Decline of genetic diversity in ancient domestic stallions in Europe

Inferences about the population history of Rangifer tarandus from Y chromosome and mtDNA phylogenies

Reindeer, called caribou in North America, has a circumpolar distribution and all extant populations belong to the same species (Rangifer tarandus). It has survived the Holocene thanks to its immense adaptability and successful coexistence with humans in different forms of hunting and herding cultures. Here, we examine the paternal and maternal history of Rangifer based on robust Y-chromosomal and mitochondrial DNA (mtDNA) trees representing Eurasian tundra reindeer, Finnish forest reindeer, Svalbard reindeer, Alaska tundra caribou, and woodland caribou. We first assembled Y-chromosomal contigs, representing 1.3 Mb of single-copy Y regions. Based on 545 Y-chromosomal and 458 mtDNA SNPs defined in 55 males, maximum parsimony trees were created. We observed two well separated clades in both phylogenies: the "EuroBeringian clade" formed by animals from Arctic Islands, Eurasia, and a few from North America and the "North American clade" formed only by caribou from North America. The time calibrated Y tree revealed an expansion and dispersal of lineages across continents after the Last Glacial Maximum. We show for the first time unique paternal lineages in Svalbard reindeer and Finnish forest reindeer and reveal a circumscribed Y haplogroup in Fennoscandian tundra reindeer. The Y chromosome in domesticated reindeer is markedly diverse indicating that several male lineages have undergone domestication and less intensive selection on males. This study places R. tarandus onto the list of species with resolved Y and mtDNA phylogenies and builds the basis for studies of the distribution and origin of paternal and maternal lineages in the future.

Refining the evolutionary tree of the horse Y chromosome

The Y chromosome carries information about the demography of paternal lineages, and thus, can prove invaluable for retracing both the evolutionary trajectory of wild animals and the breeding history of domesticates. In horses, the Y chromosome shows a limited, but highly informative, sequence diversity, supporting the increasing breeding influence of Oriental lineages during the last 1500 years. Here, we augment the primary horse Y-phylogeny, which is currently mainly based on modern horse breeds of economic interest, with haplotypes (HT) segregating in remote horse populations around the world. We analyze target enriched sequencing data of 5 Mb of the Y chromosome from 76 domestic males, together with 89 whole genome sequenced domestic males and five Przewalski's horses from previous studies. The resulting phylogeny comprises 153 HTs defined by 2966 variants and offers unprecedented resolution into the history of horse paternal lineages. It reveals the presence of a remarkable number of previously unknown haplogroups in Mongolian horses and insular populations. Phylogenetic placement of HTs retrieved from 163 archaeological specimens further indicates that most of the present-day Y-chromosomal variation evolved after the domestication process that started around 4200 years ago in the Western Eurasian steppes. Our comprehensive phylogeny significantly reduces ascertainment bias and constitutes a robust evolutionary framework for analyzing horse population dynamics and diversity.

Unlocking Horse Y Chromosome Diversity

The present equine genetic variation mirrors the deep influence of intensive breeding programs during the last 200 years. Here, we provide a comprehensive current state of knowledge on the trends and prospects on the variation in the equine male-specific region of the Y chromosome (MSY), which was assembled for the first time in 2018. In comparison with the other 12 mammalian species, horses are now the most represented, with 56 documented MSY genes. However, in contrast to the high variability in mitochondrial DNA observed in many horse breeds from different geographic areas, modern horse populations demonstrate extremely low genetic Y-chromosome diversity. The selective pressures employed by breeders using pedigree data (which are not always error-free) as a predictive tool represent the main cause of this lack of variation in the Y-chromosome. Nevertheless, the detailed phylogenies obtained by recent fine-scaled Y-chromosomal genotyping in many horse breeds worldwide have contributed to addressing the genealogical, forensic, and population questions leading to the reappraisal of the Y-chromosome as a powerful genetic marker to avoid the loss of biodiversity as a result of selective breeding practices, and to better understand the historical development of horse breeds.

