilis): mechanisms and consequences for intra-cohort cannibalism2012Ingår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 57, nr 4, s. 847-857Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1. In many populations, sufficient size variation to allow for cannibalism may develop not only among age cohorts but also within them. Here, we used data on resource dynamics, consumer body size distribution and gape size limitation to unravel mechanisms promoting cannibalism within cohorts of young-of-the-year (YOY) perch (Perca fluviatilis). 2. Perch are strongly gape limited when feeding on large zooplankton during early ontogeny. As a consequence, only initially large fish were able to shift to feeding on abundant large invertebrates, necessary to sustain fast growth. 3. We suggest that a combination of high initial size variation and exclusive access to resources for individuals with an initial size advantage is a prerequisite for the development of a size distribution sufficient for intra-cohort cannibalism to occur. 4. During the time when cannibalism was observed, growth of the largest individuals in YOY perch cohorts was faster than that of smaller individuals. However, the energy gain from cannibalism did not increase growth rate enough to reach a size necessary to feed on more abundant size classes of victims, and therefore, the effect of cannibalism on overall cohort density was minor. 5. In addition to a high energy gain from cannibalism allowing for fast growth, strong resource limitation and slow growth rates of small individuals (i.e. potential victims) are a prerequisite not only for the development of intra-cohort cannibalism but also for its persistence.

  • 14. Claessen, David
    et al.
    Andersson, Jens
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Persson, Lennart
    de Roos, André M
    Delayed evolutionary branching in small populations2007Ingår i: Evolutionary Ecology Research, Vol. 9, s. 51-69Artikel i tidskrift (Refereegranskat)
  • 15. Claessen, David
    et al.
    Andersson, Jens
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    de Roos, André M
    The effect of population size and recombination on delayed evolution of polymorphism and speciation in sexual populations2008Ingår i: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 172, nr 1, s. E18-34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent theory suggests that absolute population size may qualitatively influence the outcome of evolution under disruptive selection in asexual populations. Large populations are predicted to undergo rapid evolutionary branching; however, in small populations, the waiting time to branching increases steeply with decreasing abundance, and below a critical size, the population remains monomorphic indefinitely. Here, we (1) extend the theory to sexual populations and (2) confront its predictions with empirical data, testing statistically whether lake size affects the level of resource polymorphism in arctic char (Salvelinus alpinus) in 22 lakes of different sizes. For a given level of recombination, our model predicts qualitatively similar relations between population size and time to evolutionary branching (either speciation or evolution of genetic polymorphism) as the asexual model, while recombination further increases the delay to branching. The loss of polymorphism at certain loci, an inherent aspect of multilocus-trait evolution, may increase the delay to speciation, resulting in stable genetic polymorphism without speciation. The empirical analysis demonstrates that the occurrence of resource polymorphism depends on both lake size and the number of coexisting fish species. For a given number of coexisting species, the level of polymorphism increases significantly with lake size, thus confirming our model prediction.

  • 16.
    Claessen, David
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    de Roos, André M
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Population dynamic theory of size-dependent cannibalism.2004Ingår i: Proc Biol Sci, ISSN 0962-8452, Vol. 271, nr 1537, s. 333-40Artikel i tidskrift (Övrigt vetenskapligt)
  • 17. De Roos, A M
    et al.
    Persson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    The influence of individual growth and development on the structure of ecological communities2005Ingår i: Food webs. dynamic food webs- multispecies assemblages, ecosystem development and environmental change, Academic Press , 2005, s. 89-100Kapitel i bok, del av antologi (Refereegranskat)
  • 18. De Roos, A M
    et al.
    Persson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Unstructured population models: Do general assumptions yield general theory?2005Ingår i: Ecological paradigms lost: Routes to theory change, Academic Press , 2005, s. 31-62Kapitel i bok, del av antologi (Refereegranskat)
  • 19. de Roos, A. M.
    et al.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Population and community ecology of ontogenetic development2013Bok (Övrigt vetenskapligt)
    Abstract [en]

    Most organisms show substantial changes in size or morphology after they become independent of their parents and have to find their own food. Furthermore, the rate at which these changes occur generally depends on the amount of food they ingest. In this book, André de Roos and Lennart Persson advance a synthetic and individual-based theory of the effects of this plastic ontogenetic development on the dynamics of populations and communities. De Roos and Persson show how the effects of ontogenetic development on ecological dynamics critically depend on the efficiency with which differently sized individuals convert food into new biomass. Differences in this efficiency--or ontogenetic asymmetry--lead to bottlenecks in and thus population regulation by either maturation or reproduction. De Roos and Persson investigate the community consequences of these bottlenecks for trophic configurations that vary in the number and type of interacting species and in the degree of ontogenetic niche shifts exhibited by their individuals. They also demonstrate how insights into the effects of maturation and reproduction limitation on community equilibrium carry over to the dynamics of size-structured populations and give rise to different types of cohort-driven cycles.

