The transition of traits between genetically related lineages is a fascinating topic that provides clues to understanding the drivers of speciation and diversification.Much can be learned about this process from phylo...The transition of traits between genetically related lineages is a fascinating topic that provides clues to understanding the drivers of speciation and diversification.Much can be learned about this process from phylogeny-based trait evolution.However,such inference is often plagued by genome-wide gene-tree discordance(GTD),mostly due to incomplete lineage sorting(ILS)and/or introgressive hybridization,especially when the genes underlying the traits appear discordant.Here,by collecting transcriptomes,whole chloroplast genomes(cpDNA),and population genetic datasets,we used the coalescent model to turn GTD into a source of information for ILS and employed hemiplasy to explain specific cases of apparent“phylogenetic discordance”between different morphological traits and probable species phylogeny in the Allium subg.Cyathophora.Both concatenation and coalescence methods consistently showed the same phylogenetic topology for species tree inference based on single-copy genes(SCGs),as supported by the KS distribution.However,GTD was high across the genomes of subg.Cyathophora:~27%e38.9%of the SCG trees were in conflict with the species tree.Plasmid and nuclear incongruence was also present.Our coalescent simulations indicated that such GTD was mainly a product of ILS.Our hemiplasy risk factor calculations supported that random fixation of ancient polymorphisms in different populations during successive speciation events along the subg.Cyathophora phylogeny may have caused the character transition,as well as the anomalous cpDNA tree.Our study exemplifies how phylogenetic noise can be transformed into evolutionary information for understanding character state transitions along species phylogenies.展开更多
The antiretroviral treatment (ART) has significantly reduced the number of new HIV/AIDS infections and related deaths. However, cases of immunovirological discordance (IVD) are found in various locations. The objectiv...The antiretroviral treatment (ART) has significantly reduced the number of new HIV/AIDS infections and related deaths. However, cases of immunovirological discordance (IVD) are found in various locations. The objective of this study was to determine the profile of People living with HIV (PLHIV) with IVD and to identify associated factors. We conducted a cross-sectional study based on the records of PLHIV under ART for at least 6 months, followed at Hpital de Jour Donka from 2015 to 2017, and having both viral load (CV) and CD4 T-cell count. Prevalence of IVD was 34.57%, with 23.87% for immunological discordance (ID) and 10.7% for virological discordance (VD). Females were predominant (66.26%), and male gender influenced IVD with a statistically significant difference (p = 0.006) and was associated with VD (p = 0.007). The average age was 38.77 11.30 years. PLHIV were classified at WHO stages 3 and 4 (86.01%). The median initial haemoglobin level was 11.5 g/L [3.2 - 12]. The mean initial CD4 T-cell count was 272.84 cells/mm3 201.6. The median initial viral load (VL) was 147,337 copies/mL [1092 - 31,675,000]. The initial CD4 T-cell count 3 was associated with IVD with a statistically significant difference (p = 0.0009) and correlated with ID (p = 0.000). Prurigo was associated with IVD with a statistically significant difference (p = 0.003). Cerebral toxoplasmosis was not associated with IVD but was associated with ID (p = 0.04). This study allowed us to describe the profile of PLHIV with IVD. The main associated factors were male gender, initial CD4 T-cell count 3, toxoplasmosis, prurigo, and herpes zoster.展开更多
Confluences play a major role in the dynamics of networks of natural and man-made open channels, and field measurements on river confluences reveal that discordance in bed elevation is common.Studies of schematized co...Confluences play a major role in the dynamics of networks of natural and man-made open channels, and field measurements on river confluences reveal that discordance in bed elevation is common.Studies of schematized confluences with a step at the interface between the tributary and the main channel bed reveal that bed elevation discordance is an important additional control for the confluence hydrodynamics.This study aimed to improve understanding of the influence of bed elevation discordance on the flow patterns and head losses in a right-angled confluence of an open channel with rectangular cross-sections.A large eddy simulation (LES)-based numerical model was set up and validated with experiments by others.Four configurations with different bed discordance ratios were investigated.The results confirm that, with increasing bed elevation discordance, the tributary streamlines at the confluence interface deviate less from the geometrical confluence angle, the extent of the recirculation zone (RZ) gets smaller, the ratio of the water depth upstream to that downstream of the confluence decreases, and the water level depression reduces.The bed elevation discordance also leads to the development of a large-scale structure in the lee of the step.Despite the appearance of the large-scale structure, the reduced extent of the RZ and associated changes in flow deflection/contraction reduce total head losses experienced by the main channel with an increase of the bed discordance ratio.It turns out that bed elevation discordance converts the lateral momentum from the tributary to streamwise momentum in the main channel more efficiently.展开更多
Background： A number of studies have examined human epidermal growth factor receptor 2 （HER2） status in primary gastric cancer （GC） and associated metastasis, some showed their great concordance in FIER2 expressi...Background： A number of studies have examined human epidermal growth factor receptor 2 （HER2） status in primary gastric cancer （GC） and associated metastasis, some showed their great concordance in FIER2 expression, but others demonstrated notable discordance. There is still little consensus on HER2 discordance, therefore, a systematic review and meta-analysis was conducted to assess the status on HER2 discordance between primary GC and its paired metastasis. Methods： PubMed, EMBASE, ASCO and The Cochrane Library were searched for studies that explored the concordance between primary tumor and metastasis in patients with GC up to 10 March, 2014. Data of discordance of HER2 between primary GC and corresponding metastasis were extracted from the publications and random-effects models were used to estimate pooled discordance proportions. Results： Eighteen articles including 1,867 patients were included for the meta-analysis in accordance with the selection criteria. Pooled discordance proportions were 7% [95% confidence interval （CI）： 5-10%] for HER2 status. Pooled proportions of tumors shifting from positive to negative and from negative to positive were 17% （95% CI： 7-29%） and 4% （95% CI： 2-6%） respectively. No publication bias was found in the meta-analysis. Conclusions： The discordance of HER2 status is not rare in primary and metastatic GC through our metaanalysis. Prospective studies are needed to testify the clinical significance of the discordance of HER2 status.展开更多
