Admixed Ancestry Research Articles

Inference of admixed ancestry with Ancestry Informative Markers

Analysis of Ancestry Informative Markers (AIMs) is of interest to forensic geneticists for the purpose of assessing the origin of individuals. Often AIMs are used to produce investigative leads for potential suspects in crime cases and identification in missing persons mass disaster cases.We have previously suggested to assess the origin of the profile of interest by a likelihood ratio test on Fisher's exact test. The likelihood ratio test assesses the likelihood of the data under two competing hypotheses, where the null hypothesis assume common origin of the profile of interest and those in a specified population. However, in the case of a profile of an individual of admixed ancestry, there is an increased risk that the profile will be rejected in the constituting populations.The likelihood ratio test approach is extended by allowing for profile admixture implying the profile of interest is a mixture of profiles from two populations. The Expectation-Maximisation (EM) algorithm is used to handle the ambiguity of allocation of alleles at heterozygous markers. To demonstrate the approach, admixed profiles are simulated using AIMs genotypes in eight global meta populations.

Genetically informed captive breeding of hybrids of an extinct species of Galapagos tortoise.

Hybridization poses a major challenge for species conservation because it threatens both genetic integrity and adaptive potential. Yet, hybridization can occasionally offer unprecedented opportunity for species recovery if the genome of an extinct taxon is present among living hybrids such that selective breeding could recapture it. We explored the design elements for establishing a captive-breeding program for Galapagos tortoises (Chelonoidis spp.) built around individuals with admixed ancestry involving an extinct species. The target individuals were hybrids between the extinct species from Floreana Island, C. niger, and an extant species, C. becki, which were recently found in the endemic range of C. becki, from Wolf Volcano on Isabela Island. We combined genotypic data from 35 tortoises with high ancestry from C. niger with forward-in-time simulations to explore captive breeding strategies that maximized overall genetic diversity and ancestry from C. niger while accommodating resource constraints, species biology, and the urgency to return tortoises to Floreana Island for facilitating ecosystem restoration. Overall genetic diversity was maximized when in the simulation tortoises were organized in relatively small breeding groups. Substantial amounts of the C. niger genome were captured despite limited resources available for selectively breeding tortoises in captivity. Genetic diversity was maximized when captive-bred offspring were released to the wild rather than being used as additional breeders. Our results provide genetic-based and practical guidance on the inclusion of hybrids with genomic representation from extinct taxa into species restoration programs and informs the ongoing debate on the value of hybrids in biodiversity conservation.

Discordant Patterns of Introgression Suggest Historical Gene Flow into Thai Weedy Rice from Domesticated and Wild Relatives.

Weedy relatives of crop species infest agricultural fields worldwide, reducing harvests and threatening global food security. These weeds can potentially evolve and adapt through gene flow from both domesticated crop varieties and reproductively compatible wild relatives. We studied populations of weedy rice in Thailand to investigate the role of introgression from cultivated and wild rice in their evolution. We examined 2 complementary sources of genetic data: allelic variation at 3 rice domestication genes (Bh4, controlling hull color; Rc, controlling pericarp color and seed dormancy; and sh4, controlling seed shattering), and 12 previously published SSR markers. Sampling spanned 3 major rice growing regions in Thailand (Lower North, North East, and Central Plain) and included 124 cultivated rice accessions, 166 weedy rice accessions, and 98 wild rice accessions. Weedy rice strains were overall closely related to the cultivated varieties with which they co-occur. Domestication gene data revealed potential adaptive introgression of sh4 shattering alleles from wild rice. Introgression of potentially maladaptive rc crop alleles (conferring reduced dormancy) was also detected, with the frequency of the crop allele highest in northern populations. Although SSR markers also indicated introgression into weed populations from wild and cultivated rice, there was little overlap with domestication genes in the accessions showing admixed ancestry. This suggests that much of the introgression we detected at domestication genes most likely reflects past introgression rather than recent gene flow. This finding has implications for understanding long-term gene flow dynamics between rice and its weedy and wild relatives, including potential risks of transgene escape.

