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1.
Berchemiella wilsonii var. pubipetiolata (Rhamnaceae) is an endangered tree in eastern China. Habitat destruction has resulted in fragmentation of remnant populations
and extinction of local populations. AFLP and cpDNA markers were used to determine the population structure of remnant populations
of B. wilsonii var. pubipetiolata. Moderate nuclear genomic diversity was found within each of the four remnant populations (H
S = 0.141–0.172), while the cpDNA haplotype diversity in each population ranged from 0.356 to 0.681. Six haplotypes were identified
by a combined cpRFLP and cpSSR analysis in a total of 89 individuals. AMOVA revealed significantly AFLP genetic differentiation
within and between regions (ΦSC = 0.196, ΦCT = 0.396, respectively), and a high cpDNA haplotype differentiation between regions (ΦCT = 0.849). The results suggest low gene flow between populations of B. wilsonii var. pubipetiolata. Strong genetic divergence between two regional populations as revealed by both AFLP and cpDNA markers provided convincing
evidence that two distinct evolutionary lineages existed, and should be recognized as ‘evolutionary significant units’ (ESUs)
for conservation concerns. 相似文献
2.
Cypripedium macranthos var. rebunense is an endangered plant endemic to Rebun Island, Japan. A proper understanding of genetic diversity is needed when conducting
conservation programs for rare and endangered species. We therefore examined the genetic diversity of C. macranthos var. rebunense using allozyme markers with a view to future conservation. Our study revealed that C. macranthos var. rebunense has relatively high genetic diversity (P was 0.62, n
a and n
e were 1.85 and 1.28 respectively, and H
o and H
e were 0.163 and 0.187, respectively) when compared with other plant taxa. The natural habitats of C. macranthos var. rebunense are geographically separated into northern and the southern populations. Disappearance of alleles and increase in homozygosity
expected as a result of the bottleneck effect were observed, particularly in the southern populations composed of a small
number of plants. As additional negative effects (inbreeding depression and further genetic drift) due to fragmentation are
predicted in these populations, the southern populations may show deterioration of genetic diversity in the near future. 相似文献
3.
Berchemiella wilsonii var. pubipetiolata (Rhamnaceae) is an endangered plant with only four remnant populations in eastern China. Population genetic information is
essential for understanding population history and formulating conservation strategies for this species. Thirteen microsatellite
loci were used to investigate genetic variation and population structure of the four remnant populations. Moderate levels
of expected heterozygosity (H
E = 0.466–0.543) and low allelic diversity (A = 3.1–3.6 and A
R = 2.2–2.4, respectively) were observed within populations. Bottleneck tests found three out of four populations to deviate
from mutation-drift equilibrium under the two-phase model (TPM), suggesting a recent population decline, which is congruent
with known demographic history. The evolutionary history of the species seems dominated by genetic drift rather than gene
flow. Low historical gene flow was inferred from several different approaches and N
m ranged from 0.582 by the private allele method to 0.783 by the coalescent method. Contemporary gene flow was also found to
be even lower for only one first generation migrant was detected with individual-based assignment analysis. Restricted pollen
and seed dispersal as well as a recent decline in population size associated with habitat fragmentation may have contributed
to low levels of historical and contemporary gene flow, and resulted in a high genetic differentiation. Under this scenario,
Berchemiella wilsonii var. pubipetiolata populations are expected to display more pronounced population genetic structure in the future as a result of increased inbreeding
and genetic drift. 相似文献
4.
Shuguang Jian Yang Zhong Nian Liu Zezheng Gao Qiang Wei Zhenhua Xie Hai Ren 《Biodiversity and Conservation》2006,15(5):1681-1694
Cycas fairylakea is an endangered endemic species in China. Genetic diversity within and among four natural populations of this species in
China was investigated using amplified fragments length polymorphism (AFLP). A moderate to low level of intraspecific genetic
diversity was detected in this species (at population level: P = 39.57 %, H0 = 0.244; at species level: P = 60.22%, H0 = 0.356). The among-population component accounted for, respectively, 25.7 and 31.5% of the genetic variation, according
to AMOVA and Shannon’s index, indicating most of the genetic variation was found between individuals within populations. All
four populations have opposite pyramid age structure, and few coning individuals, which is still decreasing. Possibly because
of habitat degradation and environmental pollution, plant diseases and insect pests in the populations were extremely serious,
suggesting that the main factors threatening the survival of C. fairylakea populations were not genetic variation, but human activities and the breeding system of this species. 相似文献
5.