Copy number variation of horse Y chromosome genes in normal equine populations and in horses with abnormal sex development and subfertility: relationship of copy number variations with Y haplogroups

Structural rearrangements like copy number variations in the male-specific Y chromosome have been associated with male fertility phenotypes in human and mouse but have been sparsely studied in other mammalian species. Here, we designed digital droplet PCR assays for 7 horse male-specific Y chromosome multicopy genes and SRY and evaluated their absolute copy numbers in 209 normal male horses of 22 breeds, 73 XY horses with disorders of sex development and/or infertility, 5 Przewalski's horses and 2 kulans. This established baseline copy number for these genes in horses. The TSPY gene showed the highest copy number and was the most copy number variable between individuals and breeds. SRY was a single-copy gene in most horses but had 2-3 copies in some indigenous breeds. Since SRY is flanked by 2 copies of RBMY, their copy number variations were interrelated and may lead to SRY-negative XY disorders of sex development. The Przewalski's horse and kulan had 1 copy of SRY and RBMY. TSPY and ETSTY2 showed significant copy number variations between cryptorchid and normal males (P < 0.05). No significant copy number variations were observed in subfertile/infertile males. Notably, copy number of TSPY and ETSTY5 differed between successive male generations and between cloned horses, indicating germline and somatic mechanisms for copy number variations. We observed no correlation between male-specific Y chromosome gene copy number variations and male-specific Y chromosome haplotypes. We conclude that the ampliconic male-specific Y chromosome reference assembly has deficiencies and further studies with an improved male-specific Y chromosome assembly are needed to determine selective constraints over horse male-specific Y chromosome gene copy number and their relation to stallion reproduction and male biology.

Y Chromosome Haplotypes Enlighten Origin, Influence, and Breeding History of North African Barb Horses

In horses, demographic patterns are complex due to historical migrations and eventful breeding histories. Particularly puzzling is the ancestry of the North African horse, a founding horse breed, shaped by numerous influences throughout history. A genetic marker particularly suitable to investigate the paternal demographic history of populations is the non-recombining male-specific region of the Y chromosome (MSY). Using a recently established horse MSY haplotype (HT) topology and KASP™ genotyping, we illustrate MSY HT spectra of 119 Barb and Arab-Barb males, collected from the Maghreb region and European subpopulations. All detected HTs belonged to the Crown haplogroup, and the broad MSY spectrum reflects the wide variety of influential stallions throughout the breed’s history. Distinct HTs and regional disparities were characterized and a remarkable number of early introduced lineages were observed. The data indicate recent refinement with Thoroughbred and Arabian patrilines, while 57% of the dataset supports historical migrations between North Africa and the Iberian Peninsula. In the Barb horse, we detected the HT linked to Godolphin Arabian, one of the Thoroughbred founders. Hence, we shed new light on the question of the ancestry of one Thoroughbred patriline. We show the strength of the horse Y chromosome as a genealogical tool, enlighten recent paternal history of North African horses, and set the foundation for future studies on the breed and the formation of conservation breeding programs.

Geographical contrasts of Y-chromosomal haplogroups from wild and domestic goats reveal ancient migrations and recent introgressions

By their paternal transmission, Y-chromosomal haplotypes are sensitive markers of population history and male-mediated introgression. Previous studies identified biallelic single-nucleotide variants in the SRY, ZFY, DDX3Y genes, which in domestic goats identified four major Y-chromosomal haplotypes Y1A, Y1B, Y2A and Y2B with a marked geographic partitioning. Here, we extracted goat Y-chromosomal variants from whole-genome sequences of 386 domestic goats (75 breeds) and 7 wild goat species, which were generated by the VarGoats goat genome project. Phylogenetic analyses indicated domestic haplogroups corresponding to Y1B, Y2A and Y2B, respectively, whereas Y1A is split into Y1AA and Y1AB. All five haplogroups were detected in 26 ancient DNA samples from southeast Europe or Asia. Haplotypes from present-day bezoars are not shared with domestic goats and are attached to deep nodes of the trees and networks. Haplogroup distributions for 186 domestic breeds indicate ancient paternal population bottlenecks and expansions during the migrations into northern Europe, eastern and southern Asia and Africa south of the Sahara. In addition, sharing of haplogroups indicates male-mediated introgressions, most notably an early gene flow from Asian goats into Madagascar and the crossbreeding that in the 19^th century resulted in the popular Boer and Anglo-Nubian breeds. More recent introgressions are those from European goats into the native Korean goat population and from Boer goat into Uganda, Kenya, Tanzania, Malawi and Zimbabwe. This study illustrates the power of the Y-chromosomal variants for reconstructing the history of domestic species with a wide geographic range.

