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1.
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   

2.
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   

3.
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   

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.
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   

6.
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   

7.
Megacodon stylophorus (Clarke) Smith is a perennial alpine herb endemic to the species-rich eastern Himalayan region. Its populations are locally scattered as isolated patches throughout this region. Genetic variation within and among six populations of this species was assessed using ISSR fingerprinting with 13 primers. High levels of genetic diversity exist within species (P = 69.83%, HT = 0.1949 and Hsp = 0.3047), while the within-population diversity is low (P = 11.21%, HE = 0.0532 and Hpop = 0.0792). Extraordinarily high levels of genetic differentiation were detected among populations based on various statistics, including Neis genetic diversity analysis (72.7%), Shannons diversity index (74.01%) and AMOVA (80.70%). That is, populations shared low levels of genetic identity (I = 0.8203 ± 0.0430). This genetic structure was probably due to severe genetic drift of the small-sized patchy populations resulting from postglacial habitat fragmentations. The observed genetic structure of the populations implies that as many populations as possible should be considered for any in situ and ex situ conservation practice on this species.  相似文献   

8.
A total of twelve polymorphic microsatellite loci were developed from polyploid endangered species, Omphalogramma vincaeflora (Primulaceae). These loci were screened for variability among 45 individuals from three populations in China. The primers amplified loci with allele number ranging from 3 to 9, with an average of 4.25 per locus. Polymorphism information content ranged from 0.23 to 0.86. Nei’s genetic diversity ranged from 0.34 to 0.86. These primers provide an opportunity to use polymorphic DNA markers to study the population genetic structure and its breeding system in this species.  相似文献   

9.
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   

10.
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   

11.
Genetic variability in random amplified polymorphic DNA (RAPD) was studied in 90 individuals of Caragana microphylla, an outcrossing perennial shrub species, from five natural populations sampled in Inner Mongolia steppe of China on a small scale. Nineteen selected primers were used to amplify DNA samples, and totally 225 bands were detected. The percentage of polymorphic bands within populations ranged form 58.22% to 63.56%, with an average of 60% at the population level and 71.11% at the species level, indicating relatively high genetic variations in C. microphylla species. Shannon’s information index (l) and Nei’s gene diversity (h) showed the similar trend with each other. According to the analysis of Nei’s gene diversity, the percentage of genetic variation among populations was 7.13%, indicating a low level of genetic differentiation among populations. There existed a strong gene flow (N m = 3.26) among populations. Although AMOVA analysis also revealed most variation was within populations (ΦST = 4.1%), a significant proportion was observed among populations (P < 0.001) in the present study, suggesting genetic differentiation occurred among populations at a certain extent. Based on Mantel’s tests and the results of previous studies, the genetic structure pattern of C. microphylla accorded with the isolation-by-distance model on a very large scale, however, on a small scale, the significant genetic differentiation among populations might be enhanced by the micro-environmental divergence among the sampling sites, rather than by geographic factors. Analysis of the genetic variations of C. microphylla populations provided useful information for the adaptive strategy of Caragana species.  相似文献   

12.
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   

13.
Chinese alligator (Alligator sinensis) is a critically endangered species endemic to China. In this study, the extent of genetic variation in the captive alligators of the Changxing Reserve Center was investigated using microsatellite markers derived from American alligators. Out of 22 loci employed, 21 were successfully amplified in the Chinese alligator. Sequence analysis showed loci in American alligators had a bigger average size than that of the Chinese alligators and the longest allele of an individual locus almost always existed in the species with longer stretch of repeat units. Eight of the 22 loci were found to be polymorphic with a total of 26 alleles present among 32 animals scored, yielding an average of 3.25 alleles per polymorphic locus. The expected heterozygosity (H E) ranged at a moderate level from 0.4385 to 0.7163 in this population. Compared to that in the American alligators, a lower level of microsatellite diversity existed in the Changxing population as revealed by about 46% fewer alleles per locus and smaller H E at the homologous loci. The average exclusion power and the ability to detect shared genotypes and multiple paternity were evaluated for those markers. Results suggested that when the polymorphic loci were combined, they could be sensitive markers in genetic diversity study and relatedness inference within the Chinese alligator populations. The level of genetic diversity present in the current Changxing population indicated an important resource to complement reintroductions based on the individuals from the other population. In addition, the microsatellite markers and their associated diversity characterized in this population could be utilized to further investigate the genetic status of this species.  相似文献   