Xiao-Li Peng Chang-Ming Zhao Gui-Li Wu Jian-Quan Liu 《Trees - Structure and Function》2007,21(4):457-464
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
6.
Curcuma zedoaria (Christm.) Roscoe, a member of the family Zingiberaceae, is one of the most widely distributed Curcuma species in Bangladesh. It is a well-known and important species because of its medicinal and horticultural values. However,
some plant populations are predicted to be depleted due to habitat destruction and due to extensive collection by local inhabitants.
In order to estimate the level of genetic diversity within and between natural populations, RAPD analyses were performed using
individual plants from different populations. We used Shannon’s index to partition genetic diversity which clearly demonstrated
that hilly populations of Srimangal, Chittagong and Sitakundu maintain rather higher genetic diversity than that of plain
land and plateau land populations of Savar and Birganj, respectively. We found a high intrapopulational (H′pop/H′sp) genetic diversity of 0.717 that was higher than the interpopulation diversity G
ST[(H′sp−H′pop)/H′sp] value of 0.283. Principal Coordinates Analysis (PCoA) showed that individuals of the hilly populations were combined in
one group, separated from the plain land and plateau land populations. From a conservation point of view, our results suggest
that special attention should be kept on the small populations of plain and plateau lands that are critically threatened due
to high anthropogenic activities. 相似文献
7.
Allozyme variation at eleven loci encoding seven enzyme systems were examined in 20 populations of diploid (genome AA, 2n = 16)Scilla scilloides in China. In comparison with the average species of seed plants studied, populations of this species display a high amount of genetic variation (A = 2.0, P = 58.6%, Ho = 0.172, and He = 0.185). Allozyme variation pattern revealed predominant outcrossing within populations and considerable differentiation (FST = 0.314) among populations as well as between the subtropic and temperate regions. The wide distribution, long existence and outcrossing are presumably the main factors responsible for the high genetic diversity within populations. But the gravity dispersal of seeds and pollination by small insects set limits to the increase of genetic variation within populations and promote differentiation between populations and regions. In addition, allozyme variation does not distinguishS. scilloides var.albo-viridis and suggests that subtropic populations may be considered as a genetic entity. 相似文献
8.
Allozyme electrophoresis was used to measure levels and distribution of genetic diversity in the critically endangered (CR)
Silene sennenii (Caryophyllaceae), a narrow endemic plant species found in northeastern Catalonia (Spain). At present, only 5 populations
remain, containing no more than 5,000 individuals, which are subjected to several human pressures such as habitat fragmentation
and land use changes. Interestingly, the largest population is located in and around a fortress built in the XVIII century,
a circumstance which might facilitated its preservation until now. From the 21 satisfactorily interpreted loci, low levels
of genetic variation were detected (P = 20.9, A = 1.31 and H
e = 0.071), which may be related to small population size, isolation, and fragmentation of extant populations. Moderate to
high levels of inbreeding were also found, probably as consequence of the population’s genetic structuring. The conservation
of the population located in the fortress would allow the preservation of all the alleles detected at species level; nevertheless,
conservation of other populations, coupled with the inclusion of S. sennenii in the Spanish Catalogue of Endangered Species, would also be desirable in order to ensure the long-term survival of the
species. 相似文献
9.
E. L. Borba R. R. Funch P. L. Ribeiro E. C. Smidt V. Silva-Pereira 《Plant Systematics and Evolution》2007,267(1-4):129-146
We carried out a demographic study and evaluated the genetic and morphological variability in five populations of the endangered
Sophronitis sincorana (Orchidaceae) endemic to Northeastern Brazil, based on allozyme and morphometric analyses. Plant density was approximately
0.5 plants/m2, and the projected total number of plants was approximately 50,000 individuals. However, fruit set and recruitment of individuals
are rare. The genetic variability was very high in all populations (P = 100, A = 3.0−3.5, H
e
= 0.33−0.48), and all populations presented similar values of morphological variability. Low genetic and morphological structuring
were found in the species (F
ST = 0.053, AMRPP = 0.018). The elevated coefficient of endogamy encountered in populations of S. sincorana indicates the occurrence of structuring within the populations. The lack of correlation between morphological and genetic
variation in this species indicates that none of the markers examined should be used separately for either conservation purposes. 相似文献
10.
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
11.
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
12.
