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  • 1. Order onlineBuy this publication >>
    Akram, Usman
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Closing nutrient cycles2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Adequate and balanced crop nutrition – with nitrogen (N), phosphorus (P), and potassium (K) – is vital for sustainable crop production. Inadequate and imbalanced crop nutrition contributes to the crop yield gaps – a difference in actual and potential crop yield. Yield gap is one of the many causes of insufficient food production, thus aggravating hunger and malnourishment across the globe. On the other hand, an oversupply of nutrients is highly unsustainable, in terms of both resource conservation and global environmental health. A decreasing excreta recycling in crop production is one of the many reasons for nutrient imbalances in agriculture. Previous studies show that increasing agricultural specialization leads to spatial separation of crop and animal production. Increasing distance between excreta production and crop needs is one of the leading factors that cause reduced excreta recycling. Studies focusing on excreta recycling show that a substantial barrier to a more efficient excreta nutrient reuse is the expensive transportation of bulky volumes of excreta over long distances. In order to overcome that barrier, more detailed spatial estimates of distances between excreta production and crop nutrient needs, and the associated costs for complete excreta transport in an entire country are needed. Hence, the overall aim of this thesis was to quantify the amount of nutrients in the excreta resources compared to the crop nutrient needs at multiple scales (global, national, subnational, and local), and to analyze the need for excreta transports, total distances and costs, to meet the crop nutrient needs in a country.

    On the global scale, annual (2000-2016) excreta supply (livestock and human) could provide at least 48% of N, 57% of P, and 81% of K crop needs. Although excreta supply was not enough to cover the annual crop nutrient needs at the global scale, at least 29 countries for N, 41 for P, and 71 for K had an excreta nutrient surplus. When including the annual use of synthetic fertilizers, at least 42 additional countries had a N surplus, with the equivalent figures for P being 17 countries, whereas 8 additional countries attained a K surplus. At the same time, when accounting for the use of synthetic fertilizers, each year, at least 57 countries had an N deficit, 70 a P deficit, and 51 countries a K deficit, in total equivalent to 14% of global N and 16% of each P and K crop needs. The total surplus in other countries during the period was always higher than the deficit in the countries with net nutrient deficits, except for P for some years. Unfortunately, both the deficits of the deficit countries and surpluses of the surplus countries were increasing substantially during the 17 years. Such global divergence in nutrient deficits and surpluses have clear implications for global food security and environmental health.

    A district-scale investigation of Pakistan showed that the country had a national deficit of 0.62 million tons of P and 0.59 million tons of K, but an oversupply of N. The spatial separation was not significant at this resolution; only 6% of the excreta N supply needed to be transported between districts. Recycling all excreta, within and between districts, could cut the use of synthetic N to 43% of its current use and eliminate the need for synthetic K, but there would be an additional need of 0.28 million tons of synthetic P to meet the crop nutrient needs in the entire country. The need for synthetic fertilizers to supplement the recycled excreta nutrients would cost USD 2.77 billion. However, it might not be prohibitively expensive to correct for P deficiencies because of the savings on the costs of synthetic N, and K. Excreta recycling could promote balanced crop nutrition at the national scale in Pakistan, which in turn could eliminate the nutrient-related crop yield gaps in the country.

    The municipal-scale investigation using Swedish data showed that the country had a national oversupply of 110,000 tons of N, 6,000 tons of P, and 76,000 tons of K. Excreta could provide up to 75% of N and 81% of P, and more than 100% of the K crop needs in the country. The spatial separation was pronounced at the municipal scale in the country. Just 40% of the municipalities produced over 50% of the excreta N and P. Nutrient balance calculations showed that excreta recycling within municipalities could provide 63% of the P crop needs. Another 18% of the P crop needs must be transported from surplus municipalities to deficit municipalities. Nationally, an optimized reallocation of surplus excreta P towards the P deficit municipalities would cost USD 192 million for a total of 24,079 km truck transports. The cost was 3.7 times more than the total NPK fertilizer value transported, and that met the crop nutrient needs. It was concluded that Sweden could potentially reduce its dependence on synthetic fertilizers, but to cover the costs of an improved excreta reuse would require valuing the additional benefits of recycling.

    An investigation was also done to understand the effect of the input data resolution on the results (transport needs and distances) from a model to optimize excreta redistribution. The results showed that the need for excreta transports, distances, and spatial patterns of the excreta transports changed. Increasing resolution of the spatial data, from political boundaries in Sweden and Pakistan to 0.083 decimal grids (approximately 10 km by 10 km at the equator), showed that transport needs for excreta-N increased by 12% in Pakistan, and the transport needs for excreta-P increased by 14% in Sweden. The effect of the increased resolution on transport analysis showed inconsistency in terms of the excreta total nutrient transportation distance; the average distance decreased by 67% (to 44 km) in Pakistan but increased by 1 km in Sweden. A further increase in the data resolution to 5 km by 5 km grids for Sweden showed that the average transportation distance decreased by 9 km. In both countries, increasing input data resolution resulted in a more favorable cost to fertilizer value ratios. In Pakistan, the cost of transport was only 13% of the NPK fertilizer value transported at a higher resolution. In Sweden, the costs decreased from 3.7 (at the political resolution) to slightly higher than three times of the fertilizer value transported in excreta at the higher data resolution.

    This Ph.D. thesis shows that we could potentially reduce the total use of synthetic fertilizers in the world and still reduce the yield gaps if we can create a more efficient recycling of nutrients both within and between countries, and a more demand adapted use of synthetic fertilizers.

    List of papers
    1. Closing Pakistan’s yield gaps through nutrient recycling
    Open this publication in new window or tab >>Closing Pakistan’s yield gaps through nutrient recycling
    2018 (English)In: Frontiers in Sustainable Food Systems, E-ISSN 2571-581X, p. 1-14, article id 00024Article in journal (Refereed) Published
    Abstract [en]

    Achieving food security will require closing yield gaps in many regions, including Pakistan. Although fertilizer subsidies have facilitated increased nitrogen (N) application rates, many staple crop yields have yet to reach their maximum potential. Considering that current animal manure and human excreta (bio-supply) recycling rates are low, there is substantial potential to increase the reuse of nutrients in bio-supply. We quantified 2010 crop N, phosphorus (P), and potassium (K) needs along with bio-supply nutrient availability for Pakistani districts, and compared these values to synthetic fertilizer use and costs. We found that synthetic fertilizer use combined with low bio-supply recycling resulted in a substantial gap between nutrient supply and P and K crop needs, which would cost 3 billion USD to fill with synthetic fertilizers. If all bio-supply was recycled, it could eliminate K synthetic fertilizer needs and decrease N synthetic fertilizer needs to 43% of what was purchased in 2010. Under a full recycling scenario, farmers would still require an additional 0.28 million tons of synthetic P fertilizers, costing 2.77 billion USD. However, it may not be prohibitively expensive to correct P deficiencies. Pakistan already spends this amount of money on fertilizers. If funds used for synthetic N were reallocated to synthetic P purchases in a full bio-supply recycling scenario, crop needs could be met. Most recycling could happen within districts, with only 6% of bio-supply requiring between-district transport when optimized to meet national N crop needs. Increased recycling in Pakistan could be a viable way to decrease yield gaps.

    Place, publisher, year, edition, pages
    Frontiers Media S.A., 2018
    National Category
    Environmental Sciences
    Identifiers
    urn:nbn:se:liu:diva-148786 (URN)10.3389/fsufs.2018.00024 (DOI)000502077100001 ()
    Available from: 2018-06-19 Created: 2018-06-19 Last updated: 2023-03-28Bibliographically approved
    2. Enhancing nutrient recycling from excreta to meet crop nutrient needs in Sweden - a spatial analysis
    Open this publication in new window or tab >>Enhancing nutrient recycling from excreta to meet crop nutrient needs in Sweden - a spatial analysis
    Show others...
    2019 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 9, article id 10264Article in journal (Refereed) Published
    Abstract [en]

    Increased recycling of nutrient-rich organic waste to meet crop nutrient needs is an essential component of a more sustainable food system. However, agricultural specialization continues to pose a significant challenge to balancing crop nutrient needs and the nutrient supply from animal manure and human excreta locally. For Sweden, this study found that recycling all excreta (in 2007) could meet up to 75% of crop nitrogen and 81% of phosphorus needs, but that this would exceed crop potassium needs by 51%. Recycling excreta within municipalities could meet 63% of crop P nutrient needs, but large regional differences and imbalances need to be corrected to avoid over or under fertilizing. Over 50% of the total nitrogen and phosphorus in excreta is contained in just 40% of municipalities, and those have a surplus of excreta nutrients compared to crop needs. Reallocation of surpluses (nationally optimized for phosphorus) towards deficit municipalities, would cost 192 million USD (for 24 079 km of truck travel). This is 3.7 times more than the total NPK fertilizer value being transported. These results indicate that Sweden could reduce its dependence on synthetic fertilizers through investments in excreta recycling, but this would likely require valuing also other recycling benefits.

    Place, publisher, year, edition, pages
    NATURE PUBLISHING GROUP, 2019
    National Category
    Environmental Sciences
    Identifiers
    urn:nbn:se:liu:diva-159253 (URN)10.1038/s41598-019-46706-7 (DOI)000475558600014 ()31311977 (PubMedID)
    Note

    Funding Agencies|FORMAS, the Swedish research council for sustainable development [992023, FORMAS 942-2016-69]

    Available from: 2019-08-07 Created: 2019-08-07 Last updated: 2022-09-15
    3. Optimizing Nutrient Recycling From Excreta in Sweden and Pakistan: Higher Spatial Resolution Makes Transportation More Attractive
    Open this publication in new window or tab >>Optimizing Nutrient Recycling From Excreta in Sweden and Pakistan: Higher Spatial Resolution Makes Transportation More Attractive
    Show others...
    2019 (English)In: Frontiers in Sustainable Food Systems, E-ISSN 2571-581X, Vol. 3Article in journal (Refereed) Published
    Abstract [en]

    Recycling essential plant nutrients like nitrogen (N), phosphorus (P), and potassium (K) from organic waste such as human and animal excreta will be an essential part of sustainable food systems and a circular economy. However, transportation is often cited as a major barrier to increased recycling as organic waste is heavy and bulky, and distances between areas of abundant waste may be far from areas with a need for fertilizers. We investigated the effect of increased input data spatial resolution to an optimization model on the weight, distance, and spatial patterns of transport. The model was run in Sweden and in Pakistan to examine cost-effectiveness of transporting excess excreta to areas of crop need after local recycling. Increasing the resolution of input data from political boundaries (municipalities and districts) to 0.083 decimal grids increased the amount of N requiring transport by 12% in Pakistan and increased P requiring transport by 14% in Sweden. The average distance decreased by 67% (to 44 km) in Pakistan but increased by 1 km in Sweden. Further increasing the resolution to 5 km grids in Sweden decreased the average transportation distance by 9 km (down to 123 km). In both countries, increasing resolution also decreased the number of long-distance heavy transports, and as such costs did not increase as much as total distance and weight transported. Ultimately, transportation in Pakistan seemed financially beneficial: the cost of transport only represented 13% of the NPK fertilizer value transported, and total recycling could even cover 78% of additional fertilizer purchases required. In Sweden, the cost of transporting excreta did not seem cost effective without valuing other potential benefits of increased recycling: costs were three times higher than the fertilizer value transported in excreta at the 5 km resolution. In summary, increasing input data resolution created a more realistic picture of recycling needs. This also highlighted more favorable cost to fertilizer value ratios which could make it easier to move forward with industry and government partners to facilitate productive recycling. Our analysis shows that in both countries increased recycling can result in better spatial nutrient balances.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-160848 (URN)10.3389/fsufs.2019.00050 (DOI)000535743100001 ()
    Available from: 2019-10-10 Created: 2019-10-10 Last updated: 2023-03-28
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  • 2.
    Akram, Usman
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Metson, Genevieve
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. Linköping University, Centre for Climate Science and Policy Research, CSPR.
    Quttineh, Nils-Hassan
    Linköping University, Department of Mathematics, Optimization . Linköping University, Faculty of Science & Engineering.
    Wennergren, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Closing Pakistan’s yield gaps through nutrient recycling2018In: Frontiers in Sustainable Food Systems, E-ISSN 2571-581X, p. 1-14, article id 00024Article in journal (Refereed)
    Abstract [en]

