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1.
Population fragmentation is often correlated with loss of genetic diversity and reduced fitness. Obligate out-crossing (dioecy)
is expected to enhance genetic diversity, reduce genetic differentiation, and avoid inbreeding depression through frequent
gene flow. However, in highly fragmented populations dioecy has only diminishing effects upon genetic structure as pollination
limitations (e.g. flight distance of pollinators) most often restrict inter-population gene flow in insect pollinated species.
In fragmented dry grasslands in northeastern Germany, we analysed genetic structure, fitness, and habitat quality of the endangered
dioecious Silene otites (Caryophyllaceae). Using AFLP markers, a high level of differentiation among ten populations was found (F
st = 0.36), while the intra-population genetic diversities (H
E = 0.165–0.240) were similar as compared to hermaphroditic species. There was neither a correlation between geographic and
genetic distance nor between genetic diversity and population size, which indicates reduced gene flow among populations and
random genetic drift. Plant size was positively correlated with genetic diversity. Seed set and number of juveniles were positively
related to population size. Higher total coverage resulted in reduced plant fitness, and the number of juveniles was negatively
correlated to cryptogam cover. Additionally, we found a sex ratio bias towards more male plants in larger populations. Overall,
our results indicate that on a regional geographic scale dioecy does not necessarily prevent genetic erosion in the case
of habitat fragmentation, especially in the absence of long distance seed and pollen dispersal capacity. 相似文献
2.
Genetic variability and structure of natural and domesticated populations of Caribbean pine (Pinus caribaea Morelet) 总被引:1,自引:0,他引:1
Y.-Q. Zheng R. A. Ennos 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(5):765-771
Isozyme analysis of seed samples derived from natural and managed populations of the tropical pine Pinus caribaea vars ‘bahamensis’ and ‘caribaea’ was used to assess population genetic structure in its native range and to detect changes
occurring during early domestication of the species. Baseline data from natural populations of the two varieties showed that
populations sampled as seed are characterized by high gene diversity (mean He=0.26) and a low level of inbreeding ( mean Fis=0.15). A UPGMA tree of genetic relatedness among populations indicates that the two varieties represent distinct evolutionary
units. Within each variety there is significant differentiation among populations, and this is greater for the more fragmented
populations of var ‘bahamensis’ (Fst=0.08) than for var ‘caribaea’ (Fst=0.02). Seed from a seed orchard population of var ‘caribaea’ established within its natural range showed no change in genetic
diversity but did show a reduced inbreeding coefficient (Fis=0.09) compared with its progenitor populations, suggesting a decrease in selfing and/or biparental inbreeding. A bulked seed
sample from an exotic plantation of var ‘bahamensis’ in Australia displayed a large increase in the inbreeding coefficient
(Fis=0.324) compared with that found in natural populations, possibly due to elevated self-fertilization. Finally, a bulked seed
sample from an exotic plantation population of var ‘caribaea’ from China showed enhanced genetic diversity, an increase in
the inbreeding coefficient and more linkage disequilibrium than its presumed progenitor populations. It was also genetically
divergent from them. RFLP analysis of chloroplast DNA variation in the Chinese sample suggested that seeds of the related
taxa P. elliottii and P. taeda, or seeds derived from hybridization with these taxa growing in the seed production area, had been included in the seed crop
during harvesting. We conclude that monitoring of appropriate genetic markers may be an effective means of identifying potentially
deleterious genetic changes occurring during forest tree domestication.
Received: 10 August 1998 / Accepted: 8 September 1998 相似文献
3.
