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- Dalén, Love, et al.
(författare)
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Population structure in a critically endangered arctic fox population : does genetics matter?
- 2006
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 15:10, s. 2809-2819
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Tidskriftsartikel (refereegranskat)abstract
- The arctic fox (Alopex lagopus) in Scandinavia is classified as critically endangered after having gone through a severe decline in population size in the beginning of the 20th century, from which it has failed to recover despite more than 65 years of protection. Arctic foxes have a high dispersal rate and often disperse over long distances, suggesting that there was probably little population differentiation within Scandinavia prior to the bottleneck. It is, however, possible that the recent decline in population size has led to a decrease in dispersal and an increase in population fragmentation. To examine this, we used 10 microsatellite loci to analyse genetic variation in 150 arctic foxes from Scandinavia and Russia. The results showed that the arctic fox in Scandinavia presently is subdivided into four populations, and that the Kola Peninsula and northwest Russia together form a large fifth population. Current dispersal between the populations seemed to be very low, but genetic variation within them was relatively high. This and the relative F-ST values among the populations are consistent with a model of recent fragmentation within Scandinavia. Since the amount of genetic variation is high within the populations, but the populations are small and isolated, demographic stochasticity seems to pose a higher threat to the populations' persistence than inbreeding depression and low genetic variation.
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- Elmhagen, Bodil, 1973-, et al.
(författare)
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Trophic control of mesopredators in terrestrial ecosystems: top-down or bottom-up?
- 2007
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:3, s. 197-206
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Tidskriftsartikel (refereegranskat)abstract
- It has been argued that widespread extinctions of top predators have changed terrestrial ecosystem structures through mesopredator release, where increased abundances of medium-sized predators have detrimental effects on prey communities. This top-down concept has received much attention within conservation biology, but few studies have demonstrated the phenomenon. The concept has been criticized since alternative explanations involving bottom-up impacts from bioclimatic effects on ecosystem productivity and from anthropogenic habitat change are rarely considered. We analyse the response of a mesopredator (the red fox) to declines in top predators (wolf and Eurasian lynx) and agricultural expansion over 90 years in Sweden, taking bioclimatic effects into account. We show a top-down mesopredator release effect, but ecosystem productivity determined its strength. The impacts of agricultural activity were mediated by their effects on top predator populations. Thus, both top-down and bottom-up processes need to be understood for effective preservation of biodiversity in anthropogenically transformed ecosystems.
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- Shirley, Mark, et al.
(författare)
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Modelling the spatial population dynamics of arctic foxes : the effects of red foxes and microtine cycles
- 2009
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Ingår i: Canadian Journal of Zoology. - 0008-4301 .- 1480-3283. ; 87, s. 1170-1183
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Tidskriftsartikel (refereegranskat)abstract
- The Fennoscandian arctic fox Vulpes lagopus (L., 1758) population is critically endangered, possibly because of increased interference competition from red foxes Vulpes vulpes (L., 1758) and fading cycles in microtine rodents, which cause food shortage. It is not known how these factors drive arctic fox population trends. To test their role in arctic fox decline, we developed a spatially-explicit and individual-based model that allowed us to simulate fox interactions and food availability in a real landscape. A sensitivity analysis revealed that simulated arctic fox population size and den occupancy were strongly correlated with fecundity and mortality during the microtine crash phase, but also with red fox status. Model simulations suggested that arctic fox population trends depended on microtine cycles and that arctic fox distributions were restricted by red fox presence. We compared the model predictions with field data collected at Vindelfjällen, Sweden. The model recreated the observed arctic fox trend only with the inclusion of arctic fox avoidance of red fox home ranges. The results indicate that avoidance behaviours can affect population trends and hence, that relatively small numbers of red foxes can have a strong negative impact on arctic fox population size and distribution.
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