Genetic constraints of population expansion of the Carpathian lynx at the western edge of its native distribution range in Central Europe

Survival of Eurasian lynx in the human-dominated landscape of Europe

Survival and cause-specific mortality rates are vital for evidence-based population forecasting and conservation, particularly for large carnivores, whose populations are often vulnerable to human-caused mortalities. It is therefore important to know the relationship between anthropogenic and natural mortality causes to evaluate whether they are additive or compensatory. Further, the relation between survival and environmental covariates could reveal whether specific landscape characteristics influence demographic performance. We used telemetry data on 681 Eurasian lynx (Lynx lynx), a model apex predator with large spatial requirements, that were tracked across their European distribution. Through time-to-event analyses, we sought to determine the variables associated with differences in their survival. Illegal killing was the main cause of mortality (33.8%), and mortality rates were similar in protected and hunted populations (8.6% and 7.0% per year, respectively). Survival varied greatly across populations (70-95% per year). Across all study sites, higher hunting and anthropogenic mortality rates were partially compensated by lower rates of other mortality causes but not by natural mortality alone. Variation in survival depended on sex (female survival was 1.5 times greater than male survival) and seasonality (highest risk during hunting season and winter), and lower survival rates were correlated with higher human modification of landscapes at both coarse (home range composition) and fine (habitat use within home range) scales. Some variation in survival was driven by unobserved factors, which, given the high rates of human-caused mortalities, including illegal killing, are of foremost concern. Due to the low natural mortality rates in protected and hunted populations, we conclude that anthropogenic causes of mortality are likely close to additive, such that maintaining or increasing refuge habitat with little human disturbance is critical to lynx conservation.

Molecular Tools for Lynx spp. qPCR Identification and STR-Based Individual Identification of Eurasian Lynx (Lynx lynx) in Forensic Casework

The Eurasian lynx (Lynx lynx) is listed in CITES Appendix II and is protected under the Bern Convention and the EU Habitats Directive, yet it remains a frequent target of wildlife crime, highlighting the urgent need for reliable identification methods. This study focuses on determination and DNA quantification of the Lynx spp. using quantitative real-time PCR (qPCR). The Llynx Qplex quantification multiplex system effectively distinguishes Lynx spp. from other Feliformia species by targeting mitochondrial and nuclear markers. Additionally, we present the results of the developmental validation of the Llyn STRplex system for individual identification and databasing using six STR loci. This study followed ISFG recommendations for non-human DNA testing and developmental validation guidelines. Both systems demonstrate high sensitivity (5 pg genomic DNA for Llynx Qplex and 30 pg of mtDNA for Llyn STRplex) and high specificity to Lynx spp., confirmed by testing against 16 related Feliformia species. Robustness was evaluated, showing sensitivity to temperature variation, and both repeatability and reproducibility were successfully tested across replicates and conditions. Given that forensic casework often involves degraded and limited biological material, molecular tools must be both sensitive and specific to ensure accurate results. Developing precise and efficient tools is essential for supporting investigations of wildlife crime involving the Eurasian lynx, as well as efforts aimed at conserving the species.

Genetic Rescue of the Dinaric Lynx Population: Insights for Conservation From Genetic Monitoring and Individual-Based Modelling

Inbreeding depression poses a severe threat to small populations, leading to the fixation of deleterious mutations and decreased survival probability. While the establishment of natural gene flow between populations is an ideal long-term solution, its practical implementation is often challenging. Reinforcement of populations by translocating individuals from larger populations is a viable strategy for reducing inbreeding, increasing genetic diversity and potentially saving populations from extinction. The Dinaric population of Eurasian lynx (Lynx lynx) has faced high inbreeding levels, with effective inbreeding reaching 0.316 in 2019, endangering the population's survival. To counteract this, population reinforcement was implemented between 2019 and 2023, involving the translocation of 12 individuals from the Carpathian Mountains to the Dinaric Mountains of Slovenia and Croatia. We conducted comprehensive genetic monitoring in this area, gathering 588 non-invasive and tissue samples, which were used for individual identification and estimation of population genetic parameters. We used stochastic modelling to assess the long-term viability of the Dinaric lynx population post-translocation and formulate effective conservation strategies. The model predicts that, despite significant improvement of genetic diversity after translocations, inbreeding will return to critical levels within 45 years. Our results highlight the fact that reinforcement is just the first step and that long-term genetic management is needed to keep the population from sliding back towards extinction. The Dinaric lynx population serves as a compelling example of genetic rescue. The lessons learnt here will be essential for ensuring the viability of the Dinaric lynx in the future and also provide a useful template for conservation of other populations and species facing similar threats.

