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1.
Repeated cycles of retreat and recolonization during the Quaternary ice ages are thought to have greatly influenced current species distributions and their genetic diversity. It remains unclear how this climatic oscillation has affected the distribution of genetic diversity between populations of wind-pollinated conifers in the Qinghai-Tibetan region. In this study, we investigated the within-species genetic diversity and phylogenetic relationships of Picea likiangensis, a dominant forest species in this region using polymorphic DNA (RAPD) markers. Our results suggest that this species has high overall genetic diversity, with 85.42% of loci being polymorphic and an average expected heterozygosity (H E) of 0.239. However, there were relatively low levels of polymorphism at population levels and the differences between populations were not significant, with percentages of polymorphic bands (PPB) ranging from 46.88 to 69.76%, Nei’s gene diversity (H E) from 0.179 to 0.289 and Shannon’s indices (Hpop) from 0.267 to 0.421. In accordance with our proposed hypothesis, a high level of genetic differentiation among populations was detected based on Nei’s genetic diversity (G ST = 0.256) and AMOVA analysis (Phi st = 0.236). Gene flow between populations was found to be limited (Nm = 1.4532) and far lower than reported for other conifer species with wide distribution ranges from other regions. No clusters corresponding to three morphological varieties found in the south, north and west, respectively, were detected in either UPGMA or PCO analyses. Our results suggest that this species may have had different refugia during the glacial stages in the southern region and that the northern variety may have multiple origins from these different refugia.  相似文献   

2.
Random amplified polymorphic DNA (RAPD) analysis was used to characterize the genetic diversity and population genetic structure of Stipa krylovii populations in Inner Mongolia steppe of North China. Thirteen 10-bp oligonucleotide primers, which generated 237 RAPD bands, were used to analyze 90 plants of five populations from three regions, meadow steppe, typical steppe and desert steppe, from the east to the west. The genetic diversity of Stipa krylovii that was revealed by observed number of alleles (na), expected number of alleles (ne), Nei’s diversity index (h), Shannon’s diversity index (H), amplificated loci, polymorphic loci and the percentage of polymorphic loci (PPB) increased from the east to the west. The Pearson’s correlation analysis between genetic diversity parameters and ecological parameters indicated that the genetic diversity of Stipa krylovii was associated with precipitation and cumulative temperature variations along the longitude (humidity were calculated by precipitation and cumulative temperature). Dendrogram based on Jaccard’s genetic distance showed that the individuals from the same population formed a single subgroup. Although most variation (56.85%) was within populations, there was high genetic differentiation among populations of Stipa krylovii, high differentiation within and between regions by AMOVA analysis. Either Nei’s unbiased genetic distance (G ST) or gene flow (Nm) among pairwise populations was not correlated with geographical distance by Mantel’s test (P > 0.05), suggesting that there was no consistency with the isolation by distance model in these populations. Natural selection may have played a role in affecting the genetic diversity and population structure, but habitat destruction and degradation in northem grassland in China may be the main factor responsible for high genetic differentiation among populations, within and among regions. The text was submitted by the authors in English.  相似文献   

3.
Genetic variation in six natural populations of Scots pine (Pinus sylvestris L.) was determined with isoenzyme analyses. For this purpose, haploid female gametophytes of seeds and horizontal starch gel electrophoresis technique were used. A total of 17 loci and 58 alleles were observed in studying 10 enzyme systems. The average proportion of polymorphic loci for populations ranged from 58.8% to 70.6%. The average number of alleles per locus per population was 2.65. The mean estimated expected heterozygosity (He) of populations was 0.294. A rather high proportion of genetic diversity (96.4%) was due to within-population variation and the remaining (3.6%) was due to variation among populations. The level of gene flow (Nem) was found to be 6.69 per generation. Nei’s genetic distance coefficient ranged from 0.006 to 0.027 (mean 0.017) among all possible population pairs. The mean value of Nei’s genetic distance is similar to the values reported for other European Scots pine populations. The low mean value of Nei’s genetic distance among populations is enough to explain low interpopulation variation. According to genetic variation parameters, three out of six populations (Akdagmadeni-Yozgat, Refahiye-Erzincan and Vezirkopru-Samsun) appear to be preferable populations for genetic conservation and forest tree breeding programs.  相似文献   

