首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 453 毫秒
1.
The genetic structure of ten natural populations of Arabidopsis thaliana (L.) Heynh. at eight isozyme loci was studied. The populations were located in the northern part of the species range, 200 km from the north to the south along the Onega Lake coast in Karelia. Considerable genetic diversity (P99% = 43.7, Hobs = 0.003) was revealed that is not typical of populations of self-pollinating plant species. A direct correlation between the proportion of polymorphic loci and geographical latitude was shown (r = 0.68; P < 0.05). It is suggested that a high polymorphism level in Karelian Arabidopsis thaliana (L.) populations increasing from the south to the north is due to extreme environmental conditions in the northern part of the species range. The distribution of genetic diversity within and between populations is typical of self-pollinating species: the larger part of the total diversity resides among populations (GST = 0.583).  相似文献   

2.
In natural populations of Arabidobsis thaliana (L.) Heynh., occupying northern limits of the species range (Karelia), the level of genetic diversity was evaluated. In two insular and one mainland population variability at 82 RAPD loci was tested. Considerable genetic diversity revealed (P = 4.5%; H exp = 0.177) was not typical of self-pollinating plant species. It was demonstrated that genetic differentiation among the populations (G ST = 0.680) was rather high, pointing to the low level of gene flow in the isolated insular populations. It was suggested that the high level of Arabidopsis population polymorphism in Karelia could be associated with extreme growing conditions at the northern limits of the species range.  相似文献   

3.
Comparative analysis of genetic structure of northern natural populations of two Arabidopsis species with different degrees of panmixia was performed. The variability of 121 RAPD loci in seven populations of model plant A. thaliana possessing high degree of self fertility was studied together with 93 RAPD loci in population of cross-pollinating species A. lyrata ssp. petraea. The population of A. l. petraea demonstrated higher level of genetic variability (P 99% = 62.50%; H exp = 0.169) than the populations of A. thaliana, which is obviously connected with biological features of reproduction of the species. A significant level of genetic variability (P 99% = 42.27%; H exp = 0.126) was revealed in populations of A. thaliana, which is not typical for self-pollinating plant species. The high population polymorphism of A. thaliana in the northern part of its range may be connected with adverse environmental conditions. The genetic distances between populations of the species studied (average D N = 0.494) confirm close relatedness between A. thaliana and A. l. petraea.  相似文献   

4.
In natural populations of Arabidobsis thaliana (L.) Heynh., occupying northern limits of the species range (Karelia), the level of genetic diversity was evaluated. In two insular and one mainland population variability at 82 RAPD loci was tested. Considerable genetic diversity revealed (P = 4.5%; Hexp = 0.177) was not typical of self-pollinating plant species. It was demonstrated that genetic differentiation among the populations (G(ST)= 0.680) was rather high, pointing to the low level of gene flow in the isolated insular populations. It was suggested that the high level of Arabidopsis population polymorphism in Karelia could be associated with extreme growing conditions at the northern limits of the species range.  相似文献   

5.
Comparative analysis of genetic structure of northern natural populations of two Arabidopsis species with different degrees of panmixia was performed. The variability of 121 RAPD loci in seven populations of model plant A. thaliana possessing high degree of self fertility was studied together with 93 RAPD loci in population of cross-pollinating species A. lyrata ssp. petraea. The population of A. l. petraea demonstrated higher level of genetic variability (P 99% = 62.50%; H(exp) = 0.169) than the populations of A. Thaliana, which is obviously connected with biological features of reproduction of the species. A significant level of genetic variability (P 99% = 42.27%; H(exp) = 0.126) was revealed in populations of A. thaliana, which is not typical for self-pollinating plant species. The high population polymorphism of A. thaliana in the northern part of its range may be connected with adverse environmental conditions. The genetic distances between populations of the species studied (average DN = 0.494) confirm close relatedness between A. thaliana and A. l. petraea.  相似文献   

