The origin of Mosuo people as revealed by mtDNA and Y chromosome variation

The Mosuo, living in the Lugu Lake area in northwest Yunnan Province, China, is the only matriarchal population in China. The Mosuo was officially identified as Naxi nationality although its relationship with Naxi remains controversial. We studied the genetic relationship between the Mosuo and five other ethnic groups currently residing in northwest Yunnan, i.e. Naxi, Tibetan, Bai, Yi and Pumi, by typing the genetic variations in mtDNA HVS1 and 21 Y chromosome markers (13 SNPs & 8 STR markers). We showed that the maternal lineages of the Mosuo bear the strongest resemblance with those found in Naxi while its paternal lineages are more similar to those that are prevalent in Yunnan Tibetan. The marked difference between paternal and maternal lineages may be attributable to the genetic history, matriarchal structure, and visiting marriage.     

The origin of Mosuo people as revealed by mtDNA and Y chromosome variation

The Mosuo, living in the Lugu Lake area in northwest Yunnan Province, China, is the only matriarchal population in China. The Mosuo was officially identified as Naxi nationality although its relationship with Naxi remains controversial. We studied the genetic relationship between the Mosuo and five other ethnic groups currently residing in northwest Yunnan, i.e. Naxi, Tibetan, Bai, Yi and Pumi, by typing the genetic variations in mtDNA HVS1 and 21 Y chromosome markers (13 SNPs & 8 STR markers). We showed that the maternal lineages of the Mosuo bear the strongest resemblance with those found in Naxi while its paternal lineages are more similar to those that are prevalent in Yunnan Tibetan. The marked difference between paternal and maternal lineages may be attributable to the genetic history, matriarchal structure, and visiting marriage.     

On the edge of Bantu expansions: mtDNA, Y chromosome and lactase persistence genetic variation in southwestern Angola

Background

Ariids or sea catfishes are one of the two otophysan fish families (out of about 67 families in four orders) that inhabit mainly marine and brackish waters (although some species occur strictly in fresh waters). The group includes over 150 species placed in ~29 genera and two subfamilies (Galeichthyinae and Ariinae). Despite their global distribution, ariids are largely restricted to the continental shelves due in part to their specialized reproductive behavior (i.e., oral incubation). Thus, among marine fishes, ariids offer an excellent opportunity for inferring historical biogeographic scenarios. Phylogenetic hypotheses available for ariids have focused on restricted geographic areas and comprehensive phylogenies are still missing. This study inferred phylogenetic hypotheses for 123 ariid species in 28 genera from different biogeographic provinces using both mitochondrial and nuclear sequences (up to ~4 kb).

Results

While the topologies obtained support the monophyly of basal groups, up to ten genera validated in previous morphological studies were incongruent with the molecular topologies. New World ariines were recovered as paraphyletic and Old World ariines were grouped into a well-supported clade that was further divided into subclades mainly restricted to major Gondwanan landmasses. A general area cladogram derived from the area cladograms of ariines and three other fish groups was largely congruent with the geological area cladogram of Gondwana. Nonetheless, molecular clock estimations provided variable results on the timing of ariine diversification (~105-41 mya).

Conclusion

This study provides the most comprehensive phylogeny of sea catfishes to date and highlights the need for re-assessment of their classification. While from a topological standpoint the evolutionary history of ariines is mostly congruent with vicariance associated with the sequence of events during Gondwanan fragmentation, ambiguous divergence time estimations hinders assessing the vicariant hypothesis on a temporal framework. Further examination of ariid fossils might provide the basis for more accurate inferences on the timing of ariine diversification.     

On the edge of Bantu expansions: mtDNA, Y chromosome and lactase persistence genetic variation in southwestern Angola

Background  

Current information about the expansion of Bantu-speaking peoples is hampered by the scarcity of genetic data from well identified populations from southern Africa. Here, we fill an important gap in the analysis of the western edge of the Bantu migrations by studying for the first time the patterns of Y-chromosome, mtDNA and lactase persistence genetic variation in four representative groups living around the Namib Desert in southwestern Angola (Ovimbundu, Ganguela, Nyaneka-Nkumbi and Kuvale). We assessed the differentiation between these populations and their levels of admixture with Khoe-San groups, and examined their relationship with other sub-Saharan populations. We further combined our dataset with previously published data on Y-chromosome and mtDNA variation to explore a general isolation with migration model and infer the demographic parameters underlying current genetic diversity in Bantu populations.     

