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Background China is the birthplace of the deer family and the country with the most abundant deer resources. However, at present, China’s deer industry faces the problem that pure sika deer and hybrid deer cannot be easily distinguished. Therefore, the development of a SNP identification chip is urgently required. Results In this study, 250 sika deer, 206 red deer, 23 first-generation hybrid deer (F1), 20 s-generation hybrid deer (F2), and 20 third-generation hybrid deer (F3) were resequenced. Using the chromosome-level sika deer genome as the reference sequence, mutation detection was performed on all individuals, and a total of 130,306,923 SNP loci were generated. After quality control filtering was performed, the remaining 31,140,900 loci were confirmed. From molecular-level and morphological analyses, the sika deer reference population and the red deer reference population were established. The Fst values of all SNPs in the two reference populations were calculated. According to customized algorithms and strict screening principles, 1000 red deer-specific SNP sites were finally selected for chip design, and 63 hybrid individuals were determined to contain red deer-specific SNP loci. The results showed that the gene content of red deer gradually decreased in subsequent hybrid generations, and this decrease roughly conformed to the law of statistical genetics. Reaction probes were designed according to the screening sites. All candidate sites met the requirements of the Illumina chip scoring system. The average score was 0.99, and the MAF was in the range of 0.3277 to 0.3621. Furthermore, 266 deer (125 sika deer, 39 red deer, 56 F1, 29 F2,17 F3) were randomly selected for 1 K SNP chip verification. The results showed that among the 1000 SNP sites, 995 probes were synthesized, 4 of which could not be typed, while 973 loci were polymorphic. PCA, random forest and ADMIXTURE results showed that the 1 K sika deer SNP chip was able to clearly distinguish sika deer, red deer, and hybrid deer and that this 1 K SNP chip technology may provide technical support for the protection and utilization of pure sika deer species resources. Conclusion We successfully developed a low-density identification chip that can quickly and accurately distinguish sika deer from their hybrid offspring, thereby providing technical support for the protection and utilization of pure sika deer germplasm resources.

Inbreeding depression is of major concern for the conservation of threatened species, and inbreeding avoidance is thought to be a key driver in the evolution of mating systems. However, the estimation of individual inbreeding coefficients in natural populations has been challenging, and, consequently, the full effect of inbreeding on fitness remains unclear. Genomic inbreeding coefficients may resolve the long-standing paucity of data on inbreeding depression in adult traits and total fitness. Here we investigate inbreeding depression in a range of life history traits and fitness in a wild population of red deer (Cervus elaphus) in Scotland using individual inbreeding coefficients derived from dense Single-Nucleotide Polymorphism (SNP) data (F grm). We find associations between F grm and annual breeding success in both sexes, and between maternal inbreeding coefficient and offspring survival. We also confirm previous findings of inbreeding depression in birth weight and juvenile survival. In contrast, inbreeding coefficients calculated from a deep and comparatively complete pedigree detected inbreeding depression in juvenile survival, but not in any adult fitness component. The total effect of inbreeding on lifetime breeding success (LBS) was substantial in both sexes: for F grm = 0.125, a value resulting from a half-sib mating, LBS declined by 72% for females and 95% for males. Our results demonstrate that SNP-based estimates of inbreeding provide a powerful tool for evaluating inbreeding depression in natural populations, and suggest that, to date, the prevalence of inbreeding depression in adult traits may have been underestimated.