4.
Ni X  Huang Y  Wu L  Zhou R  Deng S  Wu D  Wang B  Su G  Tang T  Shi S 《Genetica》2006,127(1-3):177-183
Primulina tabacum Hance, is a critically endangered perennial endemic to limestone area in South China. Genetic variability within and among four extant populations of this species was assessed using AFLP markers. We expected a low genetic diversity level of this narrowly distributed species, but our results revealed that a high level of genetic diversity remains, both at population level (55.5% of markers polymorphic, H E = 0.220, I S = 0.321), and at species level (P = 85.6% of markers polymorphic, H E = 0.339, I S = 0.495), probably resulting from its refugial history and/or breeding system. High levels of genetic differentiation among populations was apparent based on Nei’s genetic diversity analysis (G st=0.350). The restricted gene flow between populations is a potential reason for the high genetic differentiation. The population genetic diversity of P. tabacum revealed here has clear implications for conservation and management. To maintain present levels of genetic diversity, in situ conservation of all populations is necessary.  相似文献   

5.
Zong M  Liu HL  Qiu YX  Yang SZ  Zhao MS  Fu CX 《Biochemical genetics》2008,46(3-4):180-196
Dysosma pleiantha, an important threatened medicinal plant species, is restricted in distribution to southeastern China. The species is capable of reproducing both sexually and asexually. In this study, inter-simple sequence repeat marker data were obtained and analyzed with respect to genetic variation and genetic structure. The extent of clonality, together with the clonal and sexual reproductive strategies, varied among sites, and the populations under harsh ecological conditions tended to have large clones with relatively low clonal diversity caused by vegetative reproduction. The ramets sharing the same genotype show a clumped distribution. Across all populations surveyed, average within-population diversity was remarkably low (e.g., 0.111 for Nei’s gene diversity), with populations from the nature reserves maintaining relatively high amounts of genetic diversity. Among all populations, high genetic differentiation (AMOVA: ΦST = 0.500; Nei’s genetic diversity: G ST = 0.465, Bayesian analysis: ΦB = 0.436) was detected, together with an isolation-by-distance pattern. Low seedling recruitment due to inbreeding, restricted gene flow, and genetic drift are proposed as determinant factors responsible for the low genetic diversity and high genetic differentiation observed.  相似文献   

6.
The clam Ruditapes decussatus is commercially important in the south of Portugal. The random amplified polymorphic DNA (RAPD) technique was applied to assess the genetic diversity and population structure of two Portuguese populations occurring in the Ria Formosa (Faro) and the Ria de Alvor, respectively. Twenty-five individuals of each population were investigated by RAPD profiles. Genetic diversity within populations, measured by the percentage of polymorphic loci (%P), varied between 68.57% (Alvor) and 73.88% (Faro). Shannon’s information index (H) and Nei’s gene diversity (h) were 0.281 and 0.176, respectively, for the Alvor population and 0.356 and 0.234 for the Faro population. Overall, genetic variation within R. decussatus populations was high. The total genetic diversity (H T) was explained by a low variation between populations (G ST = 0.145), which is consistent with high gene flow (N m = 2.9). The analysis of molecular variance (AMOVA) showed that 65% of variability is within populations and 35% between populations (ΦPT = 0.345; P ≥ 0.001). The value of Nei’s genetic distance was 0.0881, showing a low degree of population genetic distance, despite the different geographic origin. This is the first study on the population genetics of R. decussatus by RAPD technique. The results may be useful for restocking programs and aquaculture.  相似文献   