Radiographic pelvimetry in free-ranging Eurasian lynx (Lynx lynx carpathicus) from Switzerland

The observation of pelvic anomalies in two Eurasian lynx (subspecies Lynx lynx carpathicus) from a population reintroduced to Switzerland raised the question of the frequency of such anomalies, but no anatomical reference values were available for comparison. This study aimed at providing baseline data on the pelvic morphology of Carpathian lynx from Switzerland, and at detecting potential pelvic anomalies. Measurements of 10 pelvic parameters were performed on the radiographs of 56 lynx taken from 1997–2015. Two ratios (vertical diameter/acetabula; sagittal diameter/transversal diameter) and two areas (pelvic outlet and inlet) were calculated to describe pelvic shape. The results showed that the Eurasian lynx has a mesatipellic pelvis, with a pelvic length corresponding to approximatively 20% of the body length. We found growth-related pelvis size differences among age classes and evidence of sexual dimorphism in adults: two parameters reflecting pelvic width were larger in females, likely to meet the physiological requirements of parturition. By contrast, pelvis length, conjugata vera, diagonal conjugata, sagittal diameter, and tendentially also vertical diameter, were larger in males, in agreement with their larger body size. Outliers were found in five individuals but apparently without clinical significance. Extreme values were likely due to inter-individual differences and the limited sample size rather than to possible congenital or developmental pathological morphology of the pelvic cavity. We present baseline data of the pelvic morphology, including growth and sexual dimorphism, which may be useful for health monitoring and for determination of age and sex in skeletal remains of Carpathian lynx.

Mitogenome Phylogeny Including Data from Additional Subspecies Provides New Insights into the Historical Biogeography of the Eurasian lynx Lynx lynx

Previous molecular studies of the wide-ranging Eurasian lynx Lynx lynx focused mainly on its northern Palearctic populations, with the consequence that the reconstruction of this species’ evolutionary history did not include genetic variation present in its southern Palearctic distribution. We sampled a previously not considered Asian subspecies (L. l. dinniki), added published data from another Asian subspecies (L. l. isabellinus), and reassessed the Eurasian lynx mtDNA phylogeny along with previously published data from northern Palearctic populations. Our mitogenome-based analyses revealed the existence of three major clades (A: Central Asia, B: SE Europe/SW Asia, C: Europe and Northern Asia) and at least five lineages, with diversification in Lynx lynx commencing at least 28kyr earlier than hitherto estimated. The subspecies L. l. isabellinus harbors the most basal matriline, consistent with the origin of Lynx lynx in this subspecies’ current range. L. l. dinniki harbors the second most basal matriline, which is related to, and may be the source of, the mtDNA diversity of the critically endangered Balkan lynx L. l. balcanicus. Our results suggest that the Anatolian peninsula was a glacial refugium for Eurasian lynx, with previously unconsidered implications for the colonization of Europe by this species.

Multi-seasonal systematic camera-trapping reveals fluctuating densities and high turnover rates of Carpathian lynx on the western edge of its native range

