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1.
Castanea squinii Dode,an endemic tree widely distributed in China,plays an important role both in chestnut breeding and forest ecosystem function.The spatial genetic structure within and among populations is an important part of the evolutionary and ecological genetic dynamics of natural populations,and can provide insights into effective conservation of genetic resources.In the present study,the spatial genetic structure of a panmictic natural population of C.sequinii in the Dabie Mountain region was investigated using microsatellite markers.Nine prescreened microsatellite loci generated 29-33 alleles each,and were used for spatial autocorrelation analysis.Based on Moran's I coefficient,a panmictic population of C.sequinii in the Dabie Mountain region was found to be lacking a spatial genetic structure.These results suggest that a high pollen-mediated gene flow among subpopulations counteract genetic drift and/or genetic differentiation and plays an important role in maintaining a random and panmictic population structure in C.sequinii populations.Further,a spatial genetic structure was detected in each subpopulation's scale (0.228 km),with all three subpopulations showing significant fine-scale structure.The genetic variation was found to be nonrandomly distributed within 61 m in each subpopulation (Moran's I positive values).Although Moran's I values varied among the different subpopulations,Moran's I in all the three subpopulations reached the expected values with an increase in distances,suggesting a generally patchy distribution in the subpopulations.The fine-scale structure seems to reflect restricted seed dispersal and microenvironment selection in C.sequinii.These results have important implications for understanding the evolutionary history and ecological process of the natural population of C.sequinii and provide baseline data for formulating a conservation strategy of Castanea species. 相似文献
2.
采用微卫星标记对茅栗(Castanea sequinii)随机大居群以及其中各亚居群的遗传结构进行了空间自相关分析,以探讨植物自然居群内遗传变异的分布特征及其形成机制。通过9对微卫星引物所产生的119个多态位点,测定了大别山区域内茅栗居群以及各亚居群的空间自相关系数Moran's I值。结果表明:大别山分布的野生茅栗为一个缺乏空间结构的随机大居群,茅栗亚居群之间频繁的花粉流削弱了地理隔离导致的遗传漂变或分化作用在维系居群随机遗传结构中具有的重要作用。但是,在接近亚居群大小的地域范围内(0.228 km)具有一定的空间结构,即小地域尺度中的亚居群存在着空间遗传结构。取样的3个亚居群在小格局范围内都存在一定的空间结构,遗传变异基本上呈非随机分布,在短距离内(61 m)3个亚居群一致表现出不同程度的显著正相关,而随着距离的增加,Moran's I值虽然在不同亚居群间存在一定差异变化,但是总体而言趋向预期值,即不存在空间结构,说明其遗传变异在亚居群内只是在短距离内形成一定的空间结构。研究认为有限的种子散播以及微生境选择等因素可能是产生这种小格局的遗传结构的主要原因。上述研究结果有助于进一步了解植物随机大居群的进化历史和生态过程,同时也为栗属植物中国特有种的保育策略提供了科学依据。 相似文献
3.
Bingqing Hao Wang Li Mu Linchun Yao Li Zhang Rui Tang Mingxia Bao Weikai 《Biochemical genetics》2006,44(1-2):29-43
ISSR markers were used to analyze the genetic diversity and genetic structure of eight natural populations of Cupressus chengiana in China. ISSR analysis using 10 primers was carried out on 92 different samples. At the species level, 136 polymorphic loci were detected. The percentage of polymorphic bands (PPB) was 99%. Genetic diversity (H e) was 0.3120, effective number of alleles (A e) was 1.5236, and Shannon’s information index (I) was 0.4740. At the population level, PPB = 48%, A e=1.2774, H e=0.1631, and I=0.2452. Genetic differentiation (G st) detected by Nei’s genetic diversity analysis suggested 48% occurred among populations. The partitioning of molecular variance by AMOVA analysis indicated significant genetic differentiation within populations (54%) and among populations (46%; P < 0.0003). The average number of individuals exchanged between populations per generation (N
m
) was 0.5436. Samples from the same population clustered in the same population-specific cluster, and two groups of Sichuan and Gansu populations were distinguishable. A significantly positive correlation between genetic and geographic distance was detected (r=0.6701). Human impacts were considered one of the main factors to cause the rarity of C. chengiana, and conservation strategies are suggested based on the genetic characters and field investigation, e.g., protection of wild populations, reestablishment of germplasm bank, and reintroduction of more genetic diversity. 相似文献
4.
