Comparative Study of Genetic Structure and Genetic Diversity betweenWild and Cultivated Populations of Taxus cuspidata,Northeast China

Taxus cuspidata is a rare plant with important medicinal and ornamental value.Aiming at the obvious differences between wild and cultivated populations of T.cuspidata from Northeast China,a total of 61 samples,that is,33 wild yews and 28 cultivated yews were used to analyze the differences and correlations of the kinship,genetic diversity,and genetic structure between them by specific length amplified fragment sequencing(SLAF-seq).Finally,470725 polymorphic SLAF tags and 58622 valid SNP markers were obtained.Phylogenetic analysis showed that 61 samples were classified into 2 clusters:wild populations and cultivated populations,and some wild yews were categorized into the cultivated populations;the genetic diversity analysis showed that the Nei diversity index of wild populations(0.4068)was smaller than that of cultivated populations(0.4414),and the polymorphic information content(PIC)of wild populations(0.2861)was smaller than that of cultivated populations(0.3309).The genetic differentiation analysis showed that the total populations of gene diversity(H_(t))of cultivated and wild populations were respectively 0.8159 and 0.5685,the coefficient of gene differentiation(G_(st))of cultivated and wild populations was respectively 0.3021 and 0.1068,and the gene flow(N_(m))(2.4967)of wild populations was larger than cultivated populations(0.8199).The molecular variance(AMOVA)revealed that inter-population variation accounted for 29.57%of the total genetic variation,while intra-population variation accounted for 70.42% of the total genetic variation(p<0.001),this suggested that the genetic variation in the T.cuspidata is mainly attributed to within-population factors.In conclusion,the genetic distance between geographical ecological groups of wild populations was generally smaller than that of cultivated populations,and the degree of genetic diversity and genetic differentiation was smaller than that of cultivated populations.As evident,the utilization of SLAF-seq technology enables efficient and accurate development of SNP markers suitable for genetic analysis of T.cuspidata species.These developed SNP markers can provide a molecular foundation for T.cuspidata breeding,construction of genetic maps,variety identification,and association analysis of agronomic traits.

The Impact of Stream Landscape on Genetic Structure and Dispersal Patterns in Stream Salamander(Pachyhynobius shangchengensis)

Compared with other terrestrial environments,the stream environment generally presents a linear spatial structure and relatively simple environment.In a stream landscape,the dispersal direction of stream-type organisms usually presents a linear structure along the stream,which results in the limited dispersal and the genetic differentiation of stream-type organisms across different stream sections.The Shangcheng Stout Salamander(Pachyhynobius shangchengensis)is a narrowly distributed stream salamander in Dabie Mountains of East China.In the present study,we tested for the impact of stream landscape(i.e.waterfalls and underground river)on genetic structure and dispersal pattern in P.shangchengensis based on 12 nuclear microsatellite loci from 195 individuals in 3 populations(A,B and C)from three closely connected sections within one stream.Genetic diversity results suggested that Population B contains relatively high genetic diversity for P.shangchengensis when compared to the other populations(A and C).Detectable genetic differentiation was found(FST=0.008,P=0.007)among three populations,which was also supported by the Structure,FCA analysis and relatedness estimates of each pair of individuals among populations.The assignment test suggested that P.shangchengensis has philopatric males and female-biased dispersal(mean female Alc=.0.031,SE=0.225;mean male Alc=0.026,SE=0.198).Female-biased dispersal was also supported by analyses for each sex(i.e.Spatial autocorrelation,Genetic distance,Relatedness analysis).Our study indicated that small and isolated populations(A and C)had relatively low genetic diversity due to the limited population size.For stream salamanders,landscape features(i.e.waterfalls and underground river)can influence the ability of an individual to disperse through the landscape,and consequently influence the formation of strong genetic differentiation of P.shangchengensis.

