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  • 1.
    Berg, Sofia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Christianou, Maria
    Linköping University, Department of Physics, Chemistry and Biology, Biotechnology . Linköping University, The Institute of Technology.
    Jonsson, Tomas
    Research centre for Systems Biology, Univ. of Skövde, Sweden.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Using sensitivity analysis to identify keystone species and keystone links in size-based food webs2011In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 120, no 4, p. 510-519Article in journal (Refereed)
    Abstract [en]

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

  • 2.
    Berg, Sofia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Jonsson, Tomas
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Hauzy, Céline
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Säterberg, Torbjörn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Christianou, Maria
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Yearsley, Jon
    School of Biology and Environmental Science, University College Dublin, Ireland.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Rare but important: perturbations to uncommon species have disproportionately large impact on ecological communitiesManuscript (preprint) (Other academic)
    Abstract [en]

    The majority of species in the ecosystems of the world are rare. Because the contributions to community biomass and productivity of many of these species are small it has been suggested that loss of rare species should have relatively small ecological consequences. However, the extent to which rare species affect the structure and stability of ecosystems is largely unknown. Using a theoretical approach, based on analytical methods, we here   investigate how perturbations to rare as well as common species affect the structure (distribution of equilibrium abundances of species) and resilience (recovery rate) of complex ecological communities. We show that, contrary to expectation, resilience and structure of ecological communities are generally more sensitive to perturbations to rare than to common species. We find the explanation for this to lie in the cause of rarity: rare species tend to interact strongly, on a per capita basis, with other species. Our results suggest that many rare species are likely to fill important ecological roles in ecosystems.

  • 3.
    Berlow, E.L.
    et al.
    University of California, White Mountain Research Station, Bishop, CA 93514, United States, Department of Integrative Biology, University of California, Berkeley, CA 94720, United States.
    Neutel, A.-M.
    Department of Environmental Sciences, Utrecht University, PO Box 80115, 3508 TC Utrecht, Netherlands.
    Cohen, J.E.
    Rockefeller Columbia Universities, Box 20, 1230 York Avenue, New York, NY 10021-6399, United States.
    De, Ruiter P.C.
    De Ruiter, P.C., Department of Environmental Sciences, Utrecht University, PO Box 80115, 3508 TC Utrecht, Netherlands.
    Ebenman, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology .
    Emmerson, M.
    Dept. of Zool., Ecol. and Plant Sci., University College Cork, Prospect Row, Cork, Eire, Ireland.
    Fox, J.W.
    NERC Centre for Population Biology, Imperial College, Silwood Park, Ascot, Berkshire SL5 7PY, United Kingdom.
    Jansen, V.A.A.
    School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom.
    Jones, J.I.
    School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, United Kingdom.
    Kokkoris, G.D.
    Department of Marine Sciences, University of the Aegean, University Hill, 81100 Mytilene, Lesvos Island, Greece.
    Logofet, D.O.
    Laboratory of Math. Ecology, IFARAN, Pyzhevsky Pereulok 3, Moscow, 119017, Russian Federation.
    Mckane, A.J.
    Department of Theoretical Physics, University of Manchester, Manchester M13 9 PL, United Kingdom.
    Montoya, J.M.
    Complex Systems Laboratory, IMIM - UPF (GRIB), Dr Aigvader 80, 08003 Barcelona, Spain.
    Petchey, O.
    Dept. of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, United Kingdom.
    Interaction strengths in food webs: Issues and opportunities2004In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 73, no 3, p. 585-598Article, review/survey (Refereed)
    Abstract [en]

    1. Recent efforts to understand how the patterning of interaction strength affects both structure and dynamics in food webs have highlighted several obstacles to productive synthesis. Issues arise with respect to goals and driving questions, methods and approaches, and placing results in the context of broader ecological theory. 2. Much confusion stems from lack of clarity about whether the questions posed relate to community-level patterns or to species dynamics, and to what authors actually mean by the term 'interaction strength'. Here, we describe the various ways in which this term has been applied and discuss the implications of loose terminology and definition for the development of this field. 3. Of particular concern is the clear gap between theoretical and empirical investigations of interaction strengths and food web dynamics. The ecological community urgently needs to explore new ways to estimate biologically reasonable model coefficients from empirical data, such as foraging rates, body size, metabolic rate, biomass distribution and other species traits. 4. Combining numerical and analytical modelling approaches should allow exploration of the conditions under which different interaction strengths metrics are interchangeable with regard to relative magnitude, system responses, and species identity. 5. Finally, the prime focus on predator-prey links in much of the research to date on interaction strengths in food webs has meant that the potential significance of nontrophic interactions, such as competition, facilitation and biotic disturbance, has been largely ignored by the food web community. Such interactions may be important dynamically and should be routinely included in future food web research programmes.

  • 4.
    Borrvall, Charlotte
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology .
    Christianou, Maria
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology .
    Ebenman, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology .
    Biodiversity Decreases the risk of Collapse2005In: Systems shocks - Systems resilience, The 2000 Abisko Workshop,2000, London: World Scientific , 2005, p. 209-Conference paper (Refereed)
  • 5.
    Borrvall, Charlotte
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology .
    Ebenman, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology .
    Biodiversity and persistence of ecological communities in variable environments2008In: Ecological Complexity: An International Journal on Biocomplexity in the Environment and Theoretical Ecology, ISSN 1476-945X, E-ISSN 1476-9840, Vol. 5, p. 99-105Article in journal (Refereed)
  • 6.
    Borrvall, Charlotte
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Early onset of secondary extinctions in ecological communities following the loss of top predators2006In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 9, no 4, p. 435-442Article in journal (Refereed)
    Abstract [en]

    The large vulnerability of top predators to human-induced disturbances on ecosystems is a matter of growing concern. Because top predators often exert strong influence on their prey populations their extinction can have far-reaching consequences for the structure and functioning of ecosystems. It has, for example, been observed that the local loss of a predator can trigger a cascade of secondary extinctions. However, the time lags involved in such secondary extinctions remain unexplored. Here we show that the loss of a top predator leads to a significantly earlier onset of secondary extinctions in model communities than does the loss of a species from other trophic levels. Moreover, in most cases time to secondary extinction increases with increasing species richness. If local secondary extinctions occur early they are less likely to be balanced by immigration of species from local communities nearby. The implications of these results for community persistence and conservation priorities are discussed.

