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  • 1.
    Ahlgren, Hans
    et al.
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Lidén, Kerstin
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies.
    Multiple prehistoric introductions of the mountain hare (Lepus timidus) on a remote island, as revealed by ancient DNA2016In: Journal of Biogeography, ISSN 0305-0270, E-ISSN 1365-2699, Vol. 43, no 9, p. 1786-1796Article in journal (Refereed)
    Abstract [en]

    Aim: The majority of the non-volant mammals now present on the island of Gotland, Sweden, have been introduced in modern times. One exception is the mountain hare (Lepus timidus), which was present on the island more than 9000 years ago. This paper investigates the origins of the Gotland hares and temporal changes in their genetic structure, and considers how they may have reached the island.

    Location: The island of Gotland, Sweden (57°30′ N, 18°20′ E).

    Methods: Two fragments of the mitochondrial D-loop 130 + 164 base pairs in length from skeletal remains from 40 ancient mountain hares from Gotland, 38 from the Swedish mainland and five from Lithuania were analysed and compared with 90 modern L. timidus haplotypes from different locations in Eurasia and five haplotypes of the Don-hare (Lepus tanaiticus) morphotype.

    Results: The Mesolithic hares from Gotland (7304 bc–5989 bc) cluster with modern hares from Russia, Scotland, the Alps and Fennoscandia whereas the Gotland hares from the Neolithic and onwards (2848 bc–1641 ad) cluster with Neolithic hares from the Swedish mainland and modern hares from Fennoscandia. The Neolithic haplotypes from Lithuania and the Don-hare haplotypes were dispersed within the network. The level of differentiation (FST) between the Mesolithic and Neolithic hares on Gotland was twice as great as that observed on the mainland.

    Main conclusions: The ancient hares on Gotland fall into two haplogroups separated in time, indicating that the mountain hare became extinct at one point, with subsequent re-colonization events. In view of the isolated location of Gotland, it is probable that the hares were brought there by human means of transport.

  • 2.
    Angerbjörn, Anders
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Eide, Nina E.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Hellström, Peter
    Stockholm University, Faculty of Science, Department of Zoology.
    Ims, Rolf A.
    Killengreen, Siw
    Landa, Arild
    Meijer, Tomas
    Stockholm University, Faculty of Science, Department of Zoology.
    Mela, Matti
    Niemimaa, Jukka
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Tannerfeldt, Magnus
    Stockholm University, Faculty of Science, Department of Zoology.
    Yoccoz, Nigel G.
    Henttonen, Heikki
    Carnivore conservation in practice: replicatedmanagement actions on a large spatial scale2013In: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 50, no 1, p. 59-67Article in journal (Refereed)
    Abstract [en]

    More than a quarter of the world’s carnivores are threatened, often due to multiple andcomplex causes. Considerable research efforts are devoted to resolving the mechanisms behindthese threats in order to provide a basis for relevant conservation actions. However, evenwhen the underlying mechanisms are known, specific actions aimed at direct support for carnivoresare difficult to implement and evaluate at efficient spatial and temporal scales.2. We report on a 30-year inventory of the critically endangered Fennoscandian arctic foxVulpes lagopus L., including yearly surveys of 600 fox dens covering 21 000 km2. These surveysshowed that the population was close to extinction in 2000, with 40–60 adult animalsleft. However, the population subsequently showed a fourfold increase in size.3. During this time period, conservation actions through supplementary feeding and predatorremoval were implemented in several regions across Scandinavia, encompassing 79% of thearea. To evaluate these actions, we examined the effect of supplemental winter feeding andred fox control applied at different intensities in 10 regions. A path analysis indicated that47% of the explained variation in population productivity could be attributed to lemmingabundance, whereas winter feeding had a 29% effect and red fox control a 20% effect.4. This confirms that arctic foxes are highly dependent on lemming population fluctuationsbut also shows that red foxes severely impact the viability of arctic foxes. This study also highlightsthe importance of implementing conservation actions on extensive spatial and temporalscales, with geographically dispersed actions to scientifically evaluate the effects. We note thatpopulation recovery was only seen in regions with a high intensity of management actions.5. Synthesis and applications. The present study demonstrates that carnivore populationdeclines may be reversed through extensive actions that target specific threats. Fennoscandianarctic fox is still endangered, due to low population connectivity and expected climate impactson the distribution and dynamics of lemmings and red foxes. Climate warming is expected tocontribute to both more irregular lemming dynamics and red fox appearance in tundra areas;however, the effects of climate change can be mitigated through intensive managementactions such as supplemental feeding and red fox control.

  • 3.
    Angerbjörn, Anders
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Department of Animal Ecology.
    Henttonen, Heikki
    Eide, Nina
    NINA.
    Landa, Arild
    NINA.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology, Department of Animal Ecology.
    Meijer, Tomas
    Stockholm University, Faculty of Science, Department of Zoology, Department of Animal Ecology.
    Progress report 2007 LIFE03 NAT/S/000073 Saving the Endangered Fennoscandian Alopex lagopus SEFALO+.2007Report (Other (popular science, discussion, etc.))
    Abstract [en]

    In total, 36 litters were recorded in Scandinavia during the summer 2007 of which 0 in Finland, 24 inSweden and 15 in Norway. In 2001 and 2004, when the small rodent cycle was in the same increasephase as this year, we had 9 and 28 litters recorded in Scandinavia, respectively, which means thatthe population has increased strongly during the last six years. However, the population increase hasnot been similar all over Scandinavia. In the southern mountain areas, Helagsfjällen and Borgafjäll,the actions of feeding and red fox removal have been very efficient. The number of litters in theseareas has doubled between each rodent increase year. The Norwegian part of Børgefjell has acted asa control area where no actions have been implemented. There, the number of litters has remainedconstant in increase years during the project period 2001-2007. In the northern mountain areas,Vindelfjällen and areas in Norrbotten, we have not managed to keep a high intensity of actions. Thenumber of litters in these areas has been stable. The reasons for the large variation in extent ofimplemented actions between the mountain areas are mainly logistical problems due to the extent ofthe geographical areas concerned in combination with harsh winter climate. In the northern areas,due to the geographical distances, field workers would have to stay in the field for several days inorder to perform field actions which can be achieved in a single day in the southern mountain areas.