The Hengduan Mountains Region(HMR)is the largest“evolutionary frontier”of the northern temperate zone,and the origin and maintenance of species in this area is a research hotspot.Exploring species-specific responses...The Hengduan Mountains Region(HMR)is the largest“evolutionary frontier”of the northern temperate zone,and the origin and maintenance of species in this area is a research hotspot.Exploring species-specific responses to historical and contemporary environmental changes will improve our understanding of the role of this region in maintaining biodiversity.In this study,mitochondrial and microsatellite diversities were used to assess the contributions of paleogeological events,Pleistocene climatic oscillations,and contemporary landscape characteristics to the rapid intraspecific diversification of Liangshantriton taliangensis,a vulnerable amphibian species endemic to several sky-island mountains in the southeastern HMR.Divergence date estimations suggested that the East Asian monsoon,local uplifting events(Xigeda Formation strata),and Early-Middle Pleistocene transition(EMPT)promoted rapid divergence of L.taliangensis during the Pleistocene,yielding eight mitochondrial lineages and six nuclear genetic lineages.Moreover,population genetic structures were mainly fixed through isolation by resistance.Multiple in situ refugia were identified by ecological niche models and high genetic diversity,which played crucial roles in the persistence and divergence of L.taliangensis during glacial-interglacial cycles.Dramatic climatic fluctuations further promoted recurrent isolation and admixing of populations in scattered glacial refugia.The apparent mitonuclear discordance was likely the result of introgression by secondary contact and/or female-biased dispersal.Postglacial expansion generated two major secondary contact zones(Ganluo(GL)and Chuhongjue(CHJ)).Identification of conservation management units and dispersal corridors offers important recommendations for the conservation of this species.展开更多
We analyzed seafloor morphology and geophysical anomalies of the Southeast Indian Ridge(SEIR) to reveal the remarkable changes in magma supply along this intermediate fast-spreading ridge. We found systematic differen...We analyzed seafloor morphology and geophysical anomalies of the Southeast Indian Ridge(SEIR) to reveal the remarkable changes in magma supply along this intermediate fast-spreading ridge. We found systematic differences of the Australian-Antarctic Discordance(AAD) from adjacent ridge segments with the residual mantle Bouguer gravity anomaly(RMBA) being more positive, seafloor being deeper, morphology being more chaotic, M factors being smaller at the AAD. These systematic anomalies, as well as the observed Na8.0 being greater and Fe8.0 being smaller at AAD, suggest relatively starved magma supply and relatively thin crust within the AAD.Comparing to the adjacent ridges segments, the calculated average map-view M factors are relatively small for the AAD, where several Oceanic Core Complexes(OCCs) develop. Close to 30 OCCs were found to be distributed asymmetrically along the SEIR with 60% of OCCs at the northern flank. The OCCs are concentrated mainly in Segments B3 and B4 within the AAD at ~124°–126°E, as well as at the eastern end of Zone C at ~115°E. The relatively small map-view M factors within the AAD indicate stronger tectonism than the adjacent SEIR segments.The interaction between the westward migrating Pacific mantle and the relatively cold mantle beneath the AAD may have caused a reduction in magma supply, leading to the development of abundant OCCs.展开更多
For two-way contingency tables with ordered categories, the present paper gives a theorem that the independence model holds if and only if the logit uniform association model holds and equality of concordance and disc...For two-way contingency tables with ordered categories, the present paper gives a theorem that the independence model holds if and only if the logit uniform association model holds and equality of concordance and discordance for all pairs of adjacent rows and all dichotomous collapsing of the columns holds. Using the theorem, we analyze the cross-classification of duodenal ulcer patients according to operation and dumping severity.展开更多
<strong>Introduction: </strong><span style="font-family:Verdana;">Double discordance or corrected transposition of the great vessels is a rare congenital heart disease. It is an atrioventri...<strong>Introduction: </strong><span style="font-family:Verdana;">Double discordance or corrected transposition of the great vessels is a rare congenital heart disease. It is an atrioventricular and ventriculo-arterial mismatch. It is a complex and unusual form of congenital heart disease. Often asymptomatic, in its isolated form, bradycardia, murmur and cyanosis can be a mode of revelation. </span><span style="font-family:;" "=""></span><b><span style="font-family:Verdana;">Case presentation:</span></b><span style="font-family:;" "=""><span style="font-family:Verdana;"> We report the case of an 11-year-old child, asymptomatic at birth, after he started to have dyspnea on exertion, recurrent bronchitis, motivating a cardiological consultation. On cardiac physical examination, the heart sounds regular, not rapid at 81 BPM with a grade 3-4/6 systolic murmur at the 4th left EIC (Intercostal space). EKG (electrocardiogram) shows PR interval at 0.20 seconds. Cardiac ultrasound reveals atrioventricular discordance, vascular malposition, anterior aorta, the two vessels placed side by side, minimal pulmonary insufficiency, a small leak at the levels of the mitral and tricuspid valves, dystrophic pulmonary valves with an average gradient of 91 mmHg, max at 158 mmHg. Regular follow-up has been recommended through the performance of a clinical examination and cardiac ultrasound. </span><b><span style="font-family:Verdana;">Conclusion:</span></b><span style="font-family:Verdana;"> The double discordance can be asymptomatic, </span></span><span style="font-family:Verdana;">and </span><span style="font-family:Verdana;">survival can be long in the isolated forms, but the evolution is not always benign, especially in the associated forms. It depends on the function of the systemic right ventricle and associated abnormalities.</span>展开更多
BACKGROUND Discordance between endoscopic and histologic assessments in Crohn’s disease(CD)have been observed,however the prevalence and cause are unclear.AIM To assess if a protocolized approach to biopsy collection...BACKGROUND Discordance between endoscopic and histologic assessments in Crohn’s disease(CD)have been observed,however the prevalence and cause are unclear.AIM To assess if a protocolized approach to biopsy collection facilitates understanding of this discordance in patients with ileal CD.METHODS Patients with known ileal CD underwent colonoscopy with endoscopic disease activity assessment.Three protocolized biopsies were taken respectively from an ulcer edge,7-mm,and 14-mm away from the ulcer edge in patients with discrete ileal ulcer(s).In patients with no ulcers as controls,the same 3-site biopsy protocol was applied in a randomly selected area of endoscopically-unremarkable terminal ileal mucosa.A blinded pathologist assessed mucosal inflammation in each biopsy using 3 validated histologic indices.RESULTS Twenty-four participants had visible ulcer(s)on endoscopy and 12 served as no-ulcer controls.Of biopsies taken from an ulcer edge,only 67%showed histologic evidence of active(neutrophilic)inflammation,and 33%showed histologic features of ulcer or erosion;all were from either large(n=4)or very large(n=4)ulcers.In the no-ulcer controls,no biopsies showed histologic features of ulcer or erosion,but 8%showed active inflammation.CONCLUSION A striking discordance exists between endoscopic and histologic assessments for mucosal inflammation in patients with active ileal CD,even in biopsies targeted at an ulcer edge,while a higher concordance is seen in patients with no endoscopic disease activity.It remains unclear how to incorporate histologic disease activity into the treatment paradigm.Further research is needed to optimize biopsy protocols and histologic assessments for CD.展开更多
Naive pluripotent state can be obtained by several strategies from various types of cells,in which the cell fate roadmap as well as key biological events involved in the journey have been described in detail.Here,we c...Naive pluripotent state can be obtained by several strategies from various types of cells,in which the cell fate roadmap as well as key biological events involved in the journey have been described in detail.Here,we carefully explored the chromatin accessibility dynamics during the primed-to-naïve transition by adopting a dual fluorescent reporter system and the assay for transposase-accessible chromatin(ATAC)-seq.Our results revealed critical chromatin remodeling events and highlight the discordance between chromatin accessibility and transcriptional activity.We further demonstrate that the differential epigenetic modifications and transcription factor(TF)activities may play a critical role in regulating gene expression,and account for the observed variations in gene expression despite similar chromatin landscapes.展开更多