    Achieving food security will require closing yield gaps in many regions, including Pakistan. Although fertilizer subsidies have facilitated increased nitrogen (N) application rates, many staple crop yields have yet to reach their maximum potential. Considering that current animal manure and human excreta (bio-supply) recycling rates are low, there is substantial potential to increase the reuse of nutrients in bio-supply. We quantified 2010 crop N, phosphorus (P), and potassium (K) needs along with bio-supply nutrient availability for Pakistani districts, and compared these values to synthetic fertilizer use and costs. We found that synthetic fertilizer use combined with low bio-supply recycling resulted in a substantial gap between nutrient supply and P and K crop needs, which would cost 3 billion USD to fill with synthetic fertilizers. If all bio-supply was recycled, it could eliminate K synthetic fertilizer needs and decrease N synthetic fertilizer needs to 43% of what was purchased in 2010. Under a full recycling scenario, farmers would still require an additional 0.28 million tons of synthetic P fertilizers, costing 2.77 billion USD. However, it may not be prohibitively expensive to correct P deficiencies. Pakistan already spends this amount of money on fertilizers. If funds used for synthetic N were reallocated to synthetic P purchases in a full bio-supply recycling scenario, crop needs could be met. Most recycling could happen within districts, with only 6% of bio-supply requiring between-district transport when optimized to meet national N crop needs. Increased recycling in Pakistan could be a viable way to decrease yield gaps.

    Download full text (pdf)
    Closing Pakistan’s Yield Gaps Through Nutrient Recycling
  • 3.
    Akram, Usman
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Quttineh, Nils-Hassan
    Linköping University, Department of Mathematics, Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Wennergren, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Tonderski, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Metson, Genevieve
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. Linköping University, Centre for Climate Science and Policy Research, CSPR.
    Author Correction: Enhancing nutrient recycling from excreta to meet crop nutrient needs in Sweden - a spatial analysis2020In: Scientific Reports, E-ISSN 2045-2322, Vol. 10, no 1, article id 361Article in journal (Other academic)
    Download full text (pdf)
    fulltext
  • 4.
    Akram, Usman
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Quttineh, Nils-Hassan
    Linköping University, Department of Mathematics, Optimization. Linköping University, Faculty of Science & Engineering.
    Wennergren, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Tonderski, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Metson, Genevieve
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Enhancing nutrient recycling from excreta to meet crop nutrient needs in Sweden - a spatial analysis2019In: Scientific Reports, E-ISSN 2045-2322, Vol. 9, article id 10264Article in journal (Refereed)
    Abstract [en]

    Increased recycling of nutrient-rich organic waste to meet crop nutrient needs is an essential component of a more sustainable food system. However, agricultural specialization continues to pose a significant challenge to balancing crop nutrient needs and the nutrient supply from animal manure and human excreta locally. For Sweden, this study found that recycling all excreta (in 2007) could meet up to 75% of crop nitrogen and 81% of phosphorus needs, but that this would exceed crop potassium needs by 51%. Recycling excreta within municipalities could meet 63% of crop P nutrient needs, but large regional differences and imbalances need to be corrected to avoid over or under fertilizing. Over 50% of the total nitrogen and phosphorus in excreta is contained in just 40% of municipalities, and those have a surplus of excreta nutrients compared to crop needs. Reallocation of surpluses (nationally optimized for phosphorus) towards deficit municipalities, would cost 192 million USD (for 24 079 km of truck travel). This is 3.7 times more than the total NPK fertilizer value being transported. These results indicate that Sweden could reduce its dependence on synthetic fertilizers through investments in excreta recycling, but this would likely require valuing also other recycling benefits.

    Download full text (pdf)
    fulltext
    Download (pdf)
    author correction
  • 5.
    Akram, Usman
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Quttineh, Nils-Hassan
    Linköping University, Department of Mathematics, Optimization. Linköping University, Faculty of Science & Engineering.
    Wennergren, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Tonderski, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Metson, Geneviéve S.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Optimizing Nutrient Recycling From Excreta in Sweden and Pakistan: Higher Spatial Resolution Makes Transportation More Attractive2019In: Frontiers in Sustainable Food Systems, E-ISSN 2571-581X, Vol. 3Article in journal (Refereed)
    Abstract [en]

    Recycling essential plant nutrients like nitrogen (N), phosphorus (P), and potassium (K) from organic waste such as human and animal excreta will be an essential part of sustainable food systems and a circular economy. However, transportation is often cited as a major barrier to increased recycling as organic waste is heavy and bulky, and distances between areas of abundant waste may be far from areas with a need for fertilizers. We investigated the effect of increased input data spatial resolution to an optimization model on the weight, distance, and spatial patterns of transport. The model was run in Sweden and in Pakistan to examine cost-effectiveness of transporting excess excreta to areas of crop need after local recycling. Increasing the resolution of input data from political boundaries (municipalities and districts) to 0.083 decimal grids increased the amount of N requiring transport by 12% in Pakistan and increased P requiring transport by 14% in Sweden. The average distance decreased by 67% (to 44 km) in Pakistan but increased by 1 km in Sweden. Further increasing the resolution to 5 km grids in Sweden decreased the average transportation distance by 9 km (down to 123 km). In both countries, increasing resolution also decreased the number of long-distance heavy transports, and as such costs did not increase as much as total distance and weight transported. Ultimately, transportation in Pakistan seemed financially beneficial: the cost of transport only represented 13% of the NPK fertilizer value transported, and total recycling could even cover 78% of additional fertilizer purchases required. In Sweden, the cost of transporting excreta did not seem cost effective without valuing other potential benefits of increased recycling: costs were three times higher than the fertilizer value transported in excreta at the 5 km resolution. In summary, increasing input data resolution created a more realistic picture of recycling needs. This also highlighted more favorable cost to fertilizer value ratios which could make it easier to move forward with industry and government partners to facilitate productive recycling. Our analysis shows that in both countries increased recycling can result in better spatial nutrient balances.

    Download full text (pdf)
    fulltext
  • 6.
    Albouy, Camille
    et al.
    IFREMER, France.
    Archambault, Philippe
    Univ Laval, Canada.
    Appeltans, Ward
    UNESCO, Belgium.
    Araujo, Miguel B.
    CSIC, Spain; Univ Evora, Portugal; Univ Copenhagen, Denmark.
    Beauchesne, David
    Univ Quebec Rimouski, Canada.
    Cazelles, Kevin
    Univ Guelph, Canada.
    Cirtwill, Alyssa
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. Univ Canterbury, New Zealand.
    Fortin, Marie-Josee
    Univ Toronto, Canada.
    Galiana, Nuria
    CNRS, France.
    Leroux, Shawn J.
    Mem Univ, Canada.
    Pellissier, Loik
    Swiss Fed Inst Technol, Switzerland; Swiss Fed Res Inst WSL, Switzerland.
    Poisot, Timothee
    Univ Montreal, Canada; McGill Univ, Canada.
    Stouffer, Daniel B.
    Univ Canterbury, New Zealand.
    Wood, Spencer A.
    Univ Washington, WA 98195 USA.
    Gravel, Dominique
    Univ Montreal, Canada; Univ Sherbrooke, Canada.
    The marine fish food web is globally connected2019In: Nature Ecology & Evolution, E-ISSN 2397-334X, Vol. 3, no 8, p. 1153-+Article in journal (Refereed)
    Abstract [en]

    The productivity of marine ecosystems and the services they provide to humans are largely dependent on complex interactions between prey and predators. These are embedded in a diverse network of trophic interactions, resulting in a cascade of events following perturbations such as species extinction. The sheer scale of oceans, however, precludes the characterization of marine feeding networks through de novo sampling. This effort ought instead to rely on a combination of extensive data and inference. Here we investigate how the distribution of trophic interactions at the global scale shapes the marine fish food web structure. We hypothesize that the heterogeneous distribution of species ranges in biogeographic regions should concentrate interactions in the warmest areas and within species groups. We find that the inferred global metaweb of marine fish-that is, all possible potential feeding links between co-occurring species-is highly connected geographically with a low degree of spatial modularity. Metrics of network structure correlate with sea surface temperature and tend to peak towards the tropics. In contrast to open-water communities, coastal food webs have greater interaction redundancy, which may confer robustness to species extinction. Our results suggest that marine ecosystems are connected yet display some resistance to perturbations because of high robustness at most locations.

  • 7.
    Amiel, Joshua Johnstone
    et al.
    University of Sydney, Australia.
    Lindström, Tom
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology. University of Sydney, Australia.
    Shine, Richard
    University of Sydney, Australia.
    Egg incubation effects generate positive correlations between size, speed and learning ability in young lizards2014In: Animal Cognition, ISSN 1435-9448, E-ISSN 1435-9456, Vol. 17, no 2, p. 337-347Article in journal (Refereed)
    Abstract [en]

    Previous studies have suggested that body size and locomotor performance are targets of Darwinian selection in reptiles. However, much of the variation in these traits may derive from phenotypically plastic responses to incubation temperature, rather than from underlying genetic variation. Intriguingly, incubation temperature may also influence cognitive traits such as learning ability. Therefore, we might expect correlations between a reptiles size, locomotor speed and learning ability either due to selection on all of these traits or due to environmental effects during egg incubation. In the present study, we incubated lizard eggs (Scincidae: Bassiana duperreyi) under hot and cold thermal regimes and then assessed differences in hatchling body size, running speed and learning ability. We measured learning ability using a Y-maze and a food reward. We found high correlations between size, speed and learning ability, using two different metrics to quantify learning (time to solution, and directness of route), and showed that environmental effects (incubation temperature) cause these correlations. If widespread, such correlations challenge any simple interpretation of fitness advantages due to body size or speed within a population; for example, survivors may be larger and faster than nonsurvivors because of differences in learning ability, not because of their size or speed.