The tough, the wet and the hidden: Evolutionary strategies of a polyploid tropical tree in a changing environment

The Zambezian Floristic Region (ZFR) in south-central Africa experienced major environmental changes in the past and is nowadays home to numerous woody taxa of wet-tropical provenance. Within many taxa, we observe adaptations to multiple habitats, but know little about their environmental drivers. In order to gain knowledge about adaptation and speciation processes in this region, we chose the tree species complex Syzygium guineense (Willd.) DC. s. l. as a model. Using microsatellite genotyping and multivariate analysis of functional traits of nine phenotypes occupying various habitat types, we analyzed phenotypic and genetic differentiation with regard to environmental factors. We found polyploidy, weak correlation between genetic and spatial distances and three admixed genetic ancestries. Distinct growth forms and habitats characterize each of them.We identified several groups, i.e. ecotypes, which most probably mirror evolutionary strategies to overcome environmental changes happening in the ZFR over the last 10 Ma. Strong environmental filters favored the persistence of conservative ecotypes in refugia, and the evolution of ecotypes adapted to newly emerged habitats with increased disturbance regimes. Polyploidy and phenotypic plasticity possibly promoted these processes, which until now were seldom documented in adaptation to drought stress of tropical tree species. Our findings highlight the value of the Zambezian vegetation mosaic as a unique evolutionary experiment.

Microsatellite analysis reveals the resilience of genetic diversity within extant populations of three Akebia species to chronic forest fragmentation in China

The species of Akebia Decne are well-known medicinal plants and have been used in Chinese herbalism for at least 2000 years. The Akebia fruits have a delicious flavor and high nutritional value and are especially rich in antineoplastic, diuretic and antiphlogistic properties, making them worthy of being exploited as a new high-value crop. However, the nature habitats of the Akebia species have been fragmented due to rapid and intensive expansion of agricultural land. In this study, population genetics based on simple sequence repeat markers were conducted on the three most economically important Akebia species in order to reveal the genetic effects of habitat fragmentation to gain useful information for conservation and management of genetic resources of Akebia. Three Akebia species maintained high within-population genetic variation and low level of genetic differentiation. Mantel’s test indicated that there was a significantly positive correlation between genetic distance and geographic distance. Our results reveal the resilience of genetic diversity within extant populations of three Akebia species to chronic forest fragmentation. For breeding purpose, germplasm collection for sampling as many individuals as possible from many populations to maximize genetic diversity of the species is recommended. In addition, natural introgression events have been revealed by Cluster and Structure analysis where admixed ancestry occurred across three marginal populations of A. trifoliata ssp. australis, suggesting these populations should be given priority for germplasm collection.

Genetic diversity of Estonian horse breeds and their genetic affinity to northern European and some Asian breeds

Sixteen microsatellite markers were used to assess the genetic diversity in native and imported transboundary horse breeds and populations from the Baltic Sea region, North-Eastern Europe and Asia (Mongolia and Yakutia, the Russian Federation), with a special focus on Estonian horse breeds. Testing for within-breed genetic variation, Hardy-Weinberg proportions, linkage disequilibrium between genotypes across loci, molecular variance, genetic relationships and population structure was performed.The current microsatellite data indicated that the horse breeds in the Baltic Sea region, including all local Estonian, Finnhorse and Latvian horse breeds, have high within-breed variation. In terms of allelic richness and heterozygosity, the within-breed diversity was higher in the Estonian local breeds than in the Norwegian horse breeds.On the basis of genetic distances, a distinguishable polarization amongst the breeds was observed in two breeds, the Arabian and the Døle, being the most distant and defining of the warm-blooded and the Norwegian breed groups, respectively. The local Estonian breeds, together with the Finnhorse, Mezen, Mongolian and Yakutian breeds, formed a sparse intermediate aggregate with a low variability, attributed to the differences among the breeds. The population structure analysis showed admixed ancestry in this small-size (pony type) breed group. Our study suggests that the local Nordic (Northern European) breeds (N = 11) formed three genetic clusters.The introgression of genes from warm-blooded breeds was considerable in one of the Estonian local horse breeds, the Tori, as well as in the Latvian horse. Compared to the Tori and Latvian Horse, the Estonian Native, the Estonian Heavy Draught and the Finnhorse have preserved a unique gene pool to a larger extent and are more distinct.