Impact of Crop Rotation on Pathotype and Genetic Structure of Phythophthora sojae in Fields

To estimate the impact of crop rotation on the pathotype and genetic structure of Phythophthora sojae in fields, 372 isolates of P. sojae were obtained from long-term localisation experimental fields in Heilongjiang Province of China. The hypocotyl inoculation method was used to characterize the virulence of P. sojae on 13 differential cultivars, and the amplified fragment length polymorphism(AFLP) technique was used to analyze difference in the genetic structure of P. sojae. The results indicated that an abundant diversity of genetic structures and pathotypes of P. sojae, a more uniform distribution of pathotypes and less dominance of pathotypes occurred in corn-soybean and wheat-soybean rotation fields than in a continuous soybean mono-cropping field. These findings suggested that P. sojae did not easily become the dominant race in rotation fields, which maintain disease resistance in soybean varieties. Therefore, the results of this study suggested that Phytophthora stem and root rot of soybeans could be effectively controlled by rotating soybeans with non-host crops of corn and wheat.

High levels of genetic diversity and an absence of genetic structure among breeding populations of the endangered Rufous-backed Bunting in Inner Mongolia,China:implications for conservation

Background:The Rufous-backed Bunting,Emberiza jankowskii,is an endangered species that is primarily distributed in Inner Mongolia,China.The main threats to the continued persistence of this species are habitat loss and degradation.However,the impact of population loss on genetic diversity remains unclear.To support future conservation and management efforts,we assessed the genetic diversity and population structure of E.jankowskii using mitochondrial DNA and microsatellites.Methods:Blood samples were collected from 7-8-day-old nestlings in Inner Mongolia,China between May and August of 2012 and 2013.Mitochondrial DNA sequences and microsatellite markers were used to assess the genetic diversity,genetic structure and inbreeding of E.jankowskii.The results of genetic diversity and inbreeding were compared to other avian species.Results:We found an unexpectedly high level of genetic diversity in terms of mitochondrial DNA and microsatellite compared to other avian species.However,there were high levels of gene flow and minimal genetic structuring,among the fragmented breeding populations of E.jankowskii in Inner Mongolia.These findings suggest that E.jankowskii in Inner Mongolia is a metapopulation.Despite the high genetic diversity of E.jankowskii,local populations in each small patch remain at risk of extinction due to habitat loss.In addition,the E.jankowskii population has a high risk of inbreeding.Conclusions:To minimize further loss of genetic diversity of this endangered species,we suggest that the E.jankowskii in Inner Mongolia should be considered as a protected species for management purposes.Conservation efforts should concentrate on E.jankowskii habitat management.This may be most effectively achieved by protecting the current breeding habitats and prohibiting over-grazing.

Genetic Diversity and Genetic Structure of Maize Inbred Lines from Yunnan Revealed by SNP Chips

