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1.
Fengjuan Zhao Fuli Liu Jidong Liu Put O. AngJr. Delin Duan 《Journal of applied phycology》2008,20(2):191-198
Sargassum muticum is important in maintaining the structure and function of littoral ecosystems, and is used in aquaculture and alginate production,
however, little is known about its population genetic attributes. In this study, random amplified polymorphic DNA (RAPD) and
inter-simple sequence repeat (ISSR) markers were used to investigate the genetic structure of four populations of S. muticum and one outgroup of S. fusiforme (Harv.) Setchell from Shandong peninsula of China. The selected 24 RAPD primers and 19 ISSR primers amplified 164 loci and
122 loci, respectively. Estimates of genetic diversity with different indicators (P%, percentage of polymorphic loci; H, the expected heterozygosity; I, Shannon’s information index) revealed low or moderate level of genetic variations within each S. muticum population, and a high level of genetic differentiations were determined with pairwise unbiased genetic distance (D) and fixation index (F
ST
) among the populations. The Mantel test showed that two types of matrices of D and F
ST
were highly correlated whether from RAPD (r = 0.9706, P = 0.009) or ISSR data (r = 0.9161, P = 0.009). Analysis of molecular
variance (AMOVA) was conducted to apportion the variations among and within the S. muticum populations. It indicated that variations among populations were higher than those within populations, being 55.82% verse
44.18% by RAPD and 55.21% verse 44.79% by ISSR, respectively. Furthermore, the Mantel test suggested that genetic differentiations
among populations were related to the geographical distances (r > 0.6), namely, conformed to the IBD (isolation by distance)
model, as expected from UPGMA (unweighted pair group method with arithmetic averages) cluster analysis. On the whole, the
high genetic structuring among the four S. muticum populations along the distant locations was clearly indicated in RAPD and ISSR analyses (r > 0.9, P < 0.05) in our study. 相似文献
2.
Lee S. Webley Kyall R. Zenger Graham P. Hall Desmond W. Cooper 《European Journal of Wildlife Research》2007,53(1):40-46
European fallow deer are an introduced species classified as partly protected wildlife in Tasmania, Australia. Current management
practices are primarily governed under the Quality Deer Management regime, in which animals are harvested during designated
hunting seasons. Among populations, prominent morphological differences have been reported; however, the genetic relationship
of these populations has until now been poorly understood. Representative animals were sampled from three key areas across
their range and genotyped at ten polymorphic microsatellite loci to investigate genetic diversity, population structure, and
genetic bottlenecks. Allelic richness was low in all three populations and ranged between 2.20 and 2.49 alleles/locus. A genetic
bottleneck was detected in two of the three populations (P < 0.001). Population differentiation was evident between Lake Echo and Benham (q = 0.122; P < 0.001) and Benham and Connorville (q = 0.110; P < 0.001), but not between Lake Echo and Connorville (q = 0.0235), with individuals being identified as belonging to two genetic
clusters. The pattern of population differentiation from the three study populations suggests that deer from the western region
of their range are genetically distinct to those from the eastern region. This correlates with morphological variation within
Tasmanian fallow deer, in which differences between the regions maybe attributable to geographical barriers. 相似文献
3.
Potenko VV 《Biochemical genetics》2007,45(3-4):291-304
Genetic variation and differentiation of 12 populations of Picea jezoensis from the Russian Far East were studied using 20 allozyme loci. The mean number of alleles per locus was 2.63, the percent
of polymorphic loci was 88.1%, the observed heterozygosity was 0.181, and the mean value of expected heterozygosity amounted
to 0.189. The values of expected heterozygosity of the northern and central mainland populations were higher than in the southern
part of the natural range. A significant bias of Hardy–Weinberg heterozygosity to equilibrium heterozygosity (Heq) suggests that most of the mainland populations have recently experienced a severe expansion in population size while populations
from Kamchatka Peninsula have undergone a reduction in population size. Unbiased Nei’s genetic distance values were low within
and between the mainland and Sakhalin Island populations (DN=0.008). The largest values (DN=0.063) were found between the mainland/Sakhalin and Kamchatka Peninsula populations. Based on genetic distance, P. jezoensis and P. kamtschatkensis could be considered as distinct taxa, but P. ajanensis, P. microsperma, and P. komarovii do not warrant taxonomic recognition. 相似文献
4.