  • 4. Berteaux, Dominique
    et al.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Ehrich, Dorothee
    Eide, Nina E
    Fuglei, Eva
    Gallant, Daniel
    Ims, Rolf A
    Kruchenkova, Elena
    Lecomte, Nicholas
    Menuyshina, Irina
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Ovsjanikov, Nikita
    Rodnikova, Anna
    Tarroux, Arnaud
    Yoccoz, Nigel Gilles
    Arctic and red foxes2011In: Arctic WOLVES: Arctic Wildlife Observatories Linking Vulnerable EcoSystems / [ed] Gauthier, G., & D. Berteaux, Quebec City, Quebec, Canada: Centre d’études nordiques, Université Laval , 2011, p. 76-87Chapter in book (Other academic)
  • 5. Berteaux, Dominique
    et al.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Erlandsson, Rasmus
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    White, Paula A.
    Harmonizing circumpolar monitoring of Arctic fox: benefits, opportunities, challenges and recommendations2017In: Polar Research, ISSN 0800-0395, E-ISSN 1751-8369, Vol. 36, no suppl. 1, article id 2Article in journal (Refereed)
    Abstract [en]

    The biodiversity working group of the Arctic Council has developed pan-Arctic biodiversity monitoring plans to improve our ability to detect, understand and report on long-term change in Arctic biodiversity. The Arctic fox (Vulpes lagopus) was identified as a target of future monitoring because of its circumpolar distribution, ecological importance and reliance on Arctic ecosystems. We provide the first exhaustive survey of contemporary Arctic fox monitoring programmes, describing 34 projects located in eight countries. Monitored populations covered equally the four climate zones of the species’ distribution, and there were large differences between populations in long-term trends, multi-annual fluctuations, diet composition, degree of competition with red fox and human interferences. Den density, number of active dens, number of breeding dens and litter size were assessed in almost all populations, while projects varied greatly with respect to monitoring of other variables indicative of population status, ecosystem state or ecosystem function. We review the benefits, opportunities and challenges to increased integration of monitoring projects. We argue that better harmonizing protocols of data collection and data management would allow new questions to be addressed while adding tremendous value to individual projects. However, despite many opportunities, challenges remain. We offer six recommendations that represent decisive progress toward a better integration of Arctic fox monitoring projects. Further, our work serves as a template that can be used to integrate monitoring efforts of other species, thereby providing a key step for future assessments of global biodiversity.

  • 6.
    Dinca, Vlad
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Lukhtanov, V. A.
    Kodandaramaiah, U.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Dapporto, L.
    Wahlberg, N.
    Vila, R.
    Friberg, Mange
    Stockholm University, Faculty of Science, Department of Zoology.
    Reproductive isolation and patterns of genetic differentiation in a cryptic butterfly species complex2013In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 26, no 10, p. 2095-2106Article in journal (Refereed)
    Abstract [en]

    Molecular studies of natural populations are often designed to detect and categorize hidden layers of cryptic diversity, and an emerging pattern suggests that cryptic species are more common and more widely distributed than previously thought. However, these studies are often decoupled from ecological and behavioural studies of species divergence. Thus, the mechanisms by which the cryptic diversity is distributed and maintained across large spatial scales are often unknown. In 1988, it was discovered that the common Eurasian Wood White butterfly consisted of two species (Leptidea sinapis and Leptidea reali), and the pair became an emerging model for the study of speciation and chromosomal evolution. In 2011, the existence of a third cryptic species (Leptidea juvernica) was proposed. This unexpected discovery raises questions about the mechanisms preventing gene flow and about the potential existence of additional species hidden in the complex. Here, we compare patterns of genetic divergence across western Eurasia in an extensive data set of mitochondrial and nuclear DNA sequences with behavioural data on inter- and intraspecific reproductive isolation in courtship experiments. We show that three species exist in accordance with both the phylogenetic and biological species concepts and that additional hidden diversity is unlikely to occur in Europe. The Leptidea species are now the best studied cryptic complex of butterflies in Europe and a promising model system for understanding the formation of cryptic species and the roles of local processes, colonization patterns and heterospecific interactions for ecological and evolutionary divergence.

  • 7.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Berteaux, Dominique
    Burgess, Robert M.
    Ehrich, Dorothee
    Gallant, Daniel
    Henttonen, Heikki
    Ims, Rolf A.
    Killengreen, Siw T.
    Niemimaa, Jukka
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Ollila, Tuomo
    Rodnikova, Anna
    Sokolov, Alexandrs A.
    Sokolova, Natasha A.
    Stickney, Alica A.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Homage to Hersteinsson and Macdonald: climate warming and resource subsidies cause red fox range expansion and Arctic fox decline2017In: Polar Research, ISSN 0800-0395, E-ISSN 1751-8369, Vol. 36, no suppl. 1, article id 3Article, review/survey (Refereed)
    Abstract [en]

    Climate change can have a marked effect on the distribution and abundance of some species, as well as their interspecific interactions. In 1992, before ecological effects of anthropogenic climate change had developed into a topical research field, Hersteinsson and Macdonald published a seminal paper hypothesizing that the northern distribution limit of the red fox (Vulpes vulpes) is determined by food availability and ultimately climate, while the southern distribution limit of the Arctic fox (Vulpes lagopus) is determined by interspecific competition with the larger red fox. This hypothesis has inspired extensive research in several parts of the circumpolar distribution range of the Arctic fox. Over the past 25 years, it was shown that red foxes can exclude Arctic foxes from dens, space and food resources, and that red foxes kill and sometimes consume Arctic foxes. When the red fox increases to ecologically effective densities, it can cause Arctic fox decline, extirpation and range contraction, while conservation actions involving red fox culling can lead to Arctic fox recovery. Red fox advance in productive tundra, concurrent with Arctic fox retreat from this habitat, support the original hypothesis that climate warming will alter the geographical ranges of the species. However, recent studies show that anthropogenic subsidies also drive red fox advance, allowing red fox establishment north of its climate-imposed distribution limit. We conclude that synergies between anthropogenic subsidies and climate warming will speed up Arctic ecosystem change, allowing mobile species to establish and thrive in human-provided refugia, with potential spill-over effects in surrounding ecosystems.

  • 8.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Eide, Nina E.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Killengreen, Siw T.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Wallén, Johan
    Stockholm University, Faculty of Science, Department of Zoology.
    Åtgärdsprogram för fjällräv, 2017–2021 (Vulpes lagopus): Hotkategori: Starkt hotad EN2017Report (Other academic)
  • 9.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hersteinsson, Páll
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Unnsteinsdottir, Ester R.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    From breeding pairs to fox towns: the social organisation of arctic fox populations with stable and fluctuating availability of food2014In: Polar Biology, ISSN 0722-4060, E-ISSN 1432-2056, Vol. 37, no 1, p. 111-122Article in journal (Refereed)
    Abstract [en]

    Food availability can impact group formation in Carnivora. Specifically, it has been suggested that temporal variation in food availability may allow a breeding pair to tolerate additional adults in their territory at times when food abundance is high. We investigate group occurrence and intraspecific tolerance during breeding in a socially flexible canid, the arctic fox (Vulpes lagopus). We compare Iceland and Sweden where resource conditions differ considerably. A breeding pair was the most common social unit in both populations, but as predicted, groups were more frequent where food abundance varied substantially between years (Sweden: 6 %) than where food availability was stable (Iceland: ≤2 %). Within Sweden, supplemental feeding increased group occurrence from 6 to 21 %, but there was no effect of natural variation in lemming (Lemmus lemmus) availability since group formation was rare also at lemming highs. Thus, additional factors appeared to influence the trade-off between intraspecific territoriality and tolerance. We report two cases where related females showed enduring social relationships with good-neighbour strategies. Related females also engaged in alloparental behaviour in a ‘fox town’ with 31 foxes (4 adults, 3 litters). In contrast, when unrelated foxes bred close to each other, they moved or split their litters during summer, presumably because of territorial conflict. We suggest that fluctuating food availability is linked to group formation in this Arctic carnivore, but also when food availability increases, additional factors such as relatedness, alloparental benefits, competition and predator defence appear necessary to explain group formation.