Psathyrostachys huashanica Keng is a perennial grass and belongs to genus Psathyrostachys under Triticeae. sathyrostachys is found in the center of Middle Asia and the Caucasus Mountain, while P. huashanica, a species endemic to China, is only located in Mt. Hua in the Shaanxi province, China. At present, the population of this
species is decreasing, and reaching the edge of extinction. Due to the limitation in distribution and the importance as breeding
material for germplasm storage, it has been considered as first class among the national protected rare plants. For this reason,
the present study is significant in probing plant flora, origin and evolution of Triticeae, and crop breeding. Randomly amplified
polymorphic DNA (RAPD) markers were used to analyze the genetic structure and differentiation of P. huashanica populations sampled in three valleys (Huangpu, Xian, and Huashan Valleys) in Mt. Hua. One hundred and twenty-two RAPD fragments
were obtained in all 266 individuals with 20 primers with a mean of 6.1 (2–10) fragments per primer. The percentage of polymorphic
loci (PPB) was 60.66% in Huangpu Valley, 90.98% in Xian Valley, 95.08% in Huashan Valley, and the total PPB was 95.08%, which indicated a highly genetic variability of P. huashanica. The Shannon’s Information index and G
ST were 0.3306 and 0.3263, respectively, indicating that there were more genetic variations within the subpopulations than those
among the subpopulations. The gene flow among the subpopulations of P. huashanica (Nm = 1.0322) was much less than that of the common anemophytes (Nm = 5.24). Mean genetic distance is 0.1 571 (range: 0.0022–0.2901). The highest value of genetic distance was found between
the subpopulation (hp1) of Huangpu Valley and the highest altitude subpopulation (h8) of Huashan Valley. Correlation analysis
detected significant correlation between genetic distance and vertical distance of altitude. Clustering analysis and principal
coordinate analysis revealed the genetic differentiation among the populations of P. huashanica. Differentiation mainly occurred between the higher altitude subpopulations and the lower altitude subpopulations, suggesting
that altitude might be the major factor that restricted the gene flow between different altitude subpopulations and resulted
in differentiation of subpopulations.
Translated from Acta Ecologica Sinica, 2005, 25(4): 719–726 [译自: 生态学报] 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.
A total of 892 individuals sampled from a wild soybean population in a natural reserve near the Yellow River estuary located
in Kenli of Shandong Province (China) were investigated. Seventeen SSR (simple sequence repeat) primer pairs from cultivated
soybeans were used to estimate the genetic diversity of the population and its variation pattern versus changes of the sample
size (sub-samples), in addition to investigating the fine-scale spatial genetic structure within the population. The results
showed relatively high genetic diversity of the population with the mean value of allele number (A) being 2.88, expected heterozygosity (He) 0.431, Shannon diversity index (I) 0.699, and percentage of polymorphic loci (P) 100%. Sub-samples of different sizes (ten groups) were randomly drawn from the population and their genetic diversity was
calculated by computer simulation. The regression model of the four diversity indexes with the change of sample sizes was
computed. As a result, 27–52 individuals can reach 95% of total genetic variability of the population. Spatial autocorrelation
analysis revealed that the genetic patch size of this wild soybean population is about 18 m. The study provided a scientific
basis for the sampling strategy of wild soybean populations.
__________
Translated from Journal of Fudan University (Natural Science), 2006, 45(3): 322–327 [译自: 复旦学报 (自然科学版)] 相似文献
7.
Caitlin J Curry Brian W Davis Laura D Bertola Paula A White William J Murphy James N Derr 《Molecular biology and evolution》2021,38(1):48
Direct comparisons between historical and contemporary populations allow for detecting changes in genetic diversity through time and assessment of the impact of habitat fragmentation. Here, we determined the genetic architecture of both historical and modern lions to document changes in genetic diversity over the last century. We surveyed microsatellite and mitochondrial genome variation from 143 high-quality museum specimens of known provenance, allowing us to directly compare this information with data from several recently published nuclear and mitochondrial studies. Our results provide evidence for male-mediated gene flow and recent isolation of local subpopulations, likely due to habitat fragmentation. Nuclear markers showed a significant decrease in genetic diversity from the historical (HE = 0.833) to the modern (HE = 0.796) populations, whereas mitochondrial genetic diversity was maintained (Hd = 0.98 for both). Although the historical population appears to have been panmictic based on nDNA data, hierarchical structure analysis identified four tiers of genetic structure in modern populations and was able to detect most sampling locations. Mitogenome analyses identified four clusters: Southern, Mixed, Eastern, and Western and were consistent between modern and historically sampled haplotypes. Within the last century, habitat fragmentation caused lion subpopulations to become more geographically isolated as human expansion changed the African landscape. This resulted in an increase in fine-scale nuclear genetic structure and loss of genetic diversity as lion subpopulations became more differentiated, whereas mitochondrial structure and diversity were maintained over time. 相似文献
8.