7.
In contrast to many declining plant species Saxifraga tridactylites extended its distribution range in the man-made landscape of central Europe. The species naturally colonizes rocks and calcareous grasslands, but has also spread enormously in anthropogenic habitats such as railway constructions during the last decades. To analyze the genetic structure of the species 216 individuals from 8 populations in natural and 5 populations in man-made habitats were studied using AFLPs. The molecular analysis resulted in 250 scorable fragments. Population variability, measured as Nei’s gene diversity, Shannon’s Information Index and percentage of polymorphic bands, was slightly but not significantly higher in populations from natural habitats and was not correlated with population size. Mantel test indicated no significant correlation between pairwise genetic (ΦPT) and geographic distances. An analysis of molecular variance revealed significant differentiation between the two habitat types. About 9% variability were observed between natural and man-made habitats, 21% among populations within these two habitats and 70% within populations. In a neighbour joining cluster analysis populations from natural and man-made habitats were clearly separated from each other. Populations of S. tridactylites from man-made habitats do, therefore, not suffer from reduced genetic diversity. The observed genetic differentiation between populations from man-made and natural habitats could be due to reduced gene flow and/or habitat specific selection. However, the results of the study clearly demonstrate human impact on the genetic structure of plant populations in man-made landscapes.  相似文献   

8.
Ma YS  Yu H  Li YY  Yan H  Cheng X 《Biochemical genetics》2008,46(3-4):227-240
Genetic diversity and genetic structure within and among ten populations of Stephania yunnanensis H. S. Lo and three populations of S. epigaea H. S. Lo from Yunnan province were evaluated by direct amplification of length polymorphism (DALP) markers. Five primer groups were screened, and a total of 287 DNA fragments were amplified, among which 266 were polymorphic, averaging 53.2 polymorphic bands per primer group in S. yunnanensis. The percentage of polymorphic bands of S. yunnanensis was 92.68% at the species level and 61.92% within the ten populations sampled. At the species level, the observed number of alleles (N a) was 1.9268 and the effective number of alleles (N e) was 1.5933; Nei’s gene diversity (H) was 0.3414; Shannon’s information index (I) was 0.5057. At the population level, N a = 1.6192, N e = 1.4001, H = 0.2298, and I = 0.3401. Total gene diversity of S. yunnanensis was 0.3419. Gene diversity within population was 0.2298, coefficient of gene differentiation was 0.3278, and estimated gene flow was 1.0254. The results indicated that the genetic differentiation was relatively higher among populations of S. yunnanensis. DALP markers were an informative and useful method for assaying genetic diversity and authenticating species of Stephania. These data could provide basic molecular evidence for establishing a reasonable strategy for protecting and exploiting the resource of S. yunnanensis.  相似文献   

9.
Zheng W  Wang L  Meng L  Liu J 《Genetica》2008,132(2):123-129
We used random amplified polymorphic DNA markers (RAPDs) to assess genetic variation between- and within-populations of Anisodus tanguticus (Solanaceae), an endangered perennial endemic to the Qinghai-Tibetan Plateau with important medicinal value. We recorded a total of 92 amplified bands, using 12 RAPD primers, 76 of which (P = 82.61%) were polymorphic, and calculated values of Ht and Hsp of 0.3015 and 0.4459, respectively, suggesting a remarkably high rate of genetic variation at the species level. The average within-population diversity also appeared to be high, with P, He and Hpop values of 55.11%, 0.1948 and 0.2918, respectively. Analyses of molecular variance (AMOVA) showed that among- and between-population genetic variation accounted for 67.02% and 32.98% of the total genetic variation, respectively. In addition, Nei’s coefficient of differentiation (GST) was found to be high (0.35), confirming the relatively high level of genetic differentiation among the populations. These differentiation coefficients are higher than mean corresponding coefficients for outbreeding species, but lower than reported coefficients for some rare species from this region. The genetic structure of A. tanguticus has probably been shaped by its breeding attributes, biogeographic history and human impact due to collection for medicinal purposes. The observed genetic variations suggest that as many populations as possible should be considered in any planned in situ or ex situ conservation programs for this species.  相似文献   