Haplotypes of the Y chromosome in some populations of west Africa

One Y-specific DNA polymorphism (p49/Taql) was studied in a sample of 469 African males coming from twelve populations of sub-Saharan Africa. An high frequency (62.5%) of the Y-haplotype IV was observed in these populations, the most elevated percentage of this haplotype being observed in Mossis (from Burkina-Fasso). The “Arabic” haplotype V is present in these populations at a mean frequency of 8.7%. The “oriental” haplotype XI is present at a mean frequency of 11.3%, the most elevated percentage of this haplotype being observed in Songhaiis (from Niger). Laboratory of Pharmacogenetics     

Native South American genetic structure and prehistory inferred from hierarchical modeling of mtDNA

Genetic diversity in Native South Americans forms a complexpattern at both the continental and local levels. In comparingthe West to the East, there is more variation within groupsand smaller genetic distances between groups. From this pattern,researchers have proposed that there is more variation in theWest and that a larger, more genetically diverse, founding populationentered the West than the East. Here, we question this characterizationof South American genetic variation and its interpretation.Our concern arises because others have inferred regional variationfrom the mean variation within local populations without takinginto account the variation among local populations within thesame region. This failure produces a biased view of the actualvariation in the East. In this study, we analyze the mitochondrial DNA sequence betweenpositions 16040 and 16322 of the Cambridge reference sequence.Our sample represents a total of 886 people from 27 indigenouspopulations from South (22), Central (3), and North America(2). The basic unit of our analyses is nucleotide identity bydescent, which is easily modeled and proportional to nucleotidediversity. We use a forward modeling strategy to fit a seriesof nested models to identity by descent within and between allpairs of local populations. This method provides estimates ofidentity by descent at different levels of population hierarchywithout assuming homogeneity within populations, regions, orcontinents. Our main discovery is that Eastern South America harbors moregenetic variation than has been recognized. We find no evidencethat there is increased identity by descent in the East relativeto the total for South America. By contrast, we discovered thatpopulations in the Western region, as a group, harbor more identityby descent than has been previously recognized, despite thefact that average identity by descent within groups is lower.In this light, there is no need to postulate separate foundingpopulations for the East and the West because the variabilityin the East could serve as a source for the Western gene pools.     

Evolutionary history of the greater white-toothed shrew (Crocidura russula) inferred from analysis of mtDNA, Y, and X chromosome markers

We investigate the evolutionary history of the greater white-toothed shrew across its distribution in northern Africa and mainland Europe using sex-specific (mtDNA and Y chromosome) and biparental (X chromosome) markers. All three loci confirm a large divergence between eastern (Tunisia and Sardinia) and western (Morocco and mainland Europe) lineages, and application of a molecular clock to mtDNA divergence estimates indicates a more ancient separation (2.25 M yr ago) than described by some previous studies, supporting claims for taxonomic revision. Moroccan ancestry for the mainland European population is inconclusive from phylogenetic trees, but is supported by greater nucleotide diversity and a more ancient population expansion in Morocco than in Europe. Signatures of rapid population expansion in mtDNA, combined with low X and Y chromosome diversity, suggest a single colonization of mainland Europe by a small number of Moroccan shrews >38 K yr ago. This study illustrates that multilocus genetic analyses can facilitate the interpretation of species' evolutionary history but that phylogeographic inference using X and Y chromosomes is restricted by low levels of observed polymorphism.     

Global and New Caledonian patterns of population genetic variation in the deep-sea splendid alfonsino, Beryx splendens, inferred from mtDNA

Splendid alfonsino Beryx splendens is a commercial species in several countries, but is not currently exploited in New Caledonia. Information on species biology and genetics can influence the development of fisheries and assist in their management, but the genetic structuring and diversity of B. splendens populations remain largely unknown. To improve knowledge of genetic parameters, we used mitochondrial DNA sequences to conduct a comparative study of populations from throughout the world. Fragments of 815?bp of cytochrome b gene were sequenced and used to interpret the species history. We analyzed 204 individuals representing 14 geographical populations worldwide. A special focus was put on populations from New Caledonia. Analysis of variation between sequences, based on pairwise F statistics and AMOVA, demonstrated a population subdivision between the Atlantic and Indo-Pacific Oceans (Fst?=?0.11-0.32; P?相似文献   