  • 10.
    Erlandsson, Rasmus
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Hasselgren, Malin
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    The resource dispersion hypothesis – a test with a cyclic mesopredatorManuscript (preprint) (Other academic)
  • 11.
    Erlandsson, Rasmus
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Wallén, Johan
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Märkningen av fjällrävar förutsättning för effektiv och långsiktig forskning2015In: Härjedalen, ISSN 1103-9426, no 27 augustiArticle in journal (Other (popular science, discussion, etc.))
  • 12.
    Friberg, Magne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kodandaramaiah, Ullasa
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Wahlberg, Niklas
    Department of Biology, University of Turku.
    Genetic differentiation and phylogeographic patterns in European populations of Leptidea sinapis and L. realiManuscript (preprint) (Refereed)
    Abstract [en]

    The direction of a coevolutionary interaction can differ between local populations as in the butterflies Leptidea sinapis and L. reali. The morphologically virtually identical sister-species have partitioned their niches differently in different parts of their distribution by shifting habitat specialist and generalist roles between different sympatric areas. Hence, a species that is a generalist in some areas can be a local specialist in others, and vice versa. We have sequenced the mitochondrial COI gene from specimens collected across Europe in order to (i) describe the between-species variation over a large area, (ii) identify possible glacial refugia and re-colonisation routes to obtain a phylogeographic hypothesis for explaining the geographic mosaic of niche separation and (iii) apply a population genetic approach to determine the level of intraspecific genetic differentiation. The results show evidence for species distinctiveness throughout Europe. Only small variation was found in L. reali, whereas the haplotype network of L. sinapis showed a deep division into two haplotype families of which one was restricted to Spain and the other was widespread over the continent (including Spain). The widespread haplotype family was divided into two common variants, one eastern and one western, each being surrounded by rare haplotypes. The both deep and shallow genetic differentiation implies that L. sinapis might have been divided into different refugia during several glaciations. Both species showed significant genetic differentiation in pairwise ФST, and as habitat generalist populations could differ significantly from other habitat generalist populations but not from habitat specialist populations, we conclude that this study supports that the geographic mosaic of niche separation is caused by local processes rather than common ancestry of local habitat generalists or specialists within each species

  • 13. Geffen, E.
    et al.
    Kam, Michael
    Hefner, R.
    Hersteinsson, P.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Naturhistoriska riksmuseet, Molekylärsystematik.
    Fuglei, E.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Adams, J. R.
    Vucetich, J.
    Meier, T. J.
    Mech, L. D.
    von Holdt, B. M.
    Stahler, D. R.
    Wayne, R. K.
    Kin encounter rate and inbreeding avoidance in canids2011In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 20, no 24, p. 5348-5358Article in journal (Refereed)
    Abstract [en]

    Mating with close kin can lead to inbreeding depression through the expression of recessive deleterious alleles and loss of heterozygosity. Mate selection may be affected by kin encounter rate, and inbreeding avoidance may not be uniform but associated with age and social system. Specifically, selection for kin recognition and inbreeding avoidance may be more developed in species that live in family groups or breed cooperatively. To test this hypothesis, we compared kin encounter rate and the proportion of related breeding pairs in noninbred and highly inbred canid populations. The chance of randomly encountering a full sib ranged between 1–8% and 20–22% in noninbred and inbred canid populations, respectively. We show that regardless of encounter rate, outside natal groups mates were selected independent of relatedness. Within natal groups, there was a significant avoidance of mating with a relative. Lack of discrimination against mating with close relatives outside packs suggests that the rate of inbreeding in canids is related to the proximity of close relatives, which could explain the high degree of inbreeding depression observed in some populations. The idea that kin encounter rate and social organization can explain the lack of inbreeding avoidance in some species is intriguing and may have implications for the management of populations at risk

  • 14.
    Godoy, Erika
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Mating patterns in an inbred Arctic carnivore2018In: Polar Biology, ISSN 0722-4060, E-ISSN 1432-2056, Vol. 41, no 5, p. 945-951Article in journal (Refereed)
    Abstract [en]

    Mating patterns are highly context-dependent and the outcome of selection pressures formed by ecological factors, inbreeding levels and access to available partners. In small and inbred populations, matings are limited by high kin encounter rates and access to mates. In this paper, we use background pedigree data to investigate mating patterns and inbreeding avoidance in an isolated and critically endangered Arctic fox (Vulpes lagopus) population. Empirical data showed avoidance of matings within natal family. Based on 35 documented matings, we only recorded two full-sibling matings and these occurred between individuals from different natal families. Matings between second-order relatives, however, occurred to the same extent as between unrelated individuals. To test how this influenced the population development of inbreeding (f), we simulated scenarios of random mating, exclusion of natal family and exclusion of individuals in already existing pair bonds. The observed development of inbreeding did not correspond the expected scenario of random mating (linear regression, r2 = 0.354, P = 0.20), but showed a comparable outcome as the simulated development of discriminating natal family (linear regression, r2 = 0.980, P < 0.001). We conclude that behavioural, pre-copulatory inbreeding avoidance strategies occur in this population and that exclusion of mating with natal family causes a slower increase in inbreeding levels compared to random mating. This study demonstrates how long-term monitoring, pedigree construction and simulations can generate information valuable for an in-depth understanding of both conservation genetics and behavioural ecology in threatened populations.

  • 15.
    Hasselgren, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Eide, Nina E.
    Erlandsson, Rasmus
    Stockholm University, Faculty of Science, Department of Zoology.
    Flagstad, Øystein
    Landa, Arild
    Wallén, Johan
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Genetic rescue in an inbred Arctic fox (Vulpes lagopus) population2018In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 285, no 1875, article id 20172814Article in journal (Refereed)
    Abstract [en]

    Isolation of small populations can reduce fitness through inbreeding depression and impede population growth. Outcrossing with only a few unrelated individuals can increase demographic and genetic viability substantially, but few studies have documented such genetic rescue in natural mammal populations. We investigate the effects of immigration in a subpopulation of the endangered Scandinavian arctic fox (Vulpes lagopus), founded by six individuals and isolated for 9 years at an extremely small population size. Based on a long-term pedigree (105 litters, 543 individuals) combined with individual fitness traits, we found evidence for genetic rescue. Natural immigration and gene flow of three outbred males in 2010 resulted in a reduction in population average inbreeding coefficient (f), from 0.14 to 0.08 within 5 years. Genetic rescue was further supported by 1.9 times higher juvenile survival and 1.3 times higher breeding success in immigrant first-generation offspring compared with inbred offspring. Five years after immigration, the population had more than doubled in size and allelic richness increased by 41%. This is one of few studies that has documented genetic rescue in a natural mammal population suffering from inbreeding depression and contributes to a growing body of data demonstrating the vital connection between genetics and individual fitness.

