Genetic Diversity and Population Structure in Chinese Indigenous Poplar (Populus simonii) Populations Using Microsatellite Markers

Populus simonii Carr. is an important ecological and commercial breeding species in northern China; however, human interference during the last few centuries has led to the reduction and fragmentation of natural populations. To evaluate genetic diversity and differentiation within and among existing populations, we used 20 microsatellite markers to examine the genetic variation and structure of 16 natural populations. Our results indicated that the level of genetic diversity differed among populations, with average number of alleles per locus (AR) and expected heterozygosity (H _e) ranging from 3.7 to 6.11 and 0.589 to 0.731, respectively. A marginal population from Qilian in the Qinghai–Tibetan Plateau showed the highest values (AR?=?6.11, H _e?=?0.731), and the Zhangjiakou and Yishui populations showed the lowest values (AR?=?4.08, H _e?=?0.589 and AR?=?3.7, H _e?=?0.604). The inbreeding coefficient (F _IS) values for all populations were positive, which indicated an excess of homozygotes. The microsatellites allowed the identification of a significant subpopulation structure (K?=?3), consistent with an isolation by distance model for P. simonii populations. Additionally, molecular variance analysis revealed that 14.2 % of the variation resided among populations, and 85.8 % could be attributed to variation within populations. These data provide valuable information for natural resource conservation and for optimization of breeding programs in the immediate future.     

Genetic structure of three Oryza AA genome species (O. rufipogon, O. nivara and O. sativa) as assessed by SSR analysis on the Vientiane Plain of Laos

Microsatellite (SSR) markers can reveal a high level of polymorphic loci, and are increasingly being used in population genetic structure studies. On the Vientiane plain of Laos all components of the rice crop complex exist, wild annual (O. nivara), wild perennial (O. rufipogon) and weedy relatives of rice as well as rice itself. To understand gene flow in the rice complex, the genetic structures of O. rufipogon (10 populations), O. nivara (10 populations) and O. sativa (24 samples) from across the Vientiane Plain, Laos, were compared. Higher genetic differentiation was detected among O. nivara populations (G _ST = 0.77, R _ST = 0.71) than O. rufipogon populations (G _ST = 0.29, R _ST = 0.28), whereas genetic diversity for all populations of these two wild species showed similar values (H _T = 0.77 and 0.64 in O. rufipogon and O. nivara, respectively). Based on neighbor-joining tree constructed on the basis of genetic distance (D _A), three genetic clusters were detected, corresponding to (1) O. sativa samples, (2) O. nivara populations and (3) O. rufipogon populations. Pairwise tests confirmed the genetic differentiation of the three species. Although none of the wild rice individuals used in this study had any cultivated-specific phenotypic traits, genetic admixture analysis detected more than 10% O. sativa membership in three O. rufipogon and one O. nivara populations, indicating that O. sativa alleles may cryptically persist in natural populations of O. rufipogon and O. nivara on the Vientiane Plain.     

Population structure of the Southeast Asian river catfish Mystus nemurus

A total of 143 microsatellites were isolated from Mystus nemurus using a 5' anchored polymerase chain reaction technique or the random amplified hybridization microsatellite method, the first set of microsatellite markers developed for the Southeast Asian river catfish. Twenty polymorphic microsatellite loci were used as markers for population characterization of M. nemurus from six different geographical locations in Malaysia (Perak, Kedah, Johor, UPM, Sarawak and Terengganu). The number of alleles per locus ranged from 2 to 11 with 6.3 as the average number of alleles per locus. Characterization of the populations showed relatively high levels of genetic variation compared with previous studies using allozyme markers. The highest genetic similarity was found between Perak and Kedah, while the highest genetic distance was found between Terengganu and Kedah. The majority of clustering was in accordance with geographical locations and the histories of the populations. Microsatellite analysis indicated that the Sarawak population might be genetically closer to the Peninsular Malaysian populations than has been previously shown by other molecular marker studies.     