  • 20. De Roos, Andre M.
    et al.
    Metz, Johan A. J.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ontogenetic symmetry and asymmetry in energetics2013Ingår i: Journal of Mathematical Biology, ISSN 0303-6812, E-ISSN 1432-1416, Vol. 66, nr 4-5, s. 889-914Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Body size ( biomass) is the dominant determinant of population dynamical processes such as giving birth or dying in almost all species, with often drastically different behaviour occurring in different parts of the growth trajectory, while the latter is largely determined by food availability at the different life stages. This leads to the question under what conditions unstructured population models, formulated in terms of total population biomass, still do a fair job. To contribute to answering this question we first analyze the conditions under which a size-structured model collapses to a dynamically equivalent unstructured one in terms of total biomass. The only biologically meaningful case where this occurs is when body size does not affect any of the population dynamic processes, this is the case if and only if the mass-specific ingestion rate, the mass-specific biomass production and the mortality rate of the individuals are independent of size, a condition to which we refer as "ontogenetic symmetry". Intriguingly, under ontogenetic symmetry the equilibrium biomass-body size spectrum is proportional to 1/size, a form that has been conjectured for marine size spectra and subsequently has been used as prior assumption in theoretical papers dealing with the latter. As a next step we consider an archetypical class of models in which reproduction takes over from growth upon reaching an adult body size, in order to determine how quickly discrepancies from ontogenetic symmetry lead to relevant novel population dynamical phenomena. The phenomena considered are biomass overcompensation, when additional imposed mortality leads, rather unexpectedly, to an increase in the equilibrium biomass of either the juveniles or the adults (a phenomenon with potentially big consequences for predators of the species), and the occurrence of two types of size-structure driven oscillations, juvenile-driven cycles with separated extended cohorts, and adult-driven cycles in which periodically a front of relatively steeply decreasing frequencies moves up the size distribution. A small discrepancy from symmetry can already lead to biomass overcompensation; size-structure driven cycles only occur for somewhat larger discrepancies.

  • 21. de Roos, André M
    et al.
    Boukal, David S
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Evolutionary regime shifts in age and size at maturation of exploited fish stocks.2006Ingår i: Proc Biol Sci, ISSN 0962-8452, Vol. 273, nr 1596, s. 1873-80Artikel i tidskrift (Refereegranskat)
  • 22.
    de Roos, André M.
    et al.
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94084, 1090 GB Amsterdam, The Netherlands.
    Schellekens, Tim
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Van Kooten, Tobias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Stage-specific predator species help each other to persist while competing for a single prey2008Ingår i: Proceedings from the National Academy of Science of the United States of America, ISSN 0027-8424, EISSN 1091-6490, Vol. 105, nr 37, s. 13930-13935Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Prey in natural communities are usually shared by many predator species. How predators coexist while competing for the same prey is one of the fundamental questions in ecology. Here we show that competing predator species may not only coexist on a single prey but even help each other to persist, if they specialize on different life history stages of the prey. By changing the prey size distribution a predator species may in fact increase the amount of prey available for its competitor. Surprisingly, a predator may even not be able to persist at all unless its competitor is also present. The competitor thus increases significantly the range of conditions for which a particular predator can persist. This “emergent facilitation” is a long-term, population-level effect that results from asymmetric increases in the rate of prey maturation and reproduction when predation relaxes competition among prey. Emergent facilitation explains observations of correlated increases of predators on small and large conspecific prey as well as concordance in their distribution patterns. Our results suggest that emergent facilitation may promote the occurrence of complex, stable community food webs and that persistence of these communities could critically depend on diversity within predator guilds.