Changes in agricultural production methods over the last century have caused a massive reduction and fragmentation of the
area of European semi-natural grasslands. It remains unclear whether small and isolated grassland fragments can support viable
plant populations in a sustainable way. In our study area in southern Belgium, the extent of calcareous grasslands was reduced
from c. 650 ha in 1775 to less than 30 ha in 2004. We used AFLP markers to quantify the effects of present and historical
grassland fragmentation on the genetic structure of 27 populations of the rare perennial plant species Globularia bisnagarica. Given the mixed breeding system of the species and the relatively small area of the studied system, the populations were
characterized by high genetic differentiation (F
st range: 0.42–0.48; Φst=0.53). A Mantel test revealed significant isolation by distance of the populations. Average within population genetic diversity,
measured as expected heterozygosity or gene diversity, was low (H
j
=0.081) and was negatively related to population isolation. This suggests more gene flow into less isolated populations. Population
size and local habitat characteristics did not significantly influence population genetic diversity. Both, high selfing rates
in G. bisnagarica and a population genetic response to habitat fragmentation may explain our findings. Finally, a clear geographical clustering
was observed, with cluster membership partially explainable by historical grassland connectivity. If populations indeed started
to differentiate after fragmentation, this process was not (yet) strong enough to erase the genetic similarity between fragments
that historically belonged to the same large grassland fragment. 相似文献
4.
N. V. Mironenko O. A. Baranova N. M. Kovalenko L. A. Mikhailova L. P. Rosseva 《Russian Journal of Genetics》2016,52(8):771-779
The population genetic structure of plant pathogenic fungus Pyrenophora tritici-repentis was examined using microsatellite (SSR) markers. According to the geographical origin of the pathogen populations, they were designated as North Caucasian (S, 33 isolates), northwest (Nw, 39), and Omsk (Om, 43). The populations were analyzed at the nine most polymorphic SSR loci, at which 75 alleles were identified. To characterize the genetic variation within and between populations, the AMOVA algorithm as implemented in the Arlequin v. 3.5 software program was used. The number of alleles per locus ranged from 5 to 12 and their sizes varied within the range from 180 to 400 bp. The mean gene diversity at SSR loci was high for all populations (H = 0.58–0.75). The populations were considerably different in the frequencies of individual alleles of the SSR loci. Most isolates in the populations were represented by unique haplotypes. The within-population variation of the isolates at molecular markers was 86.4%; among the populations, 13.6%. Substantial interpopulation differences were found between the Om and S (Fst = 0.16) and between the Om and Nw (Fst = 0.20) populations, whereas between the S and Nw populations, these differences were small (Fst = 0.05). Thus, it was demonstrated that the population of P. tritici-repentis from Omsk oblast had the independent status of the geographical population; northwest and North Caucasian populations differed in the allelic diversity of SSR loci, and despite the low Fst value (0.05), they also belonged to independent geographical populations. 相似文献
5.
Andrew R. Whiteley Kim Hastings John K. Wenburg Chris A. Frissell Jamie C. Martin Fred W. Allendorf 《Conservation Genetics》2010,11(5):1929-1943
Following glacial recession in southeast Alaska, waterfalls created by isostatic rebound have isolated numerous replicate
populations of coastal cutthroat trout (Oncorhynchus clarkii clarkii) in short coastal streams. These replicate isolated populations offer an unusual opportunity to examine factors associated
with the maintenance of genetic diversity. We used eight microsatellites to examine genetic variation within and differentiation
among 12 population pairs sampled from above and below these natural migration barriers. Geological evidence indicated that
the above-barrier populations have been isolated for 8,000–12,500 years. Genetic differentiation among below-barrier populations
(F
ST = 0.10, 95% C.I. 0.08–0.12) was similar to a previous study of more southern populations of this species. Above-barrier populations
were highly differentiated from adjacent below-barrier populations (mean pairwise F
ST = 0.28; SD 0.18) and multiple lines of evidence were consistent with asymmetric downstream gene flow that varied among streams.