High levels of genetic divergence and inbreeding in populations of cupuassu (Theobroma grandiflorum)
Rafael M. Alves Alexandre M. Sebbenn Angela S. Artero Charles Clement Antonio Figueira 《Tree Genetics & Genomes》2007,3(4):289-298
Theobroma grandiflorum (cupuassu) is an important fruit tree native to the Brazilian Amazon. Establishing the genetic diversity and structure of
populations is critical to define long-term strategies for cupuassu conservation presently threatened by rapid deforestation.
Three natural populations collected at the putative center of diversity, three groups of accessions established at a germplasm
collection, and one derived from commercial plantings were analyzed. The genetic diversity was assessed using 21 polymorphic
microsatellite loci originally developed for Theobroma cacao, disclosing a total of 113 alleles. The estimated genetic diversity parameters averaged over cupuassu populations (A = 3.53 alleles per locus; H
e = 0.426; H
o = 0.346) were lower than the values reported for other Neotropical tree species. The three natural populations presented
a positive and significant fixation index (f), ranging from 0.133 to 0.234. Cupuassu apparently adhered to a general pattern of genetic diversity structure of some Neotropical
tree species occurring at low densities, with a low intrapopulation genetic diversity and important levels of endogamy, possibly
due to biparental inbreeding derived from the presence of spatial genetic structure in the populations. A high level of genetic
divergence was detected among the natural populations (θ
p = 0.301), a strong differentiation caused by limited gene flow, and suggesting that human interference in spreading and/or
stimulating plantings might have had a smaller effect than expected. The approximate location of the T. grandiflorum center of diversity could not be confirmed by analyzing natural populations from the putative region. 相似文献
5.
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
6.
Pramual P Gomontean B Buasay V Srikhamwiang N Suebkar P Niamlek C Donsinphoem Y Chalat-Chieo K 《Genetica》2009,135(1):51-57
The objectives of this study were to explore cytogenetic variation and the role of chromosomal change on local adaptation
and genetic differentiation of Chironomus circumdatus Kieffer from Thailand. A total of 1,505 larvae from 24 populations were examined cytologically. Twelve chromosomal inversions
were found and most of these (9 of 12) were rare inversions. All populations were in Hardy–Weinberg equilibrium. Significant
association (P < 0.001) between the A2 and B5 inversions was detected in one population. Population genetic structure analysis indicated significant genetic differentiation
between populations (F
ST = 0.037, P < 0.001). Geographic distance was the principal factor limiting gene flow between populations. Nei’s modified genetic distance
(D
A) between populations ranged from 0.001 to 0.011 with an average of 0.003. An UPGMA population phenogram depicting relationship
between populations based on D
A values revealed three groups of populations, group I, II and III each characterized by different inversions/inversion frequencies.
Significant correlation of inversion C3 and water temperature suggested that this inversion might have a role to play on adaptation to high temperature habitat.
However, if detection of significant population subdivision and relationship between genetic and geographic distance are taken
into account, relationship between C3 and water temperature will also be due to the effect of migration/drift alone without the effect of selection. 相似文献
7.
Founder group size is of prime importance in tree breeding programs. We determined whether sampling 20-plus trees for breeding
in Allanblackia floribunda, a tropical forest tree species that has been recently enrolled in tree improvement program for fruit and seed production,
would affect neutral genetic diversity and inbreeding level in both breeding and production populations. Using eight informative
microsatellite loci, we: (a) assessed the nuclear genetic diversity of ten natural populations, and of the breeding population
in the humid forest zone of Cameroon; (b) investigated temporal effective-size fluctuations in A. floribunda natural populations, with a view to identifying the role of past demographic events in the genetic structure of the studied
species; and (c) tested the hypothesis that genetic diversity in a founder group of 20 individuals is not different from that
existing in the wild. The eight loci were variable. High levels of genetic diversity (A = 4.96; H
E = 0.59) and moderate differentiation (R
ST = 0.061) were found within and among populations in wild stands. High genetic distances existed between populations
( \textaverage chord distance = 0.\text2769 ±0.00\text554 ) \left( {{\text{average chord distance}} = 0.{\text{2769}} \pm 0.00{\text{554}}} \right) . Eight of the ten surveyed populations showed signs of deviation from mutation-drift equilibrium, suggesting Pleistocene
population bottlenecks and fluctuations in effective population size. Mantel tests did not reveal any relationships between
genetic and geographic distances. A neighbor-joining dendrogram showed a population structure that could be explained by historical
factors. The hypothesis tested has been accepted. However, a slight increase in inbreeding was observed in the breeding population. 相似文献
8.