  • 23.
    de Roos, André M
    et al.
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94084, 1090 GB Amsterdam, The Netherlands.
    Schellekens, Tim
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    van Kooten, Tobias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    van de Wolfshaar, Karen
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94084, 1090 GB Amsterdam, The Netherlands.
    Claessen, David
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94084, 1090 GB Amsterdam, The Netherlands.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Food-dependent growth leads to overcompensation in stage-specific biomass when mortality increases: the influence of maturation versus reproduction regulation2007Ingår i: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 170, nr 3, s. E59-E76Artikel i tidskrift (Refereegranskat)
  • 24.
    De Roos, André M
    et al.
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94084, 1090 GB Amsterdam, The Netherlands.
    Schellekens, Tim
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Van Kooten, Tobias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Van De Wolfshaar, Karen
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94084, 1090 GB Amsterdam, The Netherlands.
    Claessen, David
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O.Box 94084, 1090 GB Amsterdam, The Netherlands.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Simplifying a physiologically structured population model to a stage-structured biomass model.2008Ingår i: Theoretical Population Biology, ISSN 0040-5809, E-ISSN 1096-0325, Vol. 73, nr 1, s. 47-62Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We formulate and analyze an archetypal consumer-resource model in terms of ordinary differential equations that consistently translates individual life history processes, in particular food-dependent growth in body size and stage-specific differences between juveniles and adults in resource use and mortality, to the population level. This stage-structured model is derived as an approximation to a physiologically structured population model, which accounts for a complete size-distribution of the consumer population and which is based on assumptions about the energy budget and size-dependent life history of individual consumers. The approximation ensures that under equilibrium conditions predictions of both models are completely identical. In addition we find that under non-equilibrium conditions the stage-structured model gives rise to dynamics that closely approximate the dynamics exhibited by the size-structured model, as long as adult consumers are superior foragers than juveniles with a higher mass-specific ingestion rate. When the mass-specific intake rate of juvenile consumers is higher, the size-structured model exhibits single-generation cycles, in which a single cohort of consumers dominates population dynamics throughout its life time and the population composition varies over time between a dominance by juveniles and adults, respectively. The stage-structured model does not capture these dynamics because it incorporates a distributed time delay between the birth and maturation of an individual organism in contrast to the size-structured model, in which maturation is a discrete event in individual life history. We investigate model dynamics with both semi-chemostat and logistic resource growth.

  • 25.
    Diehl, Sebastian
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lundberg, Peter A
    Gardfjell, Hans
    Oksanen, Lauri
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Daphnia-phytoplankton interactions in lakes: is there a need for ratio-dependent consumer-resource models?1993Ingår i: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 142, nr 6, s. 1052-1061Artikel i tidskrift (Refereegranskat)
  • 26. Eriksson, Ove
    et al.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    A Spatial Dimension of Ecology: Ilkka Hanski Crafoord Laureate in 20112011Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 40, nr 3, s. 247-Artikel i tidskrift (Refereegranskat)
  • 27. Gessner, M O
    et al.
    Inchausti, P
    Persson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Raffaelli, D G
    Giller, P S
    Biodiversity effects on ecosystem functioning: Insights from aquatic systems2004Ingår i: Oikos, Vol. 104, s. 419-422Artikel i tidskrift (Refereegranskat)
  • 28. Gårdmark, Anna
    et al.
    Casini, Michele
    Huss, Magnus
    van Leeuwen, Anieke
    Hjelm, Joakim
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    de Roos, André M.
    Regime shifts in exploited marine food webs: detecting mechanisms underlying alternative stable states using size-structured community dynamics theory2015Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences, ISSN 0962-8436, E-ISSN 1471-2970, Vol. 370, nr 1659, s. 20130262-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many marine ecosystems have undergone 'regime shifts', i.e. abrupt reorganizations across trophic levels. Establishing whether these constitute shifts between alternative stable states is of key importance for the prospects of ecosystem recovery and for management. We show how mechanisms underlying alternative stable states caused by predator-prey interactions can be revealed in field data, using analyses guided by theory on size-structured community dynamics. This is done by combining data on individual performance (such as growth and fecundity) with information on population size and prey availability. We use Atlantic cod (Gadus morhua) and their prey in the Baltic Sea as an example to discuss and distinguish two types of mechanisms, 'cultivation-depensation' and 'overcompensation', that can cause alternative stable states preventing the recovery of overexploited piscivorous fish populations. Importantly, the type of mechanism can be inferred already from changes in the predators' body growth in different life stages. Our approach can thus be readily applied to monitored stocks of piscivorous fish species, for which this information often can be assembled. Using this tool can help resolve the causes of catastrophic collapses in marine predatory-prey systems and guide fisheries managers on how to successfully restore collapsed piscivorous fish stocks.

  • 29.
    Hin, Vincent
    et al.
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, the Netherlands.
    Schellekens, Tim
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    de Roos, Andre
    Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, the Netherlands.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    The role of predation and competition in a stage-structured intraguild predation systemManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Omnivorous species can simultaneously prey on and compete with other species, a type of interaction referred to as intraguild predation (IGP). Theory predicts that coexistence in IGP systems requires a balance between predation and competition interactions, which occurs when the consumer is a superior resource competitor and resource productivity is restricted to intermediate levels. Mixed competition/predation interactions between a predator and a consumer can, however, also result from ontogenetic niche shifts (life history omnivory). When young, a life history omnivore competes with the species that becomes its prey later in life.  Resource competition with superior consumers can hence limit the development of young predators, while adult predators can cultivate a favourable environment for their young by suppressing these consumers. We formulate and analyze a model in which predators interact with consumers and resources through a mixture of basic intraguild predation and life history omnivory. The model predicts increasing coexistence when predators change to life history omnivores. Furthermore, we show that the crucial assumption enabling coexistence in case of basic intraguild predation, that consumers are superior resource competitors, demotes coexistence when predators are life history omnivores. In coexistence community dynamics are shaped primarily by predation with competitive interactions playing a marginal role. As a result, community dynamics in stage-structured IGP systems, in which predators are life history omnivores, largely resemble those of a three-species linear food chain.