[Objectives]The genetic diversity and population genetic structure of 107 inbred lines of maize in Yunnan were analyzed,in order to provide technical support for maize germplasm innovation,genetic improvement of germplasm resources,variety management,and lay a solid foundation for exploring genes related to fine traits in the future.[Methods]The 107 maize inbred lines generalized in Yunnan were selected,and 45 backbone inbred lines commonly used in China were used as reference for heterotic group classification.On Axiom Maize 56K SNP Array platform,maize SNP chips(56K)were used to scan the whole maize genome,and the NJ-tree model of Treebest was used to construct a phylogenetic tree.Principal component analysis(PCA)was conducted by GCTA(genome-wide complex trait analysis)to reveal the genetic diversity and population genetic structure.[Results]In the 107 Yunnan local inbred lines,5533 uniformly distributed high-quality SNP marker sites were finally detected.Based on the analysis of these SNP marker sites,Nei s gene diversity index(H)of 107 maize germplasm genes was 0.2981-0.5000 with an average value being 0.4832,and polymorphism information content(PIC)values were 0.2536-0.3750 with an average value being 0.3662.The minimum allele frequency value was 0.5000-0.8178 with an average value being 0.5744.The analysis of population genetic structure showed that when K=6,the maximum value of△K was the maximum,which meant that the inbred lines used in this study could be divided into six groups.They were Tangsi Pingtou blood relationship group,PB blood relationship group,335 female blood relationship group,Zi 330 and the Lüda Honggu blood relationship group,unknown group 1 and unknown group 2.No inbred lines were divided into other heterotic groups.Among them,37 inbred lines from the 2 unknown groups could not be classified into the same group as the 10 known heterotic groups in China.The results of principal component analysis showed that the 107 maize inbred lines generalized in Yunnan could be clearly distinguished from the backbone maize inbred lines commonly used in China.Most of the maize inbred lines in Yunnan were concentrated near the reference backbone inbred lines.But some Yunnan inbred lines were far away from the reference inbred lines commonly used in China.[Conclusions]The maize germplasm resources in Yunnan area were rich in genetic diversity,including multiple heterotic groups,and there was a rich genetic basis of breeding parents.They could be clearly distinguished from the backbone inbred lines commonly used in China,and some of them had a long genetic distance from the backbone inbred lines.The resources which have good application potential can be used to create new heterotic groups.

Genetic structure and recent population demographic history of Taihangshan macaque(Macaca mulatta tcheliensis),North China

Massive actions have been and are being taken into protecting the world’s primates from extinction,while the study of the properties of genetic diversity,demographic history,and ecological relationships will benefit the understand-ing of the long-term survival of a species.The Taihangshan macaque(Macaca mulatta tcheliensis),a subspecies of rhesus macaque(Macaca mulatta),is endemic to China and currently restricted to southern Mt.Taihangshan area.Herein,we evaluated the genetic diversity,population structure,and demographic history of this subspecies using mitochondrial(Cytb and high variable region I:HVR I)and nuclear markers(microsatellite loci)of 131 in-dividuals collected from 9 localities covering the distribution range of this subspecies.Both phylogenetic analyses and genetic assignment revealed that the wild populations of Taihangshan macaques could be divided into 2 major highly divergent clades,THS-east and THS-west.Low genetic diversity(π:0.00266±0.00016)but high haplotype diversity(Hd:0.80352±0.015)were detected in the Taihangshan macaques,particularly in THS-east.Analyses of demographic history suggested that the Taihangshan macaques experiencedfirst a stable historical population size from Holocene to early 19th century but a subtle decline and then slight growth in the recent 200 years.We suggest that bridging the neighbor populations(i.e.setting corridors)would facilitate the male-mediated geneflow and subsequently increase the genetic diversity of the Taihangshan macaque populations.

Analysis of genetic diversity and structure across a wide range of germplasm reveals genetic relationships among seventeen species of Malus Mill,native to China

China is a center of diversity for Malus Mill,with 27 native species including 21 wild species and six domesticated species.We applied a set of 19 simple sequence repeat markers to genotype 798 accessions of 17 species(12 wild species and five cultivated species)of Malus originating from 14 provinces in China.A total of 500 alleles were detected.Diversity statistics indicated a high level of genetic variation as quantified by the average values of the effective allele number(N_(e)).expected heterozygosity(H_(e)),and Shannon's Information Index(I)(10.309,0.886,and 2.545,respectively).Malus sieversii(MSR;H_(e)=0.814,I=2.041,N_(e)=6.054),M.baccata(MBB;H_(e)=0.848,/=2.350,N_(e)=8.652),M.toringoides(MTH;He=0.663,I=1.355,N_(e)=3.332),and M.hupehensis(MHR;H_(e)=0.539,I=0.912,N_(e)=0.579)showed a higher level of genetic diversity in this study than the previous studies.MSR and MBB contributed to the origin and evolution of some accessions of M.domestica subsp.chinensis(MDC).However,other accessions of MDC showed a closer genetic distance with MBB and cultivated species,especially M.robusta(MRB),M.asiatica(MAN),and M.prunifolia(MPB).Not all accessions of MDC were descended from MSR in Xinjiang Uygur Autonomous Region of China.This research provides novel insights into the genetic relationships of Malus native to China,which will be useful for genetic association studies,germplasm conservation,and breeding programs.