  • 16.
    Hasselgren, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Inbreeding in natural mammal populations: historical perspectives and future challenges2019In: Mammal Review, ISSN 0305-1838, E-ISSN 1365-2907Article in journal (Refereed)
    Abstract [en]

    The awareness of inbreeding as a potentially harmful process dates several centuries back in time, and occurred early in various religions, cultures, and societies. However, it was not until the 18th Century that the phenomenon was first investigated systematically through breeding experiments in domestic animals and plants. Investigations were followed by the establishment of the theoretical framework in the 19th Century by Darwin, Mendel and other pioneering evolutionary biologists. Throughout the development of this field, from breeding experiments and discoveries of the mechanism of inheritance, via heterozygosity-fitness correlations, construction of pedigrees for natural populations, emergence of the conservation genetics field, to present-day whole genome sequencing of extinct species, mammals have played a crucial role as model organisms and flagship species. In this review, we present a chronological overview of the theoretical development and empirical data on inbreeding in mammals, from the 18th Century to the present day. Furthermore, in relation to the current analytical capacity, we identify gaps in the knowledge and future challenges in the study of inbreeding and inbreeding depression in mammals.

  • 17. Johansson, Linda
    et al.
    Mangi, Anna-Carin
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Spillningsinventering av fjällräv i Norrbottens län 2009: Genetisk kartläggning av spillning insamlad vid prioriterade fjällrävslyor2009Report (Other academic)
  • 18.
    Lagerholm, Vendela K.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden; University of St Andrews, UK.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology. University of California Davis, USA.
    Ehrich, Dorothee
    Ims, Rolf A.
    Killengreen, Siw T.
    Abramson, Natalia I.
    Niemaa, Jukka
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Henttonen, Heikki
    Dalén, Love
    Run to the hills: gene flow among mountain areas leads to low genetic differentiation in the Norwegian lemming2017In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 121, no 1, p. 1-14Article in journal (Refereed)
    Abstract [en]

    The endemic Norwegian lemming (Lemmus lemmus) is an icon for cyclic species, famous since the Middle Ages for its enormous population outbreaks and mass movements. Although the drivers behind this cyclicity have been intensively investigated, virtually nothing is known about the extent to which long-distance dispersal during population peaks actually lead to gene flow among mountain tundra areas. In this article, we use nine microsatellite markers to address this question and analyse range-wide genetic diversity and differentiation between Fennoscandian sub-regions. The results revealed a high genetic variation with a surprisingly weak population structure, comparable to that of much larger mammals. The differentiation was mainly characterized as a genetic cline across the species' entire distribution, and results from spatial autocorrelation analyses suggested that gene flow occurs with sufficiently high frequency to create a genetic patch size of 100 km. Further, we found that for the equivalent distances, the southern sub-regions were genetically more similar to each other than those in the north, which indicates that the prolonged periods of interrupted lemming cyclicity recorded in the northern parts of Fennoscandia have led to increased isolation and population differentiation. In summary, we propose that mass movements during peak years act as pulses of gene flow between mountain tundra areas, and that these help to maintain genetic variation and counteract differentiation over vast geographic distances.

  • 19.
    Meijer, Tomas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Dahlgren, Johan
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Reproductive strategy in a cyclic environmentManuscript (preprint) (Other academic)
    Abstract [en]

    The ability to maximize life-time reproductive output in relation to ecological variation in time and space is central for individual fitness. In cyclic environments the optimal litter size might vary over time depending on fluctuations in food abundance, offspring survival and their future fecundity. The arctic fox in Scandinavia is highly dependent on cyclic small rodents, such as lemmings and voles, for its reproduction. The arctic foxes can adjust their litter size in relation to small rodent phase, but this adjustment cannot be explained by food abundance only. In the rodent increase phase, litters are larger than expected from food abundance, while litters are smaller than expected in the decrease phase. In this paper, we studied how arctic fox litter size is associated with variation in the offspring reproductive value, specifically if the reproductive value is higher in the increase phase of the small rodent cycle. We followed the survival and fecundity, i.e. number of offspring, of 282 ear-tagged arctic foxes for a minimum of 4 years after birth in relation to small rodent phase. We found substantial variation in reproductive values, with a 3.2 times higher reproductive value for cubs born in the increase phase (0.74) compared to the decrease phase (0.23). The most pronounced difference in reproductive value between offspring born in different phases was caused by survival from birth to the end of their first year. Of the offspring born in the increase phase, 32% survived their first year compared to only 9% in the decrease phase. Our data supports that the observed phase dependent adjustment of arctic fox litter size has a demographic (and thereby an evolutionary) advantage by maximizing the number of offspring when the reproductive value is highest.

  • 20.
    Meijer, Tomas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    The impact of maternal experience on post-weaning survival in an endangered arctic fox population2011In: European Journal of Wildlife Research, ISSN 1612-4642, E-ISSN 1439-0574, Vol. 57, no 3, p. 549-553Article in journal (Refereed)
    Abstract [en]

    Behavioural differences in parental care can influence offspring survival through variation in e.g. antipredator behaviour and ability to provide food. In a broad range of species, offspring survival has been found to be higher for experienced females compared to inexperienced first-time breeders. The increase in offspring survival for experienced females has mainly been explained by improved experience in providing food. In this paper, we have studied post-weaning juvenile survival in relation to maternal experience in an endangered population of arctic foxes (Vulpes lagopus) in Fennoscandia. For cubs raised by inexperienced and experienced females, the survival rate was 0.42 (CI 95% +/- 0.31) and 0.87 (CI 95% +/- 0.08), respectively. There was no difference in body condition between the cubs and no observations of starvation. We suggest that the difference in survival was due to lack of experience to one of the most common predators, the golden eagle (Aquila chrysaetos). Golden eagles were mainly observed on dens with litters where the females were inexperienced first-time breeders. From a conservation perspective, it is therefore important to increase adult survival through actions to enlarge the proportion of experienced breeders.

  • 21.
    Meijer, Tomas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Hellström, Peter
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Estimating population parameters in a threatened arctic fox population using molecular tracking and traditional field methods2008In: Animal Conservation, ISSN 1469-1795, Vol. 11, no 4, p. 330-338Article in journal (Refereed)
    Abstract [en]

    Comprehensive population parameter data are useful for assessing effective conservation actions. The Fennoscandian arctic fox Alopex lagopus is critically endangered and the population size is estimated at 120 individuals that are fragmented into four isolated populations. Here, we use molecular tracking and visual observations to estimate population size and survival in one of the populations on the Swedish mountain tundra during a year of low food availability. We collected 98 arctic fox faecal samples during the winter of 2006 and recorded visual observations of ear-tagged individuals during the summer of 2005 and 2006. The faecal samples were analysed for variation in nine microsatellite loci and matched to the genetic profiles of previously ear-tagged individuals from 2001 to 2005. During winter 2006, the minimum number alive was 12 individuals using visual observations, 30 using molecular tracking and 36 by combining the datasets. Population size was estimated through mark–recapture for the molecular tracking and visual observation datasets and through rarefaction analyses for molecular tracking data. The mark–recapture estimate for visual observations was uninformative due to the large confidence interval (CI) (i.e. 6–212 individuals). Based on the molecular tracking dataset combined with the minimum number alive for visual observations and molecular tracking, we concluded a consensus population size of 36–55 individuals. We also estimated the age-specific finite survival rate during 1 year (July 2005 to July 2006) by combining molecular tracking with visual observations. Juvenile survival on a yearly basis was 0.08 (95% CI 0.02–0.18) while adults had a survival of 0.59 (95% CI 0.39–0.82). Juveniles displayed a lower survival than the adults during autumn (P<0.01) whereas no age-specific survival difference during spring was found. The risk of negative effects due to the small population size and low juvenile survival is accordingly considerable.

