Long-range gene flow and the effects of climatic and ecological factors on genetic structuring in a large, solitary carnivore: the Eurasian lynx

Insights into subspecies classification and conservation priorities of Central Asian lynx populations revealed by morphometric and genetic analyses

The Eurasian lynx (Lynx lynx) exhibits geographic variability and phylogenetic intraspecific relationships. Previous morphological studies have suggested the existence of multiple lynx subspecies, but recent genetic research has questioned this classification, particularly in Central Asia. In this study, we aimed to analyse the geographic and genetic variation in Central Asian lynx populations, particularly the Turkestan lynx and Altai lynx populations, using morphometric data and mtDNA sequences to contribute to their taxonomic classification. The comparative analysis of morphometric data revealed limited clinal variability between lynx samples from the Altai and Tien Shan regions. By examining mtDNA fragments (control region and cytochrome b) obtained from Kazakhstani lynx populations, two subspecies were identified: L. l. isabellinus (represented by a unique haplotype of the South clade, H46) and L. l. wrangeli (represented by haplotypes H36, H45, and H47 of the East clade). L. l. isabellinus was recognized only in Tien Shan Mountain, while Altai lynx was likely identical to L. l. wrangeli and found in northern Kazakhstan, Altai Mountain, Saur and Tarbagatai Mountains, and Tien Shan Mountain. The morphological and mtDNA evidence presented in this study, although limited in sample size and number of genetic markers, renders the differentiation of the two subspecies challenging. Further sampling and compilation of whole-genome sequencing data are necessary to confirm whether the proposed subspecies warrant taxonomic standing.

Genome-environment association analyses reveal geographically restricted adaptive divergence across the range of the widespread Eurasian carnivore Lynx lynx (Linnaeus, 1758)

Local adaptations to the environment are an important aspect of the diversity of a species and their discovery, description and quantification has important implications for the fields of taxonomy, evolutionary and conservation biology. In this study, we scan genomes from several populations across the distributional range of the Eurasian lynx, with the objective of finding genomic windows under positive selection which may underlie local adaptations to different environments. A total of 394 genomic windows are found to be associated to local environmental conditions, and they are enriched for genes involved in metabolism, behaviour, synaptic organization and neural development. Adaptive genetic structure, reconstructed from SNPs in candidate windows, is considerably different than the neutral genetic structure of the species. A widespread adaptively homogeneous group is recovered occupying areas of harsher snow and temperature climatic conditions in the north-western, central and eastern parts of the distribution. Adaptively divergent populations are recovered in the westernmost part of the range, especially within the Baltic population, but also predicted for different patches in the western and southern part of the range, associated with different snow and temperature regimes. Adaptive differentiation driven by climate does not correlate much with the subspecies taxonomic delimitations, suggesting that subspecific divergences are mostly driven by neutral processes of genetic drift and gene flow. Our results will aid the selection of source populations for assisted gene flow or genetic rescue programs by identifying what climatic patterns to look for as predictors of pre-adaptation of individuals. Particularly, the Carpathian population is confirmed as the best source of individuals for the genetic rescue of the endangered, isolated and genetically eroded Balkan population. Additionally, reintroductions in central and western Europe, currently based mostly on Carpathian lynxes, could consider the Baltic population as an additional source to increase adaptive variation and likely improve adaptation to their milder climate.

Time is running out: Microsatellite data predict the imminent extinction of the boreal lynx (Lynx lynx) in France

The Eurasian lynx reappeared in the French Jura Mountains, in the late 1970s, as the result of the dispersion of lynxes from the Carpathian region reintroduced in Switzerland in the early 1970s. Since then, the state of this population has remained poorly known. One estimate gives the number of individuals between 120 and 150. Opportunistic observation and monitoring suggest poor connectivity with the populations in Germany or in other parts of Switzerland. Forty years after its comeback in France, we could expect a higher number of individuals, but possible inbreeding depression as well as threats such as poaching and collisions with cars may explain the limitation of number of individuals observed and may lead to a new extinction of the specie in this region. We used 23 microsatellite markers and 78 DNA samples, collected between 2008 and 2020, to establish the genetic state of the French Jura Mountain lynx population. Our results show extremely low genetic diversity with an observed heterozygosity (Ho) of 0.36 and an effective population size (Ne) of 38.2. When comparing the source population (Carpathian), the inbreeding level is very worrying (Fe = 0.41). These results are among the lowest recorded for the Eurasian lynx. To avoid extinction, which we estimate will occur in approximately 30 years, we recommend the introduction of new genetic material. Although reintroduction is controversial, solutions such as the replacement of poached lynxes and the exchange of orphan lynxes between care centers are good initial actions for population strengthening. This offers a rapid intervention while studying solutions for more sustainable conservation