  • 8.
    Andersson, Jonathan
    et al.
    Linköping University, Department of Mathematics, Analysis and Mathematics Education. Linköping University, Faculty of Science & Engineering.
    Ghersheen, Samia
    Linköping University, Department of Mathematics, Analysis and Mathematics Education. Linköping University, Faculty of Science & Engineering.
    Kozlov, Vladimir
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Mathematics, Analysis and Mathematics Education.
    Tkachev, Vladimir
    Linköping University, Department of Mathematics, Analysis and Mathematics Education. Linköping University, Faculty of Science & Engineering.
    Wennergren, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Effect of density dependence on coinfection dynamics2021In: Analysis and Mathematical Physics, ISSN 1664-2368, E-ISSN 1664-235X, Vol. 11, no 4, article id 166Article in journal (Refereed)
    Abstract [en]

    In this paper we develop a compartmental model of SIR type (the abbreviation refers to the number of Susceptible, Infected and Recovered people) that models the population dynamics of two diseases that can coinfect. We discuss how the underlying dynamics depends on the carrying capacity K: from a simple dynamics to a more complex. This can also help in understanding the appearance of more complicated dynamics, for example, chaos and periodic oscillations, for large values of K. It is also presented that pathogens can invade in population and their invasion depends on the carrying capacity K which shows that the progression of disease in population depends on carrying capacity. More specifically, we establish all possible scenarios (the so-called transition diagrams) describing an evolution of an (always unique) locally stable equilibrium state (with only non-negative compartments) for fixed fundamental parameters (density independent transmission and vital rates) as a function of the carrying capacity K. An important implication of our results is the following important observation. Note that one can regard the value of K as the natural ‘size’ (the capacity) of a habitat. From this point of view, an isolation of individuals (the strategy which showed its efficiency for COVID-19 in various countries) into smaller resp. larger groups can be modelled by smaller resp. bigger values of K. Then we conclude that the infection dynamics becomes more complex for larger groups, as it fairly maybe expected for values of the reproduction number R0≈1. We show even more, that for the values R0>1 there are several (in fact four different) distinguished scenarios where the infection complexity (the number of nonzero infected classes) arises with growing K. Our approach is based on a bifurcation analysis which allows to generalize considerably the previous Lotka-Volterra model considered previously in Ghersheen et al. (Math Meth Appl Sci 42(8), 2019).

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  • 9.
    Andersson, Jonathan
    et al.
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Mathematics, Analysis and Mathematics Education.
    Ghersheen, Samia
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Mathematics, Analysis and Mathematics Education.
    Kozlov, Vladimir
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Mathematics, Analysis and Mathematics Education.
    Tkachev, Vladimir
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Mathematics, Analysis and Mathematics Education.
    Wennergren, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Effect of density dependence on coinfection dynamics: part 22021In: Analysis and Mathematical Physics, ISSN 1664-2368, E-ISSN 1664-235X, Vol. 11, no 4, article id 169Article in journal (Refereed)
    Abstract [en]

    In this paper we continue the stability analysis of the model for coinfection with density dependent susceptible population introduced in Andersson et al. (Effect of density dependence on coinfection dynamics. arXiv:2008.09987, 2020). We consider the remaining parameter values left out from Andersson et al. (Effect of density dependence on coinfection dynamics. arXiv:2008.09987, 2020). We look for coexistence equilibrium points, their stability and dependence on the carrying capacity K. Two sets of parameter value are determined, each giving rise to different scenarios for the equilibrium branch parametrized by K. In both scenarios the branch includes coexistence points implying that both coinfection and single infection of both diseases can exist together in a stable state. There are no simple explicit expression for these equilibrium points and we will require a more delicate analysis of these points with a new bifurcation technique adapted to such epidemic related problems. The first scenario is described by the branch of stable equilibrium points which includes a continuum of coexistence points starting at a bifurcation equilibrium point with zero single infection strain #1 and finishing at another bifurcation point with zero single infection strain #2. In the second scenario the branch also includes a section of coexistence equilibrium points with the same type of starting point but the branch stays inside the positive cone after this. The coexistence equilibrium points are stable at the start of the section. It stays stable as long as the product of K and the rate γ¯γ¯ of coinfection resulting from two single infections is small but, after this it can reach a Hopf bifurcation and periodic orbits will appear.

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  • 10.
    Andersson, Jonathan
    et al.
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Kozlov, Vladimir
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Radosavljevic, Sonja
    Stockholm Resilience Centre, Stockholm University, Stockholm, Sweden.
    Tkachev, Vladimir
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Wennergren, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Density-Dependent Feedback in Age-Structured Populations2019In: Journal of Mathematical Sciences, ISSN 1072-3374, E-ISSN 1573-8795, Vol. 242, no 1, p. 2-24Article in journal (Refereed)
    Abstract [en]

    The population size has far-reaching effects on the fitness of the population, that, in its turn influences the population extinction or persistence. Understanding the density- and age-dependent factors will facilitate more accurate predictions about the population dynamics and its asymptotic behaviour. In this paper, we develop a rigourous mathematical analysis to study positive and negative effects of increased population density in the classical nonlinear age-structured population model introduced by Gurtin \& MacCamy in the late 1970s. One of our main results expresses the global stability of the system in terms of the newborn function only. We also derive the existence of a threshold population size implying the population extinction, which is well-known in population dynamics as an Allee effect.

  • 11.
    Arnoldi, Jean-Francois
    et al.
    CNRS, France.
    Barbier, Matthieu
    CIRAD, France.
    Kelly, Ruth
    Agrifood & Biosci Inst, North Ireland.
    Barabas, György
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. ELTE MTA Theoret Biol & Evolutionary Ecol Res Grp, Hungary.
    Jackson, Andrew L.
    Univ Dublin, Ireland.
    Invasions of ecological communities: Hints of impacts in the invaders growth rate2022In: Methods in Ecology and Evolution, E-ISSN 2041-210X, Vol. 13, no 1, p. 167-182Article in journal (Refereed)
    Abstract [en]

    1. Theory in ecology and evolution often relies on the analysis of invasion processes, and general approaches exist to understand the early stages of an invasion. However, predicting the long-term transformations of communities following an invasion remains a challenging endeavour. 2. We propose a general analytical method that uses both resident community and invader dynamical features to predict whether an invasion causes large long-term impacts on the invaded community. 3. This approach reveals a direction in which classic invasion analysis, based on initial invasion growth rate, can be extended. Indeed, we explain how the density dependence of invasion growth, if properly defined, synthetically encodes the long-term biotic transformations caused by an invasion, and therefore predicts its ultimate outcome. This approach further clarifies how the density dependence of the invasion growth rate is as much a property of the invading population as it is one of the invaded community. 4. Our theory applies to any stable community model, and directs us towards new questions that may enrich the toolset of invasion analysis, and suggests that indirect interactions and dynamical stability are key determinants of invasion outcomes.

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  • 12.
    Baiser, Benjamin
    et al.
    Univ Florida, FL 32611 USA.
    Gravel, Dominique
    Univ Sherbrooke, Canada.
    Cirtwill, Alyssa
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Dunne, Jennifer A.
    Santa Fe Inst, NM 87501 USA.
    Fahimipour, Ashkaan K.
    Univ Oregon, OR 97403 USA.
    Gilarranz, Luis J.
    Eawag Swiss Fed Inst Aquat Sci and Technol, Switzerland.
    Grochow, Joshua A.
    Univ Colorado, CO 80309 USA.
    Li, Daijiang
    Univ Florida, FL 32611 USA.
    Martinez, Neo D.
    Univ Arizona, AZ USA.
    McGrew, Alicia
    Univ Florida, FL USA.
    Poisot, Timothee
    Univ Montreal, Canada.
    Romanuk, Tamara N.
    Dalhousie Univ, Canada.
    Stouffer, Daniel B.
    Univ Canterbury, New Zealand.
    Trotta, Lauren B.
    Univ Florida, FL 32611 USA.
    Valdovinos, Fernanda S.
    Univ Michigan, MI 48109 USA.
    Williams, Richard J.
    Vibrant Data Inc, CA USA.
    Wood, Spencer A.
    Univ Washington, WA 98195 USA.
    Yeakel, Justin D.
    Santa Fe Inst, NM 87501 USA; Univ Calif Merced, CA USA.
    Ecogeographical rules and the macroecology of food webs2019In: Global Ecology and Biogeography, ISSN 1466-822X, E-ISSN 1466-8238, Vol. 28, no 9, p. 1204-1218Article in journal (Refereed)
    Abstract [en]

    Aim

    How do factors such as space, time, climate and other ecological drivers influence food web structure and dynamics? Collections of well‐studied food webs and replicate food webs from the same system that span biogeographical and ecological gradients now enable detailed, quantitative investigation of such questions and help integrate food web ecology and macroecology. Here, we integrate macroecology and food web ecology by focusing on how ecogeographical rules [the latitudinal diversity gradient (LDG), Bergmann's rule, the island rule and Rapoport's rule] are associated with the architecture of food webs.

    Location

    Global.

    Time period

    Current.

    Major taxa studied

    All taxa.

    Methods

    We discuss the implications of each ecogeographical rule for food webs, present predictions for how food web structure will vary with each rule, assess empirical support where available, and discuss how food webs may influence ecogeographical rules. Finally, we recommend systems and approaches for further advancing this research agenda.

    Results

    We derived testable predictions for some ecogeographical rules (e.g. LDG, Rapoport's rule), while for others (e.g., Bergmann's and island rules) it is less clear how we would expect food webs to change over macroecological scales. Based on the LDG, we found weak support for both positive and negative relationships between food chain length and latitude and for increased generality and linkage density at higher latitudes. Based on Rapoport's rule, we found support for the prediction that species turnover in food webs is inversely related to latitude.

    Main conclusions

    The macroecology of food webs goes beyond traditional approaches to biodiversity at macroecological scales by focusing on trophic interactions among species. The collection of food web data for different types of ecosystems across biogeographical gradients is key to advance this research agenda. Further, considering food web interactions as a selection pressure that drives or disrupts ecogeographical rules has the potential to address both mechanisms of and deviations from these macroecological relationships. For these reasons, further integration of macroecology and food webs will help ecologists better understand the assembly, maintenance and change of ecosystems across space and time.

  • 13.
    Barabas, György
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. Eotvos Lorand Univ, Hungary.
    Biodiversity and community structure2021In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 118, no 11, article id e2101176118Article in journal (Other academic)
    Abstract [en]

    n/a

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  • 14.
    Barabas, György
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    The coexistence problem revisited2017In: NATURE ECOLOGY and EVOLUTION, ISSN 2397-334X, Vol. 1, no 10, p. 1425-1426Article in journal (Other academic)
    Abstract [en]

    A new theoretical study warns against common misinterpretations of classical ideas on the limits to species diversity.

  • 15.
    Barabas, György
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. MTA ELTE Theoret Biol & Evolutionary Ecol Res Grp, Hungary.
    DAndrea, Rafael
    Univ Illinois, IL 61801 USA.
    Chessons coexistence theory: reply2020In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 101, no 11, article id e03140Article in journal (Other academic)
    Abstract [en]

    n/a

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  • 16.
    Barabas, György
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    D'Andrea, Rafael
    Univ Illinois, IL 61801 USA.
    Stump, Simon Maccracken
    Yale Sch Forestry and Environm Studies, CT 06511 USA.
    Chesson's coexistence theory2018In: Ecological Monographs, ISSN 0012-9615, E-ISSN 1557-7015, Vol. 88, no 3, p. 277-303Article, review/survey (Refereed)
    Abstract [en]

    We give a comprehensive review of Chesson's coexistence theory, summarizing, for the first time, all its fundamental details in one single document. Our goal is for both theoretical and empirical ecologists to be able to use the theory to interpret their findings, and to get a precise sense of the limits of its applicability. To this end, we introduce an explicit handling of limiting factors, and a new way of defining the scaling factors that partition invasion growth rates into the different mechanisms contributing to coexistence. We explain terminology such as relative nonlinearity, storage effect, and growth-density covariance, both in a formal setting and through their biological interpretation. We review the theory's applications and contributions to our current understanding of species coexistence. While the theory is very general, it is not well suited to all problems, so we carefully point out its limitations. Finally, we critique the paradigm of decomposing invasion growth rates into stabilizing and equalizing components: we argue that these concepts are useful when used judiciously, but have often been employed in an overly simplified way to justify false claims.