  • 30. Hin, Vincent
    et al.
    Schellekens, Tim
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    de Roos, Andre M.
    Coexistence of Predator and Prey in Intraguild Predation Systems with Ontogenetic Niche Shifts2011Ingår i: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 178, nr 6, s. 701-714Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In basic intraguild predation (IGP) systems, predators and prey also compete for a shared resource. Theory predicts that persistence of these systems is possible when intraguild prey is superior in competition and productivity is not too high. IGP often results from ontogenetic niche shifts, in which the diet of intraguild predators changes as a result of growth in body size (life-history omnivory). As a juvenile, a life-history omnivore competes with the species that becomes its prey later in life. Competition can hence limit growth of young predators, while adult predators can suppress consumers and therewith neutralize negative effects of competition. We formulate and analyze a stage-structured model that captures both basic IGP and life-history omnivory. The model predicts increasing coexistence of predators and consumers when resource use of stage-structured predators becomes more stage specific. This coexistence depends on adult predators requiring consumer biomass for reproduction and is less likely when consumers outcompete juvenile predators, in contrast to basic IGP. Therefore, coexistence occurs when predation structures the community and competition is negligible. Consequently, equilibrium patterns over productivity resemble those of three-species food chains. Life-history omnivory thus provides a mechanism that allows intraguild predators and prey to coexist over a wide range of resource productivity.

  • 31.
    Huss, Magnus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Effects of ontogenetic scaling on resource exploitation and cohort size distributions2010Ingår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 119, nr 2, s. 384-392Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Variation in growth rates among individuals leading to the formation of broad size distributions is commonly observed in animal cohorts. Here we use laboratory derived size-scaling relationships to identify mechanisms driving changes in size distribution patterns within cohorts during early ontogeny. We introduced young-of-the-year perch (Perca fluviatilis) cohorts with different variation in body size distributions in pond enclosures. We kept the exploitative competitive environment constant by adjusting the number of introduced fish such that metabolic requirements were constant between different treatments. Based on modelling results we theoretically derived relative growth rates of differently sized fish when only taken exploitative competitive interactions into account. In agreement with predictions we found that initial variation in body size was negatively correlated with subsequent changes in body size variation in the pond experiment. Corresponding results were obtained in a field study covering 13 studied young-of-the-year perch cohorts in a small lake. Besides having a lower maximum growth capacity, initially large fish also suffered more from resource limitation in our experiment. The results suggest that exploitation competition is a major factor behind growth patterns in young fish cohorts, generally leading to size convergence. To explain the commonly observed pattern of size divergence in animal cohorts, including fish, we suggest that differential timing of diet shifts or mechanisms not related to exploitative interactions must be taken into account. For diet shifts to lead to size divergence we suggest that individuals with an initial size advantage need access to an exclusive prey which has a high growth potential. This, in turn, allows initially larger individuals to surf on a wave of growing prey while individuals only capable to feed on a depressed initial resource experience low growth rates.

  • 32.
    Huss, Magnus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Growing through predation windows:: effects on body size development in young fish2010Ingår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 119, s. 1796-1804Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Th e degree to which growth in early life stages of animals is regulated via density-dependent feedbacks through preyresources is much debated. Here we have studied the infl uence of size- and density-dependent mechanisms as well as sizeselectivepredation pressure by cannibalistic perch Perca fl uviatilis on growth patterns of young-of-the-year (YOY) perchcovering several lakes and years. We found no infl uence of initial size or temperature on early body size development ofperch. In contrast, there was a negative relationship between reproductive output and the length of YOY perch at fi ve weeksof age. However, rather than an eff ect of density-dependent growth mediated via depressed resources the relationship wasdriven by positive size-selective cannibalism removing large individuals. Hence, given a positive correlation between thedensity of victims and predation pressure by cannibals, size-dependent interactions between cannibals and their victimsmay wrongly be interpreted as patterns of density-dependent growth in the victim cohort. Overall, our results support theview that density-dependent resource-limitation in early life stages is rare. Still, patterns of density-dependent growth mayemerge, but from variation in size-selective predation pressure rather than density as such. Th is illustrates the importanceof taking overall population demography and predatory interactions into account when studying growth patterns amongrecruiting individuals.