Microsatellite Analysis of Genetic Variation and Population Genetic Differentiation in Autotetraploid and Diploid Rice

Genetic diversity and population genetic structure of autotetraploid and diploid populations of rice collected from Chengdu Institute of Biology, Chinese Academy of Sciences, were studied based on 36 microsatellite loci. Among 50 varieties, a moderate to high level of genetic diversity was observed at the population level, with the number of alleles per locus (A _e) ranging from 2 to 6 (mean 3.028) and polymorphism information content ranging from 0.04 to 0.76 (mean 0.366). The expected heterozygosity (H _e) varied from 0.04 to 0.76 (mean 0.370) and Shannon’s index (I) from 0.098 to 1.613 (mean 0.649). The autotetraploid populations showed slightly higher levels of A _e, H _e, and I than the diploid populations. Rare alleles were observed at most of the simple sequence repeat loci in one or more of the 50 accessions, and a core fingerprint database of the autotetraploid and diploid rice was constructed. The F-statistics showed genetic variability mainly among autotetraploid populations rather than diploid populations (F _st = 0.066). Cluster analysis of the 50 accessions showed four major groups. Group I contained all of the autotetraploid and diploid indica maintainer lines and an autotetraploid and its original diploid indica male sterile lines. Group II contained only the original IR accessions. Group III was more diverse than either Group II or Group IV, comprising both autotetraploid and diploid indica restoring lines. Group IV included a japonica cluster of the autotetraploid and diploid rices. Furthermore, genetic differences at the single-locus and two-locus levels, as well as components due to allelic and gametic differentiation, were revealed between autotetraploid and diploid varieties. This analysis indicated that the gene pools of diploid and autotetraploid rice were somewhat dissimilar, as variation exists that distinguishes autotetraploid from diploid rices. Using this variation, we can breed new autotetraploid varieties with some important agricultural characters that were not found in the original diploid rice varieties.     

Genetic diversity of Cypripedium calceolus in Poland

In this work we assessed the genetic diversity of 32 C.?calceolus populations from Poland. Mean genetic diversity was moderate (P?=?36.4%, A?=?1.58, H _O?=?0.143, F _IS?=?0.059), and seven geographic regions did not differ significantly in their levels of polymorphism (p?>?0.05), although allele frequencies varied greatly. Only four unique alleles were found, at three sites in southern and southeastern Poland. Genetic (P, A) and genotypic diversity parameters (G, G _U) were significantly correlated with population size (p?<?0.001). In the 32 studied populations we separated 422 different multilocus genotypes; none was common to all populations. Overall population differentiation was moderate at 0.137 (p?<?0.001), but we found a significant pattern of isolation by distance for the whole dataset (r ²?=?0.65, p?<?0.001). Our chloroplast DNA (cpDNA) results suggest a single evolutionary lineage and a common origin for all Polish C.?calceolus populations. Information about the genetic health of C.?calceolus populations should be useful in developing conservation strategies.     

Case study of microsatellite polymorphism of European perch in selected commercially important lakes of Latvia

Polymorphism of selected microsatellite markers was described for European perch populations of inland Lake Kala and costal Lake Babites in Latvia. The data consisted of ten microsatellite loci analysed for 90 individuals from the Lake Babites (n?=?45) and the Lake Kala (n?=?45). Both lakes differ in water area, connection with the Gulf of Riga (Baltic Sea), lake type, and fish species. In the Lake Kala population, the average number of alleles per locus varied from 4 to 15 and in the population of Lake Babites from 4 to 12. Low but significant genetic differentiation was detected between populations (F_ST?=?0.046). Observed and expected heterozygosity in both lakes was similar (Kala: H_o?=?0.680 and H_e?=?0.816; Babites: H_o?=?0.693 and H_e?=?0.815). The number of unique alleles per locus was 2.3 in Lake Kala and 0.6 in Lake Babites. The present study showed relatively high polymorphism of analysed microsatellite markers.     

Genetic variation in natural populations of Austrocedrus chilensis,a cypress of the Andean-Patagonian Forest

Austrocedrus chilensis (D. Don) Pic. Ser. et Bizzarri is a dioecious conifer of the Argentinian and Chilean Subantarctic Forest with a markedly fragmentary range. The aim of the present study is to gain information about the degree and distribution of the genetic variation of this species in natural populations of Argentina. The genotypes of 387 trees from 15 Argentinian populations were determined at 12 isozyme marker loci, half of which were virtually monomorphic. Genetic variation was characterized for the species through averaging the population values of some useful parameters. The number of alleles per locus (A=1.51) and the number of effective alleles (A_e=1.16) were small, while the expected (H_e) and the observed heterozygosities (H_o) turned out to be moderate (0.143 and 0.134, respectively). The differentiation between populations was small (δ=0.043; F_ST=0.066), with a trend towards the distribution of genetic variation along a latitudinal gradient, the northerly populations being more variable. The marginal populations from the steppe were found to be the most variable. The pattern found matches several small refuges during the Last Glacial Maximum situated eastward from the Andes mountain range in xeric environments, mostly in northern locations of the present range, followed by a considerable rate of population growth.     

