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  • 1.
    Christensen, Pernilla
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ecke, F.
    Sandström, P.
    Nilsson, M.
    Hörnfeldt, Birger
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Can landscape properties predict occurrence of grey-sided voles?2008Ingår i: Population Ecology, ISSN 1438-3896, E-ISSN 1438-390X, Vol. 50, nr 2, s. 169-179Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There has been a long-term decline in spring and fall numbers of Clethrionomys rufocanus in boreal Sweden in 1971-2005. Previous studies on permanent sampling plots in the centre of 2.5 x 2.5 km landscapes suggested that habitat fragmentation (sensu destruction) could have contributed to the decline. Therefore, we tested these findings in a field study and compared trapping results on the central sampling plots of landscapes with a low degree of fragmentation (LDF) and of "hot spot" type with trapping results in managed forest landscapes with a high degree of fragmentation (HDF). We predicted that C. rufocanus would be more common on the LDF plots. We used our permanent plots supplemented with a new sample of plots, mainly of the rare LDF type, inside or just outside the long-term study area. Very few voles were trapped on both plot types, and no difference was found. However, a subsequent pilot study with trapping in a national park with large areas of pristine, unfragmented forest yielded more voles than in the managed, more fragmented, areas. Consequently, the initial field study data and some other recent data were also re-analysed from a "local patch quality" perspective. This alternative approach revealed the positive importance of large focal patches of forest > 60 years old and their content of old-growth (pine) forest (> 100 years). Interestingly, at the landscape level, the frequency distribution of patches of forest > 60 years old, old-growth (> 100 years), and especially of old-growth pine forest (> 100 years), relative to the properties of plots with C. rufocanus, suggested that there are few forest patches left that are suitable for C. rufocanus. Our current results suggest that habitat fragmentation cannot be excluded as a contributing cause to the long-term decline of C. rufocanus in boreal Sweden.

  • 2. Landi, Pietro
    et al.
    Minoarivelo, Henintsoa O.
    Brännström, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik. Evolution and Ecology Program, International Institute for Applied Systems Analysis, Laxenburg, Austria.
    Hui, Cang
    Dieckmann, Ulf
    Complexity and stability of ecological networks: a review of the theory2018Ingår i: Population Ecology, ISSN 1438-3896, E-ISSN 1438-390X, Vol. 60, nr 4, s. 319-345Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Our planet is changing at paces never observed before. Species extinction is happening at faster rates than ever, greatly exceeding the five mass extinctions in the fossil record. Nevertheless, our lives are strongly based on services provided by ecosystems, thus the responses to global change of our natural heritage are of immediate concern. Understanding the relationship between complexity and stability of ecosystems is of key importance for the maintenance of the balance of human growth and the conservation of all the natural services that ecosystems provide. Mathematical network models can be used to simplify the vast complexity of the real world, to formally describe and investigate ecological phenomena, and to understand ecosystems propensity of returning to its functioning regime after a stress or a perturbation. The use of ecological-network models to study the relationship between complexity and stability of natural ecosystems is the focus of this review. The concept of ecological networks and their characteristics are first introduced, followed by central and occasionally contrasting definitions of complexity and stability. The literature on the relationship between complexity and stability in different types of models and in real ecosystems is then reviewed, highlighting the theoretical debate and the lack of consensual agreement. The summary of the importance of this line of research for the successful management and conservation of biodiversity and ecosystem services concludes the review.

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  • 3. Sundell, J.
    et al.
    Trebatická, L.
    Oksanen, Tarja
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Ovaskainen, O.
    Haapakoski, M.
    Ylönen, H.
    Predation on two vole species by a shared predator: antipredatory response and prey preference2008Ingår i: Population Ecology, ISSN 1438-3896, E-ISSN 1438-390X, Vol. 50, nr 3, s. 257-266Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In prey communities with shared predators, variation in prey vulnerability is a key factor in shaping community dynamics. Conversely, the hunting efficiency of a predator depends on the prey community structure, preferences of the predator and antipredatory behavioural traits of the prey. We studied experimentally, under seminatural field conditions, the preferences of a predator and the antipredatory responses of prey in a system consisting of two Myodes species of voles, the grey-sided vole (M. rufocanus Sund.) and the bank vole (M. glareolus Schreb.), and their specialist predator, the least weasel (Mustela nivalis nivalis L.). To quantify the preference of the weasels, we developed a new modelling framework that can be used for unbalanced data. The two vole species were hypothesised to have different habitat-dependent vulnerabilities. We created two habitats, open and forest, to provide different escape possibilities for the voles. We found a weak general preference of the weasels for the grey-sided voles over the bank voles, and a somewhat stronger preference specifically in open habitats. The weasels clearly preferred male grey-sided voles over females, whereas in bank voles, there was no difference. The activity of voles changed over time, so that voles increased their movements immediately after weasel introduction, but later adjusted their movements to times of lowered predation risk. Females that were more active had an elevated mortality risk, whereas in the case of males, the result was the opposite. We conclude that, in vulnerability to predation, the species- or habitat-specific characteristics of these prey species are playing a minor role compared to sex-specific characteristics.

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