  • 33.
    Huss, Magnus
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Resource heterogeneity, diet shifts and intra-cohort competition: effects on size divergence in YOY fish2008Ingår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 158, nr 2, s. 249-257Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Most organisms exhibit a substantial size variation among individuals due to individual differences in experienced biotic and abiotic environmental conditions and because individuals undergo growth and development during most of their life time. One important issue in this context is how size variation within cohorts may develop over time. Here we tested the hypothesis, in gape-limited animals such as fish, that size divergence among individuals within a cohort depends on the opportunity to undergo size-dependent diet shifts, by allowing initially larger individuals to make an early diet shift when the first resource becomes limiting. We used young-of-the-year perch (Perca fluviatilis) as our study organism. Competitive intensity and the opportunity to undergo a diet shift from zooplankton to macroinvertebrates affected both mean growth rates and the extent to which inter-individual variation in growth was manifested. As predicted, increased competition combined with the presence of both zooplankton and benthic macroinvertebrates increased the degree of size variation. However, size divergence was also observed among individuals when only the initial resource, zooplankton, was available. We argue that only non-exploitative interactions, such as dominance structures and social interactions could have caused this latter pattern, as exploitative competition is expected to lead to size convergence due to the superior competitive ability of smaller individuals. Our results suggest that diet shifts are not a prerequisite for size divergence in animal cohorts and that dominance and social interactions may have similar effects on size variation within cohorts. Finally, development of size variation is suggested to have strong implications for overall cohort performance.

  • 34.
    Huss, Magnus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Strand, Åsa
    Eriksson, Lars-Ove
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Influence of growth history on the accumulation of energy reserves and winter mortality on young fish2008Ingår i: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 65, nr 10, s. 2149-2156Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In seasonal environments accumulated energy reserves are important to avoid starvation mortality during periods of low resource levels. Here we investigated patterns of energy accumulation and the importance of growth history for winter survival in young-of-the-year Eurasian perch (Perca fluviatilis). Under simulated winter conditions in aquaria’s we showed that high winter mortality most likely relate to the depletion of energy reserves in small perch. Correspondingly in a field study, using 4 lakes covering 3-6 lake years each, overwinter survival within cohorts was positively related to individual size. However, average size in autumn did not explain the variation in overwinter survival between cohorts. Instead we showed that seasonal growth history is an important factor. High growth rates late in season may increase cohort survival over winter irrespective of average size, related to a positive growth dependent increase in allocation to energy reserves when approaching winter. Mechanisms regulating within-season temporal dynamics of growth rates are therefore suggested to be important for overall cohort performance.

  • 35.
    Huss, Magnus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Borcherding, Jost
    Heermann, Lisa
    Timing of the diet shift from zooplankton to macroinvertebrates and size at maturity determine whether normally piscivorous fish can persist in otherwise fishless lakes2013Ingår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 58, nr 7, s. 1416-1424Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using a size-structured population model, life-history information and records of piscivores in systems without prey fish, we analysed the role of the timing of shifting from small-to-large invertebrate prey types in regulating piscivore performance, especially under conditions of low availability of prey fish. Large invertebrate prey are generally absent or at low densities in pelagic habitats; consequently, pelagic piscivorous fish species with a poor ability to exploit zooplankton depend on prey fish in order to persist. In contrast, our model shows that abundant large invertebrate prey in the littoral habitat may allow littoral piscivores to persist in the absence of prey fish if they can shift diet from zooplankton to macroinvertebrates early in life. However, if the diet shift from zooplankton to macroinvertebrates is delayed, or density dependence reduces growth rate, the persistence of even littoral piscivorous fish species in the absence of other prey fish is severely constrained. Our results suggest that undergoing an early diet shift from zooplankton to macroinvertebrates may be necessary to reach sizes large enough to enable successful exploitation of the piscivorous niche. These insights can help to understand the persistence of piscivorous fish species, or their absence, in otherwise fishless lakes.

  • 36.
    Huss, Magnus
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    The origin and development of individual size variation in early pelagic stages of fish2007Ingår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 153, nr 1, s. 57-67Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Size variation among individuals born at the same time in a common environment (within cohorts) is a common phenomenon in natural populations. Still, the mechanisms behind the development of such variation and its consequences for population processes are far from clear. We experimentally investigated the development of early within-cohort size variation in larval perch (Perca fluviatilis). Specifically we tested the influence of initial variation, resulting from variation in egg strand size, and intraspecific density for the development of size variation. Variation in egg strand size translated into variation in initial larval size and time of hatching, which, in turn, had effects on growth and development. Perch from the smallest egg strands performed on average equally well independent of density, whereas larvae originating from larger egg strands performed less well under high densities. We related this difference in density dependence to size asymmetries in competitive abilities leading to higher growth rates of groups consisting of initially small individuals under high resource limitation. In contrast, within a single group of larvae, smaller individuals grew substantially slower under high densities whereas large individuals performed equally well independent of density. As a result, size variation among individuals within groups (i.e. originating from the same clutch) increased under high densities. This result may be explained by social interactions or differential timing of diet shifts and a depressed resource base for the initially smaller individuals. It is concluded that to fully appreciate the effects of density-dependent processes on individual size variation and size-dependent growth, consumer feedbacks on resources need to be considered.