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  • 17.
    Barabas, György
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. University of Chicago, IL 60637 USA.
    Michalska-Smith, Matthew J.
    University of Chicago, IL 60637 USA.
    Allesina, Stefano
    University of Chicago, IL 60637 USA; Northwestern University, IL 60208 USA.
    Self-regulation and the stability of large ecological networks2017In: NATURE ECOLOGY and EVOLUTION, ISSN 2397-334X, Vol. 1, no 12, p. 1870-+Article in journal (Refereed)
    Abstract [en]

    The stability of complex ecological networks depends both on the interactions between species and the direct effects of the species on themselves. These self-effects are known as self-regulation when an increase in a species abundance decreases its per-capita growth rate. Sources of self-regulation include intraspecific interference, cannibalism, time-scale separation between consumers and their resources, spatial heterogeneity and nonlinear functional responses coupling predators with their prey. The influence of self-regulation on network stability is understudied and in addition, the empirical estimation of self-effects poses a formidable challenge. Here, we show that empirical food web structures cannot be stabilized unless the majority of species exhibit substantially strong self-regulation. We also derive an analytical formula predicting the effect of self-regulation on network stability with high accuracy and show that even for random networks, as well as networks with a cascade structure, stability requires negative self-effects for a large proportion of species. These results suggest that the aforementioned potential mechanisms of self-regulation are probably more important in contributing to the stability of observed ecological networks than was previously thought.

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  • 18.
    Barabas, György
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. ELTE MTA Theoret Biol & Evolutionary Ecol Res Grp, Hungary.
    Parent, Christine
    Univ Idaho, ID 83844 USA.
    Kraemer, Andrew
    Creighton Univ, NE 68178 USA.
    Van de Perre, Frederik
    Univ Antwerp, Belgium.
    De Laender, Frederik
    Univ Namur, Belgium.
    The evolution of trait variance creates a tension between species diversity and functional diversity2022In: Nature Communications, E-ISSN 2041-1723, Vol. 13, no 1, article id 2521Article in journal (Refereed)
    Abstract [en]

    It seems intuitively obvious that species diversity promotes functional diversity: communities with more plant species imply more varied plant leaf chemistry, more species of crops provide more kinds of food, etc. Recent literature has nuanced this view, showing how the relationship between the two can be modulated along latitudinal or environmental gradients. Here we show that even without such effects, the evolution of functional trait variance can erase or even reverse the expected positive relationship between species- and functional diversity. We present theory showing that trait-based eco-evolutionary processes force species to evolve narrower trait breadths in more tightly packed, species-rich communities, in their effort to avoid competition with neighboring species. This effect is so strong that it leads to an overall reduction in trait space coverage whenever a new species establishes. Empirical data from land snail communities on the Galapagos Islands are consistent with this claim. The finding that the relationship between species- and functional diversity can be negative implies that trait data from species-poor communities may misjudge functional diversity in species-rich ones, and vice versa. The positive relationship between species diversity and functional diversity has been shown to vary. Here, the authors use theoretical models and data from Galapagos land snail communities to show how eco-evolutionary processes can force species to evolve narrower trait breadths in more species-rich communities to avoid competition, creating a negative relationship.

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  • 19.
    Barabas, György
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. Eotvos Lorand Univ, Hungary.
    Szigeti, András
    Linköping University, Department of Culture and Society, Division of Philosophy, History, Arts and Religion. Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Culture and Society, Division of Philosophy and Applied Ethics. Lund Univ, Sweden.
    Using Quotas as a Remedy for Structural Injustice2023In: Erkenntnis, ISSN 0165-0106, E-ISSN 1572-8420, Vol. 88, p. 3631-3649Article in journal (Refereed)
    Abstract [en]

    We analyze a frequent but undertheorized form of structural injustice, one that arises due to the difficulty of reaching numerically equitable representation of underrepresented subgroups within a larger group. This form of structural injustice is significant because it could occur even if it were possible to completely eliminate bias and overt discrimination from hiring and recruitment practices. The conceptual toolkit we develop can be used to analyze such situations and propose remedies. Specifically, based on a simple mathematical model, we offer a new argument in favour of quotas, explore implications for policy-making, and consider the wider philosophical significance of the problem. We show that in order to reach more equitable representations, quota-based recruitment may often be practically unavoidable. Assuming that members of groups in statistical minority are more likely to quit due to their marginalization, their proportions can stabilize at a low level, preventing a shift towards more equal representation and conserving the minority status of the subgroup. We show that this argument has important implications for addressing, preventing, and remediating the structural injustice of unfair representation.

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  • 20. Order onlineBuy this publication >>
    Berg, Sofia
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Community Robustness Analysis: Theoretical Approaches to Identifying Keystone Structures in Ecological Communities2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Most of the world’s ecosystems suffer from stress caused by human activities such as habitat destruction, fragmentation, overexploitation of species and climate change. These factors affect the reproduction and/or survival of individual species as well as interactions between species in ecological communities. Forthcoming effects of this are altered abundances, direct species loss, and indirect cascading extinctions, with yet largely unknown consequences on community structure and functioning. Today, biodiversity loss is of global concern since human society and welfare depend upon resources and services provided by ecosystems. The importance of considering entire ecological communities as a target for conservation and management has been increasingly recognized due to the interdependencie  of species. Our ability to make predictions of the response of ecological communities to stress and biodiversity loss is in need of a deeper understanding of how structure and dynamical processes contributes to the functioning and stability of a community. In this thesis I use mathematical theory and dynamical models to study the response of community structure and resilience to a variety of disturbances affecting species and species interactions, ranging from small perturbations (Papers I-II) to large perturbations (species extinctions, Papers IIIIV).

    In Paper I we develop Community Sensitivity Analysis (CSA) as an analytical tool to study how a small permanent perturbation to the intrinsic growth rate, or mortality rate, of species is expected to affect i) the resilience (return rate) and ii) the structure (distribution of species equilibrium abundances) of an ecological community. Species interactions are described using Lotka-Volterra predator-prey dynamics. We apply CSA on the pelagic food webs of Lake Vättern and the Baltic Sea, respectively, and find that a change in the mortality rate of large-bodied species has a higher impact on community resilience and structure, compared to a perturbation to small-bodied species. However, analyzing the effect of a proportional change to the growth or mortality rate of species (elasticity analysis) shows that smallbodied species have proportionally larger effects on species equilibrium abundances, but not on resilience. CSA can also be used to study the effect of permanent (absolute or proportional) changes to inter- and intraspecific interaction strengths. For the two pelagic systems used in this study, CSA reveal that changes in the effect of a prey on its consumer tend to affect community structure and resilience significantly more than changes in the effect of a predator on its prey.

    In Paper II we assess the importance of rare species for the structure and resilience of ecological communities. First we show analytically, for a two species predator-prey system, that a change in the intrinsic growth rate of the rare species affect resilience more than a change in the growth rate of the common species. To test the generality of these results we next apply CSA on complex model food webs. In the analysis we distinguish between four trophic groups, each including only species with a similar trophic position, to separate the effect of abundance from the trophic position of species. Using mixed effect models we find support for our analytical predictions. More precisely, we find a strong negative relationship between the importance (sensitivity) of a species and its equilibrium abundance within all consumer groups and a weaker, but significant, relationship for producer species. The results from this study suggest that rare species can act as keystones through their effect on both community resilience and community structure, regardless of its trophic position.

    In Paper III we evaluate the risk of food web collapse caused by different trait-based extinction scenarios. In previous studies, groups of species, e.g. rare species, large-bodied species and top predators, have been identified to be relatively more prone to extinctions and other studies have found that extinctions of such species have comparably small effects on the remaining community. Using mathematical models of species dynamics we study the response of ecological communities to species removal (i.e. the proportion of species needed to be primarily removed to cause a 50% reduction in species richness, R50) when species are sequentially removed from the food web based on eight different traits. We show, contrary to some previous studies of sequential extinction simulations, that communities can be very vulnerable to realistic species loss. We furthermore find that the response of communities seems to depend on whether the extinction sequence follows a bottom-up or top-down direction, making it difficult to identify one particular extinction sequence as the most important/severe sequence.

    Finally, in Paper IV we aim to identify traits of species that can be used to identify keystone species, in terms of causing the highest proportion of secondary extinctions following their loss, in food webs with different degree of disassembly. Moreover, we analyze if the loss of a species that triggers a cascade of many secondary extinctions are the same species being identified as a keystones using Community Sensitivity Analysis. To answer these questions we randomly remove species from a set of 100 model communities. We analyze the relationship between the number of secondary extinctions following the randomly removed species and a range of species traits in communities where i) 75-100% of the initial number of species remain, ii) 50-75% of all species remain, iii) 25-50% of all species remain and iv) only 0-25% of all species remain. We find that the variation in secondary extinctions explained using species traits increases when the degree of food web disassembly and food web connectance are taken into account. The most important trait varies for different degrees of food web disassembly and also depends on whether basal species can go primarily extinct or not. However, due to correlation between most important traits, we conclude that the key status of different traits is rather robust against structural changes in the model food webs. Interestingly, food webs seem to be most sensitive to a random species loss after the loss of more than 25% of all initial species, suggesting that there is a threshold from which secondary extinctions increases. We also conclude that species being identified as keystones, based on the effect of their loss, are to some extent the same species being identified as having the largest effect on community structure and resilience, respectively, following a small perturbation.

    List of papers
    1. Using sensitivity analysis to identify keystone species and keystone links in size-based food webs
    Open this publication in new window or tab >>Using sensitivity analysis to identify keystone species and keystone links in size-based food webs
    2011 (English)In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 120, no 4, p. 510-519Article in journal (Refereed) Published
    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.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-66991 (URN)10.1111/j.1600-0706.2010.18864.x (DOI)000288753800005 ()
    Available from: 2011-03-24 Created: 2011-03-24 Last updated: 2017-12-11
    2. Rare but important: perturbations to uncommon species have disproportionately large impact on ecological communities
    Open this publication in new window or tab >>Rare but important: perturbations to uncommon species have disproportionately large impact on ecological communities
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    (English)Manuscript (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.

    Keywords
    Community sensitivity analysis, species abundance, species importance, food webs, stability, resilience
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-88048 (URN)
    Available from: 2013-01-29 Created: 2013-01-29 Last updated: 2013-01-29Bibliographically approved
    3. Ecological communities are vulnerable to realistic extinction sequences
    Open this publication in new window or tab >>Ecological communities are vulnerable to realistic extinction sequences
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    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Loss of species will directly change the structure of ecological communities, which in turn may cause additional species loss (secondary extinctions) due to indirect effects (e.g. loss of resources or altered population dynamics). The vulnerability of food webs to repeated species loss is expected to be affected by food web topology, species interactions and the order in which species go extinct. Species traits such as body size, abundance and connectivity probably determine the vulnerability to extinction of species and, thus, the order in which species go primarily extinct. However, how different sequences of primary extinctions affect the vulnerability of food webs to secondary extinctions, when species abundances are allowed to respond dynamically, is not well understood. So far, only one study has incorporated species dynamics when assessing the effect of different extinction sequences on community structure, and only a limited number of extinction sequences have been evaluated. Here, using complex model food webs and including population dynamics, we analyze the effect of 33 extinction sequences on community structure using R50 (the proportion of primarily removed species needed to cause a 50% reduction in species richness) as a measure of community robustness to secondary extinctions. As expected, we find community structure to be highly vulnerable to removal of primary producers. More surprisingly, removing species based on traits that are strongly linked to the trophic position of species (such as large-bodied species, rare species, species with a high net effect, species with a high trophic position) are found to be as destructive as removing only primary producers. Such top-down oriented removal of species are often considered to correspond to realistic primary extinctions of species, but earlier studies, based on topological approaches, have not found such realistic extinction sequences to have any drastic effect on the remaining community. Thus, our result suggests that ecological communities could be more vulnerable to realistic extinction sequences than previously believed.