Assessment of Eurasian lynx reintroduction success and mortality risk in north-west Poland

Despite recent local reintroductions of the Eurasian lynx Lynx lynx in central and north-eastern Poland, the increase in its population was not followed by its westward expansion. To address this problem and restore the lynx population in north-western Poland, 61 captive-born individuals of Baltic population origin were released in the province of Western Pomerania in 2019–2021. Prior to their release, all the animals underwent an adaptation training phase. They were then set free according to a hard-release protocol and subsequently monitored by means of GPS telemetry. In order to assess the short-term reintroduction success, the survival and causes of death of the released individuals were studied as a function of sex, age, training time, and release time and place. The overall survival rate was 71.15%, the median survival time 202 days. Most mortality, due to environmental factors, i.e. scabies (> 200 days) or traffic collisions (< 200 days), was recorded during the first 300 days following release. Age, year of release and training time were significantly related to survival, indicating that the older the lynx was when released, the better its survival changes. In contrast, the longer the training time, the poorer were the chances of survival. There was no evidence of any effect of sex, month of release or place of release. Based on these results, recommendations were made for the planning of further releases and measures to manage the restored population.

Purging of deleterious burden in the endangered Iberian lynx

SignificanceThe dynamics of deleterious variation under contrasting demographic scenarios remain poorly understood in spite of their relevance in evolutionary and conservation terms. Here we apply a genomic approach to study differences in the burden of deleterious alleles between the endangered Iberian lynx (Lynx pardinus) and the widespread Eurasian lynx (Lynx lynx). Our analysis unveils a significantly lower deleterious burden in the former species that should be ascribed to genetic purging, that is, to the increased opportunities of selection against recessive homozygotes due to the inbreeding caused by its smaller population size, as illustrated by our analytical predictions. This research provides theoretical and empirical evidence on the evolutionary relevance of genetic purging under certain demographic conditions.

Phylogenetic analyses of Eurasian lynx (Lynx lynx Linnaeus, 1758) including new mitochondrial DNA sequences from Iran

The Eurasian lynx (Lynx lynx) is one of the widespread felids in Eurasia; however, relatively little is known about the Asian subspecies, and especially the Iranian populations, which comprise the most southwestern part of its range. The current study aimed to assess the phylogenetic status of Iranian populations relative to other populations of Eurasia, by sequencing a 613 bp fragment of the mitochondrial control region. In total, 44 haplotypes were recorded from 83 sequences throughout Eurasia, two of which were found in Iran. The haplotype (H1) is dominant in all Iranian lynx populations and identical to specimens from SW Russia and central China. The second haplotype (H2) is unique and was recorded only from Ghazvin Province in the central Alborz Mountains. Both haplotypes occur in Ghazvin Province. The phylogenetic tree and a median-joining network identified four clades (i.e., East, West 1, West 2, and South). These results are congruent with previous studies and suggest that Eurasian lynx was restricted to the southern part of its range during the glacial maxima and expanded from there to East Asia and to Europe during several independent re-colonization events. The Caucasus region most like plays an important role as a refugium during glacial cycles.

Coat Polymorphism in Eurasian Lynx: Adaptation to Environment or Phylogeographic Legacy?