  • 7.
    Borrvall, Charlotte
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Jonsson, Tomas
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Biodiversity lessens the risk of cascading extinction in model food webs2000In: Ecology Letters, ISSN 1461-023X , Vol. 3, no 2, p. 131-136Article in journal (Refereed)
    Abstract [en]

    Due to the complex interactions between species in food webs, the extinction of one species could lead to a cascade of further extinctions and hence cause dramatic changes in species composition and ecosystem processes. We found that the risk of additional species extinction, following the loss of one species in model food webs, decreases with the number of species per functional group. For a given number of species per functional group, the risk of further extinctions is highest when an autotroph is removed and lowest when a top predator is removed. In addition, stability decreases when the distribution of interaction strengths in the webs is changed from equal to skew (few strong and many weak links). We also found that omnivory appears to stabilize model food webs. Our results indicate that high biodiversity may serve as an insurance against radical ecosystem changes.

  • 8.
    Christianou, Maria
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Keystone species and vulnerable species in ecological communities: strong or weak interactors?2005In: Journal of Theoretical Biology, ISSN 0022-5193, Vol. 35, no 1, p. 95-103Article in journal (Refereed)
    Abstract [en]

    The loss of a species from an ecological community can trigger a cascade of secondary extinctions. The probability of secondary extinction to take place and the number of secondary extinctions are likely to depend on the characteristics of the species that is lost—the strength of its interactions with other species—as well as on the distribution of interaction strengths in the whole community. Analysing the effects of species loss in model communities we found that removal of the following species categories triggered, on average, the largest number of secondary extinctions: (a) rare species interacting strongly with many consumers, (b) abundant basal species interacting weakly with their consumers and (c) abundant intermediate species interacting strongly with many resources. We also found that the keystone status of a species with given characteristics was context dependent, that is, dependent on the structure of the community where it was embedded. Species vulnerable to secondary extinctions were mainly species interacting weakly with their resources and species interacting strongly with their consumers.

  • 9.
    Christianou, Maria
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Prospects and risks of species reintroductions: a community ecological perspectiveManuscript (Other academic)
    Abstract [en]

    For many threatened species reintroduction of captive-reared individuals into the wild may offer the only hope of preventing global extinction. However, attempts to reintroduce a species into an ecological community from which it has once gone extinct often fail. This can be due to captivity-induced genetic and behavioural changes in the species itself. Here we argue that also changes in the structure of the community caused by the initial loss of the species can hinder its subsequent reintroduction. Due to the interdependences amongspecies in ecological communities the local extinction of a species leads to changes in the densities and strength of interactions among the remaining species in the community and sometimes even to a cascade of secondary extinctions. Such alterations in the structure of a community caused by the initial extinction of the species might make it impossible for the species to reinvade at a later stage. Here we show, using models of multitrophic communities, that the risk of reintroduction failure can be high and that it differs between species belonging to different trophic levels and between weakly and strongly interacting species. Specifically, there is a high risk of reintroduction failure for primary producer species and weakly interacting consumer species. We also find the risk that the reintroduction will cause new extinctions to be higher in communities where the initial loss triggered secondary extinctions. In the worst case extinctions caused by the reintroduction may lead to the subsequent extinction of the reintroduced species itself. This risk is not negligible implicating that reintroductions might sometimes aggravate the state of local communities.

  • 10.
    Christianou, Maria
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Sensitivity analysis at the community level2006Manuscript (preprint) (Other academic)
    Abstract [en]

    Human-induced changes in the birth and mortality rates of species and in the strength of interactions within and between species can lead to changes in the resilience of ecological communities. Here we derive analytical expressions for the sensitivity of community resilience to changes in the intrinsic growth rate of species and in the strengths of interaction links. These new methods are applied on model communities to illustrate how they can be used to identify keystone species and keystone links - keystone species and keystone links in the sensethat small changes in their growth rates and strengths, respectively, will have large effects on the resilience of the community. We find that small changes in the intrinsic growth rates of rare species (e.g. top predators) and strongly interacting species have larger effect on resilience than changes in the growth rates of abundant species and weakly interacting species. Moreover, we find that small changes in the strength of weak interaction links cause larger changes in resilience than changes in the strength of strong links. We believe that thecommunity sensitivity analysis developed here holds some promise for identifying species and links that are critical for the resilience of ecological communities.

  • 11.
    Curtsdotter, Alva
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Binzer, Amrei
    J.F. Blumenbach Institute of Zoology and Anthropology, Georg-August University, Göttingen, Germany.
    Brose, Ulrich
    J.F. Blumenbach Institute of Zoology and Anthropology, Georg-August University, Göttingen, Germany.
    de Castro, Fransisco
    Department of Ecology and Ecological Modelling, University of Potsdam, Germany.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Eklöf, Anna
    Department of Ecology and Evolution, University of Chicago, United States.
    O. Riede, Jens
    J.F. Blumenbach Institute of Zoology and Anthropology, Georg-August University, Göttingen, Germany.
    Thierry, Aaron
    Department of Animal and Plant Sciences, University of Sheffield, United Kingdom. Microsoft Research, JJ Thompson Avenue, Cambridge, CB3 0FB, UK.
    Rall, Björn C.
    J.F. Blumenbach Institute of Zoology and Anthropology, Georg-August University, Göttingen, Germany.
    Robustness to secondary extinctions: Comparing trait-based sequential deletions in static and dynamic food webs2011In: Basic and Applied Ecology, ISSN 1439-1791, E-ISSN 1618-0089, Vol. 12, no 7, p. 571-580Article in journal (Refereed)
    Abstract [en]