Each above-barrier population had reduced within-population genetic variation when compared to the adjacent below-barrier
population. Within-population genetic diversity was significantly correlated with the amount of available habitat in above-barrier
sites. Increased genetic differentiation of above-barrier populations with lower genetic diversity suggests that genetic drift
has been the primary cause of genetic divergence. Long-term estimates of N
e based on loss of heterozygosity over the time since isolation were large (3,170; range 1,077–7,606) and established an upper
limit for N
e if drift were the only evolutionary process responsible for loss of genetic diversity. However, it is likely that a combination
of mutation, selection, and gene flow have also contributed to the genetic diversity of above-barrier populations. Contemporary
above-barrier N
e estimates were much smaller than long-term N
e estimates, not correlated with within-population genetic diversity, and not consistent with the amount of genetic variation
retained, given the approximate 10,000-year period of isolation. The populations isolated by waterfalls in this study that
occur in larger stream networks have retained substantial genetic variation, which suggests that the amount of habitat in
headwater streams is an important consideration for maintaining the evolutionary potential of isolated populations. 相似文献
6.
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
7.
R.J. Prokopy D.R. Papaj J. Hendrichs T.T.Y. Wong 《Entomologia Experimentalis et Applicata》1992,64(3):247-257
We usedF-statistics to quantify the population structure of two sympatric species of leaf beetles,Oreina cacaliae andO. speciosissima (Chrysomelinae, Coleoptera), which share the same microhabitat since they feed on the same herbaceous host plants. We measured
genetic differentiation at six allozyme loci 1) among populations separated by relatively small distances (40 to 250 kilometers),
2) within each population, and 3) between sexes within populations. For both species, the populations studied are not panmictic.
For each population, heterozygosities are relatively high, but the observed heterozygosities are generally lower than the
expected values. Overall, within-population differentiation is high and similar for both species (F
is=0.326 forO. cacaliae and 0.332 forO. speciosissima). Additionally, populations of both species are highly differentiated (F
st=0.234 versus 0.051 forO. speciosissima). ForO. cacaliae,F
is andF
st are greater among females than among males, while forO. speciosissima,F
st is sustantially greater among the males whileF
is is slightly greater among males. Differences in gene frequency among the sexes were statistically tested using a modifiedF
st with sex as the defining category, and the sexes differed significantly with the exception of one population inO. cacaliae. Possible explanations for this difference are discussed. 相似文献
8.
为探索褐家鼠Rattus norvegicus地理种群的遗传结构及其年度变化特点,本研究以广东省湛江市的褐家鼠指名亚种和黑龙江省哈尔滨市的褐家鼠东北亚种为主要研究对象,结合我国及世界其他褐家鼠种群的D-loop序列分析这2个褐家鼠地理种群间D-loop序列的遗传分化情况及系统进化关系,重点分析2008—2015年褐家鼠湛江种群和哈尔滨种群D-loop单倍型的年度频率变化特点。结果表明,褐家鼠湛江种群和哈尔滨种群共有32种不同的单倍型,其中有11种单倍型是2个种群共有的,有4种单倍型仅在湛江种群中出现,有17种单倍型仅在哈尔滨种群中出现。褐家鼠湛江种群D-loop区的核苷酸多态性为0.005,有27个变异位点,单倍型多态性为0.695,褐家鼠哈尔滨种群D-loop区的核苷酸多态性比湛江种群略高,为0.008,有35个变异位点,单倍型多态性为 0.793。褐家鼠湛江种群和哈尔滨种群没有经历过暴发性的扩增。褐家鼠湛江、哈尔滨和湖北3个地理种群的D-loop序列之间发生了明显的遗传分化,其中湛江种群和哈尔滨种群之间的分化程度最高,遗传分化系数Fst为0.245。褐家鼠湛江种群和哈尔滨种群的单倍型数目和主单倍型频率都发生明显波动,推测主要原因可能是由于灭鼠剂的大量使用或其他灭鼠活动导致种群出现瓶颈或更替的现象。 相似文献
9.
Baoying Guo Congxin Xie Shunping He Khalid Abbas Huanling Wang Dongmei Xiong Huijuan Zhang Xin Tong 《Environmental Biology of Fishes》2009,85(3):201-206
We determined the genetic diversity of geographic populations from three spawning grounds (Nyang River, Lhasa River, Shetongmon
Reach of Yarlung Zangbo River) of Glyptosternum maculatum with amplified fragment length polymorphism (AFLP) markers. Five primer combinations detected 332 products, 51 of them (15.4%)
were polymorphic in at least one population. The Shetongmon population was found to be the richest in genetic diversity as
was indicated by the percentage of polymorphic loci and heterozygosity, followed by the Nyang population and the Lhasa population.