Channel confluences are universally present in nature. They can be divided into two types： asymmetrical river confluences and symmetric river confluences. The latter is also called as the Y-shaped confluences. Most o...Channel confluences are universally present in nature. They can be divided into two types： asymmetrical river confluences and symmetric river confluences. The latter is also called as the Y-shaped confluences. Most of previous work has paid more attention to the asymmetrical river confluences, but few studies have been conducted on the Y-shaped confluences. In this article, the effects of bed discordance on the flow patterns at ＂Y＂ shaped open-channel confluences were studied by using a 3-D numerical simulation. It is proved that the model can undertake quantitative assessment of the flow at confluences. The results indicate that there are a lot of differences between the Y-shaped confluence and asymmetrical confluence. The discordant bed height plays an important role at the Y-shaped junction.展开更多
The field of evolutionary biology has been revolutionized by phylogenomic approaches in the last decades. However, with the ever-increasing size and scope of molecular data collection, conflicting genealogies may be y...The field of evolutionary biology has been revolutionized by phylogenomic approaches in the last decades. However, with the ever-increasing size and scope of molecular data collection, conflicting genealogies may be yielded based on different datasets and analytical approaches, a phenomenon known as cytonuclear discordance(Figure 1A and B).展开更多
The angiosperm family Elaeagnaceae comprises three genera and ca.100 species distributed mainly in Eurasia and North America.Little family-wide phylogenetic and biogeographic research on Elaeagnaceae has been conducte...The angiosperm family Elaeagnaceae comprises three genera and ca.100 species distributed mainly in Eurasia and North America.Little family-wide phylogenetic and biogeographic research on Elaeagnaceae has been conducted,limiting the application and preservation of natural genetic resources.Here,we reconstructed a strongly supported phylogenetic framework of Elaeagnaceae to better understand interand intrageneric relationships,as well as the origin and biogeographical history of the family.For this purpose,we used both nuclear and plastid sequences from Hyb-Seq and genome skimming approaches to reconstruct a well-supported phylogeny and,along with current distributional data,infer historical biogeographical processes.Our phylogenetic analyses of both nuclear and plastid data strongly support the monophyly of Elaeagnaceae and each of the three genera.Elaeagnus was resolved as sister to the well-supported clade of Hippophae and Shepherdia.The intrageneric relationships of Elaeagnus and Hippophae were also well resolved.High levels of nuclear gene tree conflict and cytonuclear discordance were detected within Elaeagnus,and our analyses suggest putative ancient and recent hybridization.We inferred that Elaeagnaceae originated at ca.90.48 Ma(95%CI?89.91e91.05 Ma),and long-distance dispersal likely played a major role in shaping its intercontinentally disjunct distribution.This work presents the most comprehensive phylogenetic framework for Elaeagnaceae to date,offers new insights into previously unresolved relationships in Elaeagnus,and provides a foundation for further studies on classification,evolution,biogeography,and conservation of Elaeagnaceae.展开更多
BACKGROUND A reliable test is essential for diagnosing Helicobacter pylori(H.pylori)infection,and crucial for managing H.pylori-related diseases.Serving as an excellent method for detecting H.pylori infection,histolog...BACKGROUND A reliable test is essential for diagnosing Helicobacter pylori(H.pylori)infection,and crucial for managing H.pylori-related diseases.Serving as an excellent method for detecting H.pylori infection,histologic examination is a test that clinicians heavily rely on,especially when complemented with immunohistochemistry(IHC).Additionally,other diagnostic tests for H.pylori,such as the rapid urease test(CLO test)and stool antigen test(SA),are also highly sensitive and specific.Typically,the results of histology and other tests align with each other.However,on rare occasions,discrepancy between histopathology and other H.pylori diagnostic tests occurs.AIM To investigate the discordance between histology and other H.pylori tests,the underlying causes,and the impact on clinical management.METHODS Pathology reports of gastric biopsies were retrieved spanning August 2013 and July 2018.Reports were included in the study only if there were other H.pylori tests within seven days of the biopsy.These additional tests include CLO test,SA,and H.pylori culture.Concordance between histopathology and other tests was determined based on the consistency of results.In instances where histology results were negative while other tests were positive,the slides were retrieved for re-assessment,and the clinical chart was reviewed.RESULTS Of 1396 pathology reports were identified,each accompanied by one additional H.pylori test.The concordance rates in detecting H.pylori infection between biopsy and other tests did not exhibit significant differences based on the number of biopsy fragments.117 discrepant cases were identified.Only 20 cases(9 with CLO test and 11 with SA)had negative biopsy but positive results in other tests.Four cases initially stained with Warthin-Starry turned out to be positive for H.pylori with subsequent IHC staining.Among the remaining 16 true discrepant cases,10 patients were on proton pump inhibitors before the biopsy and/or other tests.Most patients underwent treatment,except for two who were untreated,and two patients who were lost to follow-up.CONCLUSION There are rare discrepant cases with negative biopsy but positive in SA or CLO test.Various factors may contribute to this inconsistency.Most patients in such cases had undergone treatment.展开更多
Quantum discord, one of the famous quantum correlations, has been recently generalized to multipartite systems by Radhakrishnan et al. Here we give analytical solutions of the quantum discord for a family of N-qubit q...Quantum discord, one of the famous quantum correlations, has been recently generalized to multipartite systems by Radhakrishnan et al. Here we give analytical solutions of the quantum discord for a family of N-qubit quantum states. For the bipartite system, we derive a zero quantum discord which will remain unchanged under the phase damping channel. For multiparitite systems, it is found that the quantum discord can be classified into three categories and the quantum discord for odd-partite systems can exhibit freezing under the phase damping channel, while the freezing does not exist in the even-partite systems.展开更多
In the co-evolutionary system of avian brood parasitism,egg recognition and rejection are common and generally act as effective anti-parasitic adaptations by hosts.Accordingly,most studies have examined the role of pa...In the co-evolutionary system of avian brood parasitism,egg recognition and rejection are common and generally act as effective anti-parasitic adaptations by hosts.Accordingly,most studies have examined the role of parasite egg colors and markings in detection cues in hosts;however,studies focusing on the effects of egg size and quantity are relatively scarce and have mostly concentrated on the hosts of parasitic cowbirds.Here,we studied the egg recognition behaviors of a potential host of the Common Cuckoo(Cuculus canorus)—the Green-backed Tit(Parus monticolus),to determine:(1)whether the host uses the sizes of parasite eggs and/or the quantity contrast between parasite and host eggs as cues for recognition,(2)whether the host employs the template or discordant recognition mechanism for egg recognition,and(3)whether the size and quantity of parasite eggs affect the egg rejection modes of the hosts.The results indicate that Green-backed Tits did not use parasite egg size as a primary cue for egg recognition.We hypothesized that both visual and tactile detection might be involved in egg recognition by Green-backed Tits and suggest further studies after controlling for nest light conditions.Differences in egg quantity between parasites and hosts were not used as cues for egg recognition because the hosts employed the template mechanism rather than discordance to recognize parasite eggs.However,both the relative sizes and quantity of parasite and host eggs significantly affected the rejection modes of parasite eggs,and larger or more parasite eggs triggered higher probabilities of nest desertion in hosts.展开更多