Genetic diversity of populations of a rare species of Dictamnus gymnostylis Stev. in Bashkir Cis-Urals

We examined genetic diversity in populations of Dictamnus gymnostylis Stev., a rare species growing in the Bashkir Cis-Urals, based on the analysis of 8 gene-enzyme systems and detected a fairly high level of intraspecific genetic diversity and population differentiation. We determined the average number of alleles per locus (A) as 1.57; the portion of polymorphic loci (P ₉₅) as 0.508; the observed heterozygosity (H _o) as 0.139; and the expected heterozygosity (H _e) as 0.169. Of the total genetic diversity, 88.3% stems from variability within populations, and 11.7% is due to variation among populations. The average value for the Nei’s genetic distance (D) constituted 0.028.     

Comparison of genetic variation in populations of wild rice, Oryza rufipogon, plants and their soil seed banks

Wild rice, Oryza rufipogon, has endangered species conservation status and it is subject to in situ conservation in China. To understand the potential of the seed bank in species conservation and population restoration, this study compared the genetic diversity of O. rufipogon plants with that of its soil seed banks in two marshes. A total of 11 pairs of rice SSR primers were used and 9 were polymorphic. Allele frequencies of the seeds differed significantly from those of surface plants and varied between soil layers. Relatively more alleles and higher genetic diversity (H _e) were found in plant populations, relative to seed banks. The numbers of germinable seeds and the level of genetic variation in seed banks decreased with the increasing of soil depth, indicating a rapid seed loss. Genetic differentiation was detected between sites and between plant and seed populations, as well as among seeds of different soil strata. Rapid seed loss, partly dormancy loss, and nonrandom seed mortality are discussed as the possible contributors to the pattern of reduced genetic variation within seed banks, compared to plants. These could also be responsible for the considerable genetic differentiation between populations. The seed population held about 72% of the total genetic variation of O. rufipogon in each marsh, indicating the potential of seed banks for restoring population variabilities if the plant populations were lost.     

Genetic Diversity Within and among Disjunct Populations of the Mediterranean Island Endemic Delphinium pictum and D. requienii (Ranunculaceae)

Allozyme diversity was assessed in 13 populations of Delphinium pictum and D. requienii, two short-lived and closely related insular Mediterranean endemics. While D. pictum has scattered distribution in Corsica, Sardinia and Majorca, D. requienii is found in a few small populations restricted to the Hyères Archipelago. Eleven enzyme systems were assayed, and 15 loci were resolved. Both species harboured moderate levels of genetic diversity, comparable to the values expected for endemic plants. All genetic parameters suggested higher diversity in D. pictum (A?=?1.93, P?=?40, H _e?=?0.106) than in D. requienii (A?=?1.30, P?=?26.7, H _e?=?0.096); F _IS values revealed higher inbreeding in D. requienii. Although the two species did not harbour species-specific alelles in the surveyed loci, the UPGMA dendrogram based on Nei’s genetic similarity index supported divergence between them. These results, together with significant morphological similarity and evidence of successful hybridization between the species, support the hypothesis of a recent speciation event. The moderate levels of both genetic variability and population divergence observed for D. pictum are likely attributable to its ability to establish seed banks. Given that the allozyme variation detected for D. pictum was significantly partitioned among islands, we suggest the implementation of conservation programs throughout its distribution range, and not only in Corsica as it occurs nowadays. Management strategies are also desirable for D. requienii to maintain population size and control inbreeding.     

Analysis of Genetic Diversity and Population Structure in Sophora japonica Linn. in China With Newly Developed SSR Markers

Sophora japonica is a medium-sized deciduous native tree to China. Its flower buds and fruits have special medicinal value. By using 26 highly variable nuclear microsatellites, newly reported here, we assessed the genetic diversity and population structure of 10 representative populations (180 individuals in total) within the species. The results revealed a relatively high genetic diversity in S. japonica (N_a?=?8.00, H_e?=?0.74, PIC?=?0.80, I?=?1.67), and reduced genetic variation and heterozygote excess were detected in landrace populations (N_a?=?5.59, H_e?=?0.71, A_r?=?4.11, F_IS?=???0.043) when compared with those semi-wild population (N_a?=?9.7, H_e?=?0.74, A_r?=?8.80, F_IS?=?0.082). A significant bottleneck was detected in two Landraces populations. Moderate differentiation and frequent gene flow were detected among all populations (F_ST?=?0.079, P?<?0.05, N_m?=?2.893). Mantel test detected a marginal significant pattern of isolation by distance (r?=?0.009, P?=?0.50), and strong differentiation was observed between most southern and northern populations both by the STRUCTURE clustering and principal coordinate analysis (PCoA), indicating that geographic isolation played a key role in the genetic differentiation of the species. The results from this study will benefit the breeding and conservation of S. japonica, other congener species, and tree species with similar life history traits.