Camera-trapping and capture-recapture models are the most widely used tools for estimating densities of wild felids that have unique coat patterns, such as Eurasian lynx. However, studies dealing with this species are predominantly on a short-term basis and our knowledge of temporal trends and population persistence is still scarce. By using systematic camera-trapping and spatial capture-recapture models, we estimated lynx densities and evaluated density fluctuations, apparent survival, transition rate and individual's turnover during five consecutive seasons at three different sites situated in the Czech-Slovak-Polish borderland at the periphery of the Western Carpathians. Our density estimates vary between 0.26 and 1.85 lynx/100 km² suitable habitat and represent the lowest and the highest lynx densities reported from the Carpathians. We recorded 1.5-4.1-fold changes in asynchronous fluctuated densities among all study sites and seasons. Furthermore, we detected high individual's turnover (on average 46.3 ± 8.06% in all independent lynx and 37.6 ± 4.22% in adults) as well as low persistence of adults (only 3 out of 29 individuals detected in all seasons). The overall apparent survival rate was 0.63 ± 0.055 and overall transition rate between sites was 0.03 ± 0.019. Transition rate of males was significantly higher than in females, suggesting male-biased dispersal and female philopatry. Fluctuating densities and high turnover rates, in combination with documented lynx mortality, indicate that the population in our region faces several human-induced mortalities, such as poaching or lynx-vehicle collisions. These factors might restrict population growth and limit the dispersion of lynx to other subsequent areas, thus undermining the favourable conservation status of the Carpathian population. Moreover, our study demonstrates that long-term camera-trapping surveys are needed for evaluation of population trends and for reliable estimates of demographic parameters of wild territorial felids, and can be further used for establishing successful management and conservation measures.

Genetic analysis indicates spatial-dependent patterns of sex-biased dispersal in Eurasian lynx in Finland

Conservation and management of large carnivores requires knowledge of female and male dispersal. Such information is crucial to evaluate the population's status and thus management actions. This knowledge is challenging to obtain, often incomplete and contradictory at times. The size of the target population and the methods applied can bias the results. Also, population history and biological or environmental influences can affect dispersal on different scales within a study area. We have genotyped Eurasian lynx (180 males and 102 females, collected 2003-2017) continuously distributed in southern Finland (~23,000 km2) using 21 short tandem repeats (STR) loci and compared statistical genetic tests to infer local and sex-specific dispersal patterns within and across genetic clusters as well as geographic regions. We tested for sex-specific substructure with individual-based Bayesian assignment tests and spatial autocorrelation analyses. Differences between the sexes in genetic differentiation, relatedness, inbreeding, and diversity were analysed using population-based AMOVA, F-statistics, and assignment indices. Our results showed two different genetic clusters that were spatially structured for females but admixed for males. Similarly, spatial autocorrelation and relatedness was significantly higher in females than males. However, we found weaker sex-specific patterns for the Eurasian lynx when the data were separated in three geographical regions than when divided in the two genetic clusters. Overall, our results suggest male-biased dispersal and female philopatry for the Eurasian lynx in Southern Finland. The female genetic structuring increased from west to east within our study area. In addition, detection of male-biased dispersal was dependent on analytical methods utilized, on whether subtle underlying genetic structuring was considered or not, and the choice of population delineation. Conclusively, we suggest using multiple genetic approaches to study sex-biased dispersal in a continuously distributed species in which population delineation is difficult.

The rise of a large carnivore population in Central Europe: genetic evaluation of lynx reintroduction in the Harz Mountains

Large carnivores have made a successful comeback across human-dominated landscapes in Central Europe. The Eurasian lynx, for instance, has been actively reintroduced in different regions. Genetic diversity is quickly eroding in these isolated, small populations, questioning the long-term success of lynx reintroductions. To track population development and genetic diversity in a reintroduced lynx population, we used microsatellite analysis and mtDNA haplotyping based on 379 samples collected during the initial 15 year period of lynx reintroduction in the Harz mountains National Park, Germany. The Harz lynx population shows higher genetic diversity relative to other lynx reintroductions, due to initial cross-breeding of divergent captive source lineages and a comparably high founder size. While the population shows significant population growth and spread into adjacent regions, genetic diversity is continiously declining. Expected heterozygosity values dropped from 0.63 after reintroduction (2006/2007) to 0.55 within a 10 year period. Despite this, the Harz lynx population is currently a viable component to an envisioned lynx metapopulation spanning across Central Europe. The ongoing genetic erosion in the Harz population along with a lack of geneflow from adjacent populations indicates that such connectivity is urgently needed to ensure long-term population persistence.