A single small population of chasmophytic plants is described as Mojiangia oreophila,a monotypic genus in the subtribe Crepidinae,characterised by a unique combination of morphological features,in particular densely l...A single small population of chasmophytic plants is described as Mojiangia oreophila,a monotypic genus in the subtribe Crepidinae,characterised by a unique combination of morphological features,in particular densely long-papillose homomorphic achenes with five main ribs each accompanied by two secondary ribs,coarse brownish pappus bristles,moderately many-flowered capitula,a small involucre with numerous outer phyllaries,perennial rosette herb growth and brown-woolly caudex and leaf axils.Molecular phylogenetic analysis detected that in the nrlTS phylogeny M.oreophila forms a clade of its own in the Crepidinae;in the plastid DNA phylogeny it is nested in the clade formed by the hybrid-ogenous genus Faberia,the maternal ancestor of which comes from the Crepidinae and the paternal ancestor from the Lactucinae,where Faberia is placed in nrlTS phylogenies.M.oreophila shares several morphological features with Faberia and also shares the expected chromosome number of 2n=16 with its hitherto unknown maternal ancestor.M.oreophila may therefore be a successor of the maternal ancestor of Faberia.Alternatively,cytonuclear discordance is to be assumed in Mojiangia,caused by chloroplast capture as a result of hybridisation and introgression with Faberia.展开更多
Confused geographical structure of a population and mitonuclear discordance are shaped by a combination of rapid changes in population demographics and shifts in ecology.In this study,we generated a time-calibrated ph...Confused geographical structure of a population and mitonuclear discordance are shaped by a combination of rapid changes in population demographics and shifts in ecology.In this study,we generated a time-calibrated phylogeny of Scutiger boulengeri,an endemic Xizang alpine toad occurring in mountain streams on the Qinghai-Xizang(Tibet)Plateau(QTP).Based on three mitochondrial DNA(mt DNA)genes,eight clades were assigned to three deeply divergent lineages.Analysis of nuclear DNA(nu DNA)genes revealed three distinct clusters without geographic structure,indicating significantly high rates of gene flow.Coalescent theory framework analysis(approximate Bayesian computation model DIYABC and Migrate-N)suggested that divergence of the main intraspecific clusters was the result of hybridization after secondary contact in the Holocene around 0.59 million years ago(Ma).The ratio of mt DNA FST(fixation index)to nu DNA FST was 2.3,thus failing to show male-biased dispersal.Geographic cline analysis showed that a wide hybrid zone was initially established in southwestern China,without significant reproductive isolation but with strong introgression in S.boulengeri,suggesting high hybrid fitness.Furthermore,mt DNA genes exhibited isolation by distance(IBD)while nu DNA genes exhibited significant isolation by environment(IBE).Results suggested that mitonuclear discordance may have initially been caused by geographic isolation,followed by precipitation-mediated hybridization,producing a wide hybrid zone and geographic structure confusion of nu DNA genes in S.boulengeri.This study indicated that complicated historical processes may have led to specific genetic patterns,with a specific climate factor facilitating gene flow in the system.展开更多
The complex interactions of historical,geological and climatic events on plant evolution have been an important research focus for many years.However,the role of desert formation and expansion in shaping the genetic s...The complex interactions of historical,geological and climatic events on plant evolution have been an important research focus for many years.However,the role of desert formation and expansion in shaping the genetic structures and demographic histories of plants occurring in arid areas has not been well explored.In the present study,we investigated the phylogeography of Arnebia szechenyi,a desert herb showing a near-circular distribution surrounding the Tengger Desert in Northwest China.We measured genetic diversity of populations using three maternally inherited chloroplast DNA(cpDNA)fragments and seven bi-paternally inherited nuclear DNA(nDNA)loci that were sequenced from individuals collected from 16 natural populations across its range and modelled current and historical potential habitats of the species.Our data indicated a considerably high level of genetic variation within A.szechenyi and noteworthy asymmetry in historical migration from the east to the west.Moreover,two nuclear genetic groups of populations were revealed,corresponding to the two geographic regions separated by the Tengger Desert.However,analysis of cpDNA data did not show significant geographic structure.The most plausible explanation for the discrepancy between our findings based on cpDNA and nDNA data is that A.szechenyi populations experienced long periods of geographic isolation followed by range expansion,which would have promoted generalized recombination of the nuclear genome.Our findings further highlight the important role that the Tengger Desert,together with the Helan Mountains,has played in the evolution of desert plants and the preservation of biodiversity in arid Northwest China.展开更多
基金supported by the Key Science & Technology Project of Gansu Province (22ZD6NA007)the National Key Research and Development Program of China (2021YFD2200202)Computing support was provided by the Supercomputing Center of Lanzhou University
文摘The transition of traits between genetically related lineages is a fascinating topic that provides clues to understanding the drivers of speciation and diversification.Much can be learned about this process from phylogeny-based trait evolution.However,such inference is often plagued by genome-wide gene-tree discordance(GTD),mostly due to incomplete lineage sorting(ILS)and/or introgressive hybridization,especially when the genes underlying the traits appear discordant.Here,by collecting transcriptomes,whole chloroplast genomes(cpDNA),and population genetic datasets,we used the coalescent model to turn GTD into a source of information for ILS and employed hemiplasy to explain specific cases of apparent“phylogenetic discordance”between different morphological traits and probable species phylogeny in the Allium subg.Cyathophora.Both concatenation and coalescence methods consistently showed the same phylogenetic topology for species tree inference based on single-copy genes(SCGs),as supported by the KS distribution.However,GTD was high across the genomes of subg.Cyathophora:~27%e38.9%of the SCG trees were in conflict with the species tree.Plasmid and nuclear incongruence was also present.Our coalescent simulations indicated that such GTD was mainly a product of ILS.Our hemiplasy risk factor calculations supported that random fixation of ancient polymorphisms in different populations during successive speciation events along the subg.Cyathophora phylogeny may have caused the character transition,as well as the anomalous cpDNA tree.Our study exemplifies how phylogenetic noise can be transformed into evolutionary information for understanding character state transitions along species phylogenies.