We assessed genetic variation in a total of 22 populations of the tree species Cordia africana Lam. in Ethiopia and analyzed the country-wide impact of population history, forest disturbance and alteration of land use
on extant intraspecific diversity. Amplified Fragment Length Polymorphisms (AFLPs) and chloroplast microsatellite markers
were investigated. The analyses of the AFLP data revealed high diversity in all investigated populations: the percentage of
polymorphic loci (PPL) ranged from 62.2% to 92.2% and Nei's gene diversity from 0.220 to 0.320 within the populations. The
mean PPL and the mean diversity within populations were 85.7% and 0.287, respectively. The analysis of molecular variance
revealed a moderate level of differentiation (ΦST = 0.07, p < 0.001) among the populations. The Mantel test proved a significant but low correlation (r = 0.31, p < 0.001) between the geographic distance and the genetic differentiation matrices. Only three different cpDNA haplotypes
were observed; no more than two haplotypes were found in any population. The dominant haplotype with an overall frequency
of 81% was observed in all populations. The level of differentiation among the populations was comparatively low at chloroplast
DNA (G
ST = 0.18, R
ST, N
ST = 0.22). The observed patterns and levels of genetic variation within and among the populations indicate that efficient gene
flow via pollen and seed is likely to be the main factor contributing to the maintenance of genetic diversity in natural and
disturbed conditions. 相似文献
9.
Charles Masembe Vincent B. Muwanika Silvester Nyakaana Peter Arctander Hans R. Siegismund 《Conservation Genetics》2006,7(4):551-562
Phylogeographic and population genetic studies using sequence information are frequently used to infer species boundaries and history; and to assess hybridization and population level processes. In this study, partial mitochondrial DNA (mtDNA) control region (423 bp) and cytochrome b sequences (666 bp) of Oryx beisa sampled from five isolated localities in its entire current range in Africa were analyzed to investigate the extent of genetic variation and differentiation between populations. We observed high nucleotide diversity at the control region in the total sample (6.3%) but within populations, it varied considerably ranging from 1.6% to 8.1%. Population pairwise genetic differentiation was generally significantly high (ranging from F
ST = 0.15, P<0.01 to F
ST = 0.54, P<0.001). In the total sample, 29 and 12 haplotypes were observed in the control region and the cytochrome b data sets respectively. For both data sets, the haplotypes cluster into three distinct clades (sequence divergence ranged from 6.0%–12.9% to 0.8%–1.0% for the control region and cytochrome b sequences, respectively) that do not correspond to sampling locations. Two of these clades are found in the same localities (Samburu and Marsabit), which represent the O.beisa beisa subspecies, whereas the last clade represents the fringe-eared oryx (O. beisa callotis). We interpret these findings in terms of an ancient hybridization and introgression between two formerly isolated taxa of Oryx beisa. 相似文献
10.
Elongate loach (Leptobotia elongata (Bleeker)), an endemic fish species to China, is a famous ornamental freshwater fish. Here, a comparative study of mtDNA
control region (D-loop) (835 bp) sequences was performed to analyze its wild population structure and evaluate the genetic
diversity for 110 individuals from five locations in the upper reaches of the Yangtze River, China. A total of 49 polymorphic
sites and 45 haplotypes yielded high haplotype diversity (h = 0.952), but low nucleotide diversity (π = 0.00454) as that of many fish species. Sequence divergences between haplotypes ranged from 0.0033 ± 0.0011 to 0.0050 ± 0.0012
in intra-groups, and from 0.0037 ± 0.0.0011 to 0.0050 ± 0.0012 between groups. Significant values of Tajima’s D (−1.86383, P < 0.01) and Fu’s F
S (−25.93, P < 0.01), together with uni-modal mismatch distribution, indicated a recent genetic bottleneck or population expansion of
the species. Analysis of molecular variance (AMOVA) indicated a small amount of differentiation among groups (1.7%); most
of the total variation occurred within groups (98.3%). Also, there was no significant population structure (F
ST = 0.017, P > 0.05), and estimates of gene flows among groups were extremely high (Nm = 28.88), suggesting low genetic divergence between populations in the species. The lack of genetic differentiation among
groups is most likely due to the combined gene flow from the downstream movement of eggs and larvae with currents and the
upstream or downstream migration of adults throughout the distribution. These groups of L. elongata distributed in upper reaches of the Yangtze River should be considered as a single management unit. 相似文献
11.