We studied the relationship between the variability and contemporary distribution of pelage phenotypes in one of most widely distributed felid species and an array of environmental and demographic conditions. We collected 672 photographic georeferenced records of the Eurasian lynx throughout Eurasia. We assigned each lynx coat to one of five phenotypes. Then we fitted the coat patterns to different environmental and anthropogenic variables, as well as the effective geographic distances from inferred glacial refugia. A majority of lynx were either of the large spotted (41.5%) or unspotted (uniform, 36.2%) phenotype. The remaining patterns (rosettes, small spots and pseudo-rosettes) were represented in 11.0%, 7.4%, and 3.9% of samples, respectively. Although various environmental variables greatly affected lynx distribution and habitat suitability, it was the effect of least-cost distances from locations of the inferred refugia during the Last Glacial Maximum that explained the distribution of lynx coat patterns the best. Whereas the occurrence of lynx phenotypes with large spots was explained by the proximity to refugia located in the Caucasus/Middle East, the uniform phenotype was associated with refugia in the Far East and Central Asia. Despite the widely accepted hypothesis of adaptive functionality of coat patterns in mammals and exceptionally high phenotypic polymorphism in Eurasian lynx, we did not find well-defined signs of habitat matching in the coat pattern of this species. Instead, we showed how the global patterns of morphological variability in this large mammal and its environmental adaptations may have been shaped by past climatic change.

Bottleneck-associated changes in the genomic landscape of genetic diversity in wild lynx populations

Demographic bottlenecks generally reduce genetic diversity through more intense genetic drift, but their net effect may vary along the genome due to the random nature of genetic drift and to local effects of recombination, mutation, and selection. Here, we analyzed the changes in genetic diversity following a bottleneck by comparing whole-genome diversity patterns in populations with and without severe recent documented declines of Iberian (Lynx pardinus, n = 31) and Eurasian lynx (Lynx lynx, n = 29). As expected, overall genomic diversity correlated negatively with bottleneck intensity and/or duration. Correlations of genetic diversity with divergence, chromosome size, gene or functional site content, GC content, or recombination were observed in nonbottlenecked populations, but were weaker in bottlenecked populations. Also, functional features under intense purifying selection and the X chromosome showed an increase in the observed density of variants, even resulting in higher θ W diversity than in nonbottlenecked populations. Increased diversity seems to be related to both a higher mutational input in those regions creating a large collection of low-frequency variants, a few of which increase in frequency during the bottleneck to the point they become detectable with our limited sample, and the reduced efficacy of purifying selection, which affects not only protein structure and function but also the regulation of gene expression. The results of this study alert to the possible reduction of fitness and adaptive potential associated with the genomic erosion in regulatory elements. Further, the detection of a gain of diversity in ultra-conserved elements can be used as a sensitive and easy-to-apply signature of genetic erosion in wild populations.

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.

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.

Citizen Scientists Showed a Four-Fold Increase of Lynx Numbers in Lithuania

By the early 2000s, Eurasian lynx (Lynx lynx) were nearly extirpated in Lithuania. To determine their status, we used snow-track counts in 2006–2012 and volunteer monitoring in 1999–2005 and 2015–2018. Using simple questionnaires, we collected incidental observations from hunters, foresters, and other interested citizens to estimate lynx distribution, abundance and extent of breeding. Citizen scientists provided 206 reports of 278 individual lynx that suggested expanding lynx distributions in central, western, southwestern, and southern parts of Lithuania. A decrease in range fragmentation has also been observed since 2015. Nationwide, the lynx population quadrupled from 2010 to 162 individuals in 2018. The number of breeding individuals reported was just seven in both 2007 and 2008, limited to two forests in the very north and central part of the country. This increased to 46 in 2015–2018. Our results indicate that the lynx population in Lithuania has increased and its conservation status should be reconsidered.

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.

Genomic patterns in the widespread Eurasian lynx shaped by Late Quaternary climatic fluctuations and anthropogenic impacts

Disentangling the contribution of long-term evolutionary processes and recent anthropogenic impacts to current genetic patterns of wildlife species is key to assessing genetic risks and designing conservation strategies. Here, we used 80 whole nuclear genomes and 96 mitogenomes from populations of the Eurasian lynx covering a range of conservation statuses, climatic zones and subspecies across Eurasia to infer the demographic history, reconstruct genetic patterns, and discuss the influence of long-term isolation and/or more recent human-driven changes. Our results show that Eurasian lynx populations shared a common history until 100,000 years ago, when Asian and European populations started to diverge and both entered a period of continuous and widespread decline, with western populations, except Kirov, maintaining lower effective sizes than eastern populations. Population declines and increased isolation in more recent times probably drove the genetic differentiation between geographically and ecologically close westernmost European populations. By contrast, and despite the wide range of habitats covered, populations are quite homogeneous genetically across the Asian range, showing a pattern of isolation by distance and providing little genetic support for the several proposed subspecies. Mitogenomic and nuclear divergences and population declines starting during the Late Pleistocene can be mostly attributed to climatic fluctuations and early human influence, but the widespread and sustained decline since the Holocene is more probably the consequence of anthropogenic impacts which intensified in recent centuries, especially in western Europe. Genetic erosion in isolated European populations and lack of evidence for long-term isolation argue for the restoration of lost population connectivity.