  • 22.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Genetic monitoring as a tool in conservation of the Fennoscandian arctic fox2007Licentiate thesis, monograph (Other academic)
  • 23.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Genetic structure in the North- population connectivity and social organization in the Arctic fox2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Genetic variation is distributed on different spatial and temporal scales, reflecting the ecological and geographical complexity in the habitat. In this thesis, the primary objective was to obtain a comprehensive understanding of the genetic structuring in the Arctic fox (Vulpes lagopus) and to identify the underlying factors forming these structures. Using microsatellites, presence of sea ice was identified as the main factor determining the large-scale genetic structure in the Arctic fox. Genetic distinctiveness was demonstrated for populations surrounded by year-round open water (i.e. Iceland and Scandinavia) and among areas connected by sea ice, genetic differentiation was mainly determined by the geographic distance (PAPER I). Movement across the sea ice was influenced by fluctuations in resource abundance caused by the lemming cycle. As a consequence of low lemming abundance, long-distance movement from inland habitats into coastal habitats influenced the genetic structure on a temporal scale (PAPER II). Although the global connectivity was determined by few underlying factors, local population structures were influenced by population-specific historical, demographic and ecological factors (PAPER II, III, IV). Geographical barriers determined genetic structure within the isolated population on Iceland (PAPER III), whereas immigration influenced the local genetic structure in both Svalbard (PAPER II) and Scandinavia (PAPER IV). When population size is low, few immigration events cause rapid changes in genetic composition (PAPER IV), while immigration had a less pronounced effect in larger populations (PAPER II). On the social scale, high flexibility regarding the composition of social groups was recorded as a likely response to local habitat conditions (PAPER V). Complex social groups were more common in habitats with high resource availability and presence of predators than in habitats without predation. This thesis illustrates the importance of ecology and demography forming genetic structure at different scales, and highlights the Arctic fox vulnerability to the ongoing climate change.

  • 24.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Genetic perspectives on northern population cycles: bridging the gap between theory and empirical studies2014In: Biological Reviews, ISSN 1464-7931, E-ISSN 1469-185X, Vol. 89, no 2, p. 493-510Article in journal (Refereed)
    Abstract [en]

    Many key species in northern ecosystems are characterised by high-amplitude cyclic population demography. In 1924,Charles Elton described the ecology and evolution of cyclic populations in a classic paper and, since then, a major focushas been the underlying causes of population cycles. Elton hypothesised that fluctuations reduced population geneticvariation and influenced the direction of selection pressures. In concordance with Elton, present theories concern thedirect consequences of population cycles for genetic structure due to the processes of genetic drift and selection, but alsoinclude feedback models of genetic composition on population dynamics. Most of these theories gained mathematicalsupport during the 1970s and onwards, but due to methodological drawbacks, difficulties in long-term sampling and acomplex interplay between microevolutionary processes, clear empirical data allowing the testing of these predictionsare still scarce. Current genetic tools allow for estimates of genetic variation and identification of adaptive genomicregions, making this an ideal time to revisit this subject. Herein, we attempt to contribute towards a consensus regardingthe enigma described by Elton almost 90 years ago. We present nine predictions covering the direct and genetic feedbackconsequences of population cycles on genetic variation and population structure, and review the empirical evidence.Generally, empirical support for the predictions was low and scattered, with obvious gaps in the understanding of basicpopulation processes. We conclude that genetic variation in northern cyclic populations generally is high and that thegeographic distribution and amount of diversity are usually suggested to be determined by various forms of context-and density-dependent dispersal exceeding the impact of genetic drift. Furthermore, we found few clear signaturesof selection determining genetic composition in cyclic populations. Dispersal is assumed to have a strong impact ongenetic structuring and we suggest that the signatures of other microevolutionary processes such as genetic drift andselection are weaker and have been over-shadowed by density-dependent dispersal. We emphasise that basic biologicaland demographical questions still need to be answered and stress the importance of extensive sampling, appropriatechoice of tools and the value of standardised protocols.

  • 25. Norén, Karin
    et al.
    Angerbjörn, Anders
    Ännu ett hot mot skandinaviska fjällrävar – gener från pälsfarmer2007In: Våra Rovdjur, Vol. 1, p. 8-9Article in journal (Other (popular science, discussion, etc.))
  • 26.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Hersteinsson, Páll
    Population structure in an isolated Arctic fox, Vulpes lagopus, population: the impact of geographical barriers2009In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 97, no 1, p. 18-26Article in journal (Refereed)
    Abstract [en]

    The genetic composition of a population reflects several aspects of the organism and its environment. The Icelandic Arctic fox population exceeds 8000 individuals and is comprised of both coastal and inland foxes. Several factors may affect within-population movement and subsequent genetic population structure. A narrow isthmus and sheep-proof fences may prevent movement between the north-western and central part and glacial rivers may reduce movement between the eastern and central part of Iceland. Moreover, population density and habitat characteristics can influence movement behaviour further. Here, we investigate the genetic structure in the Icelandic Arctic fox population (n = 108) using 10 microsatellite loci. Despite large glacial rivers, we found low divergence between the central and eastern part, suggesting extensive movement between these areas. However, both model- and frequency-based analyses suggest that the north-western part is genetically differentiated from the rest of Iceland (F-ST = 0.04, D-S = 0.094), corresponding to 100-200 generations of complete isolation. This suggests that the fences cannot be the sole cause of divergence. Rather, the isthmus causes limited movement between the regions, implying that protection in the Hornstrandir Nature Reserve has a minimal impact on Arctic fox population size in the rest of Iceland. (C) 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 18-26.