Arctophila fulva var. pendulina is a rare endemic perennial grass confined to seashore and riverbank meadows around the Bothnian Bay, the northernmost part
of the Baltic Sea. The number of A. fulva populations has decreased during the last few decades in Finland and Sweden, and nowadays there are only eight populations
left in the drainage area of the Bothnian Bay. We investigated the distribution of genetic variation within and between six
subpopulations in the largest remaining population at Liminka Bay, Finland, using amplified fragment length polymorphism (AFLP)
markers. Relatively high amounts of variation were found in the subpopulations, the mean Nei’s expected heterozygosity being
typical (0.267) for an outcrossing species. Despite the fact that no seedlings or viable seeds of A. fulva have been found in the previous field studies, the observed high genotypic diversity suggested that sexual reproduction has
played an important role at some time during the history of the studied A. fulva population. Analysis of population structure revealed a low level of genotypic differentiation (ΦST=0.046) between subpopulations, and also significant sub-structuring within subpopulations. Isolation-by-distance between
subpopulations was present on scales larger than 1 km. The overall pattern of genetic variation within and between subpopulations
suggest that the population has characters of both stepping-stone and metapopulation models. Because our results suggested
that subpopulations are more or less ephemeral, the conservation and management effort in this species should be targeted
to conservation of the required habitat of the species instead of extant subpopulations. 相似文献
9.
Deborah A. Randall John P. Pollinger Kifle Argaw David W. Macdonald Robert K. Wayne 《Conservation Genetics》2010,11(1):89-101
We used demographic, spatial, and microsatellite data to assess fine-scale genetic structure in Ethiopian wolves found in
the Bale Mountains and evaluated the impact of historical versus recent demographic processes on genetic variation. We applied
several analytical methods, assuming equilibrium and nonequilibrium conditions, to assess demography and genetic structure.
Genetic variation (H
E = 0.584–0.607, allelic richness = 4.2–4.3) was higher than previously reported for this species and genetic structure was
influenced by geography and social structure. Statistically significant F
ST values (0.06–0.08) implied differentiation among subpopulations. STRUCTURE analyses showed that neighbouring packs often
have shared co-ancestry and spatial autocorrelation showed higher genetic similarity between individuals within packs and
between individuals in neighbouring packs compared to random pairs of individuals. Recent effective population sizes were
lower than 2n (where n is the number of packs) and lower than the number of breeding individuals with N
e
/N ratios near 0.20. All subpopulations have experienced bottlenecks, one occurring due to a rabies outbreak in 2003. Nevertheless,
differentiation among these subpopulations is consistent with long-term migration rates and fragmentation at the end of the
Pleistocene. Enhanced drift due to population bottlenecks may be countered by higher migration into disease-affected subpopulations.
Contemporary factors such as social structure and population bottlenecks are clearly influencing the level and distribution
of genetic variation in this population, which has implications for its conservation. 相似文献
10.
Since 1985, China has established three breeding herds of Père David’s deer: the Beijing Père David’s Deer Park (39°07′N,
116°03′E), the Dafeng Père David’s Deer Nature Reserve (33°05′N, 120°49′E) and Shishou (Tianezhou) Père David’s Deer Nature
Reserve (29°49′N, 112°33′E), through reintroductions of about 30–40 founders. Since establishment, all three populations have
grown steadily. However, genetic backgrounds in those populations are still unknown. We studied the genetic diversity in Père
David’s deer and genetic consequences of population relocations in China. We revealed that genetic diversity was extremely
low in Père David’s deer populations in China. Only a single mtDNA D-loop haplotype was found in the deer, furthermore, only
five polymorphic microsatellite loci were screened out from 84 pairs of species-transferred primers. Genetic makeup in the
three Père David’s deer populations were significantly different (P < 0.01). H
E and allelic richness in the Tianezhou population were the highest (0.54, 2.60, n = 31), Beijing population (0.52, 2.4, n = 125) showed the second highest measures, while the Dafeng population (0.46, 2.39, n = 39) measured lowest. Our results suggest that effective management of a species of low genetic diversity like the Père
David’s deer should consider the genetic background of each founder to make sure genetic variations are preserved in both
source population and relocated population. Now, the Tianezhou population is the most appropriate source population in China
when establishing new Père David deer populations in the wild.