Mendelian Randomization of Arsenic Metabolism as a Risk Factor for Hypertensive- and Diabetes-Related Traits among Adults in the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) Cohort

Much of the research that connects hypertension and diabetes to arsenic has been conducted in populations exposed through drinking water. Recently, dietary rice has been recognized as a significant source of arsenic. The objective of this analysis was to evaluate whether arsenic metabolism efficiency is associated with hypertension and diabetes using a Mendelian randomization framework in a population with high rice consumption but no known water arsenic exposure.Using 12,689 participants from the Hispanic Community Health Study/Study of Latinos, this study examined the relationship between estimated arsenic metabolism efficiency (defined as the percentages of inorganic arsenic, monomethylarsenate (MMA), and dimethylarsinate (DMA) species) and three hypertensive traits and seven diabetes-related traits. The analyses implemented a two-stage Mendelian randomization approach, with the genotype-arsenic metabolism relationships extracted from published literature, and the genotype-trait relationships estimated from a mixed-effect linear model within the HCHS/SOL population that controlled for the complex survey design and admixed ancestry. The analysis was stratified by rice consumption, dichotomized at the top 10th percentile.Among high consumers of rice, each estimated percentage point increase in MMA was associated with increases of 1.08 mmHg in systolic blood pressure and 0.82 mmHg in diastolic (p=0.047 and 0.0167, respectively). Inorganic arsenic was similarly associated with increased diastolic blood pressure (1.1 mmHg/percentage point; p=0.021). DMA, which represents more efficient arsenic metabolism, was associated with lowered diastolic blood pressure (-0.5 mmHg/percentage point; p=0.017). Among low rice consumers, no associations were observed. Evidence for a relationship with diabetes was equivocal.This suggests that dietary arsenic exposure through rice may be a contributor to high blood pressure in the Hispanic/Latino community.

Implementing a biogeographic ancestry inference service for forensic casework.

The Centre of Forensic Sciences has validated the Precision ID Ancestry Panel on the Ion S5™ Massively Parallel Sequencing instrument for use in forensic casework. The focus of this paper is the development of reporting guidelines for implementation of the biogeographic ancestry inference service based on the Admixture Prediction results produced using the Torrent Suite™ Software (Thermo Fisher Scientific). The Admixture Prediction algorithm estimates the genetic ancestry of a sample using seven root populations (Europe, East Asia, Oceania, America, Africa, South Asia, and Southwest Asia). For individuals that declared a single ancestry, there was a high correlation between the declared ancestry and the ancestry predicted by the algorithm. However, some individuals with declared ancestries of Southern Europe, Southwest Asia, South Asia and Horn of Africa had Admixture Predictions that were composed of two or more root populations at 20% or greater. For individuals with known admixed ancestry, the major component of their declaration was included in their results in all but one case. Based on these results, reporting guidelines were developed and subsequently evaluated using the Admixture Predictions of additional samples. This paper discusses the development and evaluation of these reporting guidelines, along with an implementation plan for forensic casework.

An original Eurasian haplotype, HLA-DRB1*14:54-DQB1*05:03, influences the susceptibility to idiopathic achalasia.

Idiopathic achalasia is a relatively infrequent esophageal motor disorder for which major histocompatibility complex (MHC) genes are well-identified risk factors. However, no information about HLA-achalasia susceptibility in Mexicans has previously been reported. We studied a group of 91 patients diagnosed with achalasia and 234 healthy controls with Mexican admixed ancestry. HLA alleles and conserved extended haplotypes were analyzed using high-resolution HLA typing based on Sanger and next-generation sequencing technologies. Admixture estimates were determined using HLA-B and short tandem repeats. Results were analyzed by non-parametric statistical analysis and Bonferroni correction. P-values < 0.05 were considered significant. Patients with achalasia had 56.7% Native American genes, 24.7% European genes, 16.5% African genes and 2.0% Asian genes, which was comparable with the estimates in the controls. Significant increases in the frequencies of alleles DRB1*14:54 and DQB1*05:03 and the extended haplotypes DRB1*14:54-DQB1*05:03 and DRB1*11:01-DQB1*03:01, even after Bonferroni correction (pC<0.05), were found in the achalasia group compared to those in the controls. Concluding, the HLA class II alleles HLA-DRB1*14:54:01 and DQB1*05:03:01 and the extended haplotype are risk factors for achalasia in mixed-ancestry Mexican individuals. These results also suggest that the HLA-DRB1*14:54-DQB1*05:03 haplotype was introduced by admixture with European and/or Asian populations.