Muntjac deer have experienced drastic karyotype changes during their speciation, making it an ideal model for studying mechanisms and functional consequences of mammalian chromosome evolution. Here we generated chromosome-level genomes for Hydropotes inermis (2n = 70), Muntiacus reevesi (2n = 46), female and male M. crinifrons (2n = 8/9) and a contig-level genome for M. gongshanensis (2n = 8/9). These high-quality genomes combined with Hi-C data allowed us to reveal the evolution of 3D chromatin architectures during mammalian chromosome evolution. We find that the chromosome fusion events of muntjac species did not alter the A/B compartment structure and topologically associated domains near the fusion sites, but new chromatin interactions were gradually established across the fusion sites. The recently borne neo-Y chromosome of M. crinifrons , which underwent male-specific inversions, has dramatically restructured chromatin compartments, recapitulating the early evolution of canonical mammalian Y chromosomes. We also reveal that a complex structure containing unique centromeric satellite, truncated telomeric and palindrome repeats might have mediated muntjacs’ recurrent chromosome fusions. These results provide insights into the recurrent chromosome tandem fusion in muntjacs, early evolution of mammalian sex chromosomes, and reveal how chromosome rearrangements can reshape the 3D chromatin regulatory conformations during species evolution. Muntjac deer underwent rapid species radiation and dramatic chromosome fusions within a short period of time. Here the authors reveal that repeat sequences likely mediated illegitimate recombination to result in chromosome fusions and that 3D chromatin architecture around fusion sites have no significant change, while significant interactions across fusion sites were gradually established after speciation.

Background Population genomic analysis can reconstruct the phylogenetic relationship and demographic history, and identify genomic selective signatures of a species. To date, fundamental aspects of population genomic analyses, such as intraspecies taxonomy, evolutionary history, and adaptive evolution, of sika deer have not been systematically investigated. Furthermore, accumulating lines of evidences have illustrated that incorrect species delimitation will mislead conservation decisions, and even lead to irreversible mistakes in threatened species. Results In this study, we resequenced 81 wild and 71 domesticated sika deer representing 10 main geographic populations and two farms to clarify the species delimitation, demographic and divergence histories, and adaptive evolution of this species. First, our analyses of whole genomes, Y chromosomes and mitochondrial genomes revealed substantial genetic differentiation between the continental and Japanese lineages of sika deer, representing two phylogenetically distinct species. Second, sika deer in Japan were inferred to have experienced a “divergence-mixing-isolation” evolutionary scenario. Third, we identified four candidate genes ( XKR4 , NPAS3 , CTNNA3 , and CNTNAP5 ) possibly involved in body size regulation of sika deer by selective sweep analysis. Furthermore, we also detected two candidate genes ( NRP2 and EDIL3 ) that may be associated with an important economic trait (antler weight) were under selection during the process of domestication. Conclusion Population genomic analyses revealed that the continental and Japanese lineages represent distinct phylogenetic species. Moreover, our results provide insights into the genetic selection signatures related to body size differences and a valuable genomic resource for future genetic studies and genomics-informed breeding of sika deer.

The distribution of runs of homozygosity (ROH) may be shaped by a number of interacting processes such as selection, recombination and population history, but little is known about the importance of these mechanisms in shaping ROH in wild populations. We combined an empirical dataset of >3000 red deer genotyped at >35,000 genome-wide autosomal SNPs and evolutionary simulations to investigate the influence of each of these factors on ROH. We assessed ROH in a focal and comparison population to investigate the effect of population history. We investigated the role of recombination using both a physical map and a genetic linkage map to search for ROH. We found differences in ROH distribution between both populations and map types indicating that population history and local recombination rate have an effect on ROH. Finally, we ran forward genetic simulations with varying population histories, recombination rates and levels of selection, allowing us to further interpret our empirical data. These simulations showed that population history has a greater effect on ROH distribution than either recombination or selection. We further show that selection can cause genomic regions where ROH is common, only when the effective population size (Ne) is large or selection is particularly strong. In populations having undergone a population bottleneck, genetic drift can outweigh the effect of selection. Overall, we conclude that in this population, genetic drift resulting from a historical population bottleneck is most likely to have resulted in the observed ROH distribution, with selection possibly playing a minor role.