相似文献
Zhigang JiangEmail: |
11.
Jeffrey B. Olsen Klaus Wuttig Douglas Fleming Eric J. Kretschmer John K. Wenburg 《Conservation Genetics》2006,7(4):613-619
We examine sympatric anadromous (steelhead) and nonanadromous (resident) rainbow trout (Oncorhynchus mykiss) from neighboring locations to test three hypotheses: (1) the sympatric life history types are not genetically different; (2) fine-scale dispersal is the same for both sexes, and (3) fine-scale dispersal is the same for steelhead and resident individuals. Data from 13 microsatellite loci reveal no genetic difference between sympatric steelhead and resident O. mykiss but moderate population structure (F
ST=0.019–0.028) between adjacent samples, regardless of life history type. Our results provide further evidence of partial anadromy and suggest that geographic proximity and genetic history, more than migratory type, should be considered when identifying populations for use in restoration of local genetic diversity. We find evidence of resident-form dispersal bias on a fine spatial scale, however, we find no evidence that fine-scale dispersal varies by gender. Conservation strategies should aim to maintain resident and anadromous forms when they occur in sympatry, as they may be important in facilitating gene flow on small and large spatial scales, respectively. 相似文献
12.
Patella vulgata is a boreal cold temperate species and is the dominant limpet in northern Europe. Few works have focussed on the population
genetics of this species. Therefore, the aim of this work was to assess the degree of genetic and morphological differentiation
of P. vulgata on a macroscale by using 20 allozyme loci and 6 morphological variables. Samples were taken from the following locations:
Dingle Peninsula (Southwest Ireland), Port Erin (Southwest Isle of Man), St. Bees Head (north Cumbria, England), St. Agnes
Head (north Cornwall, England), Cellar Beach (south Devon, England), Whitley Bay (north Newcastle-Upon-Tyne, England), Sines
(Portugal), and Pointe de Chanchardon, La Rochelle (Bay of Biscay, France). Morphological variables were analysed by the multivariate
Canonical discriminant analysis. Genetic variation was assessed by diversity measures such as polymorphism and heterozygosity;
genetic subdivision of P. vulgata population was determined by the estimator θ of F
ST, and the genetic similarity between populations was measured by Nei’s genetic identity. No significant morphological differentiation
was observed among samples. Moderate genetic population subdivision was observed (θ = 0.137±0.074) despite great geographic
distances. The minimum genetic identity observed was between Ireland and France (I = 0.942) and maximum was observed between Portugal and north-east England (I=0.998). Two main groups were shown by UPGMA cluster analysis (I = 0.965). One formed by Irish, Manx, north Cumbria, and curiously, south Devon samples, while the second includes Portuguese,
French, north-Newcastle-upon-thyne, and north Cornwall samples. No association (g = 0.956; p>0.050) was found between pair-wise genetic divergence and geographic distance separating subpopulations, mainly due to an
unexpected pattern of genetic heterogeneity found in Southwest England. 相似文献
13.
Relationships between microhabitat variables; understory light conditions in summer and winter, altitude, slope inclination
and topographic categories (valley, ridge, and slope) and the distribution of Aucuba japonica Thunb. (Cornaceae), a common understory shrub species in Japan were examined using non-contagious 66, 20 × 20 m2 quadrats. The Morishita’s I
δ suggested that A. japonica distributions were strongly heterogeneous among the quadrats. Therefore positive spatial autocorrelation of A. japonica at a within-quadrat level (≤20 m) was obvious. Moran’s I statistics showed a significant positive spatial autocorrelation in A. japonica abundance within the distance shorter than 60 m. But the partial Mantel tests suggested that the mass effect from neighboring
quadrats would little explain A. japonica abundance in a quadrat. The partial Mantel tests also clearly showed that A. japonica distributions were strongly structured by topography and understory light conditions. Using Monte Carlo randomization tests,
we found that A. japonica was aggregately distributed in quadrats in valley which were covered by deciduous canopies. Better understory light conditions
in winter together with valley edaphic conditions may increase the abundance of A. japonica there. It is concluded that habitat niche specialization is important in structuring distribution of A. japonica in this forest community. 相似文献
14.