From the Eurasian Steppes to the Roman Circuses: A Review of Early Development of Horse Breeding and Management

Simple Summary

Horses were domesticated later than any other major livestock species. Their role in shaping ancient civilizations cannot be overestimated. As a primary means of transportation, an essential asset in warfare, and later one of the key elements of circus entertainment, horses quickly became luxurious goods. Vast amounts of money were invested in the horse industry resulted resulting in the rapid development of horse breeding and husbandry. This review examines paleogenetic, archeological, and classical studies on managing horses in antiquity. Many ancient approaches and practices in horse management are still relevant today and some of them, now abandoned, are worth re-examination.

Abstract

The domestication of the horse began about 5500 years ago in the Eurasian steppes. In the following millennia horses spread across the ancient world, and their role in transportation and warfare affected every ancient culture. Ownership of horses became an indicator of wealth and social status. The importance of horses led to a growing interest in their breeding and management. Many phenotypic traits, such as height, behavior, and speed potential, have been proven to be a subject of selection; however, the details of ancient breeding practices remain mostly unknown. From the fourth millennium BP, through the Iron Age, many literature sources thoroughly describe horse training systems, as well as various aspects of husbandry, many of which are still in use today. The striking resemblance of ancient and modern equine practices leaves us wondering how much was accomplished through four thousand years of horse breeding.

Current genetic conservation of Chinese indigenous horses revealed with Y-chromosomal and mitochondrial DNA polymorphisms

To investigate the genetic diversity of Chinese indigenous horses and determine the genetic status of extant horse breeds, novel Y chromosomal microsatellite markers and known Y chromosomal SNPs and mtDNA loop sequences, were employed to study the genetic diversity levels of 13 Chinese indigenous horse populations and four introduced breeds. Sixteen Y-chromosomal microsatellite markers, including seven newly identified loci, were used in the genotyping. The results showed that 4 out of the 16 loci were highly polymorphic in Chinese indigenous horse populations, in which the polymorphisms of 3 loci, ECAYP12, ECAYP13, and ECAYCAU3, were first reported in the present study. The polymorphic Y chromosomal microsatellite markers result in 19 haplotypes in the studied horses and formed 24 paternal lines when merged with the 14 Y chromosomal SNPs reported previously. The haplotypes CHT18 and SS24 harboring AMELY gene mutation were the ancestral haplotypes, and other haplotypes were derived from them by one or more mutation steps. The horse populations in mountainous and remote areas of southwestern China have the most ancient paternal lines, which suggests that ancient paternal lines preserved in local populations attributed to less human interventions. Our results also showed that the northern local breeds had higher mtDNA diversity than the southern ones in China. The frequency of haplogroup B, F, and G of mtDNA in Chinese indigenous horses has declined in recent years, and some breeds are in endangered status mainly due to small population sizes. Urgent actions should be taken to conserve the genetic diversity of the indigenous horse populations, especially the rare paternal lines. Our findings help to elucidate the genetic diversity and evolutionary history of Chinese domestic horses, which will facilitate the conservation of the indigenous horses in the future.

Donkey genomes provide new insights into domestication and selection for coat color

Current knowledge about the evolutionary history of donkeys is still incomplete due to the lack of archeological and whole-genome diversity data. To fill this gap, we have de novo assembled a chromosome-level reference genome of one male Dezhou donkey and analyzed the genomes of 126 domestic donkeys and seven wild asses. Population genomics analyses indicate that donkeys were domesticated in Africa and conclusively show reduced levels of Y chromosome variability and discordant paternal and maternal histories, possibly reflecting the consequences of reproductive management. We also investigate the genetic basis of coat color. While wild asses show diluted gray pigmentation (Dun phenotype), domestic donkeys display non-diluted black or chestnut coat colors (non-Dun) that were probably established during domestication. Here, we show that the non-Dun phenotype is caused by a 1 bp deletion downstream of the TBX3 gene, which decreases the expression of this gene and its inhibitory effect on pigment deposition.

A new donkey reference genome and comparisons with wild asses yields insights into the evolutionary history of donkey domestication and identifies a genetic variant that results in the non-Dun coat colours of domestic donkeys.

The Evolutionary and Historical Foundation of the Modern Horse: Lessons from Ancient Genomics

The domestication of the horse some 5,500 years ago followed those of dogs, sheep, goats, cattle, and pigs by ∼2,500-10,000 years. By providing fast transportation and transforming warfare, the horse had an impact on human history with no equivalent in the animal kingdom. Even though the equine sport industry has considerable economic value today, the evolutionary history underlying the emergence of the modern domestic horse remains contentious. In the last decade, novel sequencing technologies have revolutionized our capacity to sequence the complete genome of organisms, including from archaeological remains. Applied to horses, these technologies have provided unprecedented levels of information and have considerably changed models of horse domestication. This review illustrates how ancient DNA, especially ancient genomes, has inspired researchers to rethink the process by which horses were first domesticated and then diversified into a variety of breeds showing a range of traits that are useful to humans.