    Keywords
    Community structure, extinction sequence, food webs, species loss, community robustness
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-88050 (URN)
    Available from: 2013-01-29 Created: 2013-01-29 Last updated: 2013-01-29Bibliographically approved
    4. Using species traits to predict secondary extinctions during food web disassembly
    Open this publication in new window or tab >>Using species traits to predict secondary extinctions during food web disassembly
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    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Global change keeps pushing species towards extinction which results in altered structures of ecological communities. Consequently, the loss of certain species can trigger a cascade of secondary extinctions resulting in further degradation of the system. The importance of species for upholding the structure of communities may be linked to the traits of species. However, due to the altered structure of communities following species loss, the importance of species (and species traits) may change as the structure of the food web change. Using a dynamical approach and simulating species loss in complex model communities we analyze the potential importance of 11 species traits. We find that the most important trait varies for different degree of food web collapse and food web connectance. Though, as the most important traits of species usually are correlated we conclude that the importance of species traits is rather robust against structural changes in the communities (especially when only consumer species are targets of primarily extinctions). Interestingly, food webs display a collapse threshold (after the initial loss of approximately 25% of all species) from which secondary extinctions increases. Finally, consider only the loss of consumer species, the effect (number of secondary extinctions) on community structure caused by a large perturbation (species loss) is positively correlated to the response of food webs resulting from a small perturbation to the same species.

    Keywords
    Community structure, extinction sequence, food webs, species loss, community robustness
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-88052 (URN)
    Available from: 2013-01-29 Created: 2013-01-29 Last updated: 2013-01-29Bibliographically approved
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    Community Robustness Analysis: Theoretical Approaches to Identifying Keystone Structures in Ecological Communities
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  • 21.
    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.

  • 22.
    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.

  • 23.
    Berg, Sofia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Pimenov, Alexander
    Weierstrass Institute, Berlin, Germany.
    Palmer, Catherine
    Environmental Research Institute, University College Cork, Cork, Ireland.
    Emmerson, Mark
    Environmental Research Institute, University College Cork, Cork, Ireland.
    Jonsson, Tomas
    Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Ecological communities are vulnerable to realistic extinction sequencesManuscript (preprint) (Other academic)
    Abstract [en]

    Loss of species will directly change the structure of ecological communities, which in turn may cause additional species loss (secondary extinctions) due to indirect effects (e.g. loss of resources or altered population dynamics). The vulnerability of food webs to repeated species loss is expected to be affected by food web topology, species interactions and the order in which species go extinct. Species traits such as body size, abundance and connectivity probably determine the vulnerability to extinction of species and, thus, the order in which species go primarily extinct. However, how different sequences of primary extinctions affect the vulnerability of food webs to secondary extinctions, when species abundances are allowed to respond dynamically, is not well understood. So far, only one study has incorporated species dynamics when assessing the effect of different extinction sequences on community structure, and only a limited number of extinction sequences have been evaluated. Here, using complex model food webs and including population dynamics, we analyze the effect of 33 extinction sequences on community structure using R50 (the proportion of primarily removed species needed to cause a 50% reduction in species richness) as a measure of community robustness to secondary extinctions. As expected, we find community structure to be highly vulnerable to removal of primary producers. More surprisingly, removing species based on traits that are strongly linked to the trophic position of species (such as large-bodied species, rare species, species with a high net effect, species with a high trophic position) are found to be as destructive as removing only primary producers. Such top-down oriented removal of species are often considered to correspond to realistic primary extinctions of species, but earlier studies, based on topological approaches, have not found such realistic extinction sequences to have any drastic effect on the remaining community. Thus, our result suggests that ecological communities could be more vulnerable to realistic extinction sequences than previously believed.

  • 24.
    Berg, Sofia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology. University of Skovde, Sweden.
    Pimenov, Alexander
    Weierstrass Institute, Germany; National University of Ireland University of Coll Cork, Ireland.
    Palmer, Catherine
    Weierstrass Institute, Germany.
    Emmerson, Mark
    Queens University of Belfast, North Ireland.
    Jonsson, Tomas
    University of Skovde, Sweden; Swedish University of Agriculture Science, Sweden.
    Ecological communities are vulnerable to realistic extinction sequences2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 4, p. 486-496Article in journal (Refereed)
    Abstract [en]

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

  • 25.
    Berg, Sofia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Pimenov, Alexander
    Weierstrass Institute, Berlin, Germany.
    Palmer, Catherine
    Environmental Research Institute, University College Cork, Cork, Ireland.
    Emmerson, Mark
    Environmental Research Institute, University College Cork, Cork, Ireland.
    Jonsson, Tomas
    Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Using species traits to predict secondary extinctions during food web disassemblyManuscript (preprint) (Other academic)
    Abstract [en]

    Global change keeps pushing species towards extinction which results in altered structures of ecological communities. Consequently, the loss of certain species can trigger a cascade of secondary extinctions resulting in further degradation of the system. The importance of species for upholding the structure of communities may be linked to the traits of species. However, due to the altered structure of communities following species loss, the importance of species (and species traits) may change as the structure of the food web change. Using a dynamical approach and simulating species loss in complex model communities we analyze the potential importance of 11 species traits. We find that the most important trait varies for different degree of food web collapse and food web connectance. Though, as the most important traits of species usually are correlated we conclude that the importance of species traits is rather robust against structural changes in the communities (especially when only consumer species are targets of primarily extinctions). Interestingly, food webs display a collapse threshold (after the initial loss of approximately 25% of all species) from which secondary extinctions increases. Finally, consider only the loss of consumer species, the effect (number of secondary extinctions) on community structure caused by a large perturbation (species loss) is positively correlated to the response of food webs resulting from a small perturbation to the same species.

  • 26.
    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.

  • 27.
    Binzer, Amrei
    et al.
    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.
    Curtsdotter, Alva
    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.
    Rall, Björn C.
    J.F. Blumenbach Institute of Zoology and Anthropology, Georg-August University Göttingen, Germany.
    Riede, Jens O.
    J.F. Blumenbach Institute of Zoology and Anthropology, Georg-August University Göttingen, Germany.
    de Castro, Fransisco
    Institute for Biochemistry and Biology, University of Potsdam, Germany.
    The susceptibility of species to extinctions in model communities2011In: Basic and Applied Ecology, ISSN 1439-1791, E-ISSN 1618-0089, Vol. 12, no 7, p. 590-599Article in journal (Refereed)
    Abstract [en]

    Despite the fact that the loss of a species from a community has the potential to cause a dramatic decline in biodiversity, for example through cascades of secondary extinctions, little is known about the factors contributing to the extinction risk of any particular species. Here we expand earlier modeling approaches using a dynamic food-web model that accounts for bottom-up as well as top-down effects. We investigate what factors influence a species’ extinction risk and time to extinction of the non-persistent species. We identified three basic properties that affect a species’ risk of extinction. The highest extinction risk is born by species with (1) low energy input (e.g. high trophic level), (2) susceptibility to the loss of energy pathways (e.g. specialists with few prey species) and (3) dynamic instability (e.g. low Hill exponent and reliance on homogeneous energy channels when feeding on similarly sized prey). Interestingly, and different from field studies, we found that the trophic level and not the body mass of a species influences its extinction risk. On the other hand, body mass is the single most important factor determining the time to extinction of a species, resulting in small species dying first. This suggests that in the field the trophic level might have more influence on the extinction risk than presently recognized.

  • 28.
    Binzer, Amrei
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. University of Gottingen, Germany.
    Guill, Christian
    University of Gottingen, Germany; University of Potsdam, Germany; University of Amsterdam, Netherlands.
    Rall, Bjoern C.
    University of Gottingen, Germany; German Centre Integrat Biodivers Research iDiv, Germany; University of Jena, Germany.
    Brose, Ulrich
    University of Gottingen, Germany; German Centre Integrat Biodivers Research iDiv, Germany; University of Jena, Germany.
    Interactive effects of warming, eutrophication and size structure: impacts on biodiversity and food-web structure2016In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 22, no 1, p. 220-227Article in journal (Refereed)
    Abstract [en]

    Warming and eutrophication are two of the most important global change stressors for natural ecosystems, but their interaction is poorly understood. We used a dynamic model of complex, size-structured food webs to assess interactive effects on diversity and network structure. We found antagonistic impacts: Warming increases diversity in eutrophic systems and decreases it in oligotrophic systems. These effects interact with the community size structure: Communities of similarly sized species such as parasitoid-host systems are stabilized by warming and destabilized by eutrophication, whereas the diversity of size-structured predator-prey networks decreases strongly with warming, but decreases only weakly with eutrophication. Nonrandom extinction risks for generalists and specialists lead to higher connectance in networks without size structure and lower connectance in size-structured communities. Overall, our results unravel interactive impacts of warming and eutrophication and suggest that size structure may serve as an important proxy for predicting the community sensitivity to these global change stressors.

  • 29. Order onlineBuy this publication >>
    Borrvall, Charlotte
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Biodiversity and Species Extinctions in Model Food Webs2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Many of the earth’s ecosystems are experiencing large species losses due to human impacts such as habitat destruction and fragmentation, climate change, species invasions, pollution, and overfishing. 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. The complexity of ecological systems makes it difficult to study them empirically. The systems often consist of large species numbers with lots of interactions between species. Investigating ecological communities within a theoretical approach, using mathematical models and computer simulations, is an alternative or a complement to experimental studies. This thesis is a collection of theoretical studies. We use model food webs in order to explore how biodiversity (species number) affects the response of communities to species loss (Paper I-III) and to environmental variability (Paper IV).

    In paper I and II we investigate the risk of secondary extinctions following deletion of one species. It is shown that resistance against additional species extinctions increases with redundancy (number of species per functional group) (Paper I) in the absence of competition between basal species but decreases with redundancy in the presence of competition between basal species (Paper II). It is further shown that food webs with low redundancy run the risk of losing a greater proportion of species following a species deletion in a deterministic environment but when demographic stochasticity is included the benefits of redundancy are largely lost (Paper II). This finding implies that in the construction of nature reserves the advantages of redundancy for conservation of communities may be lost if the reserves are small in size. Additionally, food webs show higher risks of further extinctions after the loss of basal species and herbivores than after the loss of top predators (Paper I and II).

    Secondary extinctions caused by a primary extinction and mediated through direct and indirect effects, are likely to occur with a time delay since the manifestation of indirect effects can take long time to appear. In paper III 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. If local secondary extinctions occur early they are less likely to be balanced by immigration of species from local communities nearby implying that secondary extinctions caused by the loss of top predators are less likely to be balanced by dispersal than secondary extinctions caused by the loss of other species. As top predators are vulnerable to human-induced disturbances on ecosystems in the first place, our results suggest that conservation of top predators should be a priority. Moreover, in most cases time to secondary extinction is shown to increase with species richness indicating the decay of ecological communities to be slower in species-rich than in species-poor communities.