  • 37.
    Huss, Magnus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    van Kooten, Tobias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Intra-cohort cannibalism and size bimodality: a balance between hatching synchrony and resource feedbacks2010Ingår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 119, nr 12, s. 2000-2011Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cannibalistic interactions generally depend on the size relationship between cannibals and victims. In many populations, alarge enough size variation to allow for cannibalism may not only develop among age-cohorts but also within cohorts. Westudied the implications of variation in hatching period length and initial cohort size for the emergence of cannibalism andbimodal size distributions within animal cohorts using a physiologically structured population model. We found that thedevelopment of size bimodality was critically dependent on hatching period length, victim density and the presence of afeedback via shared resources. Cannibals only gained enough energy from cannibalism to accelerate in growth when victimdensity was high relative to cannibal density at the onset of cannibalism. Furthermore, we found that the opportunity forearly hatchers to initially feed on an unexploited resource increases the likelihood both for cannibalism to occur and sizebimodality to develop. Once cannibals accelerated in growth relative to victims size bimodality, reduced victim numbersand relaxed resource competition resulted. Th us, in addition to that cannibals profi ted from cannibalism through energyextraction, their potential victims also benefi ted as the resource recovered due to cannibal thinning. To ensure recruitmentsuccess, it can be critical that a few individuals can accelerate in growth and reach a size large enough to escape sizedependentpredation and winter starvation. Hence, within-cohort cannibalism may be a potentially important mechanismto explain recruitment variation especially for cannibalistic species in temperate climates with strong seasonality. However,the scope for size bimodality to develop as a result of cannibalism may be limited by low victim densities and size andfood-dependent growth rates.

  • 38.
    Jansson, Mats
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    de Roos, André M
    Jones, Roger I
    Tranvik, Lars J
    Terrestrial carbon and intraspecific size-variation shape lake ecosystems2007Ingår i: Trends in Ecology & Evolution, Vol. 22, nr 6, s. 316-322Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Conceptual models of lake ecosystem structure and function have generally assumed that energy in pelagic systems is derived from in situ photosynthesis and that its use by higher trophic levels depends on the average properties of individuals in consumer populations. These views are challenged by evidence that allochthonous subsidies of organic carbon greatly influence energy mobilization and transfer and the trophic structure of pelagic food webs, and that size variation within consumer species has major ramifications for lake community dynamics and structure. These discoveries represent conceptual shifts that have yet to be integrated into current views on lake ecosystems. Here, we assess key aspects of energy mobilization and size-structured community dynamics, and show how these processes are intertwined in pelagic food webs.

  • 39.
    Jäger, Christoph G.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Aquatic Ecosystems Analysis and Management, Helmholtz Centre for Environmental Research – UFZ, Magdeburg, Germany.
    Vrede, Tobias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Interactions between metazoans, autotrophs, mixotrophs and bacterioplankton in nutrient-depleted high DOC environments: a long-term experiment2014Ingår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 59, nr 8, s. 1596-1607Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1. Humic lakes with a high external supply of DOC and low input of nutrients can often support a high biomass of metazoan zooplankton. In such lakes, autotrophic algae compete with bacteria for inorganic nutrients, but bacteria support mixotrophic growth. Consequently, planktonic communities are often dominated by mixotrophic flagellates, while obligate autotrophic phytoplankton occurs in low numbers for extended periods.

    2. To test the importance of autotrophic phytoplankton and mixotrophic flagellates as food resources for metazoan grazers and, in turn, the feedback effects of grazers on basal food-web interactions, we conducted a long-term experiment where we simulated abiotic resource relationships of humic lakes (high DOC [glucose] and low P input). We examined the population dynamics of Daphnia galeata when inoculated in systems with autotrophic algae only, mixotrophic algae only and a mixture of autotrophic and mixotrophic algae, and how the systems changed after the inoculation of Daphnia. All combinations were run at high-and low-light conditions to analyse the effects of light on food quantity and quality.

    3. Daphnia grew to high densities only when mixotrophs were present at high-light conditions and showed no or only weak growth at low-light conditions or with autotrophs as the only food source.

    4. Autotrophic algae and bacteria showed a strong competition for nutrients. Autotrophic algae were released from competition for nutrients after Daphnia grazed on bacteria, which led to a probable change of the bacteria community to less edible but less competitive taxa. As a consequence, there was a mutualistic interaction between autotrophs and mixotrophs before Daphnia were introduced which turned into competition after Daphnia inoculation.