     

Patterns of Genetic Diversity in Platanthera bifolia (Orchidaceae) with Respect to Life History Traits and Recent Range Expansion

For evolutionary and ecological analyses, genetic diversity at different scales needs to be studied in terms of biological properties, habitat, population size and population history. We surveyed Platanthera bifolia populations from six regions in northeastern Poland to determine the impact of the mating system and population history on genetic diversity. Based on variation at allozyme markers, genetic variation was relatively moderate (P?=?22.3%, A?=?1.48, H _O?=?0.083, F _IS?=??0.015) and similar to other Platanthera species. These parameters varied between populations (P?=?13.3%–26.6%, A?=?1.26–1.66, H _O?=?0.055–0.111, F _IS?=??0.262–0.147). The genetic diversity patterns were shaped by different proportions of facilitated selfing and/or outcrossing, resulting in positive and negative F _IS values, respectively. No relationship between inbreeding coefficient and population size, however, and no impact of apomixis on the level of genetic diversity of P. bifolia were found. The relatively low level of genetic differentiation among the investigated regions (F _CT?=?0.002, P?>?0.05) and among populations (F _ST?=?0.048, P?<?0.001), and the lack of a significant relationship between genetic and geographical distance, are discussed in the context of possible scenaria of postglacial expansion.     

Genetic diversity and structure of a rare endemic cactus and an assessment of its genetic relationship with a more common congener

Endemic, obligate outcrossing plant species with narrow geographic distributions and disjunct populations are prone to loss of genetic diversity. Simultaneously, delineating clear species boundaries is important for targeted conservation efforts. The rare and endemic cactus, Sclerocactus brevihamatus subsp. tobuschii (SBT), has a parapatric relationship with Sclerocactus brevihamatus subsp. brevihamatus (SBB) but genetic distance between the two taxa is unknown. We: (1) developed taxon-specific polymorphic microsatellites, (2) assessed genetic diversity within and among nine populations of SBT, and within one population of SBB, and (3) estimated the genetic relationship between the two subspecies. Within-population genetic diversity of SBT was moderate to high (mean H_o?=?0.37; mean H_e?=?0.59). Indirect estimate of inbreeding corrected for null alleles (F_is-INEst) was low for SBT, ranging from 0.03 to 0.14 (mean F_is-INEst?=?0.07). Genetic differentiation among populations of SBT was low based on F_st (0.08) and AMOVA (Ф_PT?=?0.10). Lack of genetic and spatial correlation in SBT populations coupled with the presence of private alleles and bottleneck events in several populations suggests that reproductive isolation is occurring but that sufficient time may not have yet passed to manifest strong differentiation. Cluster analyses segregated the 10 populations into three distinct groups, and separated SBB genotypes clearly. Results suggest that while hybridization between the two subspecies may occur, SBT is clearly differentiated genetically from SBB to retain its current taxonomic status.     

Genetic diversity in the northernmost<Emphasis Type="Italic"> Oryza rufipogon</Emphasis> populations estimated by SSR markers

To estimate genetic diversity of the residual northern populations of Oryza rufipogon, a total of 232 individuals from six populations were analyzed using microsatellites (SSRs). The O. rufipogon populations with different status included three from Dongxiang (Jiangxi Province) and three from Chaling (Hunan Province) in China. The 23 rice SSR primer pairs selected from the RiceGenes Database detected a total of 115 alleles, indicating that all the SSR loci were polymorphic in this study. The total gene diversity was 0.919 in the six O. rufipogon populations, and the Donxiang populations showed higher diversity than the Chaling populations. More significant genetic differentiation and less gene flow were found among the Dongxiang populations than those from Chaling. The two putative introgressed populations showed relatively high genetic variation. One in situ conserved population from Dongxiang had the lowest level of genetic diversity. The re-introduced population from Chaling restored about 90% of the genetic variation, compared with the original source population. It is concluded from these results that a relatively high level of genetic variation resided in the northern O. rufipogon populations and continued efforts of conservation of these populations are needed; and that the conservation of some Chaling and Dongxiang populations has been effective in preventing gene flow from cultivated rice. Introgression of cultivated rice demonstrated significant impacts on genetic variability of the O. rufipogon populations, and should be carefully considered in conserving this wild rice. This study also suggested that re-introduction to its original habitats is an effective approach to restore O. rufipogon populations.Communicated by J.S. Heslop-Harrison     