Species diversity and population density affect genetic structure and gene dispersal in a subtropical understory shrub

Aims The dispersal of pollen and seeds is spatially restricted and may vary among plant populations because of varying biotic interactions,population histories or abiotic conditions.Because gene dispersal is spatially restricted,it will eventually result in the development of spatial genetic structure(SGS),which in turn can allow insights into gene dispersal processes.Here,we assessed the effect of habitat characteristics like population density and community structure on small-scale SGS and estimate historical gene dispersal at different spatial scales.Methods In a set of 12 populations of the subtropical understory shrub Ardisia crenata,we assessed genetic variation at 7 microsatellite loci within and among populations.We investigated small-scale genetic structure with spatial genetic autocorrelation statistics and heterogeneity tests and estimated gene dispersal distances based on population differentiation and on within-population SGS.SGS was related to habitat characteristics by multiple regression.Important Findings The populations showed high genetic diversity(He=0.64)within populations and rather strong genetic differentiation(F#ST=0.208)among populations,following an isolation-by-distance pattern,which suggests that populations are in gene flow–drift equilibrium.Significant SGS was present within populations(mean Sp=0.027).Population density and species diversity had a joint effect on SGS with low population density and high species diversity leading to stronger small-scale SGS.Estimates of historical gene dispersal from between-population differentiation and from within-population SGS resulted in similar values between 4.8 and 22.9 m.The results indicate that local-ranged pollen dispersal and inefficient long-distance seed dispersal,both affected by population density and species diversity,contributed to the genetic population structure of the species.We suggest that SGS in shrubs is more similar to that of herbs than to trees and that in communities with high species diversity gene flow is more restricted than at low species diversity.This may represent a process that retards the development of a positive species diversity–genetic diversity relationship.

Genetic diversity and structure of the endemic and endangered species Aristolochia delavayi growing along the Jinsha River

The traditional medicinal plant,and endangered species Aristolochia delavayi(Aristolochiaceae)is an endemic species in China and occurs in the warm and dry areas along the Jinsha river.It is also a specific host of the larvae of Byasa daemonius,a vulnerable butterfly.In this study,15 pairs of polymorphic microsatellite primers of A.delavayi were designed and screened based on the Simple Sequence Repeats(SSR)loci found by using the results of genome skimming.Based on these 15 SSR markers,the genetic diversity and structure of 193 individuals from ten natural populations were analyzed in detail.In comparison to other endemic and endangered plants in the region,the population of A.delavayi possess a relatively high genetic diversity(He=0.550,I=1.112).AMOVA analysis showed that 68.4%of the total genetic diversity was within populations and 31.6%of the variation occurred among populations.There was a significant genetic differentiation among natural populations of A.delavayi detectable,with low gene flow(Nm=0.591).This might be attributed to geographical barriers and limited seed dispersal.To test the isolation by distance(IBD),we performed Mantel test,which showed a significant correlation between the geographic and genetic distances.In order to cope with the possible biases caused by IBD,we additionally performed Bayesian genetic cluster analyses and principal coordinate analysis(PCoA).The final cluster analysis revealed three groups with distinct geographical distribution.Habitat fragmentation and limited gene flow between these populations may be the main reasons for the current genetic structure.For conservation of this species,we suggest to divide its populations into three protection management units,with subsequent focus on the Yongsheng and Luquan populations which experienced a genetic bottleneck event in the past.