    The loss of species from ecological communities can unleash a cascade of secondary extinctions, the risk and extent of which are likely to depend on the traits of the species that are lost from the community. To identify species traits that have the greatest impact on food web robustness to species loss we here subject allometrically scaled, dynamical food web models to several deletion sequences based on species’ connectivity, generality, vulnerability or body mass. Further, to evaluate the relative importance of dynamical to topological effects we compare robustness between dynamical and purely topological models. This comparison reveals that the topological approach overestimates robustness in general and for certain sequences in particular. Top-down directed sequences have no or very low impact on robustness in topological analyses, while the dynamical analysis reveals that they may be as important as high-impact bottom-up directed sequences. Moreover, there are no deletion sequences that result, on average, in no or very few secondary extinctions in the dynamical approach. Instead, the least detrimental sequence in the dynamical approach yields an average robustness similar to the most detrimental (non-basal) deletion sequence in the topological approach. Hence, a topological analysis may lead to erroneous conclusions concerning both the relative and the absolute importance of different species traits for robustness. The dynamical sequential deletion analysis shows that food webs are least robust to the loss of species that have many trophic links or that occupy low trophic levels. In contrast to previous studies we can infer, albeit indirectly, that secondary extinctions were triggered by both bottom-up and top-down cascades.

  • 12.
    Curtsdotter, Alva
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Binzer, Amrei
    J.F. Blumenbach Institute of Zoology and Anthropology, Georg-August University, Göttingen, Germany.
    Brose, Ulrich
    J.F. Blumenbach Institute of Zoology and Anthropology, Georg-August University, Göttingen, Germany.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    The interaction between species traits and community properties determine food web resistance to species loss2014Manuscript (preprint) (Other academic)
    Abstract [en]

    The ability to identify the ecosystems most vulnerable to species loss is fundamental for the allocation of conservation efforts. With this aim, the traits of keystone species have been investigated, as have the properties defining systems especially sensitive to species loss. However, these two have rarely been investigated in relation to each other. Here we show, that the traits of the species primarily lost act in conjunction with the properties of the food web from which it is lost, in determining the resistance of the system. We find that the extent of bottom-up extinction cascades is determined mainly by traits related to food web topology, while traits related to population dynamics govern the extent of top-down cascades. As different disturbances affect species with different traits, this interaction implies that the characteristics defining a sensitive community depend on the disturbance it is subjected to.

  • 13.
    Curtsdotter, Alva
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Münger, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Norberg, Jon
    Department of Systems Ecology, Stockholm University/Stockholm Resilience Centre, Stockholm University, Sweden.
    Åkesson, Anna
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    The strength of interspecific competition modulates the eco-evolutionary response to climate change2014Manuscript (preprint) (Other academic)
    Abstract [en]

    Climate change is predicted to have major implications for global biodiversity. Dispersal and evolution may become crucial for species survival, as species must either adapt or migrate to track the changing climate. However, migration and evolution do not occur in vacuum – the biotic community in which these processes play out may modulate their effect on biodiversity. Here, we use an eco-evolutionary, spatially explicit, multi-species model that allows us to examine the interactive effects of competition, adaptation and dispersal on species richness in plant communities under global warming. We find that there is a larger decline in global species richness when interspecific competition is strong. Furthermore, there is a three-way interaction between interspecific competition, evolution and dispersal that creates a complex pattern of biodiversity responses, in which both evolution and dispersal can either increase or decrease the magnitude of species loss. This interaction arises for at least two reasons: 1) different levels of dispersal, evolution and competition creates differences in local and global community structure before climate change, and 2) competitive interactions determine whether the benefits of dispersal and/or evolution (climate tracking and adaptation) outweighs the risks (competitive exclusion).

  • 14.
    Ebeman, Bo
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Lennart, PerssonUmeå universitet.
    Size-structured populations: ecology and evolution1988Collection (editor) (Other academic)
  • 15.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Dynamics of age- and size-structured populations: intraspecific competition1988In: Size-structured populations: ecology and evolution / [ed] Bo Ebenman, Lennart Persson, Berlin: Springer Berlin/Heidelberg, 1988, p. 127-139Chapter in book (Other academic)
  • 16.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Response of ecosystems to realistic extinction sequences2011In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 80, no 2, p. 307-309Article in journal (Other academic)
    Abstract [en]

    Recent research suggests that effects of species loss on the structure and functioning of ecosystems willcritically depend on the order with which species go extinct. However, there are few studies of theresponse of natural ecosystems to realistic extinction sequences. Using an extinction scenario basedon the International Union for Conservation of Nature (IUCN) Red List, de Visser et al. sequentiallydeleted species from a topological model of the Serengeti food web. Under this scenario, large-bodiedspecies like top predators and mega-herbivores go extinct first. The resulting changes in the trophicstructure of the food web might affect the robustness of the ecosystem to future disturbances.

  • 17.
    Ebenman, Bo
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology .
    Jonsson, Tomas
    Systems biology group Skövde University.
    Using community viability analysis to identify fragile systems and keystone species2005In: Trends in Ecology & Evolution, ISSN 0169-5347, E-ISSN 1872-8383, Vol. 20, no 10, p. 568-575Article in journal (Refereed)
    Abstract [en]

    Owing to interdependences among species in ecological communities, the loss of one species can trigger a cascade of secondary extinctions with potentially dramatic effects on the functioning and stability of the community. It is, therefore, important to assess the risk and likely extent of secondary extinctions. Community viability analysis is a new technique that can be used to accomplish this goal. The analysis can also be used to identify fragile community structures and keystone species and, hence, to provide guidelines for conservation priorities. Here, we describe the principles underlying community viability analysis and review its contributions to our understanding of the response of ecological communities to species loss.