    Apart from the human-induced disturbances that often force species towards extinction the environment is also, to a smaller or larger extent, varying over time in a natural way. Such environmental stochasticity influences the dynamics of populations. In paper IV we compare the responses of food webs of different sizes to environmental stochasticity. Species-rich webs are found to be more sensitive to environmental stochasticity. Particularly, species-rich webs lose a greater proportion of species than species-poor webs and they also begin losing species faster than species-poor webs. However, once one species is lost time to final extinction is longer in species-rich webs than in species-poor webs. We also find that the results differ depending on whether species respond similarly to environmental fluctuations or whether they are totally uncorrelated in their response. For a given species richness, communities with uncorrelated species responses run a considerable higher risk of losing a fixed proportion of species compared with communities with correlated species responses.

    List of papers
    1. Biodiversity lessens the risk of cascading extinction in model food webs
    Open this publication in new window or tab >>Biodiversity lessens the risk of cascading extinction in model food webs
    2000 (English)In: Ecology Letters, ISSN 1461-023X , Vol. 3, no 2, p. 131-136Article in journal (Refereed) Published
    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.

    Keywords
    Biodiversity, extinction • food webs, functional groups, redundancy, resistance, species deletion, stability
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13855 (URN)10.1046/j.1461-0248.2000.00130.x (DOI)
    Available from: 2006-06-08 Created: 2006-06-08
    2. Community viability analysis: the response of ecological communities to species loss.
    Open this publication in new window or tab >>Community viability analysis: the response of ecological communities to species loss.
    2004 (English)In: Ecology, ISSN 0012-9658, Vol. 85, no 9, p. 2591-2600Article in journal (Refereed) Published
    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.

    Keywords
    collapse risk, community viability analysis, demographic stochasticity, individual-based models, permanence, redundancy, secondary extinctions, species diversity, species loss
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13856 (URN)10.1890/03-8018 (DOI)
    Available from: 2006-06-08 Created: 2006-06-08 Last updated: 2009-05-08
    3. Early onset of secondary extinctions in ecological communities following the loss of top predators
    Open this publication in new window or tab >>Early onset of secondary extinctions in ecological communities following the loss of top predators
    2006 (English)In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 9, no 4, p. 435-442Article in journal (Refereed) Published
    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.

    Keywords
    Ecological community, food web, relaxation time, secondary extinction, species interactions, species loss, species richness, top predators, trophic level
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13857 (URN)10.1111/j.1461-0248.2006.00893.x (DOI)
    Available from: 2006-06-08 Created: 2006-06-08 Last updated: 2017-12-13
    4. Biodiversity and persistence of ecological communities in a stochastic environment
    Open this publication in new window or tab >>Biodiversity and persistence of ecological communities in a stochastic environment
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:liu:diva-13858 (URN)
    Available from: 2006-06-08 Created: 2006-06-08 Last updated: 2010-01-13
    Download full text (pdf)
    FULLTEXT01
  • 30.
    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)
  • 31.
    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)
  • 32.
    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.

  • 33.
    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.

  • 34.
    Brommesson, Peter
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Sellman, Stefan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Beck-Johnson, Lindsay
    Colorado State Univ, CO 80523 USA.
    Hallman, Clayton
    Colorado State Univ, CO 80523 USA.
    Murrieta, Deedra
    Colorado State Univ, CO 80523 USA.
    Webb, Colleen T.
    Colorado State Univ, CO 80523 USA.
    Miller, Ryan S.
    US Dept Agr Vet Serv, CO 80526 USA.
    Portacci, Katie
    US Dept Agr Vet Serv, CO 80526 USA.
    Lindström, Tom
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Assessing intrastate shipments from interstate data and expert opinion2021In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 8, no 3, article id 192042Article in journal (Refereed)
    Abstract [en]

    Live animal shipments are a potential route for transmitting animal diseases between holdings and are crucial when modelling spread of infectious diseases. Yet, complete contact networks are not available in all countries, including the USA. Here, we considered a 10% sample of Interstate Certificate of Veterinary Inspections from 1 year (2009). We focused on distance dependence in contacts and investigated how different functional forms affect estimates of unobserved intrastate shipments. To further enhance our predictions, we included responses from an expert elicitation survey about the proportion of shipments moving intrastate. We used hierarchical Bayesian modelling to estimate parameters describing the kernel and effects of expert data. We considered three functional forms of spatial kernels and the inclusion or exclusion of expert data. The resulting six models were ranked by widely applicable information criterion (WAIC) and deviance information criterion (DIC) and evaluated through within- and out-of-sample validation. We showed that predictions of intrastate shipments were mildly influenced by the functional form of the spatial kernel but kernel shapes that permitted a fat tail at large distances while maintaining a plateau-shaped behaviour at short distances better were preferred. Furthermore, our study showed that expert data may not guarantee enhanced predictions when expert estimates are disparate.

    Download full text (pdf)
    fulltext
  • 35.
    Brommesson, Peter
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Wennergren, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Lindström, Tom
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Spatiotemporal Variation in Distance Dependent Animal Movement Contacts: One Size Doesnt Fit All2016In: PLOS ONE, E-ISSN 1932-6203, Vol. 11, no 10, p. e0164008-Article in journal (Refereed)
    Abstract [en]

    The structure of contacts that mediate transmission has a pronounced effect on the outbreak dynamics of infectious disease and simulation models are powerful tools to inform policy decisions. Most simulation models of livestock disease spread rely to some degree on predictions of animal movement between holdings. Typically, movements are more common between nearby farms than between those located far away from each other. Here, we assessed spatiotemporal variation in such distance dependence of animal movement contacts from an epidemiological perspective. We evaluated and compared nine statistical models, applied to Swedish movement data from 2008. The models differed in at what level ( if at all), they accounted for regional and/or seasonal heterogeneities in the distance dependence of the contacts. Using a kernel approach to describe how probability of contacts between farms changes with distance, we developed a hierarchical Bayesian framework and estimated parameters by using Markov Chain Monte Carlo techniques. We evaluated models by three different approaches of model selection. First, we used Deviance Information Criterion to evaluate their performance relative to each other. Secondly, we estimated the log predictive posterior distribution, this was also used to evaluate their relative performance. Thirdly, we performed posterior predictive checks by simulating movements with each of the parameterized models and evaluated their ability to recapture relevant summary statistics. Independent of selection criteria, we found that accounting for regional heterogeneity improved model accuracy. We also found that accounting for seasonal heterogeneity was beneficial, in terms of model accuracy, according to two of three methods used for model selection. Our results have important implications for livestock disease spread models where movement is an important risk factor for between farm transmission. We argue that modelers should refrain from using methods to simulate animal movements that assume the same pattern across all regions and seasons without explicitly testing for spatiotemporal variation.

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  • 36.
    Brose, Ulrich
    et al.
    German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, 04103, Leipzig, Germany 2 Faculty of Biology and Pharmacy, Institute of Ecology, Friedrich Schiller University Jena, 07743, Jena, Germany.
    Blanchard, Julia L.
    Institute for Marine and Antarctic Studies and Centre for Marine Socioecology, University of Tasmania, 20 Castray Esplanade, Battery Point TAS 7004 Australia.
    Eklöf, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Galiana, Nuria
    Ecological Networks and Global Change Group, Experimental Ecology Station, Centre National de la Recherche Scientifique, 09200, Moulis, France.
    Hartvig, Martin
    Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, DK-2100, Copenhagen, Denmark 7 National Institute of Aquatic Resources, Technical University of Denmark, DK-2920, Charlottenlund, Denmark 8 Systemic Conservation Biology Group, J.F. Blumenbach Institute of Zoology and Anthropology, Georg-August University of Göttingen, 37073, Göttingen, Germany.
    Hirt, Myriam R.
    German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, 04103, Leipzig, Germany 2 Faculty of Biology and Pharmacy, Institute of Ecology, Friedrich Schiller University Jena, 07743, Jena, Germany.
    Kalinkat, Gregor
    Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, 12587, Berlin, Germany 10 Department of Fish Ecology and Evolution, Eawag, 6047, Kastanienbaum, Switzerland.
    Nordström, MArie C.
    Environmental and Marine Biology, Åbo Akademi University, FI-20520, Åbo, Finland.
    O'Gorman, Eoin J.
    Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK.
    Rall, Björn C.
    German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, 04103, Leipzig, Germany 2 Faculty of Biology and Pharmacy, Institute of Ecology, Friedrich Schiller University Jena, 07743, Jena, Germany.
    Schneider, Florian D.
    Institut des Sciences de l’Evolution, Universit´e Montpellier, CNRS, IRD, EPHE, CC065, 34095, Montpellier Cedex 05, France.
    Thébault, Elisa
    Institute of Ecology and Environmental Sciences - Paris, UMR 7618 (UPMC, CNRS, IRD, INRA, UPEC, Paris Diderot), Universit´e Pierre et Marie Curie, 75005, Paris, France.
    Jacob, Ute
    Department of Biology, Institute for Hydrobiology and Fisheries Science, Center for Earth System Research and Sustainability (CEN), KlimaCampus, University of Hamburg, 22767, Hamburg, Germany.
    Predicting the consequences of species lossusing size-structured biodiversity approaches2017In: Biological Reviews, ISSN 1464-7931, E-ISSN 1469-185X, Vol. 92, no 2, p. 684-697Article, review/survey (Refereed)
    Abstract [en]

    Understanding the consequences of species loss in complex ecological communities is one of the great challenges in current biodiversity research. For a long time, this topic has been addressed by traditional biodiversity experiments. Most of these approaches treat species as trait-free, taxonomic units characterizing communities only by species number without accounting for species traits. However, extinctions do not occur at random as there is a clear correlation between extinction risk and species traits. In this review, we assume that large species will be most threatened by extinction and use novel allometric and size-spectrum concepts that include body mass as a primary species trait at the levels of populations and individuals, respectively, to re-assess three classic debates on the relationships between biodiversity and (i) food-web structural complexity, (ii) community dynamic stability, and (iii) ecosystem functioning. Contrasting current expectations, size-structured approaches suggest that the loss of large species, that typically exploit most resource species, may lead to future food webs that are less interwoven and more structured by chains of interactions and compartments. The disruption of natural body-mass distributions maintaining food-web stability may trigger avalanches of secondary extinctions and strong trophic cascades with expected knock-on effects on the functionality of the ecosystems. Therefore, we argue that it is crucial to take into account body size as a species trait when analysing the consequences of biodiversity loss for natural ecosystems. Applying size-structured approaches provides an integrative ecological concept that enables a better understanding of each species' unique role across communities and the causes and consequences of biodiversity loss.

