Population structure in a critically endangered arctic fox population: does genetics matter?

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.</p

Mesopredator Release by an Emergent Superpredator: A Natural Experiment of Predation in a Three Level Guild

Chakarov N, Krüger O. Mesopredator Release by an Emergent Superpredator: A Natural Experiment of Predation in a Three Level Guild. PLoS ONE. 2010;5(12): e15229.Background: Intraguild predation (IGP) is widespread but it is often neglected that guilds commonly include many layers of dominance within. This could obscure the effects of IGP making unclear whether the intermediate or the bottom mesopredator will bear higher costs from the emergence of a new top predator. Methodology/Principal Findings: In one of the most extensive datasets of avian IGP, we analyse the impact of recolonization of a superpredator, the eagle owl Bubo bubo on breeding success, territorial dynamics and population densities of two mesopredators, the northern goshawk Accipiter gentilis and its IG prey, the common buzzard Buteo buteo. The data covers more than two decades and encompass three adjacent plots. Eagle owls only recolonized the central plot during the second decade, thereby providing a natural experiment. Both species showed a decrease in standardized reproductive success and an increase in brood failure within 1.5 km of the superpredator. During the second decade, territory dynamics of goshawks was significantly higher in the central plot compared to both other plots. No such pattern existed in buzzards. Goshawk density in the second decade decreased in the central plot, while it increased in both other plots. Buzzard density in the second decade rapidly increased in the north, remained unchanged in the south and increased moderately in the center in a probable case of mesopredator release. Conclusions/Significance: Our study finds support for top-down control on the intermediate mesopredator and both top-down and bottom-up control of the bottom mesopredator. In the face of considerable costs of IGP, both species probably compete to breed in predator-free refugia, which get mostly occupied by the dominant raptor. Therefore for mesopredators the outcome of IGP might depend directly on the number of dominance levels which supersede them

The Influence of Coastal Access on Isotope Variation in Icelandic Arctic Foxes

To quantify the ecological effects of predator populations, it is important to evaluate how population-level specializations are dictated by intra- versus inter-individual dietary variation. Coastal habitats contain prey from the terrestrial biome, the marine biome and prey confined to the coastal region. Such habitats have therefore been suggested to better support predator populations compared to habitats without coastal access. We used stable isotope data on a small generalist predator, the arctic fox, to infer dietary strategies between adult and juvenile individuals with and without coastal access on Iceland. Our results suggest that foxes in coastal habitats exhibited a broader isotope niche breadth compared to foxes in inland habitats. This broader niche was related to a greater diversity of individual strategies rather than to a uniform increase in individual niche breadth or by individuals retaining their specialization but increasing their niche differentiation. Juveniles in coastal habitats exhibited a narrower isotope niche breadth compared to both adults and juveniles in inland habitats, and juveniles in inland habitats inhabited a lower proportion of their total isotope niche compared to adults and juveniles from coastal habitats. Juveniles in both habitats exhibited lower intra-individual variation compared to adults. Based on these results, we suggest that foxes in both habitats were highly selective with respect to the resources they used to feed offspring, but that foxes in coastal habitats preferentially utilized marine resources for this purpose. We stress that coastal habitats should be regarded as high priority areas for conservation of generalist predators as they appear to offer a wide variety of dietary options that allow for greater flexibility in dietary strategies

Multifunctionality at what scale? A landscape multifunctionality assessment for the European Union under conditions of land use change

Context: The provision of multiple ecosystem services (ES) within a landscape is commonly referred to as landscape multifunctionality. Modifying landscapes to increase multifunctionality and reduce trade-offs with concurrent services bears the potential to enhance sustainability in human-dominated landscapes. Assessing landscape multifunctionality is thus crucial for land management and planning, but lack of a clear definition and operationalization of multifunctionality impedes comparisons of different study results. Objectives: We want to address how elements of the study design affect results of multifunctionality assessments. Furthermore, we want to quantify future multifunctionality in the European Union (EU) and indicate the role of land use change and land use diversity on multifunctionality. Methods: We analyzed diverging scenarios depicting land use change in the EU between 2000 and 2040 for their effects on landscape multifunctionality. We tested different multifunctionality indicators at various spatial scales based on the modelling of 12 ES and biodiversity indicators. Results: Particularly the analysis scale determines the interpretation of landscape multifunctionality. Coldspots identified by different indicators are in higher agreement than hotspots. We could not confirm links between land use diversity and landscape multifunctionality. While, at EU scale, multifunctionality slightly increases in future scenarios, agricultural intensification and (peri-)urban growth pose large threats to multifunctional landscapes. Conclusions: The choice of indicator and analysis scale strongly determine possible interpretations of the results. Rather than focusing on the impacts of land use change on multifunctionality, it is recommended to base land use policy on the impacts of location-specific change on ES supply and demands