The pair-wise genetic distance between populations were all very close, ranging from 0.0015 to 0.0042 with an average of 0.0024.
The genetic distance was not proportional to the geographic distance. The analysis of molecular variance demonstrated that
all variation occurred within populations. The average estimated fixation index (F
st) of three populations across all polymorphic loci was −0.0184, indicating the absence of genetic differences among the three
sampled populations. The differentiation among populations was not significant, and population structure was weak. Our observations
will help identify the genetic relationship among populations as the first approach to understand the genetic diversity of
Glyptosternum maculatum. 相似文献
10.
To understand the impact of various factors on the maintenance of genetic variation in natural populations, we need to focus
on situations where at least some of these factors are removed or controlled. In this study, we used highly variable, presumably
neutral, microsatellite and mtDNA markers to assess the nature of genetic variation in 14 island and two mainland populations
of the Australian bush rat, where there is no migration between islands. Thus we are controlling for selection and gene flow.
Both marker sets revealed low levels of diversity within the small island populations and extreme differentiation between
populations. For six microsatellite loci, all of the small island populations had less genetic variation than the mainland
populations; reduction in allelic diversity was more pronounced than loss of heterozygosity. Kangaroo Island, the large island
population, had similar levels of diversity to the mainland populations. A 442 base pair (bp) section of the mtDNA control
region was screened for variation by outgroup heteroduplex analysis/temperature gradient gel electrophoresis (OHA/TGGE). Only
three of the 13 small island populations showed haplotypic diversity: Gambier (2), Waldegrave (2), and Eyere (3). The level
of haplotypic diversity in the small island populations was similar to that on the mainland, most likely reflecting a recent
population bottleneck on the mainland. In contrast, Kangaroo Island had 9 mtDNA haplotypes. The dominant factor influencing
genetic diversity on the islands was island size. No correlation was detected between genetic diversity and the time since
isolation or distance form the mainland. The combination of genetic drift within and complete isolation among the small island
populations has resulted in rapid and extreme population divergence. Population pair-wise comparisons of allele frequency
distributions showed significant differences for all populations for all loci (F
st = 0.11–0.84, R
st = 0.07–0.99). For the mtDNA control region, 92.6% of variation was apportioned between populations; only the Pearson islands
shared a haplotype. Mantel tests of pair-wise genetic distance with pair-wise geographic distance showed no significant geographical
clustering of haplotypes. However, population substructuring was detected within populations where sampling was conducted
over a broader geographical range, as indicated by departures from Hardy-Weinberg equilibrium. Thus substructuring in the
ancestral population cannot be ruled out. The dominant evolutionary forces on the islands, after the initial founder event,
are stochastic population processes such as genetic drift and mutation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
In this study we evaluated the influence of recent landscape fragmentation on the dynamics of remnant fragments from the Brazilian
Atlantic Forest. This biome is one of the richest in the world and has been extensively deforested and fragmented. We sampled
five populations of the threatened Dalbergia nigra, a tree endemic to the Brazilian Atlantic Forest, two located in a large reserve of continuous forest and three in fragments
of different sizes and levels of disturbance. In order to assess historical changes, considering the longevity of the analyzed
species, 119 adults and 116 saplings were genotyped for six microsatellite loci. Lower levels of genetic diversity were found
in the most impacted fragments when compared to the most preserved population located inside the reserve, and there was significant
genetic structure among the populations studied (pairwise F
ST = 0.031–0.152; pairwise D
EST = 0.039–0.301). However, genetic structure among saplings (F
ST = 0.056; D
EST = 0.231) was significantly lower than among adults (F
ST = 0.088; D
EST = 0.275). Estimates of contemporary gene flow based on assignment tests corroborated this result, suggesting that fragmentation
led to an increase in gene flow. This connectivity among remnant fragments could mitigate the loss of genetic diversity through
a metapopulation dynamic, but the high rate of habitat loss and the unknown long-term genetic effects add uncertainty. These
results, taken together with the presence of private alleles in disturbed populations, highlight the importance of preserving
the extant fragments. 相似文献
12.