10.
Random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers were used to investigate the genetic structure of four subpopulations of Mystus nemurus in Thailand. The 7 RAPD and 7 ISSR primers were selected. Of 83 total RAPD fragments, 80 (96.39%) were polymorphic loci, and of 81 total ISSR fragments, 75 (92.59%) were polymorphic loci. Genetic variation and genetic differentiation obtained from RAPD fragments or ISSR fragments showed similar results. Percentage of polymorphic loci (%P), observed number of alleles, effective number of alleles, Nei’s gene diversity (H) and Shannon’s information index revealed moderate to high level of genetic variations within each M. nemurus subpopulation and overall population. High levels of genetic differentiations were received from pairwise unbiased genetic distance (D) and coefficient of differentiation. Mantel test between D or gene flow and geographical distance showed a low to moderate correlation. Analysis of molecular variance indicated that variations among subpopulations were higher than those within subpopulations. The UPGMA dendrograms, based on RAPD and ISSR, showing the genetic relationship among subpopulations are grouped into three clusters; Songkhla (SK) subpopulation was separated from the other subpopulations. The candidate species-specific and subpopulation-specific RAPD fragments were sequenced and used to design sequence-characterized amplified region primers which distinguished M. nemurus from other species and divided SK subpopulation from the other subpopulations. The markers used in this study should be useful for breeding programs and future aquacultural development of this species in Thailand.  相似文献   

11.
Allozyme analysis, microsatellite primer PCR (SSRP-PCR), and amplified fragment length polymorphism (AFLP) techniques were used to assess genetic diversity and population structure of the Chinese oriental migratory locust, Locusta migratoria manilensis. A total of 299 PCR markers (67 SSRPs and 232 AFLPs) were detected in eight populations, of which 98.7% were polymorphic markers. The proportion of polymorphic loci (95.5–98.8%) by SSRP+AFLP markers indicated no significant differences between populations, and all populations exhibited a similar level of variability; results of the allozyme analysis demonstrated that 19 loci gave rise to a lower level of polymorphism (55.6–66.7%). The genetic distances between the populations were relatively low. Shannon’s index and Nei’s gene diversity showed low differentiation among the populations. Allozyme analysis, however, reflected greater similarity and smaller differentiation between the populations than those shown by SSRP and AFLP markers. Neighbor-joining dendrograms derived from both the allozyme and SSRP+AFLP markers showed that the genetic distances among Chinese oriental migratory locust populations were not greatly influenced by geographic distance and breeding habitats.  相似文献   

12.
The red raspberry (Rubus idaeus L.) is widely distributed in Lithuania and occupies a range of habitats. The presence of coadapted gene pools in local populations of R. idaeus is a question of interest not only to plant scientists, but also to plant breeders. In this study, we investigated the genetic structure of R. idaeus and the influence of local habitats on the genetic diversity within and among populations. Nineteen populations of R. idaeus were sampled from different habitats in various agroclimatic subregions of Lithuania, and analyzed using RAPD markers. 113 RAPD bands were identified among 315 individuals; 84.31% of these were polymorphic. The mean values of Shannon’s information index for different populations ranged from 0.341 to 0.455. Nei’s gene diversity established within populations averaged 0.266. An AMOVA revealed 74% of genetic variation among individuals within populations of R. idaeus, and 23% among populations. The remaining genetic variation was distributed among populations from different agroclimatic subregions (3%). The results of this study suggest that the genetic structure of R. idaeus populations in Lithuania may be influenced partially by isolation by distance as well as by local environmental conditions.  相似文献   

13.
Random amplified polymorphic DNA (RAPD) markers were used to estimate the population structure and phylogenetic relationships among samples of the Salmo trutta complex that inhabit the Balkan Peninsula. Five random oligodecamers were selected to amplify DNA from 140 fish from seven populations. Using these primers, 55 discernible DNA fragments were generated, of which 50 (90.91%) were polymorphic. The statistical results indicated that there was low genetic diversity within populations (with an average percentage of polymorphic bands (P) of 11.69% and a Nei’s genetic diversity index (h) of 0.035), but at the same time high genetic differentiation among populations (F ST = 0.89). The distribution of genetic diversity among Balkan trout may result from their evolutionary history and reflects genetic drift coupled with bottleneck phenomena. Overall, RAPDs proved valuable tools for quick and reliable stock discrimination and provided information that might be useful regarding conservation and management of trout.  相似文献   