  • 27.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of California Davis, USA.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Wallén, Johan
    Stockholm University, Faculty of Science, Department of Zoology.
    Meijer, Tomas
    Stockholm University, Faculty of Science, Department of Zoology. National Veterinary Institute, Sweden.
    Sacks, Benjamin N.
    Red foxes colonizing the tundra: genetic analysis as a tool for population management2017In: Conservation Genetics, ISSN 1566-0621, E-ISSN 1572-9737, Vol. 18, no 2, p. 359-370Article in journal (Refereed)
    Abstract [en]

    Climate change accelerates biodiversity alterations in northern ecosystems. A prevalent example is that tundra regions are invaded by boreal species. This impacts negatively on native species through competition, predation and transmission of zoonoses. Scandinavian red foxes (Vulpes vulpes) have emerged into the tundra and have altered the structure and function of the tundra community. For instance, they threaten persistence of the endangered Swedish Arctic fox (Vulpes lagopus). County board administrations implement control of the tundra red foxes, but little is known about the underlying expansion dynamics. A broad-scale study revealed high connectivity where northern areas were supplemented with red foxes from surrounding population. However, red fox expansion is most prevalent in tundra regions and the fine-scaled expansion dynamics in these areas have not yet been disseminated. With the aim of identifying the invasive pathways of tundra red foxes, we present microsatellite data for 205 Swedish red foxes and mitochondrial sequence variation in 102 foxes sampled across the historical boreo-nemoral distribution and recently colonized tundra regions. Genetic structuring was low with high levels of ongoing, asymmetric dispersal from surrounding boreal zones into tundra habitats causing high genetic admixture. In both tundra and boreo-nemoral regions, inter-individual relatedness decreased with increasing geographic distance and data suggests male-biased dispersal patterns. Overall, fine-scaled expansion patterns were affected by multiple factors and we discuss its implications for future red fox management.

  • 28.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Carmichael, Lindsey
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Hersteinsson, Páll
    Samelius, Gustaf
    Fuglei, Eva
    Kapel, Christian M. O.
    Menyushina, Irina
    Strobeck, Curtis
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Arctic fox Vulpes lagopus population structure: circumpolar patterns and processes2011In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 120, no 6, p. 873-885Article in journal (Refereed)
    Abstract [en]

    Movement is a prominent process shaping genetic population structure. In many northern mammal species, population structure is formed by geographic distance, geographical barriers and various ecological factors that influence movement over the landscape. The Arctic fox Vulpes lagopus is a highly mobile, opportunistic carnivore of the Arctic that occurs in two main ecotypes with different ecological adaptations. We assembled microsatellite data in 7 loci for 1834 Arctic foxes sampled across their entire distribution to describe the circumpolar population structure and test the impact of (1) geographic distance, (2) geographical barriers and (3) ecotype designation on the population structure. Both Structure and Geneland demonstrated distinctiveness of Iceland and Scandinavia whereas low differentiation was observed between North America-northern Greenland, Svalbard and Siberia. Genetic differentiation was significantly correlated to presence of sea ice on a global scale, but not to geographical distance or ecotype designation. However, among areas connected by sea ice, we recorded a pattern of isolation by distance. The maximum likelihood approach in Migrate suggested that connectivity across North America-northern Greenland and Svalbard was particularly high. Our results demonstrate the importance of sea ice for maintaining connectivity between Arctic fox populations and we therefore predict that climate change will increase genetic divergence among populations in the future.

  • 29.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Carmichael, Lindsey
    Fuglei, Eva
    Eide, Nina E.
    Hersteinsson, Páll
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Pulses of movement cause temporal genetic shifts in the High ArcticManuscript (preprint) (Other academic)
  • 30.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Carmichael, Lindsey
    Fuglei, Eva
    Eide, Nina
    Hersteinsson, Pall
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Pulses of movement across the sea ice: population connectivity and temporal genetic structure in the arctic fox2011In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 166, no 4, p. 973-984Article in journal (Refereed)
    Abstract [en]

    Lemmings are involved in several important functions in the Arctic ecosystem. The Arctic fox (Vulpes lagopus) can be divided into two discrete ecotypes: “lemming foxes” and “coastal foxes”. Crashes in lemming abundance can result in pulses of “lemming fox” movement across the Arctic sea ice and immigration into coastal habitats in search for food. These pulses can influence the genetic structure of the receiving population. We have tested the impact of immigration on the genetic structure of the “coastal fox” population in Svalbard by recording microsatellite variation in seven loci for 162 Arctic foxes sampled during the summer and winter over a 5-year period. Genetic heterogeneity and temporal genetic shifts, as inferred by STRUCTURE simulations and deviations from Hardy–Weinberg proportions, respectively, were recorded. Maximum likelihood estimates of movement as well as STRUCTURE simulations suggested that both immigration and genetic mixture are higher in Svalbard than in the neighbouring “lemming fox” populations. The STRUCTURE simulations and AMOVA revealed there are differences in genetic composition of the population between summer and winter seasons, indicating that immigrants are not present in the reproductive portion of the Svalbard population. Based on these results, we conclude that Arctic fox population structure varies with time and is influenced by immigration from neighbouring populations. The lemming cycle is likely an important factor shaping Arctic fox movement across sea ice and the subsequent population genetic structure, but is also likely to influence local adaptation to the coastal habitat and the prevalence of diseases.

  • 31.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden.
    Flagstad, Øystein
    Berteaux, Dominique
    Wallén, Johan
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Evolution, ecology and conservation—revisiting three decades of Arctic fox population genetic research2017In: Polar Research, ISSN 0800-0395, E-ISSN 1751-8369, Vol. 36, no suppl. 1, article id 4Article in journal (Refereed)
    Abstract [en]

    Three decades have passed since the Arctic fox (Vulpes lagopus) was first put into a population genetic perspective. With the aim of addressing how microevolution operates on different biological levels, we here review genetic processes in the Arctic fox at the level of species, populations and individuals. Historical and present dispersal patterns, especially in the presence of sea ice, are the most powerful factors that create a highly homogeneous genetic structure across the circumpolar distribution, with low detectable divergence between the coastal and lemming ecotypes. With dispersal less pronounced or absent, other processes emerge; populations that are currently isolated, for example, because of the lack of sea ice, are genetically divergent. Moreover, small populations generally display signatures of genetic drift, inbreeding, inbreeding depression and, under specific situations, hybridization with domestic fox breeds. Mating system and social organization in the Arctic fox appear to be determined by the ecological context, with complex mating patterns and social groups being more common under resource-rich conditions. In isolated populations, complex social groups and inbreeding avoidance have been documented. We emphasize the value of genetic data to decipher many previously unknown aspects of Arctic fox biology, while these data also raise numerous questions that remain unanswered. Pronounced intra-specific ecological variation makes the Arctic fox an ideal study organism for population genetic processes and the emergence of functional genomics will generate an even deeper understanding of evolution, ecology and conservation issues for several species.