Five sympatric colour varieties of the hoplonemertean Tetrastemma nigrifrons (var. pallidum, var. bicolor, var. purpureum, var. punctata, var. albino) were found in Vostok Bay (the Sea of Japan). The taxonomic status of the varieties, some of which have been known for almost a century, was uncertain. Starch gel electrophoresis was used to compare allele frequencies of these varieties at 19 isozyme loci. Neither fixed allelic differences nor statistically significant differences in allele frequencies between different colour varieties was revealed. It was concluded therefore that all the colour varieties studied are conspecific. As estimated from the electrophoretic screening of 24 isozyme loci, the species is highly variable at the molecular level. It has high mean values of observed and expected heterozygosity estimates, H
o =0.313 ± 0.049 and H
e =0.323 ± 0.050, and is one of the most variable species among invertebrates. 相似文献
13.
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
14.
The genetic variability and population genetic structure of six populations of Praecereus euchlorus and Pilosocereus machrisii were investigated. The genetic variability in single populations of Pilosocereus vilaboensis, Pilosocereus aureispinus, and Facheiroa squamosa was also examined. All of these cacti species have a patchy geographic distribution in which they are restricted to small
areas of xeric habitats in eastern Brazil. An analysis of genetic structure was used to gain insights into the historical
mechanisms responsible for the patchy distribution of P. euchlorus and P. machrisii. High genetic variability was found at the populational level in all species (P=58.9–92.8%, Ap=2.34–3.33, He=0.266–0.401), and did not support our expectations of low variability based on the small population size. Substantial inbreeding
was detected within populations (FIS=0.370–0.623). In agreement with their insular distribution patterns, P. euchlorus and P. machrisii had a high genetic differentiation (FST=0.484 and FST=0.281, respectively), with no evidence of isolation by distance. Accordingly, estimates of gene flow (Nm) calculated from FST and private alleles were below the level of Nm=1 in P. machrisii and P. euchlorus. These results favored historical fragmentation as the mechanism responsible for the patchy distribution of these two species.
The genetic distance between P. machrisii and P. vilaboensis was not compatible with their taxonomic distinction, indicating a possible local speciation event in this genus, or the occurrence
of introgression events. 相似文献
15.
A. Q. Hurtado A. T. Critchley A. Trespoey G. Bleicher-Lhonneur 《Journal of applied phycology》2008,20(5):551-555
Kappaphycus striatum var. sacol was grown in two separate studies: (1) at two stocking densities, and (2) at four different depths, each for three different
durations of culture (30, 45 and 60 days) in order to determine the growth rate of the seaweed and evaluate the carrageenan
content and its molecular weight. The results demonstrated that stocking density, duration of culture and depth significantly
(P < 0.01) affected the growth rate, carrageenan content and molecular weight of K. striatum var. sacol. Decreasing growth rate was observed at both stocking densities and at four depths as duration of culture increased. A lower
stocking density (500 g m−1line−1) showed a higher growth rate for the shortest durations, i.e. 30 days, as compared to those grown at a higher density. Likewise,
decreasing growth rate was observed as depth increased, except at 50 cm after 60 days of culture. A 45-day culture period
produced the highest molecular weight at both stocking densities (500 g m−1line−1 = 1,079.5 ± 31.8 kDa, 1,000 g m−1line−1 = 1,167 ± 270.6 kDa). ‘Sacol’ grown for 30 days at 50 cm (1,178 kDa) to 100 cm (1,200 kDa) depth showed the highest values
of molecular weight of carrageenan extracted. The results suggested that K. striatum var. sacol is best grown at a stocking density of 500 g m−1line−1, at a depth of 50–100 cm, and for a duration of 30 days in order to provide the highest growth rate, carrageenan content
and molecular weight. 相似文献
16.
Hans Jacquemyn Rein Brys Dries Adriaens Olivier Honnay Isabel Roldán-Ruiz 《Conservation Genetics》2009,10(1):161-168
Due to societal changes and altered demands for firewood, the traditional forest management of coppicing has been largely
abandoned. As a result, many forest herbs that are specifically adapted to regular opening of the canopy, have suffered significant
declines in abundance, and the remaining populations of these species often tend to be small and isolated. Reduced population
sizes and pronounced spatial isolation may cause loss of within-population genetic diversity and increased between-population
differentiation through random genetic drift and inbreeding. In this study, we investigated genetic diversity and genetic
structure of 15 populations of the food-deceptive orchid Orchis mascula using AFLP markers. Within-population genetic diversity significantly increased with increasing population size, indicating
genetic impoverishment in small populations. Genetic differentiation, on the other hand, was rather low (ΦST = 0.083) and there was no significant relationship between genetic and geographic distances, suggesting substantial gene
flow within the study area. However, strong differences in levels of within-population diversity and among-population differentiation
were found for populations located in forests that have been regularly coppiced and populations found in forests that were
neglected for more than 50 years and that were totally overgrown by shrubs. Our data thus indicate that a lack of coppicing
leads to decreased genetic diversity and increased differentiation in this orchid species, most likely as a result of genetic
drift following demographic bottlenecks. From a conservation point of view, this study combined with previous results on the
demography of O. mascula in relation to forest management illustrates the importance of coppicing in maintaining viable populations of forest herbs
in the long-term. 相似文献
17.