  • 18.
    Ebenman, Bo
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Law, Richard
    2Biology Department, University of York, York, United Kingdom.
    Borrvall, Charlotte
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Community viability analysis: the response of ecological communities to species loss.2004In: Ecology, ISSN 0012-9658, Vol. 85, no 9, p. 2591-2600Article in journal (Refereed)
    Abstract [en]

    The loss of a species from an ecological community can set up a cascade of secondary extinctions that in the worst case could lead to the collapse of the community. Both deterministic and stochastic mechanisms may be involved in such secondary extinctions. To investigate the extent of secondary extinctions in ecological communities following the loss of a species, we here develop a community viability analysis. We introduce a measure called the “quasi-collapse risk” that is defined as the probability that the number of species in a community falls below some defined value within a fixed period of time following the loss of a species. We develop deterministic and stochastic methods for finding post-extinction communities. We use these methods to investigate the relationship between diversity (species richness) and quasi-collapse risks in model communities. It is shown that, in a deterministic context, communities with more species within trophic levels have a larger fraction of species remaining in post-extinction communities. This benefit of species richness is to a large extent lost in the presence of demographic stochasticity. The reason for this is a negative relationship between population density and species diversity. We also show that communities become increasingly triangular in shape as secondary extinctions take place, due to greater extinction risk of species at higher trophic levels. We argue that this new approach holds some promise for identifying fragile ecosystems and keystone species.

  • 19.
    Eklöf, Anna
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology.
    Ebenman, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology.
    Species loss and secondary extinctions in simple and complex model communities2006In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 75, no 1, p. 239-246Article in journal (Refereed)
    Abstract [en]
    1. The loss of a species from an ecological community can trigger a cascade of secondary extinctions. Here we investigate how the complexity (connectance) of model communities affects their response to species loss. Using dynamic analysis based on a global criterion of persistence (permanence) and topological analysis we investigate the extent of secondary extinctions following the loss of different kinds of species.
    2. We show that complex communities are, on average, more resistant to species loss than simple communities: the number of secondary extinctions decreases with increasing connectance. However, complex communities are more vulnerable to loss of top predators than simple communities.
    3. The loss of highly connected species (species with many links to other species) and species at low trophic levels triggers, on average, the largest number of secondary extinctions. The effect of the connectivity of a species is strongest in webs with low connectance.
    4. Most secondary extinctions are due to direct bottom-up effects: consumers go extinct when their resources are lost. Secondary extinctions due to trophic cascades and disruption of predator-mediated coexistence also occur. Secondary extinctions due to disruption of predator-mediated coexistence are more common in complex communities than in simple communities, while bottom-up and top-down extinction cascades are more common in simple communities.
    5. Topological analysis of the response of communities to species loss always predicts a lower number of secondary extinctions than dynamic analysis, especially in food webs with high connectance.
  • 20.
    Eklöf, Anna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Münger, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Effects of dispersal on local extinctions in multi-trophic metacommunitiesManuscript (preprint) (Other academic)
    Abstract [en]

    As a result of habitat destruction many ecological communities have a fragmented distribution and are built up of partially isolated local communities connected through dispersal of interacting species. The dynamics of such metacommunities is governed both by local processes (interactions among species coexisting within habitat patches) and regional processes (movement of species among habitat patches). Earlier theoretical work on simple metacommunities have mainly focused on the positive effects of space and dispersal for the coexistence of interacting species and hence for local and regional species diversity. However, it is plausible that dispersal might also pose some kind of risk to the dispersing individuals. Here we explore how such risks might affect the dynamics of metacommunities. We develop spatially and dynamically explicit models to investigate how the trophic structure (connectance) of local communities, the spatial structure of the metacommunity and the dispersal characteristics of species affect species extinction risks. Species extinction risks in these open communities are measured relative to the extinction risks in closed communities (i.e. no dispersal). We show that the introduction of dispersal among initially closed local communities might lead to increased probability of local species extinction. The effects of dispersal depend on migration rate, movement pattern of individuals and the density of patches in the landscape. Specifically, when dispersal involves a risk, high migration rates, global dispersal and low patch density will all lead to increased probability of local species extinctions. Furthermore, the trophic structure of local communities plays a significant role in the response of metacommunities to changes in the regional processes.

  • 21.
    Eklöf, Anna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Münger, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Kaneryd, Linda
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Can dispersal rescue metacommunities from extinction cascades?Manuscript (preprint) (Other academic)
    Abstract [en]

    Climate change and habitat loss are increasingly affecting the structure and dynamics of ecological communities both at the local and regional scale. Changes in the spatial structure of landscapes as well as in the trophic structure of local communities can be expected to have important consequences for the long-term persistence of species in metacommunities. The aim of the present work is to investigate how the spatial structure of the landscape (patch density) and dispersal patterns of species (migration rate and dispersal distance) affect a metacommunities response to local loss of species and to increased mortality of individuals during dispersal. Using a spatially and dynamically explicit metacommunity model we find that the effect of dispersal on metacommunity persistence is two-sided: on the one hand, when dispersal involves no risk, high migration rate significantly reduces the risk of bottom-up extinction cascades following the local removal of a species. The explanation for this is that recolonization rates of the locally removed species increases with increasing migration rate. On the other hand, when dispersal imposes a risk to the dispersing individuals, high migration rate increases extinction risks, especially when dispersal is global (long dispersal distances). Largebodied species with long generation times at the highest trophic level are particularly vulnerable to extinction when dispersal involves a risk. These results suggest that decreasing the mortality risk of dispersing individuals by improving the quality of the habitat matrix might greatly increase the robustness of metacommunities to local loss of species by enhancing recolonizations and rescue effects.