Khusainova R. I. Akhmetova V. L. Kutuyev I. A. Salimova A. Z. Korshunova T. Yu. Lebedev Yu. B. Khusnutdinova E. K. 《Russian Journal of Genetics》2004,40(4):443-449
NineAlu loci (Ya5NBC5, Ya5NBC27, Ya5NBC148, Ya5NBC182, YA5NBC361, ACE, ApoA1, PV92, TPA25) were analyzed in six ethnic populations (Trans-Ural Bashkirs, Tatars-Mishars, Mordovians-Moksha, Mountain Maris, Udmurts, and Komi-Permyaks) of the Volga–Ural region and in three Central Asian populations (Uzbeks, Kazakhs, and Uigurs). All Alu insertions analyzed appeared to be polymorphic in all populations examined. The frequency of insertion varied from 0.110 in Mountain Maris at the Ya5NBC5 locus to 0.914 in Tatars at the ApoA1 locus. The data on the allele frequency distribution at nine loci point to the existence of substantial genetic diversity in the populations examined. The value of the observed heterozygosity averaged over nine Alu insertions varied from 0.326 in Mountain Maris to 0.445 in Kazakhs and Uigurs. The level of the interpopulation genetic differences for the Volga–Ural population (F
st = 0.061) was higher than for the populations of Central Asia (F
st = 0.024), Europe (F
st = 0.02), and Southeastern Asia (F
st = 0.018). The populations examined were highly differentiated both in respect of linguistic characteristics and the geographical position. The data obtained confirmed the effectiveness of the marker system used for the assessment of genetic differentiation and the relationships between the ethnic groups. 相似文献
13.
Samantha M. Wisely Rachel M. Santymire Travis M. Livieri Sara A. Mueting JoGayle Howard 《Conservation Genetics》2008,9(2):389-399
Population augmentation with translocated individuals has been shown to alleviate the effects of bottlenecks and drift. The
first step to determine whether restoration for genetic considerations is warranted is to genetically monitor reintroduced
populations and compare results to those from the source. To assess the need for genetic restoration, we evaluated genetic
diversity and structure of reintroduced (n = 3) and captive populations of the endangered black-footed ferret (Mustela nigripes). We measured genotypic changes among populations using seven microsatellite markers and compared phenotypic changes with
eight morphometric characters. Results indicated that for the population which rapidly grew post-reintroduction, genetic diversity
was equivalent to the captive, source population. When growth languished, only the population that was augmented yearly maintained
diversity. Without augmentation, allelic diversity declined precipitously and phenotypic changes were apparent. Ferrets from
the genetically depaupertate population had smaller limbs and smaller overall body size than ferrets from the two populations
with greater diversity. Population divergence (F
ST = 0.10 ± 0.01) was surprisingly high given the common source of populations. Thus, it appears that 5–10 years of isolation
resulted in both genotypic divergence and phenotypic changes to populations. We recommend translocation of 30–40 captive individuals
per annum to reintroduction sites which have not become established quickly. This approach will maximize the retention of
genetic diversity, yet maintain the beneficial effects of local adaptation without being swamped by immigration. 相似文献
14.
B. Román D. Rubiales A. M. Torres J. I. Cubero Z. Satovic 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(6-7):1108-1114
The pattern of genetic variation within and among natural populations of broomrape (Orobanche crenata Forsk.) from southern Spain was analysed by RAPD markers. Hierarchical analysis of phenotypic diversity using AMOVA was performed
to analyse the partitioning of the variation among populations and among individuals. Although most of the genetic diversity
was attributable to differences among individuals within a population (94.29%), significant φst values among populations suggested the existence of phenotypic differentiation. Moreover, corresponding HOMOVA analysis revealed
that molecular variances were significantly heterogeneous among populations although no clear grouping pattern could be established.