文摘The antiretroviral treatment (ART) has significantly reduced the number of new HIV/AIDS infections and related deaths. However, cases of immunovirological discordance (IVD) are found in various locations. The objective of this study was to determine the profile of People living with HIV (PLHIV) with IVD and to identify associated factors. We conducted a cross-sectional study based on the records of PLHIV under ART for at least 6 months, followed at Hpital de Jour Donka from 2015 to 2017, and having both viral load (CV) and CD4 T-cell count. Prevalence of IVD was 34.57%, with 23.87% for immunological discordance (ID) and 10.7% for virological discordance (VD). Females were predominant (66.26%), and male gender influenced IVD with a statistically significant difference (p = 0.006) and was associated with VD (p = 0.007). The average age was 38.77 11.30 years. PLHIV were classified at WHO stages 3 and 4 (86.01%). The median initial haemoglobin level was 11.5 g/L [3.2 - 12]. The mean initial CD4 T-cell count was 272.84 cells/mm3 201.6. The median initial viral load (VL) was 147,337 copies/mL [1092 - 31,675,000]. The initial CD4 T-cell count 3 was associated with IVD with a statistically significant difference (p = 0.0009) and correlated with ID (p = 0.000). Prurigo was associated with IVD with a statistically significant difference (p = 0.003). Cerebral toxoplasmosis was not associated with IVD but was associated with ID (p = 0.04). This study allowed us to describe the profile of PLHIV with IVD. The main associated factors were male gender, initial CD4 T-cell count 3, toxoplasmosis, prurigo, and herpes zoster.
文摘Confluences play a major role in the dynamics of networks of natural and man-made open channels, and field measurements on river confluences reveal that discordance in bed elevation is common.Studies of schematized confluences with a step at the interface between the tributary and the main channel bed reveal that bed elevation discordance is an important additional control for the confluence hydrodynamics.This study aimed to improve understanding of the influence of bed elevation discordance on the flow patterns and head losses in a right-angled confluence of an open channel with rectangular cross-sections.A large eddy simulation (LES)-based numerical model was set up and validated with experiments by others.Four configurations with different bed discordance ratios were investigated.The results confirm that, with increasing bed elevation discordance, the tributary streamlines at the confluence interface deviate less from the geometrical confluence angle, the extent of the recirculation zone (RZ) gets smaller, the ratio of the water depth upstream to that downstream of the confluence decreases, and the water level depression reduces.The bed elevation discordance also leads to the development of a large-scale structure in the lee of the step.Despite the appearance of the large-scale structure, the reduced extent of the RZ and associated changes in flow deflection/contraction reduce total head losses experienced by the main channel with an increase of the bed discordance ratio.It turns out that bed elevation discordance converts the lateral momentum from the tributary to streamwise momentum in the main channel more efficiently.
基金supported by National Natural Science Foundation of China(No.81172110)National High Technology Research and Development Program(No. 2012AA 02A 504)+2 种基金Beijing Municipal Science & Technology Commission Program(No.Z11110706730000)Beijing Natural Science Foundation(7142034)China Postdoctoral Science Foundation(2013M530494)
文摘Background： A number of studies have examined human epidermal growth factor receptor 2 （HER2） status in primary gastric cancer （GC） and associated metastasis, some showed their great concordance in FIER2 expression, but others demonstrated notable discordance. There is still little consensus on HER2 discordance, therefore, a systematic review and meta-analysis was conducted to assess the status on HER2 discordance between primary GC and its paired metastasis. Methods： PubMed, EMBASE, ASCO and The Cochrane Library were searched for studies that explored the concordance between primary tumor and metastasis in patients with GC up to 10 March, 2014. Data of discordance of HER2 between primary GC and corresponding metastasis were extracted from the publications and random-effects models were used to estimate pooled discordance proportions. Results： Eighteen articles including 1,867 patients were included for the meta-analysis in accordance with the selection criteria. Pooled discordance proportions were 7% [95% confidence interval （CI）： 5-10%] for HER2 status. Pooled proportions of tumors shifting from positive to negative and from negative to positive were 17% （95% CI： 7-29%） and 4% （95% CI： 2-6%） respectively. No publication bias was found in the meta-analysis. Conclusions： The discordance of HER2 status is not rare in primary and metastatic GC through our metaanalysis. Prospective studies are needed to testify the clinical significance of the discordance of HER2 status.