Exome sequencing identifies novel dysferlin mutation in a family with pauci-symptomatic heterozygous carriers

BackgroundWe investigated a South African family of admixed ancestry in which the first generation (G1) developed insidious progressive distal to proximal weakness in their twenties, while their offspring (G2) experienced severe unexpected symptoms of myalgia and cramps since adolescence. Our aim was to identify deleterious mutations that segregate with the affected individuals in this family.MethodsExome sequencing was performed on five cases, which included three affected G1 siblings and two pauci-symptomatic G2 offspring. As controls we included an unaffected G1 sibling and a spouse of one of the G1 affected individuals. Homozygous or potentially compound heterozygous variants that were predicted to be functional and segregated with the affected G1 siblings, were further evaluated. Additionally, we considered variants in all genes segregating exclusively with the affected (G1) and pauci-symptomatic (G2) individuals to address the possibility of a pseudo-autosomal dominant inheritance pattern in this family.ResultsAll affected G1 individuals were homozygous for a novel truncating p.Tyr1433Ter DYSF (dysferlin) mutation, with their asymptomatic sibling and both pauci-symptomatic G2 offspring carrying only a single mutant allele. Sanger sequencing confirmed segregation of the variant. No additional potentially contributing variant was found in the DYSF or any other relevant gene in the pauci-symptomatic carriers.ConclusionOur finding of a truncating dysferlin mutation confirmed dysferlinopathy in this family and we propose that the single mutant allele is the primary contributor to the neuromuscular symptoms seen in the second-generation pauci-symptomatic carriers.

Widespread, long-term admixture between grey wolves and domestic dogs across Eurasia and its implications for the conservation status of hybrids.

Hybridisation between a domesticated species and its wild ancestor is an important conservation problem, especially if it results in the introgression of domestic gene variants into wild species. Nevertheless, the legal status of hybrids remains unregulated, partially because of the limited understanding of the hybridisation process and its consequences. The occurrence of hybridisation between grey wolves and domestic dogs is well documented from different parts of the wolf geographic range, but little is known about the frequency of hybridisation events, their causes and the genetic impact on wolf populations. We analysed 61K SNPs spanning the canid genome in wolves from across Eurasia and North America and compared that data to similar data from dogs to identify signatures of admixture. The haplotype block analysis, which included 38 autosomes and the X chromosome, indicated the presence of individuals of mixed wolf–dog ancestry in most Eurasian wolf populations, but less admixture was present in North American populations. We found evidence for male‐biased introgression of dog alleles into wolf populations, but also identified a first‐generation hybrid resulting from mating between a female dog and a male wolf. We found small blocks of dog ancestry in the genomes of 62% Eurasian wolves studied and melanistic individuals with no signs of recent admixed ancestry, but with a dog‐derived allele at a locus linked to melanism. Consequently, these results suggest that hybridisation has been occurring in different parts of Eurasia on multiple timescales and is not solely a recent phenomenon. Nevertheless, wolf populations have maintained genetic differentiation from dogs, suggesting that hybridisation at a low frequency does not diminish distinctiveness of the wolf gene pool. However, increased hybridisation frequency may be detrimental for wolf populations, stressing the need for genetic monitoring to assess the frequency and distribution of individuals resulting from recent admixture.