    5. We suggest that mixotrophic flagellates can be a critical resource for cladocerans and thereby also have a cascading effect on higher trophic levels, and cladocerans, in turn, have important indirect effects on basal planktonic food webs; hence, both might affect whole lake ecosystems.

  • 40.
    Karlsson, Jan
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Byström, Pär
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Ask, Jenny
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Ask, Per
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Jansson, Mats
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Light limitation of nutrient-poor lake ecosystems2009Ingår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 460, s. 506-509Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Productivity denotes the rate of biomass synthesis in ecosystems and is a fundamental characteristic that frames ecosystem function and management. Limitation of productivity by nutrient availability is an established paradigm for lake ecosystems1, 2, 3. Here, we assess the relevance of this paradigm for a majority of the world's small, nutrient-poor lakes, with different concentrations of coloured organic matter4, 5. By comparing small unproductive lakes along a water colour gradient, we show that coloured terrestrial organic matter controls the key process for new biomass synthesis (the benthic primary production) through its effects on light attenuation. We also show that this translates into effects on production and biomass of higher trophic levels (benthic invertebrates and fish). These results are inconsistent with the idea that nutrient supply primarily controls lake productivity, and we propose that a large share of the world's unproductive lakes, within natural variations of organic carbon and nutrient input, are limited by light and not by nutrients. We anticipate that our result will have implications for understanding lake ecosystem function and responses to environmental change. Catchment export of coloured organic matter is sensitive to short-term natural variability and long-term, large-scale changes, driven by climate and different anthropogenic influences6, 7. Consequently, changes in terrestrial carbon cycling will have pronounced effects on most lake ecosystems by mediating changes in light climate and productivity of lakes.

  • 41.
    Lövgren, J
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Reinikanen, M
    Persson, L
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Allochtonous input and trophic level heterogeneity: impact on an aquatic food web2006Ingår i: Oikos, Vol. 115, s. 141-147Artikel i tidskrift (Refereegranskat)
  • 42.
    Nilsson, Karin A.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lundback, Sow
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Postavnicheva-Harri, Alexandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Guppy populations differ in cannibalistic degree and adaptation to structural environments2011Ingår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 167, nr 2, s. 391-400Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is considerable variation in cannibalism between different species and also between individuals of different species, although relatively little is known about what creates this variation. We investigated the degree of cannibalism in guppy (Poecilia reticulata) populations originating from high and low predation environments in Trinidad, and also how cannibalism was affected by the presence of refuges. Females from two populations were allowed to feed on juveniles from two populations in aquaria trials. The cannibalism was size-dependent and varied depending on both juvenile and female origin. Low predation females were more efficient cannibals and low predation juveniles were better at avoiding cannibalism compared to high predation guppies when no refuges were present. The high predation females were superior cannibals and the high predation juveniles were better at escaping cannibalism than the low predation guppies when refuges were present. We discuss whether the differences in cannibalism and response to refuge addition relate to predation-induced habitat shifts and differences in the guppies' natural environment.

  • 43.
    Nilsson, Karin A.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lundbäck, Sofi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Postavnicheva-Harri, Alexandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Guppy populations differ in cannibalistic degree and adaption to structural environmentsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    We investigated the degree of cannibalism in guppy (Poecilia reticulata) populations originating from high and low predation environments in Trinidad and how cannibalism was affected by the presence of refuges. Females from two populations were allowed to feed on juveniles from two populations in aquaria trials. The cannibalism was size-dependent and varied depending on both juvenile and female origin. Low predation females were more efficient cannibals and low predation juveniles were better at avoiding cannibalism compared to high predation guppies when no refuges were present. The addition of refuges decreased cannibalism when females from the low predation population were feeding on juveniles from the high predation population. In contrast, cannibalism increased with the addition of refuges for all other combinations. The high predation females were also superior cannibals and the high predation juveniles were better at escaping cannibalism than the low predation guppies with refuges present. We discuss whether the differences in cannibalism and response to refuge addition relate to predation induced habitat shifts and differences in the guppies’ natural environment.

  • 44.
    Nilsson, Karin A.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Cannibalism and resource competition determine population structure and regulation in experimental guppy populationsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Cannibalism and intraspecific resource competition, separately or in combination, can be important factors in regulating populations. Cannibalistic voracity and size of offspring have been shown to be two important factors in determining the extent to which cannibalism can regulate a population. We investigated guppy populations originating from two different environments and that differ in cannibalistic voracity and size of offspring. We investigated mechanisms behind density independent and density dependent relationships by varying the availability of juvenile refuges and harvesting of large females.  One population (Turure) had a lower total biomass than the other population (Quare) and showed stronger density dependence in the treatments without refuges. In contrast, the Quare population showed a stronger density dependence when refuges were present. We suggest that the presence of refuges decreased cannibalism and increased competition leading to stronger density dependence through decreased fecundity of females and juvenile growth and survival. Harvest of large females decreased cannibalism but decreased reproductive output even more which led to extinctions of the Turure populations when no refuges were present. When refuges were present harvesting had only a small effect related to that few females grew large enough to be harvested.