基金supported by the National Key Research and Development Programs of China(2017YFC0505202)Construction of Basic Conditions Platform of Sichuan Science and Technology Department(2019JDPT0020)Species Conservation Project of Liziping National Nature Reserve。
文摘The Hengduan Mountains Region(HMR)is the largest“evolutionary frontier”of the northern temperate zone,and the origin and maintenance of species in this area is a research hotspot.Exploring species-specific responses to historical and contemporary environmental changes will improve our understanding of the role of this region in maintaining biodiversity.In this study,mitochondrial and microsatellite diversities were used to assess the contributions of paleogeological events,Pleistocene climatic oscillations,and contemporary landscape characteristics to the rapid intraspecific diversification of Liangshantriton taliangensis,a vulnerable amphibian species endemic to several sky-island mountains in the southeastern HMR.Divergence date estimations suggested that the East Asian monsoon,local uplifting events(Xigeda Formation strata),and Early-Middle Pleistocene transition(EMPT)promoted rapid divergence of L.taliangensis during the Pleistocene,yielding eight mitochondrial lineages and six nuclear genetic lineages.Moreover,population genetic structures were mainly fixed through isolation by resistance.Multiple in situ refugia were identified by ecological niche models and high genetic diversity,which played crucial roles in the persistence and divergence of L.taliangensis during glacial-interglacial cycles.Dramatic climatic fluctuations further promoted recurrent isolation and admixing of populations in scattered glacial refugia.The apparent mitonuclear discordance was likely the result of introgression by secondary contact and/or female-biased dispersal.Postglacial expansion generated two major secondary contact zones(Ganluo(GL)and Chuhongjue(CHJ)).Identification of conservation management units and dispersal corridors offers important recommendations for the conservation of this species.
基金The National Key R&D Program of China under contract Nos 2018YFC0310105 and 2018YFC0309800the China Ocean Mineral Resources R&D Association under contract No.DY135-S2-1-04+2 种基金the National Natural Science Foundation of China under contract Nos 41890813,91628301,41976066,41706056,41976064,91858207 and U1606401the Chinese Academy of Sciences under contract Nos Y4SL021001,QYZDY-SSW-DQC005 and 133244KYSB20180029the Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)under contract No.GML2019ZD0205
文摘We analyzed seafloor morphology and geophysical anomalies of the Southeast Indian Ridge(SEIR) to reveal the remarkable changes in magma supply along this intermediate fast-spreading ridge. We found systematic differences of the Australian-Antarctic Discordance(AAD) from adjacent ridge segments with the residual mantle Bouguer gravity anomaly(RMBA) being more positive, seafloor being deeper, morphology being more chaotic, M factors being smaller at the AAD. These systematic anomalies, as well as the observed Na8.0 being greater and Fe8.0 being smaller at AAD, suggest relatively starved magma supply and relatively thin crust within the AAD.Comparing to the adjacent ridges segments, the calculated average map-view M factors are relatively small for the AAD, where several Oceanic Core Complexes(OCCs) develop. Close to 30 OCCs were found to be distributed asymmetrically along the SEIR with 60% of OCCs at the northern flank. The OCCs are concentrated mainly in Segments B3 and B4 within the AAD at ~124°–126°E, as well as at the eastern end of Zone C at ~115°E. The relatively small map-view M factors within the AAD indicate stronger tectonism than the adjacent SEIR segments.The interaction between the westward migrating Pacific mantle and the relatively cold mantle beneath the AAD may have caused a reduction in magma supply, leading to the development of abundant OCCs.
文摘For two-way contingency tables with ordered categories, the present paper gives a theorem that the independence model holds if and only if the logit uniform association model holds and equality of concordance and discordance for all pairs of adjacent rows and all dichotomous collapsing of the columns holds. Using the theorem, we analyze the cross-classification of duodenal ulcer patients according to operation and dumping severity.
文摘<strong>Introduction: </strong><span style="font-family:Verdana;">Double discordance or corrected transposition of the great vessels is a rare congenital heart disease. It is an atrioventricular and ventriculo-arterial mismatch. It is a complex and unusual form of congenital heart disease. Often asymptomatic, in its isolated form, bradycardia, murmur and cyanosis can be a mode of revelation. </span><span style="font-family:;" "=""></span><b><span style="font-family:Verdana;">Case presentation:</span></b><span style="font-family:;" "=""><span style="font-family:Verdana;"> We report the case of an 11-year-old child, asymptomatic at birth, after he started to have dyspnea on exertion, recurrent bronchitis, motivating a cardiological consultation. On cardiac physical examination, the heart sounds regular, not rapid at 81 BPM with a grade 3-4/6 systolic murmur at the 4th left EIC (Intercostal space). EKG (electrocardiogram) shows PR interval at 0.20 seconds. Cardiac ultrasound reveals atrioventricular discordance, vascular malposition, anterior aorta, the two vessels placed side by side, minimal pulmonary insufficiency, a small leak at the levels of the mitral and tricuspid valves, dystrophic pulmonary valves with an average gradient of 91 mmHg, max at 158 mmHg. Regular follow-up has been recommended through the performance of a clinical examination and cardiac ultrasound. </span><b><span style="font-family:Verdana;">Conclusion:</span></b><span style="font-family:Verdana;"> The double discordance can be asymptomatic, </span></span><span style="font-family:Verdana;">and </span><span style="font-family:Verdana;">survival can be long in the isolated forms, but the evolution is not always benign, especially in the associated forms. It depends on the function of the systemic right ventricle and associated abnormalities.</span>
文摘BACKGROUND Discordance between endoscopic and histologic assessments in Crohn’s disease(CD)have been observed,however the prevalence and cause are unclear.AIM To assess if a protocolized approach to biopsy collection facilitates understanding of this discordance in patients with ileal CD.METHODS Patients with known ileal CD underwent colonoscopy with endoscopic disease activity assessment.Three protocolized biopsies were taken respectively from an ulcer edge,7-mm,and 14-mm away from the ulcer edge in patients with discrete ileal ulcer(s).In patients with no ulcers as controls,the same 3-site biopsy protocol was applied in a randomly selected area of endoscopically-unremarkable terminal ileal mucosa.A blinded pathologist assessed mucosal inflammation in each biopsy using 3 validated histologic indices.RESULTS Twenty-four participants had visible ulcer(s)on endoscopy and 12 served as no-ulcer controls.Of biopsies taken from an ulcer edge,only 67%showed histologic evidence of active(neutrophilic)inflammation,and 33%showed histologic features of ulcer or erosion;all were from either large(n=4)or very large(n=4)ulcers.In the no-ulcer controls,no biopsies showed histologic features of ulcer or erosion,but 8%showed active inflammation.CONCLUSION A striking discordance exists between endoscopic and histologic assessments for mucosal inflammation in patients with active ileal CD,even in biopsies targeted at an ulcer edge,while a higher concordance is seen in patients with no endoscopic disease activity.It remains unclear how to incorporate histologic disease activity into the treatment paradigm.Further research is needed to optimize biopsy protocols and histologic assessments for CD.