Genetic variants in COL13A1, ADIPOQ and SAMM50, in addition to the PNPLA3 gene, confer susceptibility to elevated transaminase levels in an admixed Mexican population

Non-alcoholic fatty liver disease (NAFLD) is the accumulation of extra fat in liver cells not caused by alcohol. Elevated transaminase levels are common indicators of liver disease, including NAFLD. Previously, we demonstrated that PNPLA3 (rs738409), LYPLAL1 (rs12137855), PPP1R3B (rs4240624), and GCKR (rs780094) are associated with elevated transaminase levels in overweight/obese Mexican adults. We investigated the association between 288 SNPs identified in genome-wide association studies and risk of elevated transaminase levels in an admixed Mexican-Mestizo sample of 178 cases of NAFLD and 454 healthy controls. The rs2896019, rs12483959, and rs3810622 SNPs in PNPLA3 and rs1227756 in COL13A1 were associated with elevated alanine aminotransferase (ALT, ≥40IU/L). A polygenic risk score (PRS) based on six SNPs in the ADIPOQ, COL13A1, PNPLA3, and SAMM50 genes was also associated with elevated ALT. Individuals carrying 9–12 risk alleles had 65.8% and 48.5% higher ALT and aspartate aminotransferase (AST) levels, respectively, than those with 1–4 risk alleles. The PRS showed the greatest risk of elevated ALT levels, with a higher level of significance than the individual variants. Our findings suggest a significant association between variants in COL13A1, ADIPOQ, SAMM50, and PNPLA3, and risk of NAFLD/elevated transaminase levels in Mexican adults with an admixed ancestry. This is the first study to examine high-density single nucleotide screening for genetic variations in a Mexican-Mestizo population. The extent of the effect of these variations on the development and progression of NAFLD in Latino populations requires further analysis.

Dissection of ancestral genetic contributions to Creole goat populations

Goats have played a key role as source of nourishment for humans in their expansion all over the world in long land and sea trips. This has guaranteed a place for this species in the important and rapid episode of livestock expansion triggered by Columbus’ arrival in the Americas in the late 1400s. The aims of this study are to provide a comprehensive perspective on genetic diversity in American goat populations and to assess their origins and evolutionary trajectories. This was achieved by combining data from autosomal neutral genetic markers obtained in more than two thousand samples that encompass a wide range of Iberian, African and Creole goat breeds. In general, even though Creole populations differ clearly from each other, they lack a strong geographical pattern of differentiation, such that populations of different admixed ancestry share relatively close locations throughout the large geographical range included in this study. Important Iberian signatures were detected in most Creole populations studied, and many of them, particularly the Cuban Creole, also revealed an important contribution of African breeds. On the other hand, the Brazilian breeds showed a particular genetic structure and were clearly separated from the other Creole populations, with some influence from Cape Verde goats. These results provide a comprehensive characterisation of the present structure of goat genetic diversity, and a dissection of the Iberian and African influences that gave origin to different Creole caprine breeds, disentangling an important part of their evolutionary history. Creole breeds constitute an important reservoir of genetic diversity that justifies the development of appropriate management systems aimed at improving performance without loss of genomic diversity.

Genetic footprint of population fragmentation and contemporary collapse in a freshwater cetacean

Understanding demographic trends and patterns of gene flow in an endangered species is crucial for devising conservation strategies. Here, we examined the extent of population structure and recent evolution of the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis). By analysing genetic variation at the mitochondrial and nuclear microsatellite loci for 148 individuals, we identified three populations along the Yangtze River, each one connected to a group of admixed ancestry. Each population displayed extremely low genetic diversity, consistent with extremely small effective size (≤92 individuals). Habitat degradation and distribution gaps correlated with highly asymmetric gene-flow that was inefficient in maintaining connectivity between populations. Genetic inferences of historical demography revealed that the populations in the Yangtze descended from a small number of founders colonizing the river from the sea during the last Ice Age. The colonization was followed by a rapid population split during the last millennium predating the Chinese Modern Economy Development. However, genetic diversity showed a clear footprint of population contraction over the last 50 years leaving only ~2% of the pre-collapsed size, consistent with the population collapses reported from field studies. This genetic perspective provides background information for devising mitigation strategies to prevent this species from extinction.