Populations of the endangered giant kangaroo rat, Dipodomys ingens (Heteromyidae), have suffered increasing fragmentation and isolation over the recent past, and the distribution of this unique
rodent has become restricted to 3% of its historical range. Such changes in population structure can significantly affect
effective population size and dispersal, and ultimately increase the risk of extinction for endangered species. To assess
the fine-scale population structure, gene flow, and genetic diversity of remnant populations of Dipodomys ingens, we examined variation at six microsatellite DNA loci in 95 animals from six populations. Genetic subdivision was significant
for both the northern and southern part of the kangaroo rat’s range although there was considerable gene flow among southern
populations. While regional gene diversity was relatively high for this endangered species, hierarchical F-statistics of northern
populations in Fresno and San Benito counties suggested non-random mating and genetic drift within subpopulations. We conclude
that effective dispersal, and therefore genetic distances between populations, is better predicted by ecological conditions
and topography of the environment than linear geographic distance between populations. Our results are consistent with and
complimentary to previous findings based on mtDNA variation of giant kangaroo rats. We suggest that management plans for this
endangered rodent focus on protection of suitable habitat, maintenance of connectivity, and enhancement of effective dispersal
between populations either through suitable dispersal corridors or translocations. 相似文献
15.
Arunrat Chaveerach Alongkod Tanomtong Runglawan Sudmoon Tawatchai Tanee 《Biologia》2006,61(3):295-298
The distribution of Nepenthes mirabilis ranges from Northeast (NE) to South (S) Thailand. Eleven individuals from NE, S and Suen Jatujak market in Bangkok, Central
(C) Thailand, were collected and divided into four populations according to their geographical areas. These four populations
were analyzed to determine a genetic diversity profile using thirteen inter-simple sequence repeat markers. The individuals
produced 75.18% polymorphic banding profiles. The Shannon’s index was used to estimate genetic diversity. Total genetic diversity
(H
T) and inter-population genetic diversity (H
S) were 0.854 and 0.678, respectively. The degree of genetic differentiation (G
ST) of the species populations is 0.206, whereas the gene flow (Nm) among all the various geographical area populations is 1.016. Both the dendrogram and the results of the Shannon’s diversity
index suggest great genetic diversity. These results support the broad range of distribution sites of Nepenthes mirabilis, which would require high genetic diversity to adapt to the environmental variations that can be found between NE, C, and
S Thailand. ANOVA shows that the genetic diversity in each population is not significantly different (P > 0.05). Mantel tests reveal that geographical distance is an important factor for affecting the genetic distances among
populations. 相似文献
16.
The phylogeographic structure of vairone (Telestes muticellus), a primary freshwater fish endangered in a large part of its distributional range, was assessed: (i) to reconstruct the
complex dispersion pattern in the upper Tyrrhenian hydrographic basins of Ligury, actually not recognised as peri-Mediterranean
ichthyogeographic district, and (ii) to evidence the shape of population genetic structure as useful tool for future conservation
strategies. A partial fragment of mitochondrial DNA cytochrome b (497 bp) was sequenced in 109 specimens sampled from eight populations, along an east–west geographic gradient. Fourteen
haplotypes were identified, confirming the evolutionary distance between the two co-generic species: T. muticellus as ‘Ligurian’ clade and T. souffia as ‘French’ clade. The Nested Clade Analysis (NCA), the population genetic variability and population structure suggested
a natural colonization occurred throughout the crossing of Alpine and Apennine watershed. The hierarchical Analysis of Molecular
Variance (AMOVA) confirmed a geographic distinction between the populations from western (WTL) and from eastern (ETL) Tyrrhenian
basins of Ligury colonised through the river capture processes along the Maritime Alpine watershed (Padano-Venetian district)
and along the Apennine watershed (Tuscano-Latium district), respectively. Our results, evidencing the lack of genetic contiguity
among vairone populations of the upper Tyrrhenian hydrographic basins of Ligury, allowed to recognise the presence of two
management units (MUs) for its conservation.
