Scandinavia and Greenland

Abstract
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.

Abstract

Territorial behaviour in wolves (Canis lupus) plays a central role in shaping social dynamics, resource access, and population structure. Although wolf packs are typically territorial, spatial overlap between neighbouring territories does occur. Understanding the drivers of these overlaps provides insight into wolf social organisation, resource competition, inter-pack conflict risk, and individual movement between packs, factors that collectively influence broader population dynamics.
This study investigates spatial overlap among neighbouring wolf territories in Scandinavia using GPS collar data, genetic relatedness, and spatial modelling. I applied Generalized Additive Models (GAMs) to model the size of spatial overlap (km²) between territorial pairs as a function of several covariates: (1) normalized difference in territory size, (2) dyadic social status (scent-marking pair vs. family group combinations), (3) genetic relatedness between alpha males and between alpha females, and (4) time since territory establishment. These covariates were selected based on ecological relevance and were derived from long-term monitoring data and pedigree records.
Spatial overlap was best predicted by territory size differences, dyadic social status, and female genetic relatedness. Overlap increased with greater disparity in territory size and was higher between scent-marking pairs compared to family groups. Female relatedness showed a non-linear effect; overlap increased with initial relatedness but declined beyond a threshold. Male relatedness had no notable effect.
Complementary Generalized Linear Mixed Models (GLMMs) were used to assess how wolves used different territorial zones (core, peripheral, overlap). These models revealed that wolves generally spent less time in overlap zones, with scent-marking pairs using these areas more than family groups. Additionally, territory age (defined as years since establishment) was negatively associated with overlap use, suggesting that older territories exhibit greater spatial stability and reduced inter-pack intrusion.
Together, these findings highlight the importance of social structure, territorial history, and genetic relationships in shaping spatial interactions among wolf packs. Understanding these drivers is essential for interpreting wolf space use in multi-use landscapes and has consequences for the management including monitoring of the population.

Abstract
Dogs were domesticated at least once from a yet-unidentified wolf population at least ~15,000 y ago. However, how domestication took place is a topic of ongoing debate, and the ability of human groups to manage wolves in their communities during early stages of domestication is poorly understood. Here, we report multiproxy data from two canids excavated from Late Neolithic and Bronze Age contexts in the Stora Förvar cave on the island of Stora Karlsö in the Baltic Sea. The island is small (2.5 sq km) and, like the neighboring island of Gotland, carries no endemic populations of terrestrial mammals. Instead, the current consensus is that human introductions account for some mammal fauna on Gotland, and for the majority of that on Stora Karlsö. Genome-wide data show that the two canids have ancestry indistinguishable from Eurasian wolves, with no shared ancestry with domestic dogs of the Canis familiaris lineage. Their genome-wide heterozygosity is lower than that observed in 72 previously published ancient wolf genomes, and instead comparable to dogs. Stable isotope data (δ13C and δ15N) reveals a diet rich in marine protein, which is consistent with habitation alongside the human groups who used Stora Karlsö as a seal-hunting, fowling, and sea fishing station, and in the Bronze Age probably also for grazing. Skeletal size is at the lower end of wolf variability, and one individual shows advanced pathology consistent with reduced mobility. While other scenarios are possible, a parsimonious explanation is that these wolves were brought to the island by humans and were possibly under human control.

Abstract

Death is an inherently spatial process. It happens to someone, somewhere, but often remains undetected in nature. Death is also the primary means by which humans regulate wildlife populations. Using a novel analytical method that accounts for the cryptic nature of the fate of individuals and one of the world’s most comprehensive non-invasive genetic monitoring datasets, we were able to map cause-specific mortality of the entire Scandinavian grey wolf (Canis lupus) population despite the fact that most mortality events (mean = 65%; [95% CrI: 50.3–76.8%]) remained undetected. Our analysis revealed strong spatial variation in mortality with, for example, areas with a high risk of mortality linked with the current wolf management policies. Furthermore, we showed that the risk of legal mortality increased, while the risk of mortality due to causes other than legal mortality decreased with local wolf population density. This illustrates the complex interactions between spatial determinants and cause-specific mortality and therefore the importance of considering spatial variation when estimating mortality. Maps of mortality can inform wildlife management and conservation by capturing an elusive process in population dynamics as it unfolds in time and space.

When new mutations arise at functional sites they are more likely to impair than improve fitness. If not removed by purifying selection, such deleterious mutations will generate a genetic load that can have negative fitness effects in small populations and increase the risk of extinction. This is relevant for the highly inbred Scandinavian wolf (Canis lupus) population, founded by only three wolves in the 1980s and suffering from inbreeding depression. We used functional annotation and evolutionary conservation scores to study deleterious variation in a total of 209 genomes from both the Scandinavian and neighbouring wolf populations in northern Europe. The masked load (deleterious mutations in heterozygote state) was highest in Russia and Finland with deleterious alleles segregating at lower frequency than neutral variation. Genetic drift in the Scandinavian population led to the loss of ancestral alleles, fixation of deleterious variants and a significant increase in the per-individual realized load (deleterious mutations in homozygote state; an increase by 45% in protein-coding genes) over five generations of inbreeding. Arrival of immigrants gave a temporary genetic rescue effect with ancestral alleles re-entering the population and thereby shifting deleterious alleles from homozygous into heterozygote genotypes. However, in the absence of permanent connectivity to Finnish and Russian populations, inbreeding has then again led to the exposure of deleterious mutations. These observations provide genome-wide insight into the magnitude of genetic load and genetic rescue at the molecular level, and in relation to population history. They emphasize the importance of securing gene flow in the management of endangered populations.

Predation and scavenging are pervasive ecological interactions in both terrestrial and aquatic environments. The ecology, evolution and conservation of scavengers, and especially predators, have received wide scientific attention and public awareness. However, the close connection that exists between predation and scavenging has not been made explicit until recently [1,2,3]. The propensity to hunt or scavenge a prey may vary within individuals, among different individuals within a population, and among different populations and species, depending on an intricate array of both intrinsic (e.g., morphology, body condition) and extrinsic (e.g., availability of alternative food sources) factors. In turn, the recognition that carnivorous animals may obtain meat by either hunting prey or scavenging their carcasses has profound implications, from individual morphology, physiology, and behavior to population, community, and ecosystem structure and functioning [1,2,3,4,5].
Given the novelty of this integrative research topic, many relevant questions have yet to be resolved. This Special Issue, through the three research papers and the three reviews that comprise it, aims to deal with some of these questions from diverse perspectives and methodological approaches.