基金supported by the Ministry of Science and Technology of China(2021YFA11020000,2022YFC2702200 and 2018YFA0108900)the National Natural Science Foundation of China(NSFC)(31721003,32022024,32370842,32100633,32270850,32070652 and 81630035)the Shuguang Program of the Shanghai Education Development Foundation and Shanghai Municipal Education Commission(22SG20).
文摘Naive pluripotent state can be obtained by several strategies from various types of cells,in which the cell fate roadmap as well as key biological events involved in the journey have been described in detail.Here,we carefully explored the chromatin accessibility dynamics during the primed-to-naïve transition by adopting a dual fluorescent reporter system and the assay for transposase-accessible chromatin(ATAC)-seq.Our results revealed critical chromatin remodeling events and highlight the discordance between chromatin accessibility and transcriptional activity.We further demonstrate that the differential epigenetic modifications and transcription factor(TF)activities may play a critical role in regulating gene expression,and account for the observed variations in gene expression despite similar chromatin landscapes.
基金supported by the National Natural Science Foundation of China(Grant No. 30490235).
文摘Channel confluences are universally present in nature. They can be divided into two types： asymmetrical river confluences and symmetric river confluences. The latter is also called as the Y-shaped confluences. Most of previous work has paid more attention to the asymmetrical river confluences, but few studies have been conducted on the Y-shaped confluences. In this article, the effects of bed discordance on the flow patterns at ＂Y＂ shaped open-channel confluences were studied by using a 3-D numerical simulation. It is proved that the model can undertake quantitative assessment of the flow at confluences. The results indicate that there are a lot of differences between the Y-shaped confluence and asymmetrical confluence. The discordant bed height plays an important role at the Y-shaped junction.
基金supported by South China Botanical Garden, Chinese Academy of Sciences (QNXM-202301)International Partnership Program of the Chinese Academy of Sciences (068GJHZ2022055FN)+1 种基金Department of Science and Technology of Guangzhou (202102080496)Department of Science and Technology of Guangdong Province (2022A0505030007)。
文摘The field of evolutionary biology has been revolutionized by phylogenomic approaches in the last decades. However, with the ever-increasing size and scope of molecular data collection, conflicting genealogies may be yielded based on different datasets and analytical approaches, a phenomenon known as cytonuclear discordance(Figure 1A and B).
基金supported by the National Natural Science Foundation of China,Key International(regional)Cooperative Research Project(no.31720103903)the Science and Technology Basic Resources Investigation Program of China(no.2019FY100900)+6 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(no.XDB31000000)the National Natural Science Foundation of China(no.31270274)the Yunling International High-end Experts Program of Yunnan Province,China(no.YNQR-GDWG-2017-002 and no.YNQR-GDWG-2018-012)the China Scholarship Council(202004910775)the Chinese Academy of Sciences(CAS)President's International Fellowship Initiative(no.2020PB0009)the China Postdoctoral Science Foundation(CPSF)the United States Department of Energy(grant no.DESC0018247 to PSS,RPG,and DES).
文摘The angiosperm family Elaeagnaceae comprises three genera and ca.100 species distributed mainly in Eurasia and North America.Little family-wide phylogenetic and biogeographic research on Elaeagnaceae has been conducted,limiting the application and preservation of natural genetic resources.Here,we reconstructed a strongly supported phylogenetic framework of Elaeagnaceae to better understand interand intrageneric relationships,as well as the origin and biogeographical history of the family.For this purpose,we used both nuclear and plastid sequences from Hyb-Seq and genome skimming approaches to reconstruct a well-supported phylogeny and,along with current distributional data,infer historical biogeographical processes.Our phylogenetic analyses of both nuclear and plastid data strongly support the monophyly of Elaeagnaceae and each of the three genera.Elaeagnus was resolved as sister to the well-supported clade of Hippophae and Shepherdia.The intrageneric relationships of Elaeagnus and Hippophae were also well resolved.High levels of nuclear gene tree conflict and cytonuclear discordance were detected within Elaeagnus,and our analyses suggest putative ancient and recent hybridization.We inferred that Elaeagnaceae originated at ca.90.48 Ma(95%CI?89.91e91.05 Ma),and long-distance dispersal likely played a major role in shaping its intercontinentally disjunct distribution.This work presents the most comprehensive phylogenetic framework for Elaeagnaceae to date,offers new insights into previously unresolved relationships in Elaeagnus,and provides a foundation for further studies on classification,evolution,biogeography,and conservation of Elaeagnaceae.
文摘BACKGROUND A reliable test is essential for diagnosing Helicobacter pylori(H.pylori)infection,and crucial for managing H.pylori-related diseases.Serving as an excellent method for detecting H.pylori infection,histologic examination is a test that clinicians heavily rely on,especially when complemented with immunohistochemistry(IHC).Additionally,other diagnostic tests for H.pylori,such as the rapid urease test(CLO test)and stool antigen test(SA),are also highly sensitive and specific.Typically,the results of histology and other tests align with each other.However,on rare occasions,discrepancy between histopathology and other H.pylori diagnostic tests occurs.AIM To investigate the discordance between histology and other H.pylori tests,the underlying causes,and the impact on clinical management.METHODS Pathology reports of gastric biopsies were retrieved spanning August 2013 and July 2018.Reports were included in the study only if there were other H.pylori tests within seven days of the biopsy.These additional tests include CLO test,SA,and H.pylori culture.Concordance between histopathology and other tests was determined based on the consistency of results.In instances where histology results were negative while other tests were positive,the slides were retrieved for re-assessment,and the clinical chart was reviewed.RESULTS Of 1396 pathology reports were identified,each accompanied by one additional H.pylori test.The concordance rates in detecting H.pylori infection between biopsy and other tests did not exhibit significant differences based on the number of biopsy fragments.117 discrepant cases were identified.Only 20 cases(9 with CLO test and 11 with SA)had negative biopsy but positive results in other tests.Four cases initially stained with Warthin-Starry turned out to be positive for H.pylori with subsequent IHC staining.Among the remaining 16 true discrepant cases,10 patients were on proton pump inhibitors before the biopsy and/or other tests.Most patients underwent treatment,except for two who were untreated,and two patients who were lost to follow-up.CONCLUSION There are rare discrepant cases with negative biopsy but positive in SA or CLO test.Various factors may contribute to this inconsistency.Most patients in such cases had undergone treatment.