RAD-sequencing improves the genetic characterization of a threatened tree peony(Paeonia ludlowii)endemic to China:Implications for conservation

Compared with traditional genetic markers,genomic approaches have proved valuable to the conservation of endangered species.Paeonia ludlowii having rarely and pure yellow flowers,is one of the world’s most famous tree peonies.However,only several wild populations remain in the Yarlung Zangbo Valley(Nyingchi and Shannan regions,Xizang)in China due to increasing anthropogenic impact on the natural habitats.We used genome-wide single nucleotide polymorphisms to elucidate the spatial pattern of genetic variation,population structure and demographic history of P.ludlowii from the fragmented region comprising the entire range of this species,aiming to provide a basis for conserving the genetic resources of this species.Unlike genetic uniformity among populations revealed in previous studies,we found low but varied levels of intra-population genetic diversity,in which lower genetic diversity was detected in the population in Shannan region compared to those in Nyingzhi region.These spatial patterns may be likely associated with different population sizes caused by micro-environment differences in these two regions.Additionally,low genetic differentiation among populations(Fst=0.0037)were detected at the species level.This line of evidence,combined with the result of significant genetic differentiation between the two closest populations and lack of isolation by distance,suggested that shared ancestry among now remnant populations rather than contemporary genetic connectivity resulted in subtle population structure.Demographic inference suggested that P.ludlowii probably experienced a temporal history of sharp population decline during the period of Last Glacial Maximum,and a subsequent bottleneck event resulting from prehistoric human activities on the Qinghai-Tibet Plateau.All these events,together with current habitat fragment and excavation might contribute to the endangered status of P.ludlowii.Our study improved the genetic characterization of the endangered tree peony(P.ludlowii)in China,and these genetic inferences should be considered when making different in situ and ex situ conservation actions for P.ludlowii in this evolutionary hotspot region.

Fine-scale spatial genetic structure in predominantly selfing plants with limited seed dispersal： a rule or exception？

Gene flow at a fine scale is still poorly understood despite its recognized importance for plant population demographic and genetic processes.We tested the hypothesis that intensity of gene flow will be lower and strength of spatial genetic structure(SGS) will be higher in more peripheral populations because of lower population density.The study was performed on the predominantly selfing Avena sterilis and included:(1) direct measurement of dispersal in a controlled environment;and(2) analyses of SGS in three natural populations,sampled in linear transects at fixed increasing inter-plant distances.We found that in A.sterilis major seed dispersal is by gravity in close(less than 2 m) vicinity of the mother plant,with a minor additional effect of wind.Analysis of SGS with six nuclear SSRs revealed a significant autocorrelation for the distance class of 1 m only in the most peripheral desert population,while in the two core populations with Mediterranean conditions,no genetic structure was found.Our results support the hypothesis that intensity of SGS increases from the species core to periphery as a result of decreased within-population gene flow related to low plant density.Our findings also show that predominant self-pollination and highly localized seed dispersal lead to SGS at a very fine scale,but only if plant density is not too high.

The roles of calving migration and climate change in the formation of the weak genetic structure in the Tibetan antelope(Pantholops hodgsonii)

Geographical barriers and distance can reduce gene exchange among animals,resulting in genetic divergence of geographically isolated populations.The Tibetan antelope(Pantholops hodgsonii)has a geographical range of approximately 1600 km across the Qinghai-Tibet Plateau,which comprises a series of tall mountains and big rivers.However,previous studies indicate that there is little genetic differentiation among their geographical­ly delineated populations.To better understand the genetic structure of P.hodgsonii populations,we collected 145 samples from the 3 major calving regions,taking into consideration their various calving grounds and mi­gration routes.We used a combination of mitochondrial sequences(Cyt b,ATPase,D-loop and COX I)to inves­tigate the genetic structure and the evolutionary divergence of the populations.Significant,albeit weak,genetic differentiation was detected among the 3 geographical populations.Analysis of the genetic divergence process revealed that the animals gradually entered a period of rapid genetic differentiation approximately 60000 years ago.The calving migration of P.hodgsonii cannot be the main cause of their weak genetic structure because this cannot fully homogenize the genetic pool.Instead,the geological and climatic events as well as the coupling vegetation succession process during this period have been suggested to greatly contribute to the genetic struc­ture and the expansion of genetic diversity.