广西油茶人工林林下植物多样性区域变化规律 总被引:1,自引:1,他引:0
为揭示广西油茶林植物多样性的区域变化规律,以广西7个区域具代表性的油茶林为研究对象,采用典型抽样法,对油茶林林下植被进行了调查,并对比分析了群落物种组成、结构特征和物种多样性。结果表明:(1)油茶林林下植被灌草层科数、属数、种数最多的是三江县油茶林(SJ)、较少的是巴马县油茶林(BM)和来宾市油茶林(LB);除巴马县油茶林(BM)灌木层优势种为共有种,其他区域油茶林的灌木层、草本层优势种均为交叉种。(2)多样性指数方面灌木层仅Margalef指数差异显著,草本层Margalef指数、Simpson指数、Shannon-Wiener指数差异显著。(3)通过回归分析,纬度与灌木层(单一种数量)、草本层(科数、属数、种数、单一种数量)以及总数量(属数、种数)、年均温度与草本层(科数、属数、种数、单一种数量)、有效积温与草本层(属数、种数、单一种数量)、年均降雨量与灌木层单一种数量之间的趋势模拟呈二次曲线关系。(4)不同区域油茶林物种相似性不高,通过相似系数矩阵进行聚类分析三江县油茶林(SJ)、贺州市八步区油茶林(HZ)、岑溪市软枝油茶种子园油茶林(CX)、南宁市油茶林(NN)为一类,凤山县油茶林(FS)、巴马县油茶林(BM)和来宾市油茶林(LB)为一类。广西油茶人工林林下植物多样性的区域变化规律可能与不同区域的生境异质性有关。 相似文献
18.
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
19.
Nakagawa M 《Journal of plant research》2004,117(5):355-361
Genetic variation at 10 allozyme loci was analyzed in 14 populations of Polygala reinii (Polygalaceae), a perennial herb endemic to central Honshu, Japan, with a fragmented geographical distribution. The levels of genetic variation within species (P=80.0, A=3.10, HE=0.303) and within populations (P=42.1, A=1.61, HE=0.163) were considerably higher than the mean for other endemic plants or short-lived perennial herbs. Genetic differentiation among populations was also high (GST=0.404). The genetic distance phenogram tended to show a clustering of the populations reflecting the fragmentation of the species range. A principal component analysis revealed the same tendency, as well as three groupings of populations in the Tokai district, on the Kii Peninsula and in the northern Kinki district. A negative correlation was obtained between the levels of gene flow and geographical distance among the populations (r=–0.745, P<0.0001). These results indicated limited gene flow among populations in P. reinii, presumably due to the geographical isolation accompanying the fragmented distribution. On the other hand, the geographical differentiation between the Japan Sea and Pacific Ocean sides was found in P. reinii, suggesting the influence of postglacial migration on the establishment of the genetic structure of this species. 相似文献
20.
为揭示我国东部归化水仙(Narcissus tazetta var. chinensis)的群体遗传多样性,利用2个叶绿体基因mat K和trn H-psb A片段对采自沪、浙、闽的5个代表群体的49株水仙进行了评估。结果表明,双基因联合序列的总长为1443bp,共定义6个单倍型,各归化群体的遗传多样性水平为DLSYPTDNJD=ZZCMD。AMOVA分析表明,群体内变异为遗传变异的主要来源(91.98%),群体间的遗传分化较低(Fst=0.080 22)。群体物种水平上的谱系结构不显著(Nst=0.020Gst=0.031;P0.05)。Mantel检验表明水仙群体间的遗传距离与地理距离呈显著的线性相关(r=0.929,P=0.02 0.05)。中性检验和错配分布分析结果均暗示水仙群体背离了快速扩张模型的假设。单倍型分布的中介网络图结合系统发育NJ树均将所有群体划分为2大分支。因此,我国东部沿海水仙归化群体整体遗传多样性水平较低,各群体间遗传分化较弱,遗传变异主要来自群体内,物种近期未经历扩张事件,可能是基因流受海岛隔离、自身生物学特征、生境异质性与及人为干扰的综合作用影响。 相似文献