基金partially supported by the National Natural Science Foundation of China (Grant No. 11601338)。
文摘Quantum discord, one of the famous quantum correlations, has been recently generalized to multipartite systems by Radhakrishnan et al. Here we give analytical solutions of the quantum discord for a family of N-qubit quantum states. For the bipartite system, we derive a zero quantum discord which will remain unchanged under the phase damping channel. For multiparitite systems, it is found that the quantum discord can be classified into three categories and the quantum discord for odd-partite systems can exhibit freezing under the phase damping channel, while the freezing does not exist in the even-partite systems.
基金funded by the Education Department of Hainan Province(No.HnjgY,2022–12)the National Natural Science Foundation of China(No.32260127 to C.Y.)Doctoral Start-up Funds of China West Normal University(No.493002 to P.Y.).
文摘In the co-evolutionary system of avian brood parasitism,egg recognition and rejection are common and generally act as effective anti-parasitic adaptations by hosts.Accordingly,most studies have examined the role of parasite egg colors and markings in detection cues in hosts;however,studies focusing on the effects of egg size and quantity are relatively scarce and have mostly concentrated on the hosts of parasitic cowbirds.Here,we studied the egg recognition behaviors of a potential host of the Common Cuckoo(Cuculus canorus)—the Green-backed Tit(Parus monticolus),to determine:(1)whether the host uses the sizes of parasite eggs and/or the quantity contrast between parasite and host eggs as cues for recognition,(2)whether the host employs the template or discordant recognition mechanism for egg recognition,and(3)whether the size and quantity of parasite eggs affect the egg rejection modes of the hosts.The results indicate that Green-backed Tits did not use parasite egg size as a primary cue for egg recognition.We hypothesized that both visual and tactile detection might be involved in egg recognition by Green-backed Tits and suggest further studies after controlling for nest light conditions.Differences in egg quantity between parasites and hosts were not used as cues for egg recognition because the hosts employed the template mechanism rather than discordance to recognize parasite eggs.However,both the relative sizes and quantity of parasite and host eggs significantly affected the rejection modes of parasite eggs,and larger or more parasite eggs triggered higher probabilities of nest desertion in hosts.
文摘A single small population of chasmophytic plants is described as Mojiangia oreophila,a monotypic genus in the subtribe Crepidinae,characterised by a unique combination of morphological features,in particular densely long-papillose homomorphic achenes with five main ribs each accompanied by two secondary ribs,coarse brownish pappus bristles,moderately many-flowered capitula,a small involucre with numerous outer phyllaries,perennial rosette herb growth and brown-woolly caudex and leaf axils.Molecular phylogenetic analysis detected that in the nrlTS phylogeny M.oreophila forms a clade of its own in the Crepidinae;in the plastid DNA phylogeny it is nested in the clade formed by the hybrid-ogenous genus Faberia,the maternal ancestor of which comes from the Crepidinae and the paternal ancestor from the Lactucinae,where Faberia is placed in nrlTS phylogenies.M.oreophila shares several morphological features with Faberia and also shares the expected chromosome number of 2n=16 with its hitherto unknown maternal ancestor.M.oreophila may therefore be a successor of the maternal ancestor of Faberia.Alternatively,cytonuclear discordance is to be assumed in Mojiangia,caused by chloroplast capture as a result of hybridisation and introgression with Faberia.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP,2019QZKK05010503)Biodiversity Survey and Assessment Project of the Ministry of Ecology and Environment,China(2019HJ2096001006)+1 种基金Construction of Basic Conditions Platform of Sichuan Science and Technology Department(2019JDPT0020)China Biodiversity Observation Networks(Sino BON)。
文摘Confused geographical structure of a population and mitonuclear discordance are shaped by a combination of rapid changes in population demographics and shifts in ecology.In this study,we generated a time-calibrated phylogeny of Scutiger boulengeri,an endemic Xizang alpine toad occurring in mountain streams on the Qinghai-Xizang(Tibet)Plateau(QTP).Based on three mitochondrial DNA(mt DNA)genes,eight clades were assigned to three deeply divergent lineages.Analysis of nuclear DNA(nu DNA)genes revealed three distinct clusters without geographic structure,indicating significantly high rates of gene flow.Coalescent theory framework analysis(approximate Bayesian computation model DIYABC and Migrate-N)suggested that divergence of the main intraspecific clusters was the result of hybridization after secondary contact in the Holocene around 0.59 million years ago(Ma).The ratio of mt DNA FST(fixation index)to nu DNA FST was 2.3,thus failing to show male-biased dispersal.Geographic cline analysis showed that a wide hybrid zone was initially established in southwestern China,without significant reproductive isolation but with strong introgression in S.boulengeri,suggesting high hybrid fitness.Furthermore,mt DNA genes exhibited isolation by distance(IBD)while nu DNA genes exhibited significant isolation by environment(IBE).Results suggested that mitonuclear discordance may have initially been caused by geographic isolation,followed by precipitation-mediated hybridization,producing a wide hybrid zone and geographic structure confusion of nu DNA genes in S.boulengeri.This study indicated that complicated historical processes may have led to specific genetic patterns,with a specific climate factor facilitating gene flow in the system.
基金supported by the National Natural Science Foundation of China(41861008)Science Foundation of Yunnan Education Department(2018JS347)the Ten-thousand Talents Program of Yunnan Province(YNWR-QNBJ-2020).
文摘The complex interactions of historical,geological and climatic events on plant evolution have been an important research focus for many years.However,the role of desert formation and expansion in shaping the genetic structures and demographic histories of plants occurring in arid areas has not been well explored.In the present study,we investigated the phylogeography of Arnebia szechenyi,a desert herb showing a near-circular distribution surrounding the Tengger Desert in Northwest China.We measured genetic diversity of populations using three maternally inherited chloroplast DNA(cpDNA)fragments and seven bi-paternally inherited nuclear DNA(nDNA)loci that were sequenced from individuals collected from 16 natural populations across its range and modelled current and historical potential habitats of the species.Our data indicated a considerably high level of genetic variation within A.szechenyi and noteworthy asymmetry in historical migration from the east to the west.Moreover,two nuclear genetic groups of populations were revealed,corresponding to the two geographic regions separated by the Tengger Desert.However,analysis of cpDNA data did not show significant geographic structure.The most plausible explanation for the discrepancy between our findings based on cpDNA and nDNA data is that A.szechenyi populations experienced long periods of geographic isolation followed by range expansion,which would have promoted generalized recombination of the nuclear genome.Our findings further highlight the important role that the Tengger Desert,together with the Helan Mountains,has played in the evolution of desert plants and the preservation of biodiversity in arid Northwest China.