Modern Northern Domestic Horses Carry Mitochondrial DNA Similar to Przewalski’s Horse

Several recent studies have suggested past gene flow between the Przewalski’s horse and modern domestic horse and questioned the wild origin of the Przewalski’s horse. Mitochondrial DNA has placed representatives of the Przewalski’s horse into three among the eighteen haplogroups detected from the modern horse. Of these, two haplogroups have so far been found exclusively in the Przewalski’s horse, while the one shared with the domestic horse includes captive individuals that have uncertain pedigrees. We recently found five domestic horse individuals of North European horse breeds to carry a mitochondrial haplogroup that was previously confined only to the Przewalski’s horse. These individuals were sequenced for 6039 bp of mitochondrial DNA and used, together with domestic and Przewalski’s horse sequences presenting all horse haplogroups, to examine the phylogenetic relationships and to date the divergence time between Przewalski’s and domestic horse clusters within this haplogroup. The divergence was dated to have likely occurred about 13,300–11,400 years ago, which coincides with the time of the Younger Dryas.

A Genetic Window on Sardinian Native Horse Breeds through Uniparental Molecular Systems

Simple Summary

The horse is a mammalian species showing a high variation among maternal lineages but a limited variability in the paternal inheritance. The female phylogenetic history is commonly investigated by analyzing the maternally transmitted mitochondrial DNA (mtDNA), while the male perspective is provided by the paternally inherited portion of the Y chromosome (NRY). Here we explored the variation of both non-recombining genetic systems in three horse breeds present in Sardinia: Giara, Sarcidano, and Sardinian Anglo-Arab. The analysis of 34 stallions revealed three differentially distributed NRY types: (i) the first and most ancestral one is typical of Sarcidano; (ii) the second is well represented in Giara and seems to derive from Neapolitan/Oriental stallions; (iii) the third confirms the Thoroughbred influence in the Sardinian Anglo-Arab breed. By extending the analysis to 178 mtDNAs, we observed a common maternal origin for Giara and Sarcidano. Contrarily, the outlier behavior of the Sardinian Anglo-Arab is due to its higher mitochondrial variability, testifying for multiple maternal lineages in its current population. Our preliminary findings highlight the importance of a parallel molecular screening of NRYs and mtDNAs to reconstruct both paternal and maternal phylogenetic histories and to fully evaluate the extent of autochthonous genetic resources in the island.

Abstract

Sardinia, an island located to the west of Italy in the Mediterranean Sea, boasts three native horse breeds: Giara, Sarcidano, and Sardinian Anglo-Arab. Here, we have investigated for the first time three loci of the non-recombining region of the Y chromosome (NRY) in 34 stallions from these breeds and performed a phylogenetic analysis of the maternal relationships among 178 previously published mitochondrial control regions. We found that the current NRY diversity of Sardinian horse breeds is linked to three haplotypes (HT), all identified within Sarcidano. Each breed showed a typical HT: HT1 (ancestral) was the most represented in Sarcidano, HT2 (Neapolitan/Oriental wave) in Giara, and HT3 (Thoroughbred wave) in Sardinian Anglo-Arab. The specificity of each haplotype suggests the influence of independent breeding strategies and the effect of genetic drift in each Sardinian population. The female counterpart, extended to 178 horses, showed a low genetic variability and a common maternal origin for Giara and Sarcidano. The higher variability of the Sardinian Anglo-Arab indicates multiple mare lineages in its current population. Further genetic analyses will be crucial to understand the paternal history of male horses, preserve the endangered mares’ and stallions’ lineages, and improve the enhancement of autochthonous genetic resources on this island.