These results are to be expected considering the predominant outcrossing behaviour of O. crenata.
Received: 10 January 2001 / Accepted: 12 February 2001 相似文献
15.
Warangkana Prakoon Suriyan Tunkijjanukij Thuy T. T. Nguyen Uthairat Na-Nakorn 《Marine biotechnology (New York, N.Y.)》2010,12(5):506-515
The culture of green mussel (Perna viridis) in the Gulf of Thailand depends on natural spat which are believed to come from spawning grounds adjacent to major river
mouths. In the present paper, genetic diversity of spatial and temporal populations of green mussel in the Gulf of Thailand
was investigated using five microsatellite loci. The results showed moderate genetic variation of all 11 populations (averaged
number of alleles per locus, A = 10.4–12.2; effective number of alleles per locus, A
e = 5.36–6.59; mean allelic richness, A
r = 10.23–12.06; observed heterozygosity, H
o = 0.52–0.63, and expected heterozygosity, H
e = 0.66–0.73) without significant differences among populations. No sign of bottleneck or genetic disequilibrium was observed.
Genetic differentiation among spatial populations was low (F
ST = 0.0046, CI0.95 = 0.0020–0.0083 for the samples collected in January, 2007, and F
ST = 0.0088, CI0.95 = 0.0010–0.0162 for the samples collected in July, 2007) while temporal variation was significant as revealed by the analysis
of molecular variance. Multidimensional scaling separated temporal population groups with minor exception. The assignment
test revealed that most of the recruits were from other populations. 相似文献
16.
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
17.
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
18.
Brook L. Fluker Bernard R. Kuhajda Nicholas J. Lang Phillip M. Harris 《Conservation Genetics》2010,11(6):2267-2279
Species endemic to coldwater springs in the southeastern United States are some of the rarest and most imperiled in this region,
yet little is known about their genetic composition and conservation needs. Here, microsatellite based levels of genetic diversity
and estimates of effective population size (N
e) were compared between a narrow spring endemic fish, Etheostoma nuchale, and its widespread stream-dwelling relative, E. swaini. We applied several analytical methods to assess how demographic history is reflected in contemporary levels of genetic diversity
for populations of E. nuchale. Phylogenetic analyses based on mitochondrial and nuclear DNA sequence data revealed a complex history among E. nuchale and E. swaini, but suggested ancient divergence and historic periods of isolation since colonization of spring habitats by E. nuchale. Populations of E. nuchale have levels of genetic diversity approximately one-half that of E. swaini, a result most likely due to founder effects and recent bottlenecks. Statistically significant F
st values (0.05−0.27) and STRUCTURE analyses implied high levels of differentiation among E. nuchale populations. Estimates of current N
e suggest relatively consistent levels across populations of E. nuchale, but one population may suffer from habitat degradation. We suggest that high levels of population structure and low levels
of genetic diversity may be typical in other spring endemics inhabiting this region. Therefore, effective management planning
for these unique species will require a detailed knowledge of the genetic and demographic history of each population. 相似文献
19.
Understanding the population genetic structure is a prerequisite for conservation of a species. The degree of genetic variability
characteristic of the mitochondrial DNA control region has been widely exploited in studies of population genetic structure
and can be useful in identifying meaningful population subdivisions. To estimate the genetic profile of the Yangtze finless
porpoise (Neophocaena phocaenoides asiaeorientalis), an endangered freshwater population endemic to China, the complete mtDNA control region was examined in 39 individuals
belonging to seven different stocks inhabiting the middle and lower reaches of the Yangtze River. Very low genetic diversity
was found (nucleotide diversity 0.0011± 0.0002 and haplotypic diversity 0.65± 0.05). The mtDNA genetic pattern of the Yangtze
population appears to indicate a founder event in its evolutionary history and to support the marine origin for this population.
Analyses by Fst and Φst yielded statistically significant population genetic structure (Fst = 0.44, P < 0.05; Φst = 0.36, P < 0.05). These results may have significant implications for the management and conservation of the Yangtze finless porpoise
in the future. 相似文献