  • 37.
    Brose, Ulrich
    et al.
    Technical University of Darmstadt, Germany.
    Pavao-Zuckerman, Mitchell
    University of Arizona, Tucson, Arizona, USA.
    Eklöf, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Bengtsson, Janne
    Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Berg, Matty P.
    Vrije Universiteit Amsterdam, The Netherlands.
    Cousins, Steven H.
    Cranfield University, United Kingdom.
    Mulder, Christian
    National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
    Verhoef, Herman A.
    Vrije Universiteit Amsterdam, The Netherlands.
    Wolters, Volkmar
    Justus-Liebig-University, Giessen, Germany.
    Spatial aspects of food webs2005In: Dynamic Food Webs: Multispecies Assemblages, Ecosystem Development and Environmental Change / [ed] P.C. deRuiter, V. Wolters & J.C. Moore, London, UK: Elsevier, 2005, Vol. 3, p. 463-469Conference paper (Refereed)
    Abstract [en]

    Aspects of spatial scale have until recently been largely ignored in empirical and theoretical food web studies (e.g., Cohen & Briand 1984, Martinez 1992, but see Bengtsson et al. 2002, Bengtsson & Berg, this book). Most ecologists tend to conceptualize and represent food webs as static representations of communities, depicting a community assemblage as sampled at a particular point in time, or highly aggregated trophic group composites over broader scales of time and space (Polis et al. 1996). Moreover, most researchers depict potential food webs, which contain all species sampled and all potential trophic links based on literature reviews, several sampling events, or laboratory feeding trials. In reality, however, not all these potential feeding links are realized as not all species co-occur, and not all samples in space or time can contain all species (Schoenly & Cohen 1991), hence, yielding a variance of food web architecture in space (Brose et al. 2004). In recent years, food web ecologists have recognized that food webs are open systems – that are influence by processes in adjacent systems – and spatially heterogeneous (Polis et al. 1996). This influence of adjacent systems can be bottom-up, due to allochthonous inputs of resources (Polis & Strong 1996, Huxel & McCann 1998, Mulder & De Zwart 2003), or top-down due to the regular or irregular presence of top predators (e.g., Post et al. 2000, Scheu 2001). However, without a clear understanding of the size of a system and a definition of its boundaries it is not possible to judge if flows are internal or driven by adjacent systems. Similarly, the importance of allochthony is only assessable when the balance of inputs and outputs are known relative to the scale and throughputs within the system itself. At the largest scale of the food web – the home range of a predator such as wolf, lion, shark or eagle of roughly 50 km2 to 300 km2 –the balance of inputs and outputs caused by wind and movement of water may be small compared to the total trophic flows within the home range of the large predator (Cousins 1990). Acknowledging these issues of space, Polis et al (1996) argued that progress toward the next phase of food web studies would require addressing spatial and temporal processes. Here, we present a conceptual framework with some nuclei about the role of space in food web ecology. Although we primarily address spatial aspects, this framework is linked to a more general concept of spatio-temporal scales of ecological research.

  • 38.
    Buhnerkempe, Michael G.
    et al.
    Colorado State University, CO 80523 USA .
    Tildesley, Michael J.
    University of Warwick, England .
    Lindström, Tom
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Grear, Daniel A.
    Colorado State University, CO 80523 USA .
    Portacci, Katie
    US Anim and Plant Health Inspect Serv, CO USA US Anim and Plant Health Inspect Serv, CO USA .
    Miller, Ryan S.
    US Anim and Plant Health Inspect Serv, CO USA US Anim and Plant Health Inspect Serv, CO USA .
    Lombard, Jason E.
    US Anim and Plant Health Inspect Serv, CO USA US Anim and Plant Health Inspect Serv, CO USA .
    Werkman, Marleen
    University of Warwick, England .
    Keeling, Matt J.
    University of Warwick, England .
    Wennergren, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Webb, Colleen T.
    Colorado State University, CO 80523 USA .
    The Impact of Movements and Animal Density on Continental Scale Cattle Disease Outbreaks in the United States2014In: PLOS ONE, E-ISSN 1932-6203, Vol. 9, no 3, p. 0091724-Article in journal (Refereed)
    Abstract [en]

    Globalization has increased the potential for the introduction and spread of novel pathogens over large spatial scales necessitating continental-scale disease models to guide emergency preparedness. Livestock disease spread models, such as those for the 2001 foot-and-mouth disease (FMD) epidemic in the United Kingdom, represent some of the best case studies of large-scale disease spread. However, generalization of these models to explore disease outcomes in other systems, such as the United Statess cattle industry, has been hampered by differences in system size and complexity and the absence of suitable livestock movement data. Here, a unique database of US cattle shipments allows estimation of synthetic movement networks that inform a near-continental scale disease model of a potential FMD-like (i.e., rapidly spreading) epidemic in US cattle. The largest epidemics may affect over one-third of the US and 120,000 cattle premises, but cattle movement restrictions from infected counties, as opposed to national movement moratoriums, are found to effectively contain outbreaks. Slow detection or weak compliance may necessitate more severe state-level bans for similar control. Such results highlight the role of large-scale disease models in emergency preparedness, particularly for systems lacking comprehensive movement and outbreak data, and the need to rapidly implement multi-scale contingency plans during a potential US outbreak.

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  • 39.
    Carpentier, Camille
    et al.
    Univ Namur, Belgium.
    Barabas, György
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. MTA ELTE Theoret Biol & Evolutionary Ecol Res Grp, Hungary.
    Spaak, Jurg Werner
    Univ Namur, Belgium; Cornell Univ, NY USA.
    De Laender, Frederik
    Univ Namur, Belgium.
    Reinterpreting the relationship between number of species and number of links connects community structure and stability2021In: Nature Ecology & Evolution, E-ISSN 2397-334X, Vol. 5, no 8, p. 1102-1109Article in journal (Refereed)
    Abstract [en]

    For 50 years, ecologists have examined how the number of interactions (links) scales with the number of species in ecological networks. Here, we show that the way the number of links varies when species are sequentially removed from a community is fully defined by a single parameter identifiable from empirical data. We mathematically demonstrate that this parameter is network-specific and connects local stability and robustness, establishing a formal connection between community structure and two prime stability concepts. Importantly, this connection highlights a local stability-robustness trade-off, which is stronger in mutualistic than in trophic networks. Analysis of 435 empirical networks confirmed these results. We finally show how our network-specific approach relates to the classical across-network approach found in literature. Taken together, our results elucidate one of the intricate relationships between network structure and stability in community networks. This paper demonstrates that the scaling relationship between the number of species and the number of interactions (links) in a network can explain its local stability and robustness to secondary extinctions.

  • 40.
    Childers, Daniel L.
    et al.
    Arizona State Univ, AZ 85287 USA.
    Bois, Paul
    Unistra, France.
    Hartnett, Hilairy E.
    Arizona State Univ, AZ USA; Arizona State Univ, AZ USA.
    McPhearson, Timon
    New Sch, NY USA; Cary Inst Ecosyst Studies, NY USA; Stockholm Resilience Ctr, Sweden.
    Metson, Genevieve
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Sanchez, Christopher A.
    Arizona State Univ, AZ USA.
    Urban Ecological Infrastructure: An inclusive concept for the non-built urban environment2019In: Elementa: Science of the Anthropocene, E-ISSN 2325-1026, Vol. 7, article id 46Article, review/survey (Refereed)
    Abstract [en]

    It is likely that half of the urban areas that will exist in 2050 have not yet been designed and built. This provides tremendous opportunities for enhancing urban sustainability, and using "nature in cities" is critical to more resilient solutions to urban challenges. Terms for "urban nature" include Green Infrastructure (GI), Green-Blue Infrastructure (GBI), Urban Green Space (UGS), and Nature-Based Solutions (NBS). These terms, and the concepts they represent, are incomplete because they tend to reduce the importance of non-terrestrial ecological features in cities. We argue that the concept of Urban Ecological Infrastructure (UEI), which came from a 2013 forum held in Beijing and from several subsequent 2017 publications, is a more inclusive alternative. In this paper we refine the 2013 definition of UEI and link the concept more directly to urban ecosystem services. In our refined definition, UEI comprises all parts of a city that support ecological structures and functions, as well as the ecosystem services provided by UEI that directly affect human outcomes and wellbeing. UEI often includes aspects of the built environment, and we discuss examples of this "hybrid infrastructure". We distinguish terrestrial, aquatic, and wetland UEI because each type provides different ecosystem services. We present several examples of both "accidental" UEI and UEI that was explicitly designed and managed, with an emphasis on wetland UEI because these ecotonal ecosystems are uniquely both terrestrial and aquatic. We show how both accidental and planned UEI produces unexpected ecosystem services, which justifies recognizing and maintaining both purposeful and serendipitous types of UEI in cities. Finally, we posit that by incorporating both "ecological" and "infrastructure", UEI also helps to bridge urban scientists and urban practitioners in a more transdisciplinary partnership to build more resilient and sustainable cities.

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  • 41.
    Christianou, Maria
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Interaction strength and responses of ecological communities to disturbances2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Ecological communities are continuously exposed to natural or anthropogenic disturbances of varied intensity and frequency. The way communities respond to disturbances can depend on various factors, such as number of species, structural characteristics of the community, stability properties, species characteristics and the nature of the disturbance. This thesis is a collection of theoretical studies on how ecological communities respond to different kind of disturbances, mainly in relation to interaction strength between species, a measure of how strongly or weakly species interact with each other.

    A major disturbance for natural communities is the loss of a species. Although species extinctions is a natural process in the geological time scale, it has lately been dangerously accelerated due to human activities and interferences. Extinction of a species can have dramatic consequences for the community, can trigger a cascade of secondary species extinction and can even lead to community collapse. In Paper I, we identify species whose loss can trigger a large number of secondary extinctions (namely keystone species), species that are particularly vulnerable to become extinct following the loss of another species and mechanisms behind the sequence of secondary extinctions. We also highlight the fact that the keystone status of a species can be context dependent, that is, it is dependent on the structure of the community where it is embedded.

    Although the global extinction of a species is an irreversible process, in cases of local extinction, conservation and restoration plans can include reintroduction of the species to their former location. Such reintroduction or translocation attempts often fail, due to characteristics of the reintroduced species and to changes in the community structure caused by the initial loss of the species (Paper II ). Using model communities we show that this risk of reintroduction failure can be high - even in cases where the initial species loss did not cause any secondary extinctions - and it differs between attempts to reintroduce weakly or strongly interacting species (Paper II ).

    Disturbances are not always as profound as species extinction. Human activities and environmental changes can cause small and permanent changes in birth and mortality rates of species and in the strength of interaction between species. Such disturbances can change the stability properties of ecological communities making them more vulnerable to further disturbances. In Paper III, we derive analytical expressions for the sensitivity of resilience to changes in the intrinsic growth rate of species and in the strength of interaction links. We also apply the method to model communities and identify keystone species and links, i.e. species and links whose small disturbance would cause large changes in community resilience. We found that changes in the growth rate of strongly interacting species have a larger impact on resilience than changes in the growth rate of weakly interacting species, which is in line with the main findings of the species deletion study (Paper I ).

    Community complexity - mainly expressed as number of species and links - was one of the first community characteristics to be related to stability properties and the way communities respond to disturbances. Many theoretical works support the hypothesis that complexity reduces stability, contradicting intuition, observation and many experimental studies. In Paper IV, we state that this could be, at least partly, due to methodological misconceptions and misinterpretations. We propose a new sampling method for parameterizing model communities and we highlight the importance of feasibility of model communities (all species densities are strictly positive), for a more proper estimation of stability probability of communities with different degrees of complexity.

    List of papers
    1. Keystone species and vulnerable species in ecological communities: strong or weak interactors?
    Open this publication in new window or tab >>Keystone species and vulnerable species in ecological communities: strong or weak interactors?
    2005 (English)In: Journal of Theoretical Biology, ISSN 0022-5193, Vol. 35, no 1, p. 95-103Article in journal (Refereed) Published
    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.