Ancient DNA shows domestic horses were introduced in the southern Caucasus and Anatolia during the Bronze Age

Despite the important roles that horses have played in human history, particularly in the spread of languages and cultures, and correspondingly intensive research on this topic, the origin of domestic horses remains elusive. Several domestication centers have been hypothesized, but most of these have been invalidated through recent paleogenetic studies. Anatolia is a region with an extended history of horse exploitation that has been considered a candidate for the origins of domestic horses but has never been subject to detailed investigation. Our paleogenetic study of pre- and protohistoric horses in Anatolia and the Caucasus, based on a diachronic sample from the early Neolithic to the Iron Age (~8000 to ~1000 BCE) that encompasses the presumed transition from wild to domestic horses (4000 to 3000 BCE), shows the rapid and large-scale introduction of domestic horses at the end of the third millennium BCE. Thus, our results argue strongly against autochthonous independent domestication of horses in Anatolia.

Ancient Genomes Reveal Unexpected Horse Domestication and Management Dynamics

The horse was essential to past human societies but became a recreational animal during the twentieth century as the world became increasingly mechanized. As the author reviews here, recent studies of ancient genomes have revisited the understanding of horse domestication, from the very early stages to the most modern developments. They have uncovered several extinct lineages roaming the far ends of Eurasia some 4000 years ago. They have shown that the domestic horse has been significantly reshaped during the last millennium and experienced a sharp decline in genetic diversity within the last two centuries. At a time when no truly wild horses exist any longer, this calls for enhanced conservation in all endangered populations. These include the Przewalski's horse native to Mongolia, and the many local breeds side-lined by the modern agenda, but yet representing the living heritage of over five millennia of horse breeding.

Ten years of the horse reference genome: insights into equine biology, domestication and population dynamics in the post-genome era

The horse reference genome from the Thoroughbred mare Twilight has been available for a decade and, together with advances in genomics technologies, has led to unparalleled developments in equine genomics. At the core of this progress is the continuing improvement of the quality, contiguity and completeness of the reference genome, and its functional annotation. Recent achievements include the release of the next version of the reference genome (EquCab3.0) and generation of a reference sequence for the Y chromosome. Horse satellite‐free centromeres provide unique models for mammalian centromere research. Despite extremely low genetic diversity of the Y chromosome, it has been possible to trace patrilines of breeds and pedigrees and show that Y variation was lost in the past approximately 2300 years owing to selective breeding. The high‐quality reference genome has led to the development of three different SNP arrays and WGSs of almost 2000 modern individual horses. The collection of WGS of hundreds of ancient horses is unique and not available for any other domestic species. These tools and resources have led to global population studies dissecting the natural history of the species and genetic makeup and ancestry of modern breeds. Most importantly, the available tools and resources, together with the discovery of functional elements, are dissecting molecular causes of a growing number of Mendelian and complex traits. The improved understanding of molecular underpinnings of various traits continues to benefit the health and performance of the horse whereas also serving as a model for complex disease across species.

Population Genetic Analysis of the Estonian Native Horse Suggests Diverse and Distinct Genetics, Ancient Origin and Contribution from Unique Patrilines

The Estonian Native Horse (ENH) is a medium-size pony found mainly in the western islands of Estonia and is well-adapted to the harsh northern climate and poor pastures. The ancestry of the ENH is debated, including alleged claims about direct descendance from the extinct Tarpan. Here we conducted a detailed analysis of the genetic makeup and relationships of the ENH based on the genotypes of 15 autosomal short tandem repeats (STRs), 18 Y chromosomal single nucleotide polymorphisms (SNPs), mitochondrial D-loop sequence and lateral gait allele in DMRT3. The study encompassed 2890 horses of 61 breeds, including 33 ENHs. We show that the expected and observed genetic diversities of the ENH are among the highest within 52 global breeds, and the highest among 8 related Northern European ponies. The genetically closest breeds to the ENH are the Finn Horse, and the geographically more distant primitive Hucul and Konik. ENH matrilines are diverse and relate to draught and Pontic-Caspian breeds. ENH patrilines relate to draught breeds, and to a unique haplogroup not described before. None of the 33 ENHs carried the "gait" mutation, but the mutation was found in 2 Huculs. The study demonstrates that the ENH is a genetically distinct and diverse breed of ancient origin with no notable pressure of selective breeding.

Genetic variability and history of a native Finnish horse breed

Background

The Finnhorse was established as a breed more than 110 years ago by combining local Finnish landraces. Since its foundation, the breed has experienced both strong directional selection, especially for size and colour, and severe population bottlenecks that are connected with its initial foundation and subsequent changes in agricultural and forestry practices. Here, we used sequences of the mitochondrial control region and genomic single nucleotide polymorphisms (SNPs) to estimate the genetic diversity and differentiation of the four Finnhorse breeding sections: trotters, pony-sized horses, draught horses and riding horses. Furthermore, we estimated inbreeding and effective population sizes over time to infer the history of this breed.