Handling editor: Christian Sturmbauer 相似文献
17.
Spatial autocorrelation within a korean population ofRaphanus sativus var.hortensis f.raphanstroides
Man Kyu Huh 《Journal of Plant Biology》1999,42(4):273-278
Spatial autocorrelation was applied to microgeographic variations in Korean wild radish,Raphanus sativus var.hortensis Baker f.raphanstroides. Separate counts of each type of join (combination of genotypes at a single locus) for each allele, and for each distance
class of separation, were tested for significant deviation from random expectations by calculating the Standard Normal Deviation.
Moran’s / was significantly different from the expected value in 16 of 112 cases (14.3%). Eleven of these values (9.8%) were
negative, indicating genetic dissimilarity among pairs of individuals in the eight distance classes. Populations of wild radish
are small in Korea and are distributed with tractors used for fishing. Occasional cutting of seed-bearing stems as fodder
for animals also may bring a high level of gene flow. Thus, disturbance by many anglers, as well as by farmers, may contribute
to the fact that the wild radish population of Onsan is unusual in lacking spatial genetic structure. 相似文献
18.
Cymbidium goeringii is a diploid and nonrewarding, bumblebee-pollinated species, which is distributed in China, Japan and Korea Peninsula. This
species is now highly endangered due to the mass collection and forest clearance in China. In the present study, we investigated
the distribution of genetic variation within and between eleven populations of Cymbidium goeringii in central China by using Inter-simple sequence repeats (ISSR) markers. Eleven primers produced a total of 127 clear and
reproducible bands of which 112 were polymorphic. High genetic diversity was detected in Cymbidium goeringii for both population level (P = 63.1%; He = 0.194 5) and species level (P = 88.2%; He = 0.262 8). A higher level of genetic differentiation was detected among populations (G
ST = 0.244 0, F
ST = 0.220 7) with Nei’s G
ST analysis and analysis of molecular variance (AMOVA), and no correlation was found between geographical and genetic distance.
Genetic drift rather than gene flow played an important role in forming the present population structure of Cymbidium goeringii. Limited gene flow among populations and gene drift increase the extinction risk of local populations. Some conservation
concerns are therefore discussed together with possible strategies for implementing in situ and ex situ conservation.
__________
Translated from Biodiversity Science, 2006, 14(3): 250–257 [译自: 生物多样性]
Equally contributed authors 相似文献
19.
Intrapopulational spatial genetic structure was examined in two populations ofChionographis japonica var.japonica, a self-incompatible perennial, by spatial autocorrelation analysis of enzyme polymorphism. Although most spatial autocorrelation
indices (Moran'sI) in the shortes distance class were significantly positive, most in the other distance classes did not significantly deviate
from the values expected from random distributions of genotypes in both populations. This contrasts with a spatial genetic
pattern previously reported for a population of the predominantly selfing congener,C. japonica var.kurohimensis, indicating that pollen-mediated gene flow highly impedes genetic substructuring within populations of outcrossingC. japonica var.japonica. Genetic similarity in very proximate distance found in outcrossingC. japonica var.japonica is probably due to restricted dispersal of seeds. 相似文献
20.
Russell Lande 《Evolution; international journal of organic evolution》1992,46(2):381-389
Additive genetic variance maintained by mutation in a selectively neutral quantitative character is analyzed for an ideal population distributed on n islands, each with local effective size N, that exchange migrants at a small rate, m. In a stable population structure, the expected genetic variance maintained within islands is identical to that in a panmictic population of the same total size, regardless of the migration rate (m > 0). This result contrasts with Wright's classical conclusion, based on inbreeding coefficients, that at least one immigrant per island every other generation (Nm > ½) is necessary for the genetic variance within local populations to approach that under panmixia. The expected genetic variance maintained among islands is inversely proportional to m and increases with the number of islands, but is independent of N. Local extinction and colonization diminish the genetic variance maintained within islands by reducing the effective size of island populations through the founder effect, although the expected genetic variance within islands is nearly as large as that in a panmictic population of the same total effective size. If the founders of new colonies originate from more than one island, rates of local extinction and colonization larger than about twice the migration rate will substantially reduce the genetic variance maintained among islands. These results indicate the importance of mutation and migration in maintaining quantitative genetic variance within small local populations. 相似文献