Role of seed size, phenology, oogenesis and host distribution in the specificity and genetic structure of seed weevils (Curculio spp.) in mixed forests

Synchrony between seed growth and oogenesis is suggested to largely shape trophic breadth of seed-feeding insects and ultimately to contribute to their co-existence by means of resource partitioning or in the time when infestation occurs.Here we investigated:(i)the role of seed phenology and sexual maturation of females in the host specificity of seed-feeding weevils(Curculio spp.)predating in hazel and oak mixed forests;and(ii)the consequences that trophic breadth and host distribution have in the genetic structure of the weevil populations.DNA analyses were used to establish unequivocally host specificity and to determine the population genetic structure.We identified 4 species with different specificity,namely Curculio nucum females matured earlier and infested a unique host(hazelnuts,Corylus avellana)while 3 species(Curculio venosus,Curculio glandium and Curculio elephas)predated upon the acorns of the 2 oaks(Quercus ilex and Quercus pubescens).The high specificity of C.nucum coupled with a more discontinuous distribution of hazel trees resulted in a significant genetic structure among sites.In addition,the presence of an excess of local rare haplotypes indicated that C.nucum populations went through genetic expansion after recent bottlenecks.Conversely,these effects were not observed in the more generalist Curculio glandium predating upon oaks.Ultimately,co-existence of weevil species in this multi-host-parasite system is influenced by both resource and time partitioning.To what extent the restriction in gene flow among C.nucum populations may have negative consequences for their persistence in a time of increasing disturbances(e.g.drought in Mediterranean areas)deserves further research.

Genetic structure of the oriental white stork (Ciconia boyciana): implications for a breeding colony in a non-breeding area

The oriental white stork (Ciconia boyciana) is a threatened species, and their numbers are still in decline due tohabitat loss and poaching. China is a breeding and main wintering area for this animal and in recent years someindividuals have been found breeding in wintering areas and at some stopover sites. These new breeding coloniesare an exciting sign, however, little is understood of the genetic structure of this species. Based on the analysis ofa 463-bp mitochondrial DNA (mtDNA) control region, we investigated the genetic structure and genetic diversity of66 wild oriental white storks from a Chinese population. We analyzed the sequences of 66 storks obtained in thisstudy and the data of 17 storks from a Japanese population. Thirty-seven different haplotypes were detected amongthe 83 samples. An analysis of molecular variance showed a significant population subdivision between the twopopulations (FST = 0.316, P < 0.05). However, the phylogenetic analysis revealed that the samples from the differentpopulations did not form separate clusters and that there were genetic exchanges between the two populations.Compared with the Japanese population, the Chinese population had a relatively higher genetic diversity with ahaplotype diversity (h ± SD) of 0.953 ± 0.013 and a nucleotide diversity (π ± SD) of 0.013 ± 0.007. The high haplotypediversity and low nucleotide diversity indicate that this population might be in a rapidly increasing period from asmall effective population. A neighbor-joining tree analysis indicated that genetic exchange had occurred betweenthe newly arisen southern breeding colony and the northern breeding colony wintering in the middle and lowerYangtze River floodplain. These results have important implications for the conservation of the oriental white storkpopulation in China.

