Mikael Åkesson

Understanding how genetic drift and inbreeding can shape phenotypic traits and the expression of rare genetic variants can be important for conservation management in small and isolated populations. Following the recolonization of the grey wolf (Canis lupus) on the Scandinavian peninsula, the population has remained small and semi-isolated. The population traces back to seven founders, only and is highly inbred. Inbreeding depression has been demonstrated including effects on reproductive output and several congenital deformities. Some wolves also show anomalous coat color, characterized by hypopigmentation displayed as white tail tips, or even larger areas of white fur. In this study, we utilized four decades of monitoring data, dating back to the recolonization of the Scandinavian peninsula in 1983, to examine the occurrence of expressed anomalous coat color investigating its origin and inheritance, genetic architecture, and the effect of inbreeding. SNP genotyping revealed a distinct haplotype linked to the Melanocyte-inducing transcription factor (MITF) gene that co-segregated with anomalous coat color, suggesting a direct causal effect of this variant. The MITF gene regulates mammal melanocyte development, which in turn affects pigmentation. Our findings demonstrate that the identified gene variant is recessive, which in the homozygous state likely causes the disruption of normal melanocyte development, leading to unpigmented or hypopigmented areas. The origin of this haplotype was traced back to a third founder, reproducing for the first time in 1991. Indeed, the genetic constraints and subsequent inbreeding shaped by few founders, small population size, and semi-isolation over several decades point towards the importance of genetic diversity and facilitated gene flow between populations, but also how such vital immigration can bring about unforeseen side effects if inbreeding continues within the immigrant lineages.

Under inventeringsperioden 2025/2026 påvisades 39 reproducerande vargpar i Skandinavien. En immigrant och sex avkommor till immigranter (så kallade F1:or) reproducerade sig. Den genomsnittliga inavelskoefficienten i familjegrupper bestående av nya kullar och/eller fjolårskullar var 𝐹̅ = 0,24, vilket var högre än vintern innan. Förklaring till den förhöjda inavelnivån kan vara en minskad frekvens av reproducerande F1:or (från sju under 2024/2025 till sex under 2025/2026) samt en förhöjd frekvens av incestuösa par i förhållande till det tidigare året. Medelsläktskapet var 𝑟̅ = 0,18 mellan 71 par som kan bidra till minskad inavel framöver.

Genetic monitoring is an essential tool for managing threatened or commercially valuable wildlife species. Ideally, genetic monitoring relies on straightforward protocols for genotyping and data handling, accommodates varying sample volumes, applies to non-invasive samples such as scat and hair, produces reliable and repeatable genotypes, and is cost-effective. Moreover, the marker panel itself should be tailored to specific species and/or population management information needs. We describe the development of a microarray-based 96-SNP panel specifically designed for non-invasive genetic monitoring of the Finnish wolf population. The panel was developed to meet four specific needs for this population: identification of wolf genotypes from the non-target species (fox, raccoon dog, golden jackal), sexing, individual identification, and kinship resolution. We demonstrate the utility of the SNP panel using a subset of the genetic monitoring data collected in 2022–2023, including an overview of the data analysis workflow. The development and successful application of this SNP panel, along with a comparison with similar studies in the field, provide valuable insights for researchers and conservationists aiming to implement similar strategies for other species.

In the face of ongoing habitat loss and fragmentation, examining the genetic effects of range expansion can provide insight into the resilience and adaptability of large carnivore populations returning to parts of their former range. This study investigates the genetic structure of the Eurasian lynx (Lynx lynx) population during its natural range expansion into southern Sweden, an area from which it had been extirpated for over a century. We utilized genomic data from 600 individual lynx collected throughout the recolonization period to assess heterozygosity, inbreeding, and genetic differentiation. Our results indicate no significant genetic structure or barriers to gene flow during this recolonization event, despite potential physical barriers such as lakes, farmland, and human infrastructure. Observed and expected heterozygosity, as well as the inbreeding coefficient did not show significant variation over time or across latitude, suggesting that connectivity with the source population was maintained. Spatial principal component analysis, cluster analysis, and discriminant analysis of principal components further supported these findings, showing little spatial or temporal structure. This lack of genetic structure contrasts with the experience of smaller and more isolated lynx populations, which have become inbred. Our study, thus, provides valuable insights into the natural range expansion of a large carnivore in human-dominated landscapes and underscores the importance of ensuring genetic connectivity for successful recolonization and conservation efforts.

To reach reproduction, individuals must survive the juvenile stage, a critical period of low survival rates in large carnivores. We analysed data from 582 wolves ( Canis lupus ) identified by DNA during their first year in Sweden and Norway, to investigate intrinsic and extrinsic factors within the natal territory affecting the probability to reach reproduction, i.e. having pups surviving at least 5 months of age. Factors included main prey density, road density, human density, and proximity to non-breeding zones, as well as sex, inbreeding and being collared. Of the 582 wolves identified, 21% reached reproduction. Human density and whether a wolf was collared were the most significant factors. Both were associated with an increased probability to reach reproduction, potentially linked to poaching. Degree of inbreeding was negatively associated with the probability to reach reproduction, while gravel road density and being born in Sweden were positively associated with it. Our findings suggest an influence of legal and illegal human activities on the juvenile stage of wolves for the probability to reach reproduction. Our study enhances the understanding of how early-life conditions and intrinsic traits shape reproduction and underscores the challenges of wolf conservation in anthropized landscapes.

Under inventeringsperioden 2024/2025 påvisades 40 familjegrupper av varg i Skandinavien. Inför parningssäsongen 2024 fanns i en av dessa familjegrupper en revirmarkerande immigrant och i sju av familjegrupperna fanns revirmarkerande avkommor till immigranter (så kallade F1:or). Den genomsnittliga inavelskoefficienten bland nya kullar under vintern 2024/2025 (𝐹̅ = 0,21) var lägre än vintern innan. En möjlig förklaring till minskade inaveln är den fortsatta reproduktionen av en grundare samt ett ökande genetiskt släktskap med tidigare immigranter i populationen. Detta kan bero på en högre relativ parbildningsframgång för F1:or och senare generationer, samt på en licensjakt som selektivt gynnar reproduktionen för immigranter och F1:or.

Not-yet-known not-yet-known not-yet-known unknown In the face of ongoing habitat loss and fragmentation, examining the genetic dynamics of range ex-pansion provides important insights into the resilience and adaptability of large carnivore populations returning to parts of its former range. This study investigates the genetic structure of the Eurasian lynx (Lynx lynx) population during its natural range expansion into southern Sweden, an area from which it had been extirpated for over a century. We utilized genomic data from 600 individual lynx collected throughout the recolonization period to assess heterozygosity, inbreeding, and genetic dif-ferentiation. Our results indicate no significant genetic structure or barriers to gene flow during this recolonization event, despite potential physical barriers such as lakes, farmland, and human infra-structure. Observed and expected heterozygosity, as well as the inbreeding coefficient did not show significant variation over time or across latitude, suggesting that connectivity with the source popula-tion was maintained. Spatial principal component analysis, cluster analysis, and discriminant analysis of principal components further supported these findings, showing little spatial or temporal structure. This lack of genetic structure contrasts with the experience of smaller and more isolated lynx popula-tions, which have become inbred. Our study, thus, provides valuable insights into the natural range expansion of a large carnivore in human-dominated landscapes and underscores the importance of ensuring genetic connectivity for successful recolonization and conservation efforts.