6.
Limonium narbonense Miller is a fertile tetraploid species with a sporophytic self-incompatibility system. This sea lavender is found in coastal salt marshes which have been under intense human pressure during the past decades resulting in significant habitat fragmentation. Eleven microsatellite loci specifically designed for this species were amplified in 135 individuals from five populations. These markers were used to investigate the polyploid nature, the levels of genetic diversity and population structure in this species. L. narbonense showed high levels of genetic diversity (A = 7.82, P = 100% H T = 0.446), consistent with its likely autotetraploid origin revealed in this study and obligate outcrossing breeding system. Inbreeding (F IS) values were low in the three southern populations (mean F IS = 0.062), and higher in the northern populations (mean F IS = 0.184). Bayesian analysis of population structure revealed that populations could be grouped into two genetic clusters, one including three southern populations and the other the two northernmost ones. Individuals from the two northernmost populations showed higher admixture of the two genetic clusters than individuals from the three southern ones. A thorough analysis of microsatellite electrophoretic patterns suggests an autotetraploid origin for L. narbonense. The genetic structure revealed in this study is attributed to a recent migration from the southern area. This result suggests a net gene flow from the south to the north, likely facilitated by migratory movements of birds visiting the temporary flooded ponds occupied by L. narbonense.  相似文献   

7.
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   

8.
The geographical distribution of existing populations of horse chestnut (Aesculus hippocastanum L.) in Europe is determined by past demographic events during the Quaternary. In the present study we evaluate the imprints that northward expansions originated from common ancestry at southern Europe may have left on the present patterns of genetic variation for horse chestnut across the continent. Genetic diversity and levels of population structure in a European south–north gradient, ranging from the Balkans to the Scandinavian Peninsula, were determined with Amplified Fragment Length Polymorphism (AFLP) markers in 159 loci. A family of rarefaction techniques for the estimation of gene diversity was used to exclude potential confounding effects as a result of the unequal sample sizes. The results indicate that northern populations are not more genetically depleted than southern populations, thus suggesting that diversity for this species is not correlated with latitudinal distribution. Detailed hypotheses based on prediction models for different historical events associated with human‐mediated spread of cultivation are examined for a better understanding of the current genetic patterns of regional differentiation.  相似文献   

9.
Blood protein polymorphism of gelada baboon (Theropithecus gelada) to the south of the Rift Valley, Arsi Region, were examined for 36 genetic loci using three electrophoresis techniques for 48 blood samples from three localities, and compared with the northern geladas. New variant alleles and genetic markers of Hb-α, PA-2, and TBPA loci were detected. The distribution patterns of the variant alleles of Hb-α, PA-2, TBPA, Pi, Gc, PGM-II, and TBPA loci were localized in the geographic regions of south and north gelada populations, respectively. Genetic variability of southern geladas was estimated as Ppoly=0.083 and , which was comparable to northern geladas. A remarkably high genetic differentiation between the two geographic populations was shown byNei's genetic distance=0.071 and GST value=0.420. Our results of genetic analysis suggest that the southern and northern gelada populations have been separated for several hundred thousand years, and gene flow between the two geographic populations is severely restricted. The southern gelada baboon may be regarded as a distinct subspecies.  相似文献   

10.
Carex digitata and Melica nutans are forest understorey herbs with wide European distributions and their northern range margins in Fennoscandia. The species have closely similar habitat requirements, occur in small populations in old forest stands on base-rich to neutral soils and have restricted dispersal abilities at the present day. This study investigates the structure of allozyme variation (12 and 8 loci, respectively) in material of both species (38 and 37 populations, respectively) from throughout southern Sweden and southern Finland. Both species show a relatively low overall genetic diversity (HT excluding monomorphic loci=0.17 and 0.18, respectively). The hierarchic structuring of allelic diversity in the species is similar, with a relatively high between-population component of diversity (GST=0.36 and 0.37, respectively). Neither of the species shows a clear intraspecific pattern of geographic differentiation. The lack of large-scale patterns of geographic differentiation is not consistent with a simple scenario of discrete and independent waves of immigration into Fennoscandia. However, particularly in M. nutans, a group of populations from a lowland belt across southwestern Finland and southern central Sweden is somewhat differentiated from populations to the north and south. A number of rare alleles in both species are widely, but patchily distributed in low frequencies. Hybridization may account for the scattered occurence of some of the rare alleles in Carex digitata, but cannot explain the distribution of rare alleles in Melica nutans. Received July 23, 2001 Accepted December 6, 2001  相似文献   