14.
Amplified fragment length polymorphism (AFLP) markers were used to estimate the genetic diversity of seven wild populations of Sinopodophyllum hexandrum (Royle) Ying from the Tibetan region of Sichuan Province, China. Six primer combinations generated a total of 428 discernible DNA fragments, of which 111 were polymorphic. The percentage of polymorphic bands (PPB) was 25.93 at the species level, and PPB within population ranged from 4.91 to 12.38%. Genetic diversity (H E) within populations varied from 0.01 to 0.04, averaging 0.05 at the species level. As revealed by the results of AMOVA analysis, 58.8% of the genetic differentiation occurred between populations, and 41.2% within populations. The genetic differentiation was, perhaps, due to the limited gene flow (N m=0.43) of the species. The correlation coefficient (r) between genetic and geographical distance using Mantel's test for all populations was 0.698 (P=0.014). The UPGMA cluster analysis revealed a similar result in that the genetic distances among the populations show, to a certain extent, a spatial pattern corresponding to their geographic locations. On the basis of the genetic and ecological information, we propose some appropriate strategies for conserving the endangered S. hexandrum in this region.  相似文献   

15.
The distribution of Nepenthes mirabilis ranges from Northeast (NE) to South (S) Thailand. Eleven individuals from NE, S and Suen Jatujak market in Bangkok, Central (C) Thailand, were collected and divided into four populations according to their geographical areas. These four populations were analyzed to determine a genetic diversity profile using thirteen inter-simple sequence repeat markers. The individuals produced 75.18% polymorphic banding profiles. The Shannon’s index was used to estimate genetic diversity. Total genetic diversity (H T) and inter-population genetic diversity (H S) were 0.854 and 0.678, respectively. The degree of genetic differentiation (G ST) of the species populations is 0.206, whereas the gene flow (Nm) among all the various geographical area populations is 1.016. Both the dendrogram and the results of the Shannon’s diversity index suggest great genetic diversity. These results support the broad range of distribution sites of Nepenthes mirabilis, which would require high genetic diversity to adapt to the environmental variations that can be found between NE, C, and S Thailand. ANOVA shows that the genetic diversity in each population is not significantly different (P > 0.05). Mantel tests reveal that geographical distance is an important factor for affecting the genetic distances among populations.  相似文献   

16.
Varicorhinus alticorpus (Cyprinidae) is an endangered freshwater fish with a scattered distribution in the southern and eastern regions of Taiwan. We described the development of nine polymorphic microsatellite loci in V. alticorpus for genetic studies. These new markers were tested in 20 individuals of the rare species. The number of alleles ranged from 4 to 13. Expected (H E) and observed (H O) heterozygosities ranged from 0.692 to 0.892 (averaged at 0.821) and from 0.000 to 0.350 (averaged at 0.088), respectively. All loci are significantly deviated from Hardy–Weinberg expectations due to the heterozygote deficiency. This suite of highly polymorphic microsatellites provides the first chance to undertake a conservation program for this species in Taiwan. It is essential to evaluate its genetic diversity and the fine-scale population structure. Tzen-Yuh Chiang, Teh-Wang Lee, and Feng-Jiau Lin contributed equally to this work.  相似文献   

17.
Genetic variation of four populations of Sargassum thunbergii (Mert.) O. Kuntze and one outgroup of S. fusiforme (Harv.) Setchell from Shandong peninsula of China was studied with random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers. A total of 28 RAPD primers and 19 ISSR primers were amplified, showing 174 loci and 125 loci, respectively. Calculation of genetic diversity with different indicators (P%, percentage of polymorphic loci; H, the expected heterozygosity; I, Shannon’s information index) revealed low or moderate levels of genetic variations within each S. thunbergii population. High genetic differentiations were determined with pairwise Nei’s unbiased genetic distance (D) and fixation index (F ST ) between the populations. The Mantel test showed that two types of matrices of D and F ST were highly correlated, whether from RAPD or ISSR data, r = 0.9310 (P  = 0.008) and 0.9313 (P = 0.009) respectively. Analysis of molecular variance (AMOVA) was used to apportion the variations between and within the S. thunbergii populations. It indicated that the variations among populations were higher than those within populations, being 57.57% versus 42.43% by RAPD and 59.52% versus 40.08% by ISSR, respectively. Furthermore, the Mantel test suggested that the genetic differentiations between the four populations were related to the geographical distances (r > 0.5), i.e., they conformed to the IBD (isolation by distance) model, as expected from UPGMA (unweighted pair group method with arithmetic averages) cluster analysis. As a whole, the high genetic structuring between the four S. thunbergii populations along distant locations was clearly indicated in the RAPD and ISSR analyses (r > 0.8) in our study.  相似文献   

