Identification of an ancestral haplotype in the mitochondrial phylogeny of the ovine haplogroup B

Population Genomic History of the Endangered Anatolian and Cyprian Mouflons in Relation to Worldwide Wild, Feral, and Domestic Sheep Lineages

Once widespread in their homelands, the Anatolian mouflon (Ovis gmelini anatolica) and the Cyprian mouflon (Ovis gmelini ophion) were driven to near extinction during the 20th century and are currently listed as endangered populations by the International Union for Conservation of Nature. While the exact origins of these lineages remain unclear, they have been suggested to be close relatives of domestic sheep or remnants of proto-domestic sheep. Here, we study whole genome sequences of n = 5 Anatolian mouflons and n = 10 Cyprian mouflons in terms of population history and diversity, comparing them with eight other extant sheep lineages. We find reciprocal genetic affinity between Anatolian and Cyprian mouflons and domestic sheep, higher than all other studied wild sheep genomes, including the Iranian mouflon (O. gmelini). Studying diversity indices, we detect a considerable load of short runs of homozygosity blocks (<2 Mb) in both Anatolian and Cyprian mouflons, reflecting small effective population size (Ne). Meanwhile, Ne and mutation load estimates are lower in Cyprian compared with Anatolian mouflons, suggesting the purging of recessive deleterious variants in Cyprian sheep under a small long-term Ne, possibly attributable to founder effects, island isolation, introgression from domestic lineages, or differences in their bottleneck dynamics. Expanding our analyses to worldwide wild and feral Ovis genomes, we observe varying viability metrics among different lineages and a limited consistency between viability metrics and International Union for Conservation of Nature conservation status. Factors such as recent inbreeding, introgression, and unique population dynamics may have contributed to the observed disparities.

Phenotype transition from wild mouflon to domestic sheep

The domestication of animals started around 12,000 years ago in the Near East region. This "endless process" is characterized by the gradual accumulation of changes that progressively marked the genetic, phenotypic and physiological differences between wild and domesticated species. The main distinctive phenotypic characteristics are not all directly attributable to the human-mediated selection of more productive traits. In the last decades, two main hypotheses have been proposed to clarify the emergence of such a set of phenotypic traits across a variety of domestic species. The first hypothesis relates the phenotype of the domesticated species to an altered thyroid hormone-based signaling, whereas the second one relates it to changes in the neural crest cells induced by selection of animals for tameness. These two hypotheses are not necessarily mutually exclusive since they may have contributed differently to the process over time and space. The adaptation model induced by domestication can be adopted to clarify some aspects (that are still controversial and debated) of the long-term evolutionary process leading from the wild Neolithic mouflon to the current domestic sheep. Indeed, sheep are among the earliest animals to have been domesticated by humans, around 12,000 years ago, and since then, they have represented a crucial resource in human history. The aim of this review is to shed light on the molecular mechanisms and the specific genomic variants that underlie the phenotypic variability between sheep and mouflon. In this regard, we carried out a critical review of the most recent studies on the molecular mechanisms that are most accredited to be responsible for coat color and phenotype, tail size and presence of horns. We also highlight that, in such a complicate context, sheep/mouflon hybrids represent a powerful and innovative model for studying the mechanism by which the phenotypic traits related to the phenotypic responses to domestication are inherited. Knowledge of these mechanisms could have a significant impact on the selection of more productive breeds. In fact, as in a journey back in time of animal domestication, the genetic traits of today's domestic species are being progressively and deliberately shaped according to human needs, in a direction opposite to that followed during domestication.

Genetic diversity and relationship among Indonesian local sheep breeds on Java Island based on mitochondrial cytochrome b gene sequences

BACKGROUND

The cytochrome b (Cyt b) gene is one of the most studied mitochondrial DNA (mtDNA) genes to determine sheep's genetic profile. This study aimed to determine the genetic diversity and relationships of several Indonesian local sheep populations on Java Island, Indonesia, based on the mtDNA Cyt b gene sequences. Blood samples were collected from forty-one individual sheep in seven populations of Indonesia local sheep breeds on Java Island (Priangan = 6, Garut = 6, Batur = 7, Wonosobo = 5, Javanese Thin-Tailed/JTT = 7, Javanese Fat-Tailed/JFT = 5, and Sapudi = 5). DNA extraction was performed on blood samples, and the mtDNA Cyt b gene was amplified using specific primers (Alek-CBF: 5'-CAACCCCACCACTTACAA-3' and Alek-CBR: 5'-CCTTGAGTCTTAGGGAGGTT-3'). The polymerase chain reaction (PCR) products were then sequenced, and data were analyzed using the MEGA version 7.0, DNA SP version 6.0, and NTSYS-pc version 2.11 software.