Shanxi Province is the northernmost distribution range of Chinese forest musk deer ( Moschus berezovskii ), with wild populations scattered across Zhongtiao (ZT), Lüliang (LL), and Taiyue (TY) mountain ranges. Using line transect surveys and local guide assistance, coupled with infrared camera data, this study systematically collected fecal samples from wild forest musk deer from five nature reserves across the three mountain ranges. Genetic diversity was analyzed using the mtDNA control region, which yielded 129 effective sequences of 656 bp and 20 distinct haplotypes. Haplotype and nucleotide diversities were 0.916 and 0.01505, respectively, indicating a relatively high overall genetic diversity in the studied populations. Significant genetic differentiation was observed between the Lüliang–Taiyue (LLTY) and ZT mountain range populations, with most of the genetic variation existing within the populations. No significant correlation was detected between the geographical and genetic distances of the samples, which may have resulted from historical agricultural activities in Shanxi impeding gene flow among populations. Therefore, genetic exchange programs are recommended to improve the genetic diversity and population fitness of forest musk deer in this region to facilitate their recovery and growth.

The Wnt signaling pathway is ubiquitous in animals, playing a crucial role in embryonic development and adult tissue homeostasis in multicellular organisms. Wnt proteins act as ligands in this pathway, and their gene family encodes secreted signaling proteins involved in regulating vital physiological processes such as cell proliferation, migration, differentiation, polarity establishment, and maintenance. Based on the third-generation genome of the forest musk deer (FMD, Moschus berezovskii ), this study aimed to identify members of the Wnt gene family, elucidate their physicochemical properties, analyze their chromosomal localization and gene structure, construct a systematic evolutionary tree, and predict the two-dimensional and three-dimensional structures of the Wnt protein family. Genome-wide identification was performed using BLASTP searches. Phylogenetic relationships were reconstructed using the Maximum Likelihood method, and 3D structures were predicted using SWISS-MODEL. Results revealed 18 Wnt ( MbWnt ) gene family members distributed across 8 chromosomes, with cDNA lengths ranging from 819 to 1900 base pairs in the FMD. The number of amino acids in the Wnt family proteins of the FMD ranged from 349 to 586aa, with isoelectric points (pI) between 7.96 and 10.24, and molecular weights concentrated between 30 and 62 kilodaltons. Signal peptide analysis showed that only MbWnt1 , MbWnt2 , MbWnt4 , MbWnt6 , and MbWnt9b contained signal peptides. Subcellular localization analysis indicated that the Wnt gene family is primarily located in the nucleus and cytoplasm. MbWnt proteins shared six conserved motifs. Phylogenetic analysis demonstrated high consistency in Wnt conservation and grouping in the genomes of cattle ( Bos taurus ), goat ( Capra hircus ), sheep (Ovis aries) , and red deer ( Cervus elaphus ). Genome collinearity analysis demonstrated substantial chromosomal correspondence and orthologous conservation between the FMD and the three species of Bovinae and Ce. elaphus. The level of chromosome homology is relatively low, but the level of genome homology is relatively high among these species. Musk gland transcriptomic datasets indicated that the expression of MbWnt genes were stage-specific at musk secretion stage and non-secretory stage. RT-qPCR analysis indicated that six MbWnt genes were significantly highly expressed during the musk secretion stage, whereas two genes showed no significant differential expression.

The threat of isolation to red deer ( Cervus elaphus ) has been described in numerous European studies. The consequences range from reduced genetic diversity and increased inbreeding to inbreeding depression. It has been shown that the underlying factors cannot be generalised, but vary greatly in their effects depending on local conditions. The aim of this study was to analyse in detail the genetics of red deer in a large German federal state with a population density of 532 inhabitants per km 2 and 23.8% settlement and traffic area, in order to generate data for future management of the region. 1199 individual samples of red deer were collected in all 20 Administrative Management Units (AMUs) and compared with existing results from the neighbouring state of Hesse (19 AMUs). All 2490 individuals from both states were clustered using Bayesian methods and connectivity between neighbouring AMUs was quantified. Overall, 30% of the AMUs were found to be highly isolated, mostly with effective population sizes (Ne) < 100. In contrast, 47.5% of the AMUs still had clear connectivity, allowing them to be merged into 4 larger red deer regions. For the small isolated areas, low genetic diversity was found in units with high homozygosity and low Ne. With high sampling density and identical methodology, detailed information on AMUs can be obtained and the degree of vulnerability of individual AMUs as part of the overall population can specifically be validated. Such data can help improve future wildlife management.