  • 22.
    Eklöf, Anna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Platts, Philip
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Cascading extinctions in spatially coupled food websManuscript (preprint) (Other academic)
    Abstract [en]

    The spatial structure of ecological communities as well as the dynamics and structure of local communities can be expected to have important consequences for the long-term persistence of metacommunities, that is, their resistance to different kind of perturbations. The aim of the present work is to investigate how web connectance of local communities and number of local habitat patches affects a metacommunity’s response to the global loss of a species. We find that the inclusion of space significantly reduces the risk of global and local cascading extinctions. It is shown that communities with sparsely connected food webs are the most sensitive to species loss, but also that they are particularly well stabilized by the introduction of space. In agreement with theoretical studies of non-spatial habitats, species at the highest trophic level are the most vulnerable to secondary extinction, although they often take the longest time to die out. This is particularly pronounced in spatial habitats, where the top predators appear to be the least well adapted to exploit the stabilizing properties of space.

  • 23.
    Gilljam, David
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Curtsdotter, Alva
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Adaptive rewiring aggravates the effects of species loss in ecosystems2015In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 6, article id 8412Article in journal (Refereed)
    Abstract [en]

    Loss of one species in an ecosystem can trigger extinctions of other dependent species. For instance, specialist predators will go extinct following the loss of their only prey unless they can change their diet. It has therefore been suggested that an ability of consumers to rewire to novel prey should mitigate the consequences of species loss by reducing the risk of cascading extinction. Using a new modelling approach on natural and computer-generated food webs we find that, on the contrary, rewiring often aggravates the effects of species loss. This is because rewiring can lead to overexploitation of resources, which eventually causes extinction cascades. Such a scenario is particularly likely if prey species cannot escape predation when rare and if predators are efficient in exploiting novel prey. Indeed, rewiring is a two-edged sword; it might be advantageous for individual predators in the short term, yet harmful for long-term system persistence.

  • 24.
    Gilljam, David
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    High dynamic dimensionality promotes the persistence of ecological networks in a variable world2016Manuscript (preprint) (Other academic)
    Abstract [en]

    The long-term persistence of ecological communities depends on the strength of destabilizing stochastic forces relative to the strength of stabilizing feedbacks caused by interactions among and within species. What characteristics of a community that tip the balance of these forces in favour of persistence is not clear. Here we show that long-term persistence of a community is positively related to its dynamic dimensionality (DD). A high DD means that the system approaches the equilibrium from all directions at a similar rate. On the other hand, when DD is low the deterministic forces pulling the system towards equilibrium is weak in many directions compared to the stochastic forces pushing the system away from the equilibrium. As a consequence persistence decreases as DD decreases. This result illustrates the potential importance of dynamic dimensionality of ecosystems for their persistence in a variable world and by extension for their vulnerability to changes in the strength and patterns of climate variability caused by global warming.

  • 25.
    Gilljam, David
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Patterns of resource utilisation within and between species affect the dynamic dimensionality and stability of ecological communities2016Manuscript (preprint) (Other academic)
    Abstract [en]

    In many ecological communities, individuals within species pass through a wide spectrum of sizes, spanning several orders of magnitude, during the independent part of their life cycle. Such a large size-variation within a species will affect the structure of its niche, since the size of an individual affects the type of prey it can consume as well as what predators will attack it. Here we use highly resolved individual-based empirical data to investigate patterns in the niche structure of several aquatic food webs. We quantify within and between species components of resource use in these webs and explore its consequences for dynamical dimensionality and community stability using simple food web models with stage-structured consumer species. Among the natural food webs there are webs where species overlap widely in their resource use while the resource use of size-classes within species differs. There are also webs where differences in resource use among species is relatively large and the niches of sizeclasses within species are more similar. Model systems with the former structure are found to have low dynamical dimensionality and to be less stable compared to systems with the latter structure. Thus, although differential resource use among individuals within a species is likely to decrease the intensity of intraspecific competition and favor individuals specializing on less exploited resources it can destabilize the community in which the individuals are embedded.

  • 26.
    Gilljam, David
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Thierry, Aaron
    University of Sheffield, UK.
    Edwards, Francois K.
    Centre of Ecology and Hydrology, Wallingford, UK.
    Figueroa, David
    School of BIological and Chemical Sciences, Queen Mary University of London, UK.
    Ibbotson, Anton T.
    Game and Wildlife Conservation Trust, UK.
    Jones, Iwan J.
    School of BIological and Chemical Sciences, Queen Mary University of London, UK.
    Lauridsen, Rasmus B.
    School of BIological and Chemical Sciences, Queen Mary University of London, UK.
    Petchey, Owen L.
    University of Zürick, Switzerland.
    Woodward, Guy
    School of BIological and Chemical Sciences, Queen Mary University of London, UK.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Seeing Double: Size-Based and Taxonomic Views of Food Web Structure2011In: Advances in Ecological Research, ISSN 0065-2504, E-ISSN 2163-582X, Vol. 45, p. 67-133Article in journal (Refereed)
  • 27.
    Hauzy, Céline
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology. Université Pierre et Marie Curie, Paris, France.
    Nadin, Grégoir
    CNRS, UMR7598- Laboratoire Jaques-Louis, Paris, France.
    Canard, Elsa
    Institut des Sciences de l'Evolution, Université de Montepellier II, Montepellier, France.
    Gounand, Isabelle
    Institut des Sciences de l'Evolution, Université de Montepellier II, Montepellier, France.
    Mouquet, Nicolas
    Institut des Sciences de l'Evolution, Université de Montepellier II, Montepellier, France.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Confronting the Paradox of Enrichment to the Metacommunity Perspective2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 12, p. e82969-Article in journal (Refereed)
    Abstract [en]