RESULTS

A total of 1140 bp complete mtDNA Cyt b gene sequences in this study obtained 1134 monomorphic sites (I), six polymorphic sites (V), one segregation site (S), and five parsimony informative sites (P) with a nucleotide diversity (Pi), the average number of nucleotide differences (K), and sequence conservation (SC) were 0.00119, 1.35610, and 0.9947, respectively. There were six haplotypes consisting of two unique haplotypes and four shared haplotypes with a haplotype diversity (Hd) of 0.5415. The genetic distance within and between populations ranged from 0.0000 to 0.0016 and 0.0000 to 0.0020, respectively. Wonosobo, JFT, and Sapudi sheep have the closest relationship, and then these three breeds were close to JTT sheep, followed by Batur, Priangan, and Garut sheep. Two haplogroups have been found based on the Ovine haplogroup clustering. All Wonosobo, JTT, JFT, Sapudi sheep, and most Batur sheep were clustered into haplogroup B. In contrast, Garut sheep were mostly clustered into haplogroup A, while Priangan sheep were clustered into both haplogroups with the same percentage.

CONCLUSION

Seven Indonesian local sheep breeds on Java Island have a close relationship clustered into two haplogroups, namely haplogroups A and B. Most Indonesian local sheep breeds on Java Island in this study were clustered into haplogroup B, except for Garut and Priangan sheep.

Sheep Post-Domestication Expansion in the Context of Mitochondrial and Y Chromosome Haplogroups and Haplotypes

Mitochondrial DNA and nonrecombinant parts of Y-chromosome DNA are a great tool for looking at a species’ past. They are inherited for generations almost unaffected because they do not participate in recombination; thus, the time of occurrence of each mutation can be estimated based on the average mutation rate. Thanks to this, male and female haplogroups guide confirming events in the distant past (potential centers of domestication, settlement of areas, trade connections) as well as in modern breeding (crossbreeding, confirmation of paternity). This research focuses mainly on the development of domestic sheep and its post-domestication expansion, which has occurred through human trade from one continent to another. So far, five mitochondrial and five Y-chromosome haplogroups and dozens of their haplotypes have been detected in domestic sheep through studies worldwide. Mitochondrial DNA variability is more or less correlated with distance from the domestication center, but variability on the recombinant region of the Y chromosome is not. According to available data, central China shows the highest variability of male haplogroups and haplotypes.

Spatial genetic structure and Ovis haplogroup as a tool for an adaptive conservation management of the endangered Cyprus mouflon

The mouflon (Ovis gmelini ophion) is the largest wild terrestrial mammal of Cyprus. Regarded as the local flagship species, its population range is limited to the mountainous Paphos Forest and adjacent areas including part of Troodos National Forest Park (> 700 Km²). This species, protected by both national and international legislation, is classified as Endangered by the IUCN, with livestock intrusion, poaching and habitat loss as the main threatening factors. We determined the spatial genetic structure by investigating sexes separately and shed further light on the Cyprus mouflon placement among Ovis haplogroups (HGs) to enforce its protection within an adaptive conservation framework. We genotyped 108 samples collected across the entire species' range at both14 loci of the microsatellite DNA and the mitochondrial DNA Control Region (CR). Microsatellite genotyping indicated that the wild population retained low genetic variability, which, however, was not associated with a level of inbreeding raising particular concern (F_IS = 0.12). An overall weak spatial genetic structure was disclosed, consistently with the limited extension of the mouflon range, the lack of significant physical barriers to dispersal and the intense gene flow mostly occurring along a northeast-southwest axis across the forest. Nevertheless, evidences of structure were found for females in compliance with their philopatric behaviour. The disclosure of unique features compared to Mediterranean and Near East conspecifics, such as the occurrence of a six-fold 76 bp-long repeated motif in the Cyprus mouflon CR, along with the outcome of a phylogenetic reconstruction (based on a far higher number of Ovis GenBank records and Cyprus haplotypes than in previous studies) inspired the proposal of a new haplogroup (HGC2) which included the Anatolian mouflon (O. g. anatolica, former HGX) as sister taxon. While both high habitat heterogeneity and low human disturbance were the main drivers in determining the overall spatial structure, future conservation efforts to preserve this valuable genetic resource should focus on avoiding possible introgressive hybridisation with co-grazing livestock to the edge of its range.

Genetic characterization and implications for conservation of the last autochthonous Mouflon population in Europe

Population genetic studies provide accurate information on population structure, connectivity, and hybridization. These are key elements to identify units for conservation and define wildlife management strategies aimed to maintain and restore biodiversity. The Mediterranean island of Sardinia hosts one of the last autochthonous mouflon populations, descending from the wild Neolithic ancestor. The first mouflon arrived in Sardinia ~ 7000 years ago and thrived across the island until the twentieth century, when anthropogenic factors led to population fragmentation. We analysed the three main allopatric Sardinian mouflon sub-populations, namely: the native sub-populations of Montes Forest and Mount Tonneri, and the reintroduced sub-population of Mount Lerno. We investigated the spatial genetic structure of the Sardinian mouflon based on the parallel analysis of 14 highly polymorphic microsatellite loci and mitochondrial D-loop sequences. The Montes Forest sub-population was found to harbour the ancestral haplotype in the phylogeny of European mouflon. We detected high levels of relatedness in all the sub-populations and a mitochondrial signature of hybridization between the Mount Lerno sub-population and domestic sheep. Our findings provide useful insights to protect such an invaluable genetic heritage from the risk of genetic depletion by promoting controlled inter-population exchange and drawing informed repopulation plans sourcing from genetically pure mouflon stocks.