Spatial Genetic Structure of Campanula sabatia, a Threatened Narrow Endemic Species of the Mediterranean Basin

Campanula sabatia is endemic to NW Italy (Liguria) and it was included in the European Red list of endangered species due to the heavy human pressure on its habitat. AFLP markers were used to detect the genetic diversity within and among ten populations (totalling 83 individuals) representing the range of the species. In spite of the limited distribution of this endemic taxon, high levels in percentage of polymorphic bands (PPB), gene diversity (H _S and H _T) and Shannon??s information index (I) were detected both at population (PPB?=?60?%, H _S?=?0.1853, I?=?0.2836) and at species level (PPB?=?100?%, H _T?=?0.2415, I?=?0.3871). The coefficient of genetic differentiation among population (G??_ST) was 0.1935, while the level of gene flow (N?? _m) was estimated to be 2.0832. AMOVA analysis identified a genetic variation within populations of 83?% of the total. Bayesian clustering methods assigned individuals to two geographical groups partly found within the same population, probably due to a high rate of genetic exchange among its populations. Conservation measures are suggested on the basis of the genetic diversity detected to ensure an effective protection for this endemic species.     

Allozyme Diversity and Geographic Variation among Populations of the Locally Endangered Taxon Carex magellanica subsp. irrigua (Cyperaceae)

Carex magellanica subsp. irrigua is a wet habitat taxon that is extinct or declining in the Baltic States and Central Europe, but still quite common in northern areas, in Fennoscandia and Alaska. We investigated the extent of genetic variation within and among populations and geographic regions of this subspecies. Isozyme electrophoresis in polyacrylamide gels was applied to characterize genetic diversity with allozymes as genetic markers. Of the nine putative isozyme loci assessed, five (56%) were found to be polymorphic. The genetic diversity in small and fragmented Estonian populations was lower (H _e?=?0.034) than in larger Fennoscandian and Alaskan populations (average H _e?=?0.082). All standard genetic parameters (A _e, H _o, H _e, P, F _is, t) showed the lowest values in Estonian populations. The heterozygosity level in Fennoscandian populations was low (H _o?=?0.01), whereas no heterozygotes were found in Estonian and Alaskan populations. High F _is values indicate that C. magellanica subsp. irrigua is predominantly inbreeding. The main reason for its decline in Estonia is the destruction of suitable habitats. More attention to the protection of Estonian habitats is needed to maintain genetic diversity and stop further decline of this taxon.     

Genetic characterization of <Emphasis Type="Italic">Perna viridis</Emphasis> L. in peninsular Malaysia using microsatellite markers

A total of 19 polymorphic microsatellite loci were used to analyse levels of genetic variation for 10 populations of Perna viridis L. collected from all over peninsular Malaysia. The populations involved in this study included Pulau Aman in Penang, Tanjung Rhu in Kedah, Bagan Tiang in Perak, Pulau Ketam in Selangor, Muar, Parit Jawa, Pantai Lido and Kampung Pasir Puteh in Johore, and Kuala Pontian and Nenasi in Pahang state. The number of alleles per locus ranged from two to seven, with an average of 3.1. Heterozygote deficiencies were observed across all the 10 populations. Characterization of the populations revealed that local populations of P. viridis in peninsular Malaysia were genetically similar enough to be used as a biomonitoring agent for heavy metal contamination in the Straits of Malacca. Cluster analysis grouped the P. viridis populations according to their geographical distributions with the exception of Parit Jawa. The analysis also revealed that P. viridis from the northern parts of peninsular Malaysia were found to be the most distant populations among the populations of mussels investigated and P. viridis from the eastern part of peninsular Malaysia were closer to the central and southern populations than to the northern populations.     