The bad side of a good gene The unique long-term study of the red deer populations on the Isle of Rum, off the west coast of Scotland, has revealed the existence of sexually antagonistic fitness variation in a long-lived, sexually-dimorphic species in the wild. The finding proves what has been expected from theory and recent Drosophila laboratory experiments: genes that make a good male do not necessarily make a good female, and vice versa. The consequence of this effect is the selection against males that carry genes for high female fitness, which may have profound effects on the selection and maintenance of genetic variation in natural populations. Use of a long-term data set demonstrates the existence of sexually antagonistic fitness variation in a long-lived, sexually-dimorphic species in the wild — genes that make a good male do not make a good female, and vice versa. This sexually antagonistic effect results in selection against males that carry genes for high female fitness. Evolutionary theory predicts the depletion of genetic variation in natural populations as a result of the effects of selection, but genetic variation is nevertheless abundant for many traits that are under directional or stabilizing selection 1 . Evolutionary geneticists commonly try to explain this paradox with mechanisms that lead to a balance between mutation and selection 2 . However, theoretical predictions of equilibrium genetic variance under mutation–selection balance are usually lower than the observed values, and the reason for this is unknown 3 . The potential role of sexually antagonistic selection in maintaining genetic variation has received little attention in this debate, surprisingly given its potential ubiquity in dioecious organisms. At fitness-related loci, a given genotype may be selected in opposite directions in the two sexes. Such sexually antagonistic selection will reduce the otherwise-expected positive genetic correlation between male and female fitness 4 . Both theory 5 , 6 , 7 and experimental data 8 , 9 , 10 , 11 , 12 suggest that males and females of the same species may have divergent genetic optima, but supporting data from wild populations are still scarce 13 , 14 , 15 . Here we present evidence for sexually antagonistic fitness variation in a natural population, using data from a long-term study of red deer ( Cervus elaphus ). We show that male red deer with relatively high fitness fathered, on average, daughters with relatively low fitness. This was due to a negative genetic correlation between estimates of fitness in males and females. In particular, we show that selection favours males that carry low breeding values for female fitness. Our results demonstrate that sexually antagonistic selection can lead to a trade-off between the optimal genotypes for males and females; this mechanism will have profound effects on the operation of selection and the maintenance of genetic variation in natural populations.

This study investigates the genomic landscape of Sika deer populations, emphasizing the detection and characterization of runs of homozygosity (ROH) and their contribution towards components of fitness. Using 85,001 high-confidence SNPs, the investigation into ROH distribution unveiled nuanced patterns of autozygosity across individuals especially in 2 out of the 8 farms, exhibiting elevated ROH levels and mean genome coverage under ROH segments. The prevalence of shorter ROH segments (0.5-4 Mb) suggests historical relatedness and potential selective pressures within these populations. Intriguingly, despite observed variations in ROH profiles, the overall genomic inbreeding coefficient (FROH) remained relatively low across all farms, indicating a discernible degree of genetic exchange and effective mitigation of inbreeding within the studied Sika deer populations. Consensus ROH (cROH) were found to harbor genes for important functions viz., EGFLAM gene which is involved in the vision function of the eye, SKP2 gene which regulates cell cycle, CAPSL involved in adipogenesis, SPEF2 which is essential for sperm flagellar assembly, DCLK3 involved in the heat stress. This first ever study on ROH in Sika deer, to shed light on the adaptive role of genes in these homozygous regions. The insights garnered from this study have broader implications in the management of genetic diversity in this vulnerable species.