Genetic diversity and population structure of Camellia huana(Theaceae),a limestone species with narrow geographic range,based on chloroplast DNA sequence and microsatellite markers

Camellia huana is an endangered species with a narrow distribution in limestone hills of northern Guangxi and southern Guizhou provinces,China.We used one chloroplast DNA(cpDNA)fragment and 12 pairs of microsatellite(simple sequence repeat;SSR)markers to assess the genetic diversity and structure of 12 C.huana populations.A total of 99 alleles were detected for 12 polymorphic loci,and eight haplotypes and nine polymorphic sites were detected within 5200 bp of cpDNA.C.huana populations showed a low level of genetic diversity(n=8,Hd=0.759,Pi=0.00042 for cpDNA,NA=3.931,HE=0.466 for SSRs),but high genetic differentiation between populations(FST=0.2159 for SSRs,FST=0.9318 for cpDNA).This can be attributed to the narrow distribution and limestone habitat of C.huana.STRUCTURE analysis divided natural C.huana populations into two groups,consistent with their geographical distribution.Thus,we suggest that five natural C.huana populations should be split into two units to be managed effectively.

Population genetic structure and demographic history of the Chinese endemic Mongoloniscus sinensis(Dollfus,1901) (Isopoda:Oniscidea)

The soil animal Mongoloniscus sinensis(Dollfus,1901) is distributed in Northern China together with three other congeneric species only found in Asia.Compared to European and North American Oniscidea,little phylogeographic information about this Asian genus has been reported.Herein,we infer the genetic structure and demographic history of M.sinensis based on mitochondrial cytochrome c oxidase subunit I(mtCoI).The total dataset included 193 individuals from 26 locations in four provinces(Shanxi,Henan,Hebei and Shandong) of China.Most of the 87 haplotypes were unique to a sampling location,but seven haplotypes were shared among the populations.The results showed that high genetic differentiation exists both within populations and among the groups and populations of M.sinensis.According to the distribution of phylogenic clades and geographic analyses,it is suggested that mountain ranges play an important role in population separation and that the possible evolutionary trajectory of this species is from north to south.The most likely place of origin is the Northeast Plain of China with an estimated time of isolation separating populations around 8 Mya.

Subpopulation genetic structure of a plant panmictic population of Castanea sequinii as revealed by microsatellite markers

Castanea squinii Dode,an endemic tree widely distributed in China,plays an important role both in chestnut breeding and forest ecosystem function.The spatial genetic structure within and among populations is an important part of the evolutionary and ecological genetic dynamics of natural populations,and can provide insights into effective conservation of genetic resources.In the present study,the spatial genetic structure of a panmictic natural population of C.sequinii in the Dabie Mountain region was investigated using microsatellite markers.Nine prescreened microsatellite loci generated 29-33 alleles each,and were used for spatial autocorrelation analysis.Based on Moran’s I coefficient,a panmictic population of C.sequinii in the Dabie Mountain region was found to be lacking a spatial genetic structure.These results suggest that a high pollen-mediated gene flow among subpopulations counteract genetic drift and/or genetic differentiation and plays an important role in maintaining a random and panmictic population structure in C.sequinii populations.Further,a spatial genetic structure was detected in each subpopulation’s scale(0.228 km),with all three subpopulations showing significant fine-scale structure.The genetic variation was found to be nonrandomly distributed within 61 m in each subpopulation(Moran’s I positive values).Although Moran’s I values varied among the different subpopulations,Moran’s I in all the three subpopulations reached the expected values with an increase in distances,suggesting a generally patchy distribution in the subpopula-tions.The fine-scale structure seems to reflect restricted seed dispersal and microenvironment selection in C.sequinii.These results have important implications for understanding the evolutionary history and ecological process of the natural population of C.sequinii and provide baseline data for formulating a conservation strategy of Castanea species.

Genetic diversity and structure of Drimys brasiliensis in southern Brazil:insights for conservation

Population genetics studies are widely recognized for generating useful knowledge for biodiversity conservation.To date,however,little is known about the levels and distribution of genetic diversity of Drymis brasiliensis(Miers LC),a tree species from the Atlantic Rainforest.Therefore,in this study,we investigated how genetic diversity is distributed within and among populations of D.brasiliensis from southern Brazil using allozyme markers to genotype reproductive trees(8 populations)and seedlings(3 populations).Furthermore,in two populations,we established two permanent plots(5.1 and 1 ha)to analyze fine-scale genetic structure(FSGS).Studied populations presented low levels of genetic diversity(reproductive=0.085;seedlings=0.054)and high fixation indexes(reproductive=0.396;seedlings=0.231).Genetic divergence among populations was equal to 0.05,which is significant,signaling that few populations can conserve large portions of the species total genetic diversity.FSGS was only detected for one population,when reproductive individuals were separated by less than40 m.Low genetic diversity combined with high fixation indexes clearly signal a risk of losing diversity.Therefore,conservation efforts should be aimed at enhancing gene flow within the studied populations.