Venetian Local Corn (Zea mays L.) Germplasm: Disclosing the Genetic Anatomy of Old Landraces Suited for Typical Cornmeal Mush Production

Due to growing concern for the genetic erosion of local varieties, four of the main corn landraces historically grown in Veneto (Italy)—Sponcio, Marano, Biancoperla and Rosso Piave—were characterized in this work. A total of 197 phenotypically representative plants collected from field populations were genotyped at 10 SSR marker loci, which were regularly distributed across the 10 genetic linkage groups and were previously characterized for high polymorphism information content (PIC), on average equal to 0.5. The population structure analysis based on this marker set revealed that 144 individuals could be assigned with strong ancestry association (&gt;90%) to four distinct clusters, corresponding to the landraces used in this study. The remaining 53 individuals, mainly from Sponcio and Marano, showed admixed ancestry. Among all possible pairwise comparisons of individual plants, these two landraces exhibited the highest mean genetic similarity (approximately 67%), as graphically confirmed through ordination analyses based on PCoA centroids and UPGMA trees. Our findings support the hypothesis of direct gene flow between Sponcio and Marano, likely promoted by the geographical proximity of these two landraces and their overlapping cultivation areas. Conversely, consistent with its production mainly confined to the eastern area of the region, Rosso Piave scored the lowest genetic similarity (&lt;59%) to the other three landraces and firmly grouped (with average membership of 89%) in a separate cluster, forming a molecularly distinguishable gene pool. The elite inbred B73 used as tester line scored very low estimates of genetic similarity (on average &lt;45%) with all the landraces. Finally, although Biancoperla was represented at K = 4 by a single subgroup with individual memberships higher than 80% in almost all cases (57 of 62), when analyzed with an additional level of population structure for K = 6, it appeared to be entirely (100%) constituted by individuals with admixed ancestry. This suggests that the current population could be the result of repeated hybridization events between the two accessions currently bred in Veneto. The genetic characterization of these heritage landraces should prove very useful for monitoring and preventing further genetic erosion and genetic introgression, thus preserving their gene pools, phenotypic identities and qualitative traits for the future.

Analysis of ancestry informative markers in three main ethnic groups from Ecuador supports a trihybrid origin of Ecuadorians

Ancestry inference is traditionally done using autosomal SNPs that present great allele frequency differences among populations from different geographic regions. These ancestry informative markers (AIMs) are useful for determining the most likely biogeographic ancestry or population of origin of an individual. Due to the growing interest in AIMs and their applicability in different fields, commercial companies have started to develop AIM multiplexes targeted for Massive Parallel Sequencing platforms.This project focused on the study of three main ethnic groups from Ecuador (Kichwa, Mestizo, and Afro-Ecuadorian) using the Precision ID Ancestry panel (Thermo Fisher Scientific). In total, 162 Ecuadorian individuals were investigated. The Afro-Ecuadorian and Mestizo showed higher average genetic diversities compared to the Kichwa. These results are consistent with the highly admixed nature of the first two groups. The Kichwa showed the highest proportion of Native Amerindian (NAM) ancestry relative to the other two groups. The Mestizo had an admixed ancestry of NAM and European with a larger European component, whereas the Afro-Ecuadorian were highly admixed presenting proportions of African, Native Amerindian, and European ancestries. The comparison of our results with previous studies based on uniparental markers (i.e. Y chromosome and mtDNA) highlighted the sex-biased admixture process in the Ecuadorian Mestizo.Overall, the data generated in this work represent one important step to assess the application of ancestry inference in admixed populations in a forensic context.

Redefining the Role of Admixture and Genomics in Species Conservation

AbstractThe generation of genome‐wide sequence data has brought with it both exciting opportunities for conservation and challenges for determining appropriate management practices in the face of complex evolutionary histories. Genomic data can provide deep insight into taxa with complex evolutionary origins, and is a powerful tool for biologists to obtain a more complete view of ancestry. Many policy decisions are encumbered by patterns of gene flow between species that reveal complex evolutionary histories. Here, we review conservation decisions in admixed species and highlight genomics research that demonstrates the commonality of hybridization in wildlife. We encourage a shift toward a web‐of‐life framework with emphasis on the need to incorporate flexibility in conservation practices by establishing a policy for lineages of admixed ancestry. In particular, we promote a conceptual framework under which hybridization, even extensive hybridization, no longer disqualifies a species from protection; instead, we encourage customized case‐by‐case management to protect evolutionary potential and maintain processes that sustain ecosystems.