14.
ISSR markers were used to analyze the genetic diversity and genetic structure of eight natural populations of Cupressus chengiana in China. ISSR analysis using 10 primers was carried out on 92 different samples. At the species level, 136 polymorphic loci were detected. The percentage of polymorphic bands (PPB) was 99%. Genetic diversity (H e) was 0.3120, effective number of alleles (A e) was 1.5236, and Shannon’s information index (I) was 0.4740. At the population level, PPB = 48%, A e=1.2774, H e=0.1631, and I=0.2452. Genetic differentiation (G st) detected by Nei’s genetic diversity analysis suggested 48% occurred among populations. The partitioning of molecular variance by AMOVA analysis indicated significant genetic differentiation within populations (54%) and among populations (46%; P < 0.0003). The average number of individuals exchanged between populations per generation (N m ) was 0.5436. Samples from the same population clustered in the same population-specific cluster, and two groups of Sichuan and Gansu populations were distinguishable. A significantly positive correlation between genetic and geographic distance was detected (r=0.6701). Human impacts were considered one of the main factors to cause the rarity of C. chengiana, and conservation strategies are suggested based on the genetic characters and field investigation, e.g., protection of wild populations, reestablishment of germplasm bank, and reintroduction of more genetic diversity.  相似文献   

15.
A genetic analysis of nuclear DNA was performed by inter-simple sequence repeat-polymerase chain reaction (ISSR-PCR) technique on 32 populations of Ageratina adenophora, an invasive triploid weed in China. Among the 100 ISSR markers detected, 12 showed genetic variation both within and among the populations. Among the 446 amplified bands, 93.5% were found polymorphic. Most individuals (99%) displayed a unique ISSR fingerprint pattern, which yielded a high level of polymorphism (P o = 93.5%) and genetic diversity (Nei’s H T = 0.2354). The estimates of population variation, based on ISSR-PCR, were high, as measured by the analysis of molecular variance (AMOVA, F ST = 0.3140), the Wright’s F-statistics (G ST = 0.3453), and the Shannon’s information index (H sp = 0.3716). AMOVA revealed 68.6% genetic variation within the populations and 91.2% within the provinces. The Mantel test showed that genetic distance was significantly correlated with geographic distance. Published in Russian in Fiziologiya Rastenii, 2009, Vol. 56, No. 3, pp. 453–459. This text was submitted by the authors in English.  相似文献   

16.
Genetic variation in 12 Pinus pinaster (maritime pine) populations spanning most of the distribution range of the species in Portugal was evaluated using six polymorphic chloroplast microsatellite (cpSSR) loci. Thirty-two haplotypes were found. There were indications of very weak differentiation among populations (Weir’s θcoefficient, 0.023), and the R ST value, derived from the stepwise mutation model (SMM), was not significantly different from zero. The pattern, in which similarities in allele size, in base pairs, do not contribute to the genetic structure, may be due to the recent mixing of genetic material from different stands through plantations. Overall, a high level of haplotypic variation within populations was detected. Using the SMM estimator (mean genetic distance of individuals within populations, D 2 sh –––) we divided the populations into two groups, with above and below average values. The first group contained 5 populations, mainly from the central part of the country, which possess, in general, high levels of haplotypic diversity. Among them, 2 populations were divergent from the others based on the pair-wise Nei’s distance. The results indicate that there is no discernible geographic genetic pattern for the Portuguese populations of P. pinaster investigated. The history of expansion of the species range in Portugal during the twentieth century (mainly due to human activity) and extensive gene flow among populations associated with the expansion could explain this finding. Received: 15 February 2000 / Accepted: 14 April 2000  相似文献   

17.
Western white pine (Pinus monticola) is an economically and ecologically important species in western North America that has declined in prominence over the past several decades, mainly due to the introduction of Cronartium ribicola (cause of white pine blister rust) and reduced opportunities for regeneration. Amplified fragment length polymorphism (AFLP) markers were used to assess the genetic diversity and structure among populations at 15 sites (e.g., provenances) across the native range of western white pine. The level of genetic diversity was different among 15 populations tested using 66 polymorphic AFLP loci. Nei’s gene diversity (H E) at the population level ranged from 0.187 to 0.316. Genetic differentiation (G ST) indicated that 20.1% of detected genetic variation was explained by differences among populations. In general, populations below 45oN latitude exhibited a higher level of genetic diversity than higher latitude populations. Genetic distance analysis revealed two major clades between northern and southern populations, but other well-supported relationships are also apparent within each of the two clades. The complex relationships among populations are likely derived from multiple factors including migration, adaptation, and multiple glacial refugia, especially in higher latitudes. Genetic diversity and structure revealed by this study will aid recognition and selection of western white pine populations for species management and conservation programs, especially in consideration of current and future climate changes.  相似文献   