The genetic profiles and maternal origin of local sheep breeds on Java Island (Indonesia) based on complete mitochondrial DNA D-loop sequences

Background and Aim:

Java Island is one of the islands in Indonesia which has local sheep breeds with specific characteristics and native development geography in certain regions. This study aimed to determine the genetic profiles and maternal origin of six local sheep breeds on Java Island.

Materials and Methods:

This study was conducted by identifying the profiles of complete mitochondrial DNA (mtDNA) displacement loop (D-loop) region sequences on a total of 22 individual in six local sheep breeds on Java Island, including Javanese thin-tailed (JTT), Javanese Fat-Tailed (JFT), Batur (BTR), Wonosobo (WSB), Garut (GRT), and Priangan (PRG) sheep. The D-loop region was amplified using specific primers, and the polymerase chain reaction (PCR) was performed. The PCR products were purified and sequenced.

Results:

The mtDNA D-loop analysis identified 21 haplotypes in the analyzed 22 animals with 123 polymorphic sites (V) consisting of 60 singleton variable sites (S) and 63 parsimony informative sites (P). Within all breeds tested, the haplotype diversity, the average number of pairwise differences (K), and nucleotide diversity (Pi) were 0.99567, 25.36364, and 0.02153, respectively. The genetic distance (D) within groups and between groups was 0.001-0.006 and 0.004-0.036, respectively. The phylogeny resulted in the presence of two haplogroups (Hap), which are 5 Hap A and 16 Hap B. All JTT, JFT, BTR, and WSB breeds were in the same cluster in Hap B, whereas GRT and PRG breeds were in clusters in both Hap A and Hap B.

Conclusion:

The high genetic diversity in six local sheep breeds on Java Island suggests that they originated from different genetic sources. JTT sheep have closer genetic relationships to JFT, BTR, and WSB sheep, and they are close to European sheep, whereas GRT sheep have closer genetic relationships to PRG sheep. Both are closer to Asian sheep than to European sheep.

Identification of Ancestry Informative Marker (AIM) Panels to Assess Hybridisation between Feral and Domestic Sheep

Simple Summary

Once present in the entirety of Europe, mouflon (wild sheep) became extinct due to intense hunting, but remnant populations survived and became feral on the Mediterranean islands of Corsica and Sardinia. Although now protected by regional laws, Sardinian mouflon is threatened by crossbreeding with domestic sheep causing genetic hybridisation. The spread of domestic genes can be detrimental for wild populations as it dilutes the genetic features that characterise them. This work aimed to identify diagnostic tools that could be applied to monitor the level of hybridisation between mouflon and domestic sheep. Tens of thousands of genetic markers known as single nucleotide polymorphisms (SNPs) were screened and we identified the smallest number of SNPs necessary to discriminate between pure mouflon and sheep. We produced four SNP panels of different sizes which were able to assess the hybridisation level of a mouflon and we verified that the SNP panels efficacy is independent of the domestic sheep breed involved in the hybrid. The implementation of these results into actual diagnostic tools will help the conservation of this unique and irreplaceable mouflon population, and the methodology applied can easily be transferred to other case studies of interest.

Abstract

Hybridisation of wild populations with their domestic counterparts can lead to the loss of wildtype genetic integrity, outbreeding depression, and loss of adaptive features. The Mediterranean island of Sardinia hosts one of the last extant autochthonous European mouflon (Ovis aries musimon) populations. Although conservation policies, including reintroduction plans, have been enforced to preserve Sardinian mouflon, crossbreeding with domestic sheep has been documented. We identified panels of single nucleotide polymorphisms (SNPs) that could act as ancestry informative markers able to assess admixture in feral x domestic sheep hybrids. The medium-density SNP array genotyping data of Sardinian mouflon and domestic sheep (O. aries aries) showing pure ancestry were used as references. We applied a two-step selection algorithm to this data consisting of preselection via Principal Component Analysis followed by a supervised machine learning classification method based on random forest to develop SNP panels of various sizes. We generated ancestry informative marker (AIM) panels and tested their ability to assess admixture in mouflon x domestic sheep hybrids both in simulated and real populations of known ancestry proportions. All the AIM panels recorded high correlations with the ancestry proportion computed using the full medium-density SNP array. The AIM panels proposed here may be used by conservation practitioners as diagnostic tools to exclude hybrids from reintroduction plans and improve conservation strategies for mouflon populations.