  • 32.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Kvaloy, Kirsti
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Detection of farm fox and hybrid genotypes among wild arctic foxes in Scandinavia2005In: Conservation Genetics, Vol. 6, p. 885-894Article in journal (Refereed)
  • 33.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Godoy, Erika
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology. Swedish Museum of Natural History, Sweden.
    Meijer, Tomas
    Stockholm University, Faculty of Science, Department of Zoology. National Veterinary Institute, Sweden.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Inbreeding depression in a critically endangered carnivore2016In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 25, no 14, p. 3309-3318Article in journal (Refereed)
    Abstract [en]

    Harmful effects arising from matings between relatives (inbreeding) is a long-standing observation that is well founded in theory. Empirical evidence for inbreeding depression in natural populations is however rare because of the challenges of assembling pedigrees supplemented with fitness traits. We examined the occurrence of inbreeding and subsequent inbreeding depression using a unique data set containing a genetically verified pedigree with individual fitness traits for a critically endangered arctic fox (Vulpes lagopus) population. The study covered nine years and was comprised of 33 litters with a total of 205 individuals. We recorded that the present population was founded by only five individuals. Over the study period, the population exhibited a tenfold increase in average inbreeding coefficient with a final level corresponding to half-sib matings. Inbreeding mainly occurred between cousins, but we also observed two cases of full-sib matings. The pedigree data demonstrated clear evidence of inbreeding depression on traditional fitness traits where inbred individuals displayed reduced survival and reproduction. Fitness traits were however differently affected by the fluctuating resource abundande. Inbred individuals born at low-quality years displayed reduced first-year survival, while inbred individuals born at high-quality years were less likely to reproduce. The documentation of inbreeding depression in fundamental fitness traits suggests that inbreeding depression can limit population recovery. Introducing new genetic material to promote a genetic rescue effect may thus be necessary for population long-term persistence.

  • 34.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hersteinsson, Pall
    Samelius, Gustaf
    Eide, Nina E.
    Fuglei, Eva
    Elmhagen, Bodil
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Meijer, Tomas
    Stockholm University, Faculty of Science, Department of Zoology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    From monogamy to complexity: social organization of arctic foxes (Vulpes lagopus) in contrasting ecosystems2012In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 90, no 9, p. 1102-1116Article in journal (Refereed)
    Abstract [en]

    Canids display pronounced intraspecific variation in social organization, ranging from single breeding females to large and complex groups. Despite several hypotheses in this matter, little is understood about the ecological factors underlying this flexibility. We have used the arctic fox (Vulpes lagopus (L., 1758)) to investigate how contrasting ecosystem conditions concerning resources and predation influence group formation. We predicted that complex groups are more common in resource-rich ecosystems with predators, whereas simple groups occur in more marginal ecosystems without predators. Samples from 54 groups were collected from four populations of arctic foxes with contrasting prey resources and predation and these samples were genotyped in 10 microsatellite loci. We found considerable variation between ecosystems and a significant relationship between resources and formation of complex groups. We conclude that sufficient amounts of food is a prerequisite for forming complex groups, but that defense against predation further increases the benefits of living in larger groups. We present a conceptual model suggesting that a trade-off between the cost of resource depletion and the benefits obtained for guarding against predators explain the differences in social organization. The variable ecology of  the arctic foxes makes it is a plausible model species for understanding the connection between ecology and social organization also in other species.

  • 35.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hersteinsson, Páll
    Samelius, Gustaf
    Eide, Nina E.
    Fuglei, Eva
    Elmhagen, Bodil
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Meijer, Tomas
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    From monogamy to complexity: Arctic fox social organizationManuscript (preprint) (Other academic)
  • 36.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kvaloy, Kirsti
    Nyström, Veronica
    Stockholm University, Faculty of Science, Department of Zoology.
    Landa, Arild
    Dalén, Love
    Stockholm University, Faculty of Science, Department of Zoology.
    Eide, Nina E.
    Ostbye, Eivind
    Henttonen, Heikki
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    Farmed arctic foxes on the Fennoscandian mountain tundra: implications for conservation2009In: Animal Conservation, ISSN 1367-9430, E-ISSN 1469-1795, Vol. 12, no 5, p. 434-444Article in journal (Refereed)
    Abstract [en]

    Hybridization between wild and captive-bred individuals is a serious conservation issue that requires measures to prevent negative effects. Such measures are, however, often considered controversial by the public, especially when concerning charismatic species. One of the threats to the critically endangered Fennoscandian arctic fox Alopex lagopus is hybridization with escaped farm foxes, conveying a risk of outbreeding depression through loss of local adaptations to the lemming cycle. In this study, we investigate the existence of escaped farm foxes among wild arctic foxes and whether hybridization has occurred in the wild. We analysed mitochondrial control region sequences and 10 microsatellite loci in samples from free-ranging foxes and compared them with reference samples of known farm foxes and true Fennoscandian arctic foxes. We identified the farm fox specific mitochondrial haplotype H9 in 25 out of 182 samples, 21 of which had been collected within or nearby the wild subpopulation on Hardangervidda in south-western Norway. Genetic analyses of museum specimens collected on Hardangervidda (1897–1975) suggested that farm fox genotypes have recently been introduced to the area. Principal component analysis as well as both model- and frequency-based analyses of microsatellite data imply that the free-ranging H9s were farm foxes rather than wild arctic foxes and that the entire Hardangervidda population consisted of farm foxes or putative hybrids. We strongly recommend removal of farm foxes and hybrids in the wild to prevent genetic pollution of the remaining wild subpopulations of threatened arctic foxes.

  • 37.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of California Davis, USA.
    Statham, Mark J.
    Ågren, Erik O.
    Isomursu, Marja
    Flagstad, Öystein
    Eide, Nina E.
    Björneboe, Thomas
    Bech-Sanderhoff, Lene
    Sacks, Benjamin N.
    Genetic footprints reveal geographic patterns of expansion in Fennoscandian red foxes2015In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 21, no 9, p. 3299-3312Article in journal (Refereed)
    Abstract [en]

    Population expansions of boreal species are among the most substantial ecological consequences of climate change, potentially transforming both structure and processes of northern ecosystems. Despite their importance, little is known about expansion dynamics of boreal species. Red foxes (Vulpes vulpes) are forecasted to become a keystone species in northern Europe, a process stemming from population expansions that began in the 19th century. To identify the relative roles of geographic and demographic factors and the sources of northern European red fox population expansion, we genotyped 21 microsatellite loci in modern and historical (1835–1941) Fennoscandian red foxes. Using Bayesian clustering and Bayesian inference of migration rates, we identified high connectivity and asymmetric migration rates across the region, consistent with source-sink dynamics, whereby more recently colonized sampling regions received immigrants from multiple sources. There were no clear clines in allele frequency or genetic diversity as would be expected from a unidirectional range expansion from south to north. Instead, migration inferences, demographic models and comparison to historical red fox genotypes suggested that the population expansion of the red fox is a consequence of dispersal from multiple sources, as well as in situ demographic growth. Together, these findings provide a rare glimpse into the anatomy of a boreal range expansion and enable informed predictions about future changes in boreal communities.