18.
Ouma JO  Marquez JG  Krafsur ES 《Genetica》2007,130(2):139-151
Genetic diversity and differentiation within and among nine G. morsitans morsitans populations from East and southern Africa was assessed by examining variation at seven microsatellite loci and a mitochondrial locus, cytochrome oxidase (COI). Mean COI diversity within populations was 0.63 ± 0.33 and 0.81 taken over all populations. Diversities averaged over microsatellite loci were high (mean number of alleles/locus ≥7.4; mean H E ≥ 65%) in all populations. Diversities averaged across populations were greater in East Africa (mean number of alleles = 22 ± 2.6; mean h e = 0.773 ± 0.033) than in southern Africa (mean number of alleles = 18.7 ± 4.0; mean h e = 0.713 ± 0.072). Differentiation among all populations was highly significant (R ST = 0.25, F ST = 0.132). Nei’s G ij statistics were 0.09 and 0.19 within regions for microsatellites and mitochondria, respectively; between regions, G ij was 0.14 for microsatellites and 0.23 for mitochondria. G ST among populations was 0.23 for microsatellite loci and 0.40 for mitochondria. The F, G and R statistics indicate highly restricted gene flow among G. m. morsitans populations separated over geographic scales of 12–917 km.  相似文献   

19.
Amentotaxus, a genus of the Taxaceae, represents an ancient lineage that has long existed in Eurasia. All Amentotaxus species experienced frequent population expansion and contraction over periodical glaciations in Tertiary and Quaternary. Among them, Amentotaxus argotaenia complex consists of three morphologically alike species, A. argotaenia, Amentotaxus yunnanensis, and Amentotaxus formosana. This complex is distributed in the subtropical region of mainland China and Taiwan where many Pleistocene refugia have been documented. In this study, genetic diversity and population structuring within and between species were investigated based on the inter-simple sequence repeats (ISSR) fingerprinting. Mean genetic diversity within populations was estimated in three ways: (1) the percentage of polymorphic loci out of all loci (P) (2) Neis unbiased expected heterozygosity (He), and (3) Shannons index of phenotypic diversity. For a total of 310 individuals of 15 populations sampled from the three species, low levels of ISSR genetic variation within populations were detected, with P=4.66–16.58%, He=0.0176–0.0645 and Hpop=0.0263–0.0939, agreeing with their seriously threatened status. AMOVA analyses revealed that the differences between species only accounted for 27.38% of the total variation, whereas differences among populations and within populations were 57.70 and 14.92%, respectively, indicating substantial isolation between the patch-like populations. A neighbor-joining tree identified a close affinity between A. yunnanensis and A. formosana. Genetic drift due to small population size, plus limited current gene flow, resulted in significant genetic structuring. Low levels of intrapopulational genetic variation and considerable interpopulational divergence were also attributable to demographic bottlenecks during and/or after the Pleistocene glaciations.  相似文献   

20.
Li Q  Xiao M  Guo L  Wang L  Tang L  Xu Y  Yan F  Chen F 《Biochemical genetics》2005,43(7-8):445-458
The genetic diversity and genetic structure of Trillium tschonoskii (Maxim) were investigated using amplified fragment length polymorphism markers. Eight primer combinations were carried out on 105 different individuals sampled from seven populations. Of the 619 discernible DNA fragments generated, 169 (27.3%) were polymorphic. The percentage of polymorphic bands within populations ranged from 4.52 to 10.50. Genetic diversity (HE) within populations ranged from 0.0130 to 0.0379, averaging 0.0536 at the species level. Genetic differentiation among populations was detected based on Nei's genetic diversity analysis (53.03%) and analysis of molecular variance (AMOVA) (52.43%). AMOVA indicated significant genetic differentiation among populations (52.43% of the variance) and within populations (47.57% of the variance) (p < 0.0002). Gene flow was low (0.4429) among populations. Species breeding system and limited gene flow among populations are plausible reasons for the high genetic differentiation observed for this species. We propose an appropriate strategy for conserving the genetic resources of T. tschonoskii in China.  相似文献   

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