Results

We found a high level of mitochondrial genetic variation and identified 16 of the 18 haplogroups described in present-day horses. Interestingly, one of these detected haplogroups was previously reported only in the Przewalski’s horse. Female effective population sizes were in the thousands, but declines were evident at the times when the breed and its breeding sections were founded. By contrast, nuclear variation and effective population sizes were small (approximately 50). Nevertheless, inbreeding in Finnhorses was lower than in many other horse breeds. Based on nuclear SNP data, genetic differentiation among the four breeding sections was strongest between the draught horses and the three other sections (F_ST = 0.007–0.018), whereas based on mitochondrial DNA data, it was strongest between the trotters and the pony-sized and riding horses (Φ_ST = 0.054–0.068).

Conclusions

The existence of a Przewalski’s horse haplogroup in the Finnhorse provides new insights into the domestication of the horse, and this finding supports previous suggestions of a close relationship between the Finnhorse and eastern primitive breeds. The high level of mitochondrial DNA variation in the Finnhorse supports its domestication from a large number of mares but also reflects that its founding depended on many local landraces. Although inbreeding in Finnhorses was lower than in many other horse breeds, the small nuclear effective population sizes of each of its breeding sections can be considered as a warning sign, which warrants changes in breeding practices.

Electronic supplementary material

The online version of this article (10.1186/s12711-019-0480-8) contains supplementary material, which is available to authorized users.

Tracking Five Millennia of Horse Management with Extensive Ancient Genome Time Series

Horse domestication revolutionized warfare and accelerated travel, trade, and the geographic expansion of languages. Here, we present the largest DNA time series for a non-human organism to date, including genome-scale data from 149 ancient animals and 129 ancient genomes (≥1-fold coverage), 87 of which are new. This extensive dataset allows us to assess the modern legacy of past equestrian civilizations. We find that two extinct horse lineages existed during early domestication, one at the far western (Iberia) and the other at the far eastern range (Siberia) of Eurasia. None of these contributed significantly to modern diversity. We show that the influence of Persian-related horse lineages increased following the Islamic conquests in Europe and Asia. Multiple alleles associated with elite-racing, including at the MSTN "speed gene," only rose in popularity within the last millennium. Finally, the development of modern breeding impacted genetic diversity more dramatically than the previous millennia of human management.

The horse Y chromosome as an informative marker for tracing sire lines

Analysis of the Y chromosome is the best-established way to reconstruct paternal family history in humans. Here, we applied fine-scaled Y-chromosomal haplotyping in horses with biallelic markers and demonstrate the potential of our approach to address the ancestry of sire lines. We de novo assembled a draft reference of the male-specific region of the Y chromosome from Illumina short reads and then screened 5.8 million basepairs for variants in 130 specimens from intensively selected and rural breeds and nine Przewalski's horses. Among domestic horses we confirmed the predominance of a young'crown haplogroup' in Central European and North American breeds. Within the crown, we distinguished 58 haplotypes based on 211 variants, forming three major haplogroups. In addition to two previously characterised haplogroups, one observed in Arabian/Coldblooded and the other in Turkoman/Thoroughbred horses, we uncovered a third haplogroup containing Iberian lines and a North African Barb Horse. In a genealogical showcase, we distinguished the patrilines of the three English Thoroughbred founder stallions and resolved a historic controversy over the parentage of the horse 'Galopin', born in 1872. We observed two nearly instantaneous radiations in the history of Central and Northern European Y-chromosomal lineages that both occurred after domestication 5,500 years ago.

Targeted PCR Amplification and Multiplex Sequencing of Ancient DNA for SNP Analysis

The analysis of single-nucleotide polymorphisms (SNPs) has proven to be advantageous for addressing variation within samples of highly degraded or low-quality DNA samples. This is because only short fragments need to be amplified to analyze SNPs, and this can be achieved by multiplex PCR. Here, we present a sensitive method for the targeted sequencing of SNP loci that requires only small amounts of template DNA. The approach combines multiplex amplification of very short fragments covering SNP positions followed by sample barcoding and next-generation sequencing. This method allows generation of data from large sample sets of poorly preserved specimens, such as fossil remains, forensic samples, and museum specimens. The approach is cost-effective, rapid, and applicable to forensics, population genetics, and phylogenetic research questions.