18.
Tamarix chinensis, with its important ecological significance, is a vital dominant plant in the Yellow River Delta of China. To understand its genetic structure and population dynamics, five populations of T. chinensis, consisting of 140 individuals, were analyzed in this study using inter simple sequence repeat markers. Seventy-eight polymerase chain reaction fragments were scored, of which 62 were polymorphic. The mean percentage of polymorphic loci (P), the mean Nei’s gene diversity (h), and the mean Shannon’s information index (I) were 79.5%, 0.239, and 0.363, respectively. These indexes indicated that a moderate level of genetic diversity existed in T. chinensis populations of the Yellow River Delta. Both analysis of molecular variance (AMOVA) (Φ st = 0.169) and Popgene (G st = 0.159) analyses revealed the low level of genetic differences among the five populations of T. chinensis. The results implied that relatively frequent gene flow existed among populations. However, slightly uneven genetic diversity was also found among populations. Unweighted pair group method with arithmetic mean and principal component analysis showed that populations with similar soil salinity had a close relationship, rather than populations with closer geographical distance. A significant negative correlation between genetic diversity and soil salinity of the five populations (r = −0.958, p < 0.01) showed that soil salinity played an important role in shaping the population genetic structure of T. chinensis in the Yellow River Delta, China.  相似文献   

19.
Echinacea laevigata (Boynton and Beadle) Blake is a federally endangered flowering plant species restricted to four states in the southeastern United States. To determine the population structure and outcrossing rate across the range of the species, we conducted AFLP analysis using four primer combinations for 22 populations. The genetic diversity of this species was high based on the level of polymorphic loci (200 of 210 loci; 95.24%) and Nei’s gene diversity (ranging from 0.1398 to 0.2606; overall 0.2611). There was significant population genetic differentiation (GST = 0.294; ӨII = 0.218 from the Bayesian f = 0 model). Results from the AMOVA analysis suggest that a majority of the genetic variance is attributed to variation within populations (70.26%), which is also evident from the PCoA. However, 82% of individuals were assigned back to the original population based on the results of the assignment test. An isolation by distance analysis indicated that genetic differentiation among populations was a function of geographic distance, although long-distance gene dispersal between some populations was suggested from an analysis of relatedness between populations using the neighbor-joining method. An estimate of the outcrossing rate based on genotypes of progenies from six of the 22 populations using the multilocus method from the program MLTR ranged from 0.780 to 0.912, suggesting that the species is predominantly outcrossing. These results are encouraging for conservation, signifying that populations may persist due to continued genetic exchange sustained by the outcrossing mating system of the species.  相似文献   

20.
Fourteen efficient inter-simple sequence repeat (ISSR) primers were screened and optimized for detecting the genetic diversity in wild populations of Glycyrrhiza uralensis Fisch. By using these primers, 249 polymorphic bands out of a total of 270 (92.2 %) were generated from 70 individuals of 4 wild G. uralensis populations sampled from Inner Mongolia Province of China. Nei’s gene diversity (h) and Shannon index (I) calculated from the data matrix of the ISSR phenotypes revealed a high level of genetic diversity with h = 0.268 and I = 0.415 within this plant. Analysis of molecular variation (AMOVA) showed that most of the genetic variation (81 %) occurred within the populations, whereas the variance among populations was only 19 %. The UPGMA tree based on Nei’s unbiased genetic diversity illustrated that populations from Bulage and Bayanwusu were genetically close related, while the population from Shanghaimiao was found to be the most diverse from the other three. The high genetic diversity implies that the wild resources of this species could be restored soon if an appropriate and efficient protection strategy was employed. Our results also provided an optimized method for evaluating genetic diversity of G. uralensis using ISSR markers which was useful for further investigation.  相似文献   

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