Nucleotide variation at several cold candidate genes including seven members of the dehydrin gene family was surveyed in haplotypes
of Scots pine (Pinus sylvestris) sampled in populations showing divergence for cold tolerance in Europe. Patterns of nucleotide diversity, linkage disequilibrium,
and frequency spectrum of alleles were compared between north and south populations to search for signs of directional selection
potentially underlying adaptation to cold. Significant differentiation between populations in allelic frequency or haplotype
structure was detected at dhn1, dhn3, and abaH loci. Allelic dimorphism with no evidence of haplotype clustering by geographical distribution was found at dhn9. An excess of fixed non-synonymous mutations as compared to the outgroup P. pinaster pine species was found at dhn1. Differences in nucleotide polymorphisms were found between the members of the Kn class of dehydrin upregulated during cold
acclimation (average πsil = 0.004) as compared to the SKn class (average πsil = 0.024). The multilocus nucleotide diversity at silent sites (θ
W = 0.009) was moderate compared to other conifer species, but higher than previous estimates for Scots pine. There was an
excess of rare and high frequency derived variants as revealed by significantly negative multilocus value of Tajima’s D (D = −0.72, P < 0.01) and negative mean value of Fay and Wu H statistics (H = −0.50). The level of linkage disequilibrium decayed rapidly with an average expected r
2 of 0.2 at about 200 bp. Overall, there was a positive correlation between polymorphism and divergence at ten loci when outgroup
sequence was available. The discovered polymorphism will be used for further evaluation of the adaptive role of genes through
association mapping studies.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
12.
Lan Q Shen M Garcia-Rossi D Chanock S Zheng T Berndt SI Puri V Li G He X Welch R Zahm SH Zhang L Zhang Y Smith M Wang SS Chiu BC Linet M Hayes R Rothman N Yeager M 《Immunogenetics》2007,59(11):839-852
Selection and genetic drift can create genetic differences between populations. Cytokines and chemokines play an important
role in both hematopoietic development and the inflammatory response. We compared the genotype frequencies of 45 SNPs in 30
cytokine and chemokine genes in two healthy Chinese populations and one Caucasian population. Several SNPs in IL4 had substantial genetic differentiation between the Chinese and Caucasian populations (F
ST ~0.40), and displayed a strikingly different haplotype distribution. To further characterize common genetic variation in
worldwide populations at the IL4 locus, we genotyped 9 SNPs at the IL4 gene in the Human Diversity Panel’s (N = 1056) individuals from 52 world geographic regions. We observed low haplotype diversity, yet strikingly different haplotype
frequencies between non-African populations, which may indicate different selective pressures on the IL4 gene in different parts of the world. SNPs in CSF2, IL6, IL10, CTLA4, and CX3CR1 showed moderate genetic differentiation between the Chinese and Caucasian populations (0.15 < F
ST < 0.25). These results suggest that there is substantial genetic diversity in immune genes and exploration of SNP associations
with immune-related diseases that vary in incidence across these two populations may be warranted. 相似文献
13.
We investigated the extent of genetic differentiation among populations of fujihatazao,Arabis serrata along an altitudinal gradient at Mt. Fuji in Shizuoka Prefecture. This species is a perennial plant, widely distributed in
Japan forming small isolated populations. However, at Mt. Fuji, this species constitutes a large population distributed from
1440 to 2400 m altitude. A total of 411 individuals were sampled from ten subpopulations. Eighteen loci were detected on eleven
enzyme systems. Eleven loci were monomorphic and seven loci were polymorphic with a mean of 2.11 alleles per loci. Nei's genetic
distance (mean 0.01) and genetic identity (mean 0.968) were very similar among populations indicating a low genetic differentiation.
The total genetic diversity (H
T
) estimated for the polymorphic loci was, in average, 0.396. The mean gene differentiation (GST=0.091) was very low. Gene frequency of seven polymorphic loci was analyzed by spatial autocorrelation methods based on Moran's
indexes. Only Pgi-3 exhibited a significant negative autocorrelation (−0.160;P<0.05); other loci values ranged from −0.134 to 0.027. Gene flow estimated by indirect methods varied between genes but most
of the values were high (meanNm=20.8) suggesting that subpopulations at different altitudes are probably connected. Despite plants at different altitudes
present different ecological traits (e.g., differences in phenology, growth and reproductive traits), subpopulations ofA. serrata are still low differentiated, at least for the loci studied. This may be explained by the recent origin of some habitats
(e.g., second crater and surrounded areas) in this locality. 相似文献
14.