  • 38.
    Norén, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of California Davis, USA.
    Statham, Mark J.
    Ågren, Erik O.
    Isomursu, Marja
    Flagstad, Øystein
    Eide, Nina E.
    Berg, Thomas Bjørneboe G.
    Bech-Sanderhoff, Lene
    Sacks, Benjamin N.
    Genetic footprints reveal geographic patterns of expansion in Fennoscandian red foxes2015In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 21, no 9, p. 3299-3312Article in journal (Refereed)
    Abstract [en]

    Population expansions of boreal species are among the most substantial ecological consequences of climate change, potentially transforming both structure and processes of northern ecosystems. Despite their importance, little is known about expansion dynamics of boreal species. Red foxes (Vulpes vulpes) are forecasted to become a keystone species in northern Europe, a process stemming from population expansions that began in the 19th century. To identify the relative roles of geographic and demographic factors and the sources of northern European red fox population expansion, we genotyped 21 microsatellite loci in modern and historical (1835–1941) Fennoscandian red foxes. Using Bayesian clustering and Bayesian inference of migration rates, we identified high connectivity and asymmetric migration rates across the region, consistent with source‐sink dynamics, whereby more recently colonized sampling regions received immigrants from multiple sources. There were no clear clines in allele frequency or genetic diversity as would be expected from a unidirectional range expansion from south to north. Instead, migration inferences, demographic models and comparison to historical red fox genotypes suggested that the population expansion of the red fox is a consequence of dispersal from multiple sources, as well as in situ demographic growth. Together, these findings provide a rare glimpse into the anatomy of a boreal range expansion and enable informed predictions about future changes in boreal communities.

  • 39. Statham, Mark J.
    et al.
    Edwards, Ceridwen J.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Soulsbury, Carl D.
    Sacks, Benjamin N.
    Genetic analysis of European red foxes reveals multiple distinct peripheral populations and central continental admixture2018In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 197, p. 257-266Article in journal (Refereed)
    Abstract [en]

    Temperate terrestrial species in Europe were hypothesized to have been restricted to southern peninsular refugia (Iberia, Italy, Balkans) during the height of the last glacial period. However, recent analyses of fossil evidence indicate that some temperate species existed outside these areas during the last glacial maximum (LGM). Red foxes (Vulpes vulpes) in particular, could have been distributed across the southern half of the continent, potentially forming one continuous population. To investigate these hypotheses, we used 21 nuclear microsatellite loci and two fragments (768 bp) of mitochondrial DNA to characterize the population structure among a continent-wide sample of 288 European red foxes. We tested whether European red foxes clustered into discrete populations corresponding to the hypothetical peninsular refugia. Additionally, we sought to determine if distinct northern populations were formed after post-glacial recolonization. Our results indicated that only the foxes of Iberia appeared to have remained distinct over a considerable period of time (32–104 kya). Spanish red foxes formed their own genotypic cluster; all mtDNA haplotypes were endemic and closely related, and together both the mitochondrial and nuclear datasets indicated this population contributed little to postglacial recolonization of Northern Europe. In contrast, red foxes from Italy and the Balkans contributed significantly to, or were part of, a wider, admixed population stretching across mid-latitude Europe. In Northern Europe, we identified a Scandinavian population that had an ancestral relationship with red foxes to the south, and a more recent relationship with those to the east, in Russia. We also resolved two distinct populations on the islands of Ireland and Britain that had been separated from one another, and from those on the continent, since the late Pleistocene/mid Holocene (∼4–24 kya).

  • 40.
    Wallén, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Statham, Mark J.
    Ågren, Erik
    Isomursu, Marja
    Flagstad, Øystein
    Bjørneboe-Berg, Thomas
    Sacks, Benjamin N.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology. University of California Davis, USA.
    Multiple recolonization routes towards the north: population history of the Fennoscandian red fox (Vulpes vulpes)2018In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 124, no 4, p. 621-632Article in journal (Refereed)
    Abstract [en]

    Understanding the response of boreal species to past climate warming can help to predict future responses to climate change. In the Northern Hemisphere, the distribution and abundance of northern populations have been influenced by previous glaciations. In this study, we investigated the population history of the Fennoscandian red fox (Vulpes vulpes), which is a generalist carnivore currently undergoing range expansion in the tundra ecosystem. By analysing a 696 bp sequence of the mitochondrial DNA (N = 259) and two Y chromosome-specific microsatellite loci (N = 120), we specifically investigated where the red fox survived the Last Glacial Maximum and how Fennoscandia was recolonized. There was high genetic continuity across most of Fennoscandia, and we identified at least two recolonization pathways: one from continental Europe and one from the northeast (Siberia). Mitochondrial haplotype diversity displayed a significant decline with increasing latitude, consistent with expectations of unidirectional colonization. Each region displayed signatures of recent demographic and/or range expansions. For Finland, an additional recolonization route was suggested from the mismatch distribution analysis and identification of novel haplotypes. We concluded that, as with many boreal generalist species, the Fennoscandian red fox originates from multiple refugia, suggesting that it has benefited from diverse evolutionary histories, potentially enhancing its tolerance to different habitat conditions.

  • 41. Westbury, Michael
    et al.
    Dalerum, Fredik
    Stockholm University, Faculty of Science, Department of Zoology. University of Oviedo, Spain; University of Pretoria, South Africa.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Hofreiter, Michael
    Complete mitochondrial genome of a bat-eared fox (Otocyon megalotis), along with phylogenetic considerations2017In: Mitochondrial DNA Part B: Resources, ISSN 0343-1223, E-ISSN 2014-1130, Vol. 2, no 1, p. 298-299Article in journal (Refereed)
    Abstract [en]

    The bat-eared fox, Otocyon megalotis, is the only member of its genus and is thought to occupy a basal position within the dog family. These factors can lead to challenges in complete mitochondrial reconstructions and accurate phylogenetic positioning. Here, we present the first complete mitochondrial genome of the bat-eared fox recovered using shotgun sequencing and iterative mapping to three distantly related species. Phylogenetic analyses placed the bat-eared fox basal in the Canidae family within the clade including true foxes (Vulpes) and the raccoon dog (Nyctereutes) with high support values. This position is in good agreement with previously published results based on short fragments of mitochondrial and nuclear genes, therefore adding more support to the basal positioning of the bat-eared fox within Canidae.

  • 42.
    Wiklund, Christer
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Norén, Karin
    Stockholm University, Faculty of Science, Department of Zoology.
    Ryman, Nils
    Stockholm University, Faculty of Science, Department of Zoology.
    Friberg, Magne
    Local monophagy and between-site diversity in host use in the European swallowtail butterfly, Papilio machaon2018In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 123, no 1, p. 179-190Article in journal (Refereed)
    Abstract [en]

    The majority of herbivorous insects are specialized in host use. Even among insects that use many hosts, local specialization is common with a single host plant often being used in any given locality. Here, we establish such a pattern for the European swallowtail butterfly, Papilio machaon. We sampled larvae on five different natural hosts at eight sites in Sweden, each locality showing local monophagy. We ask what is the underlying reason for this pattern, (1) local genetic adaptation with each population being genetically adapted to the local host, (2) Hopkins' host selection principle with adult females retaining a memory of the larval host and preferring to oviposit on that plant, or (3) the preference/performance hypothesis which posits that females should oviposit on the local plant(s) on which larval fitness is highest. Allozyme analysis supported a relatively low level of population structuring, and oviposition preference tests showed that females from all sites had similar preference rankings of the five host plants. Hence, there was no support for local genetic adaptation or Hopkins' host selection principle. Instead, the results are consistent with the preference/performance hypothesis with local monophagy probably being implemented by a preference ranking of plants in accordance with larval performance.

1 - 42 of 42
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