A novel set of single-copy nuclear gene markers in white oak and implications for species delimitation

Oaks have often been the focus of research on plant evolution owing to their propensity to intercross and their important role in ecology and economy. Compared with traditional molecular markers, such as amplified fragment length polymorphisms (AFLPs) and simple sequence repeats (SSRs), multiple single-copy nuclear genes (SCNGs) are of greater utility in inferring evolutionary processes in oaks. Nineteen primer pairs were developed from expressed sequence tags (ESTs) of Quercus mongolica and Q. robur that could produce orthologous products in Chinese white oaks (section Quercus). These SCNG markers showed a moderate to high level of nucleotide polymorphism in 42 individuals of two closely related white oaks, Q. mongolica and Q. liaotungensis, and demonstrated high transferability across seven white oaks, four oaks from section Cerris, and one oak from section Lobatae. A phylogenetic tree based on these SCNGs provided resolution at deep nodes and robust support for delimiting populations of Q. mongolica and Q. liaotungensis; Bayesian analysis clustered individuals into their respective species with high probability and no admixture. When the same individuals were used, Bayesian clusters based on either 194 AFLPs or 19 SSRs gave comparable results, but one or several individuals respectively were identified as having admixed ancestry. This indicates that the hybridization rate between these two oaks may have been overestimated using SSR markers due to the occurrence of homoplasy. The SCNGs are powerful for species delimitation of white oaks, and these markers could be useful for future phylogenetics and phylogeography research in white oaks.

Mixing of porpoise ecotypes in southwestern UK waters revealed by genetic profiling.

Contact zones between ecotypes are windows for understanding how species may react to climate changes. Here, we analysed the fine-scale genetic and morphological variation in harbour porpoises (Phocoena phocoena) around the UK by genotyping 591 stranded animals at nine microsatellite loci. The data were integrated with a prior study to map at high resolution the contact zone between two previously identified ecotypes meeting in the northern Bay of Biscay. Clustering and spatial analyses revealed that UK porpoises are derived from two genetic pools with porpoises from the southwestern UK being genetically differentiated, and having larger body sizes compared to those of other UK areas. Southwestern UK porpoises showed admixed ancestry between southern and northern ecotypes with a contact zone extending from the northern Bay of Biscay to the Celtic Sea and Channel. Around the UK, ancestry blends from one genetic group to the other along a southwest--northeast axis, correlating with body size variation, consistent with previously reported morphological differences between the two ecotypes. We also detected isolation by distance among juveniles but not in adults, suggesting that stranded juveniles display reduced intergenerational dispersal. The fine-scale structure of this admixture zone raises the question of how it will respond to future climate change and provides a reference point for further study.

African ancestry is associated with facial melasma in women: a cross-sectional study

BackgroundMelasma is a chronic acquired focal hypermelanosis affecting photoexposed areas, especially for women during fertile age. Several factors contribute to its development: sun exposure, sex steroids, medicines, and family history. Melanic pigmentation pathway discloses several SNPs in different populations. Here, we evaluated the association between genetic ancestry and facial melasma.MethodsA cross-sectional study involving women with melasma and an age-matched control group from outpatients at FMB-Unesp, Botucatu-SP, Brazil was performed. DNA was extracted from oral mucosa swabs and ancestry determined by studying 61 INDELs. The genetic ancestry components were adjusted by other known risk factors by multiple logistic regression.ResultsWe evaluated 119 women with facial melasma and 119 controls. Mean age was 39 ± 9 years. Mean age at beginning of disease was 27 ± 8 years. Pregnancy (40%), sun exposure (37%), and hormonal oral contraception (22%) were the most frequently reported melasma triggers. All subjects presented admixed ancestry, African and European genetic contributions were significantly different between cases and controls (respectively 10% vs 6%; 77% vs 82%; p < 0.05). African ancestry (OR = 1.04; 95% CI 1.01 to 1.07), first generation family history (OR = 3.04; 95% CI 1.56 to 5.94), low education level (OR = 4.04; 95% CI 1.56 to 5.94), and use of antidepressants by individuals with affected family members (OR = 6.15; 95% CI 1.13 to 33.37) were associated with melasma, independently of other known risk factors.ConclusionsFacial melasma was independently associated with African ancestry in a highly admixed population.