    Resource enrichment can potentially destabilize predator-prey dynamics. This phenomenon historically referred as the "paradox of enrichment" has mostly been explored in spatially homogenous environments. However, many predator-prey communities exchange organisms within spatially heterogeneous networks called metacommunities. This heterogeneity can result from uneven distribution of resources among communities and thus can lead to the spreading of local enrichment within metacommunities. Here, we adapted the original Rosenzweig-MacArthur predator-prey model, built to study the paradox of enrichment, to investigate the effect of regional enrichment and of its spatial distribution on predator-prey dynamics in metacommunities. We found that the potential for destabilization was depending on the connectivity among communities and the spatial distribution of enrichment. In one hand, we found that at low dispersal regional enrichment led to the destabilization of predator-prey dynamics. This destabilizing effect was more pronounced when the enrichment was uneven among communities. In the other hand, we found that high dispersal could stabilize the predator-prey dynamics when the enrichment was spatially heterogeneous. Our results illustrate that the destabilizing effect of enrichment can be dampened when the spatial scale of resource enrichment is lower than that of organismss movements (heterogeneous enrichment). From a conservation perspective, our results illustrate that spatial heterogeneity could decrease the regional extinction risk of species involved in specialized trophic interactions. From the perspective of biological control, our results show that the heterogeneous distribution of pest resource could favor or dampen outbreaks of pests and of their natural enemies, depending on the spatial scale of heterogeneity.

  • 28.
    Jonsson, A.
    et al.
    Rockefeller University, 20, 1230 York Avenue, New York, NY 10021, United States.
    Ebenman, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology .
    Are certain life histories particularly prone to local extinction?2001In: Journal of Theoretical Biology, ISSN 0022-5193, E-ISSN 1095-8541, Vol. 209, no 4, p. 455-463Article in journal (Refereed)
    Abstract [en]

    Using stochastic simulations and elasticity analysis, we show that there are inherent differences in the risk of extinction between life histories with different demographies. Which life history is the most vulnerable depends on which vital rate varies. When juvenile survival varies semelparous organisms with delayed reproduction are the most vulnerable ones, while a varying developmental rate puts a greater threat to semelparous organisms with rapid development. Iteroparous organisms are the most vulnerable ones when adult survival varies. Generally, we do not expect to observe organisms in nature having variation in vital rates that produce a high risk of extinction. Given the results here we therefore predict that iteroparous organisms should show low variation in adult survival. Moreover, we predict that semelparous organisms should show low variation in juvenile survival and low variation in developmental rate. The effect of temporal correlation on extinction risk is most pronounced in organisms with semelparous life histories. © 2001 Academic Press.

  • 29.
    Kaneryd, Linda
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Borrvall, Charlotte
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Berg, Sofia
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Curtsdotter, Alva
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Eklöf, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Hauzy, Céline
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Jonsson, Tomas
    Skövde University, Sweden.
    Münger, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Setzer, Malin
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Säterberg, Torbjörn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Species-rich ecosystems are vulnerable to cascading extinctions in an indreasingly variable world2012In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 2, no 4, p. 858-874Article in journal (Refereed)
    Abstract [en]

    Global warming leads to increased intensity and frequency of weather extremes. Such increased environmental variability might in turn result in increased variation in the demographic rates of interacting species with potentially important consequences for the dynamics of food-webs. Using a theoretical approach we here explore the response of food-webs to a highly variable environment. We investigate how species richness and correlation in the responses of species to environmental fluctuations affect the risk of extinction cascades. We find that the risk of extinction cascades increases with increasing species richness, especially when correlation among species is low. Initial extinctions of primary producer species unleash bottom-up extinction cascades, especially in webs with specialist consumers. In this sense, species-rich ecosystems are less robust to increasing levels of environmental variability than species-poor ones. Our study thus suggests that highly species-rich ecosystems like coral reefs and tropical rainforests might be particularly vulnerable to increased climate variability.

  • 30.
    Kaneryd, Linda
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Münger, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Robustness of food webs whose structures have been shaped by extinctions in the past2011Manuscript (preprint) (Other academic)
    Abstract [en]

    Extinctions of species might lead to changes in the trophic structure of food webs with consequences for the robustness of the webs. Using a theoretical approach we here investigate 1) how ‘natural’ extinctions of species in a variable environment affect the trophic structure of food webs and 2) which consequences these structural changes will have for the topological and dynamical robustness of the webs to further, future disturbances. We show that food webs whose structure have been shaped by extinctions in the past (disassembled webs) are structurally different and more robust to disturbances (species deletion and exposure to high levels of environmental variability) than food webs of equal size (number of species) that have not gone through a phase of disassembly. The increased robustness of the disassembled webs is due to the preservation of certain link structures, structures that have been found to promote topological and dynamical stability. Thus, our results suggest that ‘natural’ extinctions lead to changes in the trophic structure of food webs which make them more resistant to future perturbations.

  • 31.
    Kaneryd, Linda
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Münger, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Eklöf, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Risk of global extinctions in metacommunities exposed to a highly variable environment: local and spatial processesManuscript (preprint) (Other academic)
    Abstract [en]

    Here we analyze how metacommunities (a set of local communities coupled by species dispersal) in spatially explicit landscapes respond to environmental variation. We examine how this response is affected by 1) species richness in the local communities, 2) the degree of correlation in species response to the environmental variation both between species within patches (species correlation) and among patches (spatial correlation) and 3) dispersal pattern of species. We find that the risk of global extinction increases with increasing species richness in the local communities and with decreasing correlation among species in their response to environmental fluctuations. We also show that the pattern of spatial correlation is of great importance; the risk of global extinctions increases with increasing spatial correlation. Moreover, we find that the pattern and rate of dispersal are important; a high migration rate in combination with localized dispersal decrease the risk of global extinctions whereas a global dispersal pattern increases the risk of global extinctions. When dispersal is global the subpopulations of a species become more synchronized which reduces the potential for a patch to become recolonized following extinctions. We also demonstrate the importance of both local and spatial processes when examining the temporal stability of primary production at the scale of metapopulations, local communities and metacommunities.