Mao-feng Yue Ren-chao Zhou Ye-lin Huang Guo-rong Xin Su-hua Shi Li Feng 《Journal of Plant Biology》2010,53(2):165-171
High levels of genetic variation enable species to adapt to changing environments and provide plant breeders with the raw
materials necessary for artificial selection. In the present study, six AFLP primer pairs were used to assess the genetic
diversity of Desmodium triflorum (L.) DC. from 12 populations in South China. A high percentage of polymorphic loci (P = 76.16%) and high total gene diversity (H
T = 0.310) were found, indicating that the genetic diversity of D. triflorum is high at the species level. Genetic diversity was also relatively high at the population level (P = 55.85%, H
e = 0.230). The coefficient of gene differentiation among populations (G
ST) was 0.255, indicating that while most genetic diversity resided within populations, there was also considerable differentiation
among populations. AMOVA also indicated 24.29% of the total variation to be partitioned among populations (ΦST = 0.243). UPGMA clustering analysis based on genetic distances showed that the 12 populations could be separated into three
subgroups: an eastern, a western, and a central-southern subgroup. However, a Mantel test revealed no significant correlation
(r = 0.286, p = 0.983) between the geographical distances and genetic distances separating these populations; mountain barriers to gene
flow and human disturbance may have confounded these correlations. The present study has provided some fundamental genetic
data that will be of use in the exploitation of D. triflorum. 相似文献
15.
Subspecific taxa of species complexes can display cryptic morphological variation, and individuals and populations can often
be difficult to identify with certainty. However, accurate population identification is required for comprehensive conservation
and breeding strategies and for studies of invasiveness and gene flow. Using five informative microsatellite markers and a
Bayesian statistical approach, we developed an efficient polymerase chain reaction-based diagnostic tool for the rapid identification
of individuals and populations of the Acacia saligna species complex of Western Australia. We genotyped 189 individuals from 14 reference populations previously characterised
based on morphology and used these data to investigate population structure in the species complex. High total genetic diversity
(H
T = 0.729) and high population differentiation (θ = 0.355) indicated strong intraspecific structuring. With the provision of prior population information, the reference data
set was optimally resolved into four clusters, each corresponding to one of the four main proposed subspecies, with very high
membership values (Q > 97%). The reference data set was then used to assign individuals and test populations to one of the four subspecies. Assignment
was unequivocal for all test individuals from two populations of subsp. lindleyi and for all but one individual of subsp. stolonifera. Individuals from populations of subsp. saligna and subsp. pruinescens showed a degree of genetic affinity for the two subspecies in their assignments, although the majority of individuals were
correctly assigned to subspecies. The diagnostic tool will assist in characterising populations of A. saligna, especially naturalised and invasive populations of unknown origin. 相似文献
16.
Yoshiaki Tsuda Haruo Sawada Takafumi Ohsawa Katsuhiro Nakao Hiroki Nishikawa Yuji Ide 《Tree Genetics & Genomes》2010,6(3):377-387
We evaluated the genetic structure of 16 Betula maximowicziana populations in the Chichibu mountain range, central Japan, located within a 25-km radius; all but two populations were at
altitudes of 1,100–1,400 m. The results indicate the effects of geographic topology on the landscape genetic structure of
the populations and should facilitate the development of local-scale strategies to conserve and manage them. Analyses involving
11 nuclear simple sequence repeat loci showed that most populations had similar intrapopulation genetic diversity parameters.
Population differentiation (F
ST = 0.021, G′ST = 0.033) parameters for the populations examined were low but were relatively high compared to those obtained in a previous
study covering populations in a much larger area with a radius of approximately 1,000 km (F
ST = 0.062, G′ST = 0.102). Three populations (Iriyama, Kanayamasawa, and Nishizawa) were differentiated from the other populations by Monmonier’s
and spatial analysis of molecular variance algorithms or by STRUCTURE analysis. Since a high mountain ridge (nearly 2,000 m)
separates the Kanayamasawa and Nishizawa populations from the other 14 populations and the Kanayamasawa and Nishizawa populations
are themselves separated by another mountain ridge, the genetic structure appears to be partly due to mountain ridges acting
as genetic barriers and restricting gene flow. However, the Iriyama population is genetically different but not separated
by any clear geographic barrier. These results show that the landscape genetic structure is complex in the mountain range
and we need to pay attention, within landscape genetic studies and conservation programs, to geographic barriers and local
population differentiation. 相似文献
17.