  • 45.
    Nilsson, Karin A.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Refuge availability and within-species differences in cannibalism determine population variability and dynamics2013Ingår i: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 4, nr 8, s. 100-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Theoretical studies show that both cannibalism and intraspecific resource competition can have major effects on population dynamics. Cannibalistic intensity, offspring size, harvesting and refuge availability are important factors affecting the interplay between cannibalism and competition. We studied two populations of the common guppy (Poecilia reticulata) that differed in their cannibalistic voracity as well as offspring size. We manipulated the availability of refuges for juveniles and harvesting intensity of large adults to investigate how these factors influenced the dynamics of the two populations. Overall population dynamics was mainly affected by the origin of the founder populations and the presence of refuges. The population with a higher cannibalistic propensity and smaller offspring exhibited higher population variability, and the presence of refuges reduced cannibalism and stabilised the dynamics in both populations. Harvest of large cannibalistic females destabilised the dynamics and caused extinctions of several populations without refuges. Both populations displayed cannibal-driven cycles with repression of recruitment when no refuges were present. Cycle periods were shorter with refuges present and the dynamics were more cohort like with synchronised peaks in density of vulnerable juveniles and cannibals. We suggest that increased number of refuging juveniles led to intensified resource competition in the population. The harvest yield was low in the refuge treatments as few females grew large due to resource competition, leading to a small impact of harvesting in these treatments.

  • 46.
    Nilsson, Karin A.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Persson, Lennart
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    van Kooten, Tobias
    Wageningen IMARES, PO Box 68, 1970 AB IJmuiden, the Netherlands.
    Complete compensation in Daphnia fecundity and stage-specific biomass in response to size-independent mortality2010Ingår i: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 79, nr 4, s. 871-878Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1. Recent theory suggests that compensation or even overcompensation in stage-specific biomass can arise in response to increased mortality. Which stage that will show compensation depends on whether maturation or reproduction is the more limiting process in the population. Size-structured theory also provides a strong link between the type of regulation and the expected population dynamics as both depend on size/stage specific competitive ability.

    2. We imposed a size-independent mortality on a consumer-resource system with Daphnia pulex feeding on Scenedesmus obtusiusculus to asses the compensatory responses in Daphnia populations. We also extended an existing stage-structured biomass model by including several juvenile stages to test whether this extension affected the qualitative results of the existing model.

    3. We found complete compensation in juvenile biomass and total population fecundity in response to harvesting. The compensation in fecundity was caused by both a higher proportion of fecund females and a larger clutch size under increased mortality. We did not detect any difference in resource levels between treatments.

    4. The model results showed that both stages of juveniles have to be superior to adults in terms of resource competition for the compensatory response to take place in juvenile biomass.

    5. The results are all in correspondence with that the regulating process within the population was reproduction. From this we also conclude that juveniles were superior competitors to adults, which has implications for population dynamics and the kind of cohort cycles seen in Daphnia populations.

    6. The compensatory responses demonstrated in this experiment have major implications for community dynamics and are potentially present in any organisms with food-dependent growth or development.

  • 47.
    Persson, L
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Bertolo, A
    De Roos, A M
    Temporal stability in size distributions and growth rates of three pike Esox lucius L. populations – a result of cannibalism?2006Ingår i: Journal of Fish Biology, Vol. 69, s. 461-472Artikel i tidskrift (Refereegranskat)
  • 48.
    Persson, L
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Byström, P
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    Wahlström, E
    Westman, E
    Trophic dynamics in a whole lake experiment: size-structured interactions and recruitment variation2004Ingår i: Oikos, Vol. 106, s. 263-274Artikel i tidskrift (Refereegranskat)
  • 49.
    Persson, L
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Claessen, D
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    De Roos,, A M
    Byström, P
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sjögren, S
    Svanbäck, Richard
    Wahlström, E
    Westman, E
    Cannibalism in a size-structured population: energy extraction and control2004Ingår i: Ecological Monographs, Vol. 74, s. 135-157Artikel i tidskrift (Refereegranskat)
  • 50.
    Persson, L
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Ekologi, miljö och geovetenskap.
    De Roos, A M
    Body size scaling and the dynamics of ecological systems2005Ingår i: Food webs. dynamic food webs- multispecies assemblages, ecosystem development and environmental change, Academic Press , 2005, s. 157-166Kapitel i bok, del av antologi (Refereegranskat)
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