  • 32.
    Petchey, Owen L.
    et al.
    Department of Animal and Plant Sciences, University of Sheffield, United Kingdom.
    Eklöf, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Borrvall, Charlotte
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Trophically Unique Species Are Vulnerable to Cascading Extinction2008In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 171, no 5, p. 568-579Article in journal (Refereed)
    Abstract [en]

    Understanding which species might become extinct and the consequences of such loss is critical. One consequence is a cascade of further, secondary extinctions. While a significant amount is known about the types of communities and species that suffer secondary extinctions, little is known about the consequences of secondary extinctions for biodiversity. Here we examine the effect of these secondary extinctions on trophic diversity, the range of trophic roles played by the species in a community. Our analyses of natural and model food webs show that secondary extinctions cause loss of trophic diversity greater than that expected from chance, a result that is robust to variation in food web structure, distribution of interactions strengths, functional response, and adaptive foraging. Greater than expected loss of trophic diversity occurs because more trophically unique species are more vulnerable to secondary extinction. This is not a straightforward consequence of these species having few links with others but is a complex function of how direct and indirect interactions affect species persistence. A positive correlation between a species’ extinction probability and the importance of its loss defines high-risk species and should make their conservation a priority.

  • 33.
    Riede, James O.
    et al.
    J.F. Blumenbach Institute of Zoology and Anthropology, Systemic Conservation Biology Group, Georg-August University Goettingen, Germany.
    Brose, Ulrich
    J.F. Blumenbach Institute of Zoology and Anthropology, Systemic Conservation Biology Group, Georg-August University Goettingen, Germany.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Jakob, Ute
    Institute for Hydrobiology and Fisheries Science, University Hamburg, Germany.
    Thompson, Ross
    School of Biological Sciences, Monash Univerity, Australia.
    Townsend, Colin R.
    Department of Zoology, University of Otago, New Zealand.
    Jonsson, Tomas
    Ecological Modelling Group, Systems Biology Research Centre, University of Skövde, Sweden.
    Stepping in Elton's footprints: a general scaling model for body masses and trophic levels across ecosystems2011In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 14, no 2, p. 169-178Article in journal (Other academic)
    Abstract [en]

    Despite growing awareness of the significance of body-size and predator–prey body-mass ratios for the stability of ecological networks,our understanding of their distribution within ecosystems is incomplete. Here, we study the relationships between predator and prey size,body-mass ratios and predator trophic levels using body-mass estimates of 1313 predators (invertebrates, ectotherm and endothermvertebrates) from 35 food-webs (marine, stream, lake and terrestrial). Across all ecosystem and predator types, except for streams (whichappear to have a different size structure in their predator–prey interactions), we find that (1) geometric mean prey mass increases withpredator mass with a power-law exponent greater than unity and (2) predator size increases with trophic level. Consistent with ourtheoretical derivations, we show that the quantitative nature of these relationships implies systematic decreases in predator–prey bodymassratios with the trophic level of the predator. Thus, predators are, on an average, more similar in size to their prey at the top of foodwebsthan that closer to the base. These findings contradict the traditional Eltonian paradigm and have implications for our understandingof body-mass constraints on food-web topology, community dynamics and stability.

  • 34.
    Sellman, Stefan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Säterberg, Torbjörn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Pattern of functional extinctions in ecological networks with a variety of interaction types2016In: Theoretical Ecology, ISSN 1874-1738, E-ISSN 1874-1746, Vol. 9, no 1, p. 83-94Article in journal (Refereed)
    Abstract [en]

    There is a strong trend of declining populations in many species of both animals and plants. Dwindling numbers of species can eventually lead to their functional extinction. Functional, or ecological, extinction occurs when a species becomes too rare to fulfill its ecological, interactive role in the ecosystem, leading to true (numerical) extinction of other depending species. Recent theoretical work on food webs suggests that the frequency of functional extinction might be surprisingly high. However, little is known about the risk of functional species extinctions in networks with other types of interactions than trophic ones. Here, we explore the frequency of functional extinctions in model ecological networks having different proportions of antagonistic and mutualistic links. Furthermore, we investigate the topological relationship between functionally and numerically extinct species. We find that (1) the frequency of functional extinctions is higher in networks containing a mixture of antagonistic and mutualistic interactions than in networks with only one type of interaction, (2) increased mortality rate of species having both mutualistic and antagonistic links is more likely to lead to extinction of another species than to extinction of the species itself compared to species having only mutualistic or antagonistic links, and (3) trophic distance (shortest path) between functionally and numerically extinct species is, on average, longer than one, indicating the importance of indirect effects. These results generalize the findings of an earlier study on food webs, demonstrating the potential importance of functional extinction in a variety of ecological network types.

  • 35.
    Säterberg, Torbjörn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Sellman, Stefan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    High frequency of functional extinctions in ecological networks2013In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 499, no 7459, p. 468-+Article in journal (Refereed)
    Abstract [en]

    Intensified exploitation of natural populations and habitats has led to increased mortality rates and decreased abundances of many species(1,2). There is a growing concern that this might cause critical abundance thresholds of species to be crossed(1,3-5), with extinction cascades and state shifts in ecosystems as a consequence(4,6,7). When increased mortality rate and decreased abundance of a given species lead to extinction of other species, this species can be characterized as functionally extinct even though it still exists. Although such functional extinctions have been observed in some ecosystems(3,4,8), their frequency is largely unknown. Here we use a new modelling approach to explore the frequency and pattern of functional extinctions in ecological networks. Specifically, we analytically derive critical abundance thresholds of species by increasing their mortality rates until an extinction occurs in the network. Applying this approach on natural and theoretical food webs, we show that the species most likely to go extinct first is not the one whose mortality rate is increased but instead another species. Indeed, up to 80% of all first extinctions are of another species, suggesting that a species ecological functionality is often lost before its own existence is threatened. Furthermore, we find that large-bodied species at the top of the food chains can only be exposed to small increases in mortality rate and small decreases in abundance before going functionally extinct compared to small-bodied species lower in the food chains. These results illustrate the potential importance of functional extinctions in ecological networks and lend strong support to arguments advocating a more community-oriented approach in conservation biology, with target levels for populations based on ecological functionality rather than on mere persistence(8-11).