Genetic evidence of female kin clusters in a continuous population of a solitary carnivore, the Eurasian lynx

Large terrestrial carnivores can sometimes display strong family bonds affecting the spatial distribution of related individuals. We studied the spatial genetic relatedness and family structure of female Eurasian lynx, continuously distributed in southern Finland. We hypothesized that closely related females form matrilineal assemblages, clustering together with relatives living in the neighboring areas. We evaluated this hypothesis using tissue samples of 133 legally harvested female lynx (from year 2007 to 2015), genotyped with 23 microsatellite markers, and tested for possible spatial genetic family structure using a combination of Bayesian clustering, spatial autocorrelation, and forensic genetic parentage analysis. The study population had three potential family genetic clusters, with a high degree of admixture and geographic overlap, and showed a weak but significant negative relationship between pairwise genetic and geographic distance. Moreover, parentage analysis indicated that 64% of the females had one or more close relatives (sister, mother, or daughter) within the study population. Individuals identified as close kin consistently assigned to the same putative family genetic cluster. They also were sampled closer geographically than females on average, although variation was large. Our results support the possibility that Eurasian lynx forms matrilineal assemblages, and comparisons with males are now required to further assess this hypothesis.

Targeted resequencing of coding DNA sequences for SNP discovery in nonmodel species

Targeted capture coupled with high-throughput sequencing can be used to gain information about nuclear sequence variation at hundreds to thousands of loci. Divergent reference capture makes use of molecular data of one species to enrich target loci in other (related) species. This is particularly valuable for nonmodel organisms, for which often no a priori knowledge exists regarding these loci. Here, we have used targeted capture to obtain data for 809 nuclear coding DNA sequences (CDS) in a nonmodel organism, the Eurasian lynx Lynx lynx, using baits designed with the help of the published genome of a related model organism (the domestic cat Felis catus). Using this approach, we were able to survey intraspecific variation at hundreds of nuclear loci in L. lynx across the species' European range. A large set of biallelic candidate SNPs was then evaluated using a high-throughput SNP genotyping platform (Fluidigm), which we then reduced to a final 96 SNP-panel based on assay performance and reliability; validation was carried out with 100 additional Eurasian lynx samples not included in the SNP discovery phase. The 96 SNP-panel developed from CDS performed very successfully in the identification of individuals and in population genetic structure inference (including the assignment of individuals to their source population). In keeping with recent studies, our results show that genic SNPs can be valuable for genetic monitoring of wildlife species.

Spatiotemporal Dynamics of Genetic Variation in the Iberian Lynx along Its Path to Extinction Reconstructed with Ancient DNA

There is the tendency to assume that endangered species have been both genetically and demographically healthier in the past, so that any genetic erosion observed today was caused by their recent decline. The Iberian lynx (Lynx pardinus) suffered a dramatic and continuous decline during the 20th century, and now shows extremely low genome- and species-wide genetic diversity among other signs of genomic erosion. We analyze ancient (N = 10), historical (N = 245), and contemporary (N = 172) samples with microsatellite and mitogenome data to reconstruct the species' demography and investigate patterns of genetic variation across space and time. Iberian lynx populations transitioned from low but significantly higher genetic diversity than today and shallow geographical differentiation millennia ago, through a structured metapopulation with varying levels of diversity during the last centuries, to two extremely genetically depauperate and differentiated remnant populations by 2002. The historical subpopulations show varying extents of genetic drift in relation to their recent size and time in isolation, but these do not predict whether the populations persisted or went finally extinct. In conclusion, current genetic patterns were mainly shaped by genetic drift, supporting the current admixture of the two genetic pools and calling for a comprehensive genetic management of the ongoing conservation program. This study illustrates how a retrospective analysis of demographic and genetic patterns of endangered species can shed light onto their evolutionary history and this, in turn, can inform conservation actions.