Gene pool structure of Russian populations from the European part of Russia inferred from the data on Y chromosome haplogroups distribution

Population structure of Russian population from the European part of Russia was investigated by analyzing the distribution of 23 SNP makers of Y chromosome in Russian populations from Kaluga, Yaroslavl’, Vladimir, Nizhni Novgorod, Pskov, Tula, Belgorod, and Novgorod oblasts. In the populations studied a total of 14 Y-chromosome haplogroups (E, F*, I, J, K*, N3a, N2, P*, R1*, R1a1, C3, G, H, and A) were discovered, of which haplogroups R1a1, I, and N3a were the prevailing. Analysis of Φ statistics in the populations grouped in accordance to the dialect subdivision of the Russian language, showed the absence of statistically significant differences between Russian population groups. Analysis of the Y-chromosome markers distribution patterns among Russian population (10 population groups) in comparison with the population of Germany (11 population groups) and Poland (8 population groups) revealed statistically significant differences between the gene pools of Slavs (Russians and Poles) and Teutons (Germans).     

Gene pool structure of Russian populations from the European part of Russia inferred from the data on Y chromosome haplogroups distribution

Population structure of Russian population from the European part of Russia was investigated by analyzing the distribution of 23 SNP makers of Y chromosome in Russian populations from Kaluga oblast, Yaroslavl' oblast, Vladimir oblast, Nizhny Novgorod oblast, Pskov oblast, Tula oblast, Belgorod oblast, and Novgorod oblast. In the populations studied a total of 14 Y-chromosome haplogroups (E, F*, I, J, K*, N3a, N2, P*, R1*, R1a1, C3, H, and A) were discovered, of which haplogroups R1a1, I, and N3a were the prevailing. Analysis of Phi statistics in the populations grouped in accordance to the dialect subdivision of the Russian language, showed the absence of statistically significant differences between Russian population groups. Analysis of the Y-chromosome markers distribution patterns among Russian population (10 population groups) in comparison with the population of Germany (11 population groups) revealed statistically significant differences between the gene pools of Slavs (Russians and Poles) and Teutons (Germans).     

Contrasting patterns of Y chromosome variation in Ashkenazi Jewish and host non-Jewish European populations

The molecular basis of more than 25 genetic diseases has been described in Ashkenazi Jewish populations. Most of these diseases are characterized by one or two major founder mutations that are present in the Ashkenazi population at elevated frequencies. One explanation for this preponderance of recessive diseases is accentuated genetic drift resulting from a series of dispersals to and within Europe, endogamy, and/or recent rapid population growth. However, a clear picture of the manner in which neutral genetic variation has been affected by such a demographic history has not yet emerged. We have examined a set of 32 binary markers (single nucleotide polymorphisms; SNPs) and 10 microsatellites on the non-recombining portion of the Y chromosome (NRY) to investigate the ways in which patterns of variation differ between Ashkenazi Jewish and their non-Jewish host populations in Europe. This set of SNPs defines a total of 20 NRY haplogroups in these populations, at least four of which are likely to have been part of the ancestral Ashkenazi gene pool in the Near East, and at least three of which may have introgressed to some degree into Ashkenazi populations after their dispersal to Europe. It is striking that whereas Ashkenazi populations are genetically more diverse at both the SNP and STR level compared with their European non-Jewish counterparts, they have greatly reduced within-haplogroup STR variability, especially in those founder haplogroups that migrated from the Near East. This contrasting pattern of diversity in Ashkenazi populations is evidence for a reduction in male effective population size, possibly resulting from a series of founder events and high rates of endogamy within Europe. This reduced effective population size may explain the high incidence of founder disease mutations despite overall high levels of NRY diversity.Electronic Supplementary Material Supplementary material is available in the online version of this article at D.M. Behar and D. Garrigan contributed equally to this workElectronic database information: URLs for the data in this article are as follows:ARLEQUIN,     

Sex-dependent selection differentially shapes genetic variation on and off the guppy Y chromosome

Because selection is often sex-dependent, alleles can have positive effects on fitness in one sex and negative effects in the other, resulting in intralocus sexual conflict. Evolutionary theory predicts that intralocus sexual conflict can drive the evolution of sex limitation, sex-linkage, and sex chromosome differentiation. However, evidence that sex-dependent selection results in sex-linkage is limited. Here, we formally partition the contribution of Y-linked and non-Y-linked quantitative genetic variation in coloration, tail, and body size of male guppies (Poecilia reticulata)-traits previously implicated as sexually antagonistic. We show that these traits are strongly genetically correlated, both on and off the Y chromosome, but that these correlations differ in sign and magnitude between both parts of the genome. As predicted, variation in attractiveness was found to be associated with the Y-linked, rather than with the non-Y-linked component of genetic variation in male ornamentation. These findings show how the evolution of Y-linkage may be able to resolve sexual conflict. More generally, they provide unique insight into how sex-specific selection has the potential to differentially shape the genetic architecture of fitness traits across different parts of the genome.     