Host-associated genetic differentiation in rice grasshopper, Oxya japonica, on wild vs. cultivated rice

Rice grasshopper, Oxya japonica, is one of the most important pests in south China, mainly inhabiting fields of wild rice (Oryza rufipogon) and cultivated rice (Oryza sativa). In this study, we used AFLP marker to investigate the genetic diversity and population structure of rice grasshoppers collected from south China, with emphasis on testing the hypothesis that there was significant genetic differentiation among grasshopper populations associated with different hosts (i.e. wild vs. cultivated rice). Seven populations consisting of 104 individuals were sampled from Hainan Island and the mainland of south China. Eight primer combinations produced 564 reliable bands, of which 563 were polymorphic. O. japonica showed considerable genetic variation at population level, with gene diversity (H_E) ranging from 0.1103 to 0.2035. Genetic diversity were studied on seven populations, and generally three populations from wild rice had higher levels of genetic diversity (H_E = 0.1635) than the other four populations feeding on cultivated rice (H_E = 0.1327). We observed high population differentiation, with F_st ranging from 0.4172 to 0.7652 among the seven populations. However, Mantel test detected no significant correlation between genetic distance and geographical distance (r = 0.3541; p = 0.0689). By contrast, we found significant genetic differentiation between groups collected from different hosts. These data suggested that the anthropogenic activity in cultivated rice fields (i.e. pesticides, fertilization and cultivation) could have played an important role in shaping the genetic structure of O. japonica.     

Genetic diversity of natural populations of Taxus mairei

Taxus mairei (Lemée & Lév.) S.Y. Hu ex T. S. Liu is a vulnerable tree species, and it is also a precious timber species in China. We used 13 microsatellites to assess the genetic diversity and differentiation of 665 T. mairei samples from 18 natural populations. A total of 291 alleles were detected. The average number of alleles (N_a?=?22.39), expected heterozygosity (H_e?=?0.74), polymorphic information content (PIC?=?0.86) and Shannon diversity index (I?=?1.66) of the loci indicated a high level of genetic diversity in natural T. mairei populations. Moreover, gene flow was more active among populations (N_m?=?1.62) than within populations. Among the 18 populations, the Xinfeng population in Jiangxi Province has the highest genetic diversity. Although each of the studied populations should be protected from further deforestation and agricultural expansion, the Xinfeng population deserves the highest conservation priority. The results based on analysis of molecular variance showed that genetic variation occurred mainly within populations (84.90%; P?<?0.001), which indicated that the degree of genetic differentiation of the natural populations of T. mairei was low. Based on UPGMA, the 18 populations were categorized into two groups. A Mantel test showed that there was no significant correlation between standard genetic distance and geographical distance or altitude differences among the populations. The genetic clustering results also indicated that there are varying degrees of gene penetration among natural populations of T. mairei. The information presented here forms the basis for the development of genetic guidelines for appropriate conservation programs.

     

北沙柳群体遗传多样性和遗传结构分析

以内蒙古北沙柳(Salix psammophila)国家种质资源库内9个群体(P1~P9)288个无性系为实验材料,利用TP-M13-SSR技术,选取22对具有多态性EST-SSR北沙柳引物,采用毛细管电泳对PCR产物进行检测,分析北沙柳遗传多样性、分化程度和群体遗传结构,为北沙柳种质资源库遗传管理、无性系鉴定、品种选育、遗传改良和构建指纹图谱提供理论依据。结果显示:(1)22对EST-SSR引物共检测到222个等位基因,各位点平均等位基因数(A)为10,四倍体基因型丰富度(G)和特异基因型(G1)总和分别为1 460和802个,平均特异基因型比率(P1)和种质鉴别率(P2)分别为45.86%和13.21%。(2)9个群体平均等位基因数(A)为7.475,基因型丰富度(G)为15.586,观察杂合度(Ho)和期望杂合度(He)分别为0.577和0.638。以期望杂合度He为标准,北沙柳群体遗传多样性水平最低的是P1和P9。(3)北沙柳群体遗传分化系数仅为0.02,AMOVA分子变异分析显示,北沙柳群体大部分遗传变异来自群体内(97%),群体间变异仅为3%。(4)三维主成分、聚类和Structure群体遗传结构分析显示,9个群体被划分为2个组,Mantel检验表明北沙柳遗传距离与地理距离极显著相关(r=0.684 P0.001)。研究表明,北沙柳种质资源具有丰富的遗传多样性,这是其具有耐旱、耐寒、耐高温、耐沙埋和抗风蚀等适应性较强的分子基础;北沙柳的遗传变异集中在群体内;分布区群体呈现由中心向边缘群体扩张分化的趋势。