    Keywords
    Species loss; Keystone species; Interaction strength; Community dynamics; Permanence; Secondary extinction
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-14053 (URN)10.1016/j.jtbi.2004.12.022 (DOI)
    Available from: 2006-10-04 Created: 2006-10-04
    2. Prospects and risks of species reintroductions: a community ecological perspective
    Open this publication in new window or tab >>Prospects and risks of species reintroductions: a community ecological perspective
    (English)Manuscript (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.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-14054 (URN)
    Available from: 2006-10-04 Created: 2006-10-04 Last updated: 2012-11-14
    3. Sensitivity analysis at the community level
    Open this publication in new window or tab >>Sensitivity analysis at the community level
    2006 (English)Manuscript (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.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-14055 (URN)
    Available from: 2006-10-04 Created: 2006-10-04 Last updated: 2012-11-14
    4. Diversity-stability relation from a methodological point of view
    Open this publication in new window or tab >>Diversity-stability relation from a methodological point of view
    (English)Manuscript (Other academic)
    Abstract [en]

    The complexity - stability relation has been a central issue in ecology for a long time. Both theoretical and empirical studies have been investigating whether complexity promotes stability or not, which could be the underlying mechanisms creating a positive or negative cmnplexity-stability relation and which are the structures, characteristics and constraints that would allow complex ecological systems to persist and be stable. In this paper we approach the subject from amethodological point of view. We study the effect of parameterizing the communities in a certain way and illustrate the effect of treating feasibility (i.e. densities of all species are strictly positive) separately from stability. We observe that increasing number of species in the communities requires a more skewed interaction strength distribution toward weak interactions, in order for the communities to theoretically exist. Using model Lotka-Volterra competition communities we illustrate that probability of feasibility decreases with increasing interaction strength and number of species in the community. However, forfeasible systems we find that local stability probability and resilience do not significantly differ between communities with few or many species, in contrast with earlier studies that, did not account for feasibility and concluded that species poor communities had higher probability of being locally stable than species rich communities.

    Keywords
    Local stability, resilience, feasibility, Lotka-Volterra model, competition community, Central Limit Theorem
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-14056 (URN)
    Note

    Alternative title: Complexity - Stability relation from a methodological point of view

    Available from: 2006-10-04 Created: 2006-10-04 Last updated: 2012-11-14
  • 42.
    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.

  • 43.
    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.

  • 44.
    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.

  • 45.
    Christianou, Maria
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Kokkoris, Giorgos D.
    Dept. of Marine Sciences, Faculty of Environment, University of the Aegean, Mytilene, Lesvos Island, Greece.
    Diversity-stability relation from a methodological point of viewManuscript (Other academic)
    Abstract [en]

    The complexity - stability relation has been a central issue in ecology for a long time. Both theoretical and empirical studies have been investigating whether complexity promotes stability or not, which could be the underlying mechanisms creating a positive or negative cmnplexity-stability relation and which are the structures, characteristics and constraints that would allow complex ecological systems to persist and be stable. In this paper we approach the subject from amethodological point of view. We study the effect of parameterizing the communities in a certain way and illustrate the effect of treating feasibility (i.e. densities of all species are strictly positive) separately from stability. We observe that increasing number of species in the communities requires a more skewed interaction strength distribution toward weak interactions, in order for the communities to theoretically exist. Using model Lotka-Volterra competition communities we illustrate that probability of feasibility decreases with increasing interaction strength and number of species in the community. However, forfeasible systems we find that local stability probability and resilience do not significantly differ between communities with few or many species, in contrast with earlier studies that, did not account for feasibility and concluded that species poor communities had higher probability of being locally stable than species rich communities.

  • 46.
    Cirtwill, Alyssa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Dalla Riva, Giulio V.
    Department of Statistics, University of British Columbia, Vancouver, Canada; School of Mathematics and Statistics, University of Canterbury, Christchurch, New Zealand.
    Gaiarsa, Marilia P.
    Departamento de Ecologia Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil; Department of Entomology, University of California, Riverside, California, USA.
    Bimler, Malyon D.
    School of Biological Sciences, University of Queensland, Brisbane, Australia.
    Cagua, E. Fernando
    Centre for Integrative Ecology, School of Biological Sciences, University of Canterbury, Christchurch, New Zealand.
    Coux, Camille
    UMR 1065 Santé et Agroécologie du Vignoble, INRA Bordeaux-Aquitaine, France; Centre d’Etudes Biologiques de Chizé UMR 7372, CNRS, Université de La Rochelle, France.
    Dehling, D. Matthias
    Centre for Integrative Ecology, School of Biological Sciences, University of Canterbury, Christchurch, New Zealand.
    A review of species role concepts in food webs2018In: Food Webs, E-ISSN 2352-2496, Vol. 16, article id e00093Article in journal (Refereed)
    Abstract [en]

    Many different concepts have been used to describe species' roles in food webs (i.e., the ways in which species participate in their communities as consumers and resources). As each concept focuses on a different aspect of food-web structure, it can be difficult to relate these concepts to each other and to other aspects of ecology. Here we use the Eltonian niche as an overarching framework, within which we summarize several commonly-used role concepts (degree, trophic level, motif roles, and centrality). We focus mainly on the topological versions of these concepts but, where dynamical versions of a role concept exist, we acknowledge these as well. Our aim is to highlight areas of overlap and ambiguity between different role concepts and to describe how these roles can be used to group species according to different strategies (i.e., equivalence and functional roles). The existence of “gray areas” between role concepts make it essential for authors to carefully consider both which role concept(s) are most appropriate for the analyses they wish to conduct and what aspect of species' niches (if any) they wish to address. The ecological meaning of differences between species' roles can change dramatically depending on which role concept(s) are used.

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  • 47.
    Cirtwill, Alyssa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. Stockholm Univ, Sweden.
    Eklöf, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Roslin, Tomas
    Swedish Univ Agr Sci, Sweden.
    Wootton, Kate
    Swedish Univ Agr Sci, Sweden.
    Gravel, Dominique
    Univ Sherbrooke, Canada.
    A quantitative framework for investigating the reliability of empirical network construction2019In: Methods in Ecology and Evolution, E-ISSN 2041-210X, Vol. 10, no 6, p. 902-911Article in journal (Refereed)
    Abstract [en]

    Descriptions of ecological networks typically assume that the same interspecific interactions occur each time a community is observed. This contrasts with the known stochasticity of ecological communities: community composition, species abundances and link structure all vary in space and time. Moreover, finite sampling generates variation in the set of interactions actually observed. For interactions that have not been observed, most datasets will not contain enough information for the ecologist to be confident that unobserved interactions truly did not occur. Here, we develop the conceptual and analytical tools needed to capture uncertainty in the estimation of pairwise interactions. To define the problem, we identify the different contributions to the uncertainty of an interaction. We then outline a framework to quantify the uncertainty around each interaction by combining data on observed co-occurrences with prior knowledge. We illustrate this framework using perhaps the most extensively sampled network to date. We found significant uncertainty in estimates for the probability of most pairwise interactions. This uncertainty can, however, be constrained with informative priors. This uncertainty scaled up to summary measures of network structure such as connectance and nestedness. Even with informative priors, we are likely to miss many interactions that may occur rarely or under different local conditions. Overall, we demonstrate the importance of acknowledging the uncertainty inherent in network studies, and the utility of treating interactions as probabilities in pinpointing areas where more study is needed. Most importantly, we stress that networks are best thought of as systems constructed from random variables, the stochastic nature of which must be acknowledged for an accurate representation. Doing so will fundamentally change network analyses and yield greater realism.

  • 48.
    Cirtwill, Alyssa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. University of Canterbury, New Zealand; University of Otago, New Zealand.
    Lagrue, Clement
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Poulin, Robert
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Stouffer, Daniel B.
    University of Canterbury, New Zealand.
    Host taxonomy constrains the properties of trophic transmission routes for parasites in lake food webs2017In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 98, no 9, p. 2401-2412Article in journal (Refereed)
    Abstract [en]

    Some parasites move from one host to another via trophic transmission, the consumption of the parasite (inside its current host) by its future host. Feeding links among free-living species can thus be understood as potential transmission routes for parasites. As these links have different dynamic and structural properties, they may also vary in their effectiveness as trophic transmission routes. That is, some links may be better than others in allowing parasites to complete their complex life cycles. However, not all links are accessible to parasites as most are restricted to a small number of host taxa. This restriction means that differences between links involving host and non-host taxa must be considered when assessing whether transmission routes for parasites have different food web properties than other links. Here we use four New Zealand lake food webs to test whether link properties (contribution of a link to the predators diet, prey abundance, prey biomass, amount of biomass transferred, centrality, and asymmetry) affect trophic transmission of parasites. Critically, we do this using both models that neglect the taxonomy of free-living species and models that explicitly include information about which free-living species are members of suitable host taxa. Although the best-fit model excluding taxonomic information suggested that transmission routes have different properties than other feeding links, when including taxonomy, the best-fit model included only an intercept. This means that the taxonomy of free-living species is a key determinant of parasite transmission routes and that food-web properties of transmission routes are constrained by the properties of host taxa. In particular, many intermediate hosts (prey) attain high biomasses and are involved in highly central links while links connecting intermediate to definitive (predator) hosts tend to be dynamically weak.

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  • 49.
    Cirtwill, Alyssa R.
    et al.
    Univ Canterbury, New Zealand; Stockholm Univ, Sweden.
    Dalla Riva, Giulio V.
    Univ Canterbury, New Zealand; Univ Canterbury, New Zealand.
    Baker, Nick J.
    Univ Canterbury, New Zealand.
    Ohlsson, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering.
    Norstrom, Isabelle
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Wohlfarth, Inger-Marie
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Thia, Joshua A.
    Univ Canterbury, New Zealand.
    Stouffer, Daniel B.
    Univ Canterbury, New Zealand.
    Related plants tend to share pollinators and herbivores, but strength of phylogenetic signal varies among plant families2020In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 226, no 3, p. 909-920Article in journal (Refereed)
    Abstract [en]

    Related plants are often hypothesized to interact with similar sets of pollinators and herbivores, but this idea has only mixed empirical support. This may be because plant families vary in their tendency to share interaction partners. We quantify overlap of interaction partners for all pairs of plants in 59 pollination and 11 herbivory networks based on the numbers of shared and unshared interaction partners (thereby capturing both proportional and absolute overlap). We test for relationships between phylogenetic distance and partner overlap within each network; whether these relationships varied with the composition of the plant community; and whether well-represented plant families showed different relationships. Across all networks, more closely related plants tended to have greater overlap. The strength of this relationship within a network was unrelated to the composition of the networks plant component, but, when considered separately, different plant families showed different relationships between phylogenetic distance and overlap of interaction partners. The variety of relationships between phylogenetic distance and partner overlap in different plant families probably reflects a comparable variety of ecological and evolutionary processes. Considering factors affecting particular species-rich groups within a community could be the key to understanding the distribution of interactions at the network level.

  • 50.
    Cirtwill, Alyssa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, Faculty of Science & Engineering. Univ Canterbury, New Zealand.
    Roslin, Tomas
    Swedish Univ Agr Sci, Sweden; Univ Helsinki, Finland.
    Rasmussen, Claus
    Aarhus Univ, Denmark.
    Olesen, Jens Mogens
    Aarhus Univ, Denmark.
    Stouffer, Daniel B.
    Univ Canterbury, New Zealand.
    Between-year changes in community composition shape species' roles in an Arctic plant-pollinator network2018In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 127, no 8, p. 1163-1176Article in journal (Refereed)
    Abstract [en]

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

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