Worldwide genetic relationships of pigs as inferred from X chromosome SNPs

The phylogeography of the porcine X chromosome has not been studied despite the unique characteristics of this chromosome. Here, we genotyped 59 single nucleotide polymorphisms (SNPs) in 312 pigs from around the world, representing 39 domestic breeds and wild boars in 30 countries. Overall, widespread commercial breeds showed the highest heterozygosity values, followed by African and American populations. Structuring, as inferred from F_ST and analysis of molecular variance, was consistently larger in the non‐pseudoautosomal (NPAR) than in the pseudoautosomal regions (PAR). Our results show that genetic relationships between populations can vary widely between the NPAR and the PAR, underscoring the fact that their genetic trajectories can be quite different. NPAR showed an increased commercial‐like genetic component relative to the PAR, probably because human selection processes to obtain individuals with high productive parameters were mediated by introgressing boars rather than sows.     

Out of Africa and back again: nested cladistic analysis of human Y chromosome variation

We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544 individuals from Africa, Asia, Europe, Oceania, and the New World. Phylogenetic analyses of these nine sites resulted in a tree for 10 distinct Y haplotypes with a coalescence time of approximately 150,000 years. The 10 haplotypes were unevenly distributed among human populations: 5 were restricted to a particular continent, 2 were shared between Africa and Europe, 1 was present only in the Old World, and 2 were found in all geographic regions surveyed. The ancestral haplotype was limited to African populations. Random permutation procedures revealed statistically significant patterns of geographical structuring of this paternal genetic variation. The results of a nested cladistic analysis indicated that these geographical associations arose through a combination of processes, including restricted, recurrent gene flow (isolation by distance) and range expansions. We inferred that one of the oldest events in the nested cladistic analysis was a range expansion out of Africa which resulted in the complete replacement of Y chromosomes throughout the Old World, a finding consistent with many versions of the Out of Africa Replacement Model. A second and more recent range expansion brought Asian Y chromosomes back to Africa without replacing the indigenous African male gene pool. Thus, the previously observed high levels of Y chromosomal genetic diversity in Africa may be due in part to bidirectional population movements. Finally, a comparison of our results with those from nested cladistic analyses of human mtDNA and beta-globin data revealed different patterns of inferences for males and females concerning the relative roles of population history (range expansions) and population structure (recurrent gene flow), thereby adding a new sex-specific component to models of human evolution.      

Y chromosome variation of mice and men

DNA sequences from the nonrecombining portion of the Y chromosome were compared with autosomal and X-linked sequences from mice and humans to test the neutral prediction that ratios of polymorphism to divergence are the same for different genes. Intraspecific variation within Mus domesticus was compared with divergence between M. domesticus and Mus caroli for Sry, a region 5' to Sry, and four X-linked genes, Hprt, Plp, Amg, and Glra2. None of these comparisons revealed significantly reduced variation on the Y chromosome. Intraspecific variation within humans was compared with divergence between humans and chimpanzees for three Y-linked loci (Zfy, the YAP region, and the Sry region), seven X- linked loci (Il2rg, Plp, Hprt, Gk, Ids, Pdhal, and Dmd), and the beta- globin locus on chromosome 11. In these comparisons, the observed level of variation on the human Y chromosome was slightly lower than expected, but was significantly lower in only one case (Sry region vs. Dmd). These results suggest that the levels of variability on the Y chromosome in mice and humans are close to expected values given the effective population size and mutation rates for these loci. There is at most only a modest reduction in variability that may be attributed to natural selection (either genetic hitchhiking or background selection).      