  • 36.
    Westwood, Luke
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Kaneryd, Linda
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Münger, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Keystone patches: upholding diversity in multi-trophic metacommunitiesManuscript (preprint) (Other academic)
    Abstract [en]

    Due to the destruction of their habitat some organisms have an uneven distribution across the landscape. In affected areas a community of interacting organisms may be fragmented into a network of smaller patches connected through dispersal of individuals of the different species. These metacommunities can be modelled with explicit dynamics and spatial structure, with dependence on both local processes (interactions between species within a patch) and global processes (dispersal of individuals between patches). Dispersal between patches is important for the operation of processes like recolonizations and ‘rescue effects’, processes which can counteract local extinctions and hence reduce the risk of global extinctions. Recent studies have applied network theory to real ecological communities, with a wide selection of indices available to characterise either an individual patch or the whole patch network. Certain keystone patches may be the most important in upholding the local or global diversity of a metacommunity and may then be identified by such a network index. A range of network indices were calculated for the patches in a large set of simulated metacommunities and all of the indices identified the keystone patch quality to a certain degree. Some of the indices were consistently better than the others and the dependence of the keystone quality on these indices was at least two times larger than for the others. The quality identified by the indices was of being more important for upholding local rather than global diversity. Many parameters were varied between the different metacommunities and as a result of this the models for identifying keystone patches yielded small R2 values and therefore were not proven to be dependable predictors if applied to particular metacommunities.

  • 37.
    Woodward, G.
    et al.
    School of Biological Sciences, Queen Mary University of London, London, E1 4NS, United Kingdom.
    Ebenman, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology .
    Emmerson, M.
    Department of Zoology, Ecology and Plant Science, University College Cork, Ireland.
    Montoya, J.M.
    Complex Systems Lab., Universitat Pompeu Fabra, Dr. Aiguader 80, 08003 Barcelona, Department of Ecology, University of Alcalá, Madrid, Spain.
    Olesen, J.M.
    Department of Ecology and Genetics, University of Aarhus, Ny Munkegade B540, DK-8000, Aarhus C, Denmark.
    Valido, A.
    Integrative Ecology Group, Estación Biológica de Doñana, CSIC, Apdo. 1056, 41080 Sevilla, Spain.
    Warren, P.H.
    Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, S10 2TN, United Kingdom.
    Body size in ecological networks2005In: Trends in Ecology & Evolution, ISSN 0169-5347, E-ISSN 1872-8383, Vol. 20, no 7, p. 402-409Article, review/survey (Refereed)
    Abstract [en]

    Body size determines a host of species traits that can affect the structure and dynamics of food webs, and other ecological networks, across multiple scales of organization. Measuring body size provides a relatively simple means of encapsulating and condensing a large amount of the biological information embedded within an ecological network. Recently, important advances have been made by incorporating body size into theoretical models that explore food web stability, the patterning of energy fluxes, and responses to perturbations. Because metabolic constraints underpin body-size scaling relationships, metabolic theory offers a potentially useful new framework within which to develop novel models to describe the structure and functioning of ecological networks and to assess the probable consequences of biodiversity change. © 2005 Elsevier Ltd. All rights reserved.

  • 38.
    Woodward, Guy
    et al.
    Queen Mary University of London.
    Ebenman, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology .
    Emmerson, Marc C.
    University College Cork.
    Montoya, Jowé M.
    Universiyt of Alcalá, Madrid.
    Olesen, J.M.
    Universiyt of Aarhus, Denmark.
    Valido, A.
    Bkológica de Doñana, CSIC Sevilla.
    Warren, Philip H.
    Universiyt of Sheffield.
    Body-size determinants of the structure and dynamics of ecological networks: scaling from the individual to the ecosystem2005In: Fod Web Symposium 2003,2003, London: Elsevier , 2005Conference paper (Refereed)
  • 39.
    Yvon-Durocher, Gabriel
    et al.
    Queen Mary University London.
    Reiss, Julia
    Queen Mary University London.
    Blanchard, Julia
    Cefas Lowestoft Lab.
    Ebenman, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, The Institute of Technology.
    Perkins, Danie lM
    Queen Mary University London.
    Reuman, Daniel C
    University London Imperial College of Science Technology and Medicine.
    Thierry, Aaron
    University of Sheffield.
    Woodward, Guy
    Queen Mary University London.
    Petchey, Owen L
    University of Sheffield.
    Across ecosystem comparisons of size structure: methods, approaches and prospects2011In: OIKOS, ISSN 0030-1299, Vol. 120, no 4, p. 550-563Article in journal (Refereed)
    Abstract [en]

    Understanding how ecological communities are structured and how this may vary between different types of ecosystems is a fundamental question in ecology. We develop a general framework for quantifying size-structure within and among different ecosystem types (e. g. terrestrial, freshwater or marine), via the use of a suite of bivariate relationships between organismal size and properties of individuals, populations, assemblages, pair-wise interactions, and network topology. Each of these relationships can be considered a dimension of size-structure, along which real communities lie on a continuous scale. For example, the strength, slope, or elevation of the body mass-versus-abundance or predator size-versus-prey size relationships may vary systematically among ecosystem types. We draw on examples from the literature and suggest new ways to use allometries for comparing among ecosystem types, which we illustrate by applying them to published data. Finally, we discuss how dimensions of size-structure are interconnected and how we could approach this complex hierarchy systematically. We conclude: (1) there are multiple dimensions of size-structure; (2) communities may be size-structured in some of these dimensions, but not necessarily in others; (3) across-system comparisons via rigorous quantitative statistical methods are possible, and (4) insufficient data are currently available to illuminate thoroughly the full extent and nature of differences in size-structure among ecosystem types.

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