The missing lynx of Eurasia at its Southern edge: a connection to the critically endangered Balkan lynx

The populations of Eurasian lynx in Anatolia are as fragmented as the European populations. Although the origins of and the connections between the European lynx populations have been elucidated, there have been no genetic studies on the lynx populations in Turkey. The lack of genetic and evolutionary information about lynx in Anatolia, which is considered to be a biodiversity hotspot, makes it difficult to track the migration routes during the Quaternary. In this study, we present the genetic characteristics of two isolated lynx populations in Southwest Taurus Mountains and the Turkish Caucasus as well as two individuals from Erzincan area. DNA purified from the ecological scat samples collected from Çığlıkara Nature Reserve in Elmalı-Antalya and Allahuekber Mountains in Sarıkamış-Kars, as well as two roadkill samples from Erzincan, has been analysed for phylogenetic markers such as the mitochondrial DNA control region and cytochrome b. The DNA sequences were compared with haplotypes previously detected in populations from Europe and the Caucasus in order to determine the evolutionary relationships of the populations. This study compares the current genetic structure of some of the Turkish lynx populations to the other lynx genetic data, mostly carried out with museum samples around the world. Three haplotypes were found in three different regions of Anatolia. The Northeast and Southwest populations harbour genetically distinct haplotypes, the latter one, a new haplotype: H13-TR is the only phylogenetic connection to the critically endangered Balkan lynx yet to be described.

Selection and drift influence genetic differentiation of insular Canada lynx (Lynx canadensis) on Newfoundland and Cape Breton Island

Island populations have long been important for understanding the dynamics and mechanisms of evolution in natural systems. While genetic drift is often strong on islands due to founder events and population bottlenecks, the strength of selection can also be strong enough to counteract the effects of drift. Here, we used several analyses to identify the roles of genetic drift and selection on genetic differentiation and diversity of Canada lynx (Lynx canadensis) across eastern Canada, including the islands of Cape Breton and Newfoundland. Specifically, we assessed whether we could identify a genetic component to the observed morphological differentiation that has been reported across insular and mainland lynx. We used a dinucleotide repeat within the promoter region of a functional gene that has been linked to mammalian body size, insulin-like growth factor-1 (IGF-1). We found high genetic differentiation at neutral molecular markers but convergence of allele frequencies at the IGF-1 locus. Thus, we showed that while genetic drift has influenced the observed genetic structure of lynx at neutral molecular markers, natural selection has also played a role in the observed patterns of genetic diversity at the IGF-1 locus of insular lynx.

Does kinship affect spatial organization in a small and isolated population of a solitary felid: The Eurasian lynx?

Social organization in wild carnivores is mostly determined by patterns of family bonds, which may shape the degree of relatedness among individuals in the population. We studied kinship in a small and isolated population of a solitary carnivore, the Eurasian lynx (Lynx lynx) to evaluate its effect on spatial distribution of individuals. We investigated the relationship between spatial location and pair-wise kinship among 28 lynx individuals identified in 2004-2011 by telemetry, non-invasive sampling and genotyping with the use of 12 autosomal microsatellites in the Białowieża Primeval Forest, Poland. The average relatedness of the lynx population was relatively low (Lynch and Ritland's R = 0.03). Females were significantly more related to each other than males with other males. The inferred pedigree showed that the population was dominated by only 2 familial groups. We did not find significant correlations between the relatedness and the extent of home range overlap or the straight-line distances between the home ranges' central points. These results suggest that the dynamics of kinship in this solitary felid may not differ from the random mating processes described in social carnivores. Although the chances of random mating could be limited to a few resident males and females, the presence of unrelated floaters may provide a "breeding buffer" that may prevent an increase of relatedness and likely inbreeding in the population. This system is likely to fail in preserving genetic diversity in small, highly isolated populations; therefore, restoring habitat connectivity is crucial to ensure sufficient immigration from neighboring populations.