Biochemical genetic variation between four populations of Labeobarbus polylepis from three river systems in South Africa

The genetic variation within four Labeobarbus polylepis populations from both river and dam environments in the Limpopo, Incomati and Phongolo River systems was studied. Gene products of 22 enzyme-coding loci were resolved using horizontal starch gel electrophoresis. Fourteen (64%) of the 22 loci were monoallelic in all populations. Levels of polymorphism (P_0.95) ranged between 9.1% and 22.7%. The heterozygosity varied from 0.028 for the Westoe Dam population (Phongolo River system) to 0.093 in the Spekboom River population (Limpopo River system). The genetic distance, F_ST and N_EM values, as well as pair-wise contingency χ² analyses indicate a lack of gene flow between populations, as expected for isolated fish. Evidence of foreign genetic material in one population was also observed.     

Genetic ecological monitoring in human populations: heterozygosity, mtDNA haplotype variation, and genetic load

Yu. P. Altukhov suggested that heterozygosity is an indicator of the state of the gene pool. The idea and a linked concept of genetic ecological monitoring were applied to a new dataset on mtDNA variation in East European ethnic groups. Haplotype diversity (an analog of the average heterozygosity) was shown to gradually decrease northwards. Since a similar trend is known for population density, interlinked changes were assumed for a set of parameters, which were ordered to form a causative chain: latitude increases, land productivity decreases, population density decreases, effective population size decreases, isolation of subpopulations increases, genetic drift increases, and mtDNA haplotype diversity decreases. An increase in genetic drift increases the random inbreeding rate and, consequently, the genetic load. This was confirmed by a significant correlation observed between the incidence of autosomal recessive hereditary diseases and mtDNA haplotype diversity. Based on the findings, mtDNA was assumed to provide an informative genetic system for genetic ecological monitoring; e.g., analyzing the ecology-driven changes in the gene pool.     

mtDNA variation in the South African Kung and Khwe-and their genetic relationships to other African populations

The mtDNA variation of 74 Khoisan-speaking individuals (Kung and Khwe) from Schmidtsdrift, in the Northern Cape Province of South Africa, was examined by high-resolution RFLP analysis and control region (CR) sequencing. The resulting data were combined with published RFLP haplotype and CR sequence data from sub-Saharan African populations and then were subjected to phylogenetic analysis to deduce the evolutionary relationships among them. More than 77% of the Kung and Khwe mtDNA samples were found to belong to the major mtDNA lineage, macrohaplogroup L* (defined by a HpaI site at nucleotide position 3592), which is prevalent in sub-Saharan African populations. Additional sets of RFLPs subdivided macrohaplogroup L* into two extended haplogroups-L1 and L2-both of which appeared in the Kung and Khwe. Besides revealing the significant substructure of macrohaplogroup L* in African populations, these data showed that the Biaka Pygmies have one of the most ancient RFLP sublineages observed in African mtDNA and, thus, that they could represent one of the oldest human populations. In addition, the Kung exhibited a set of related haplotypes that were positioned closest to the root of the human mtDNA phylogeny, suggesting that they, too, represent one of the most ancient African populations. Comparison of Kung and Khwe CR sequences with those from other African populations confirmed the genetic association of the Kung with other Khoisan-speaking peoples, whereas the Khwe were more closely linked to non-Khoisan-speaking (Bantu) populations. Finally, the overall sequence divergence of 214 African RFLP haplotypes defined in both this and an earlier study was 0.364%, giving an estimated age, for all African mtDNAs, of 125,500-165,500 years before the present, a date that is concordant with all previous estimates derived from mtDNA and other genetic data, for the time of origin of modern humans in Africa.     

Genetic variation of Mytilus coruscus Gould (Bivalvia: Mytilidae) populations in the East China Sea inferred from mtDNA COI gene Sequence

In order to characterize the genetic relationship of six populations of Mytilus coruscus Gould in the East China Sea, a 681 bp region of mtDNA COI gene was sequenced and analyzed. Eighty four individuals in total were collected from three cultured populations and three wild populations from three localities of the coast of East China Sea. The sequences from these different populations identified 62 polymorphic sites, which included 41 singleton variable sites and 21 parsimony informative sites that defined 45 distinct haplotypes. Phylogenetic analysis showed that most haplotypes were highly interconnected with each other. Thirty seven of the 45 haplotypes were only found in their own populations, seven were found at two-four localities and only haplotype NO.2 was found in all six populations, indicating that most haplotypes were locally restricted. All haplotypes had shaped two similar branches, each including individuals from all six strains. The results of F_ST values indicated that the genetic distances between populations are not closely associated with their geographic distances.