Nora H. Oleas Alan W. Meerow Javier Francisco‐Ortega 《Botanical journal of the Linnean Society. Linnean Society of London》2016,182(1):169-179
Phaedranassa schizantha (Amaryllidaceae) is an endangered species endemic to Ecuador and two varieties have been described: P. schizantha var. schizantha and P. schizantha var. ignea. We assessed population genetic structure and demographic patterns in 11 populations across the range of the species using 13 microsatellite loci. Our data show that genetic diversity was generally lower in the southern part of the range and was especially low in populations closest to cities. We found significant population differentiation (FST = 0.14, DEST = 0.34) and evidence of a genetic bottleneck. Genetic variation did not show isolation by distance. Instead, results suggest genetic barriers around two main cities. Bayesian analysis identified two genetic groups, neither of which represents either of the two varieties previously recognized. Coalescent analysis indicates a relatively recent colonization pattern between the two genetic groups (< 3000 generations). Conservation efforts need to be taken to facilitate genetic exchange between the groups, especially between locations that seem to be genetically isolated. 相似文献
18.
H. Huang F. Dane J. D. Norton 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1994,88(8):981-985
Allozyme genetic variability in three chestnut (Castanea) species was investigated using 19 loci from ten enzyme systems. G-tests of heterogeneity of isozymic allele distribution showed significant differences between the three species at 15 of the 19 loci, and between the 13 C. mollissima populations at 13 of the 19 loci examined. C. mollissima was found to possess a significantly-higher value of mean gene heterozygosity (H=0.3050±0.0419), the percentage of polymorphic loci (P=84.21%) and the average number of alleles per locus (A=2.05), than any other species in the Castanea section Eucastanon. When the genetic variability of populations of C. mollissima from four regions in China was investigated, the population from the Changjiang river region showed a markedly higher mean gene heterozygosity (H=0.3480±0.0436) than populations from the other regions. Genetic relationships among the four regions were assessed by Nei's genetic identity I and standard genetic distance D. An approximately-identical distance between the population from the Changjiang river region and populations from the three other regions was observed, while populations from the latter regions showed almost the same genetic distance from each other. These data, when considered with information existing prior to this study, contribute to an understanding of the possible origin and progenitor of the chestnut species. 相似文献
19.
Melinda D. Peters Qiu-Yun Xiang David T. Thomas Jon Stucky Noah K. Whiteman 《Conservation Genetics》2009,10(1):1-14
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.
Konstantin V. Krutovsky John Bradley St. Clair Robert Saich Valerie D. Hipkins David B. Neale 《Tree Genetics & Genomes》2009,5(4):641-658
Characterizing population structure using neutral markers is an important first step in association genetic studies in order
to avoid false associations between phenotypes and genotypes that may arise from non-selective demographic factors. Population
structure was studied in a wide sample of ∼1,300 coastal Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco var. menziesii] trees from Washington and Oregon. This sample is being used for association mapping between cold hardiness and phenology
phenotypes and single-nucleotide polymorphisms in adaptive-trait candidate genes. All trees were genotyped for 25 allozyme
and six simple sequence repeat (SSR) markers using individual megagametophytes. Population structure analysis was done separately
for allozyme and SSR markers, as well as for both datasets combined. The parameter of genetic differentiation (θ or F
ST) was standardized to take into account high within-population variation in the SSR loci and to allow comparison with allozyme
loci. Genetic distance between populations was positively and significantly correlated with geographic distance, and weak
but significant clinal variation was found for a few alleles. Although the STRUCTURE simulation analysis inferred the same
number of populations as used in this study and as based on previous analysis of quantitative adaptive trait variation, clustering
among populations was not significant. In general, results indicated weak differentiation among populations for both allozyme
and SSR loci (θ
s = 0.006–0.059). The lack of pronounced population subdivision in the studied area should facilitate association mapping in
this experimental population, but we recommend taking the STRUCTURE analysis and population assignments for individual trees
(Q-matrix) into account in association mapping. 相似文献