Genetic structure and differentiation of Psathyrostachys huashanica populations detected with RAPD markers

Psathyrostachys huashanica Keng is a perennial grass and belongs to genus Psathyrostachys under Triticeae.sathyrostachys is found in the center of Middle Asia and the Caucasus Mountain,while P.huashanica,a species endemic to China,is only located in Mt.Hua in the Shaanxi province,China.At present,the population of this species is decreasing,and reaching the edge of extinction.Due to the limitation in distribution and the importance as breeding material for germplasm storage,it has been considered as first class among the national protected rare plants.For this reason,the present study is significant in probing plant flora,origin and evolu-tion of Triticeae,and crop breeding.Randomly amplified polymorphic DNA(RAPD)markers were used to analyze the genetic structure and differentiation of P.huashanica popula-tions sampled in three valleys(Huangpu,Xian,and Huashan Valleys)in Mt.Hua.One hundred and twenty-two RAPD fragments were obtained in all 266 individuals with 20 prim-ers with a mean of 6.1(2-10)fragments per primer.The percentage of polymorphic loci(PPB)was 60.66%in Huangpu Valley,90.98%in Xian Valley,95.08%in Huashan Valley,and the total PPB was 95.08%,which indicated a highly genetic variability of P.huashanica.The Shannon’s Information index and GST were 0.3306 and 0.3263,respectively,indicating that there were more genetic variations within the subpopulations than those among the subpopulations.The gene flow among the subpopulations of P.huashanica(Nm=1.0322)was much less than that of the common ane-mophytes(Nm=5.24).Mean genetic distance is 0.1571(range:0.0022-0.2901).The highest value of genetic distance was found between the subpopulation(hp1)of Huangpu Valley and the highest altitude subpopulation(h8)of Huashan Valley.Correlation analysis detected significant correlation between genetic distance and vertical distance of altitude.Clustering analysis and principal coordinate analysis revealed the genetic differentiation among the populations of P.huashanica.Differentiation mainly occurred between the higher altitude subpopulations and the lower altitude sub-populations,suggesting that altitude might be the major factor that restricted the gene flow between different altitude subpopulations and resulted in differentiation of subpopulations.

Analysis of genetic diversity and prediction of Larix species distribution in the Qinghai–Tibet Plateau,China

Larix resources in the Qinghai-Tibet Plateau have important ecological and economic values.However,the lack of genetic diversity background and related research hinders the development of conservation strategies.In this study,genetic diversity and distribution of fi ve Larix species were investigated.Using 19 polymorphic microsatellite markers to study 272 representative individuals from 13 populations,the results show low genetic diversity at the population level,with variation explained mainly by diff erentiation among populations.The Larix populations were classifi ed into two clades,one formed by eight populations,including three of the species in this study,L.kongboensis,L.speciosa,and L.potaninii var.australis.The other clade consists of fi ve populations,including the other two species in this study,L.griffi thii and L.himalaica.Genetic distance of the species was aff ected by geographical isolation and genetic diversity was mainly aff ected by altitude.The area suitable for Larix spp.decreased during the Last Glacial Maximum compared to the current distribution according to the niche model,but should increase in future climate scenarios(2050s),expanding westward along the Himalayas.These results provide an important scientifi c basis for the development of conservation strategies and further the sustainable utilization of Larix resources in the Qinghai-Tibet Plateau.