11.
Aim Climatic changes and fluctuations in the past have strongly influenced the distribution of animal and plant species. Such fluctuations are also reflected in the patterns of genetic diversity on both local and global scales. The genetic pattern of the pearly heath butterfly, Coenonympha arcania, was used to evaluate the genetic differentiation of isolated (in north‐western Europe), peripheral (in north‐eastern Europe) and central (in southern Europe) populations in the context of post‐glacial distributional changes of the species. Location Europe (Sweden, Germany, the Baltic states, Italy, Slovenia, Hungary, Romania, Bulgaria). Thus, samples were collected from large parts of the species’ distribution representing the three categories mentioned above. Methods We analysed 18 loci of 569 individuals from 28 populations by allozyme electrophoresis. We used both individual‐based and population‐based analyses, including F‐statistics, various clustering methods and Markov chain Monte Carlo simulations. Results All loci, except Fum, were polymorphic. The mean FST for all samples was 0.18. The mean genetic distance among populations was 0.046. Two major genetic lineages were distinguished. Populations from the centre of the distributional range in southern Europe and the northern periphery of the distributional range differed significantly in their level of genetic variability. The central populations of south‐eastern Europe showed high levels of genetic diversity and no differentiation among populations. Main conclusions Most probably the two major genetic lineages evolved during glacial isolation in two disjunct Mediterranean refugia. The lack of genetic differentiation across south‐eastern Europe implies a continuous Würm ice age distribution in this area, thus supporting the functional existence of steppe forests throughout this region. The peripheral‐isolated populations in Sweden seem to have suffered from one or more severe bottlenecks, resulting in substantial genetic impoverishment. The peripheral‐connected eastern Baltic populations, on the other hand, are affected by post‐glacial and possibly recurrent gene flow from more central parts of the distribution.  相似文献   

12.
There is an urgent need to maintain and restore a broad genetic base for the management of Dalbergia monticola, a very economically important but endangered tree species in Madagascar. Random amplified polymorphism DNAs (RAPDs) and chloroplast microsatellite markers were used to quantify the genetic variation and to analyse the geographic distribution of diversity. Ten locations covering most of the natural range were sampled. Sixty-three RAPD polymorphic and 15 monomorphic loci were obtained from 122 individuals. Genetic diversity was low and very close among populations and regions. The unrooted neighbour-joining tree exhibited 4 groups, representing 6% (p = 0.000) of the total variation. The greater part of the variance, 81%, was observed within populations. A Mantel test suggested that genetic distances between populations were weakly correlated with geographic distances (R = 0.46, p = 0.12). The three chloroplast microsatellite primers assayed on 100 individuals gave 13 chlorotypes. Most of the populations showed 2 or 3 haplotypes. Haplotype diversity for the total population was equal to HeCp = 0.83 and ranged from 0.00 to 0.80 among the populations. The unrooted neighbour-joining tree exhibited 4 groups corresponding to the four regions representing 80% (p = 0.0000) of the total variation. Genetic diversity varies with regions, the north and south being less variable. Chlorotype distribution, the phylogenetic tree and historical information suggest that putative refugias in the centre-north region originating from the early Holocene could explain the pattern of variation observed today. By combining the results obtained at nuclear and organellar loci, a strategy of conservation based on evolutionarily significant units is proposed.  相似文献   

13.
Aim This work investigates the population genetic effects of periodic altitudinal migrations and interstadial fragmentation episodes in long‐term Scots pine (Pinus sylvestris L.) populations at a regional scale. Location The study focuses on Scots pine populations in the northern Meseta and peripheral mountain chains, central and north‐western Iberian Peninsula. The ample macrofossil record in the area shows that this 60,000‐km2 region represent a glacial refugium for Scots pine. The species occupied large areas on the Meseta plains during glacial cold stages, but it has periodically sheltered at high elevation in the surrounding mountain chains during warm episodes, conforming to a fragmented pattern similar to its present‐day distribution. Methods We perform a fine‐scale chloroplast microsatellite (cpSSR) survey to assess the genetic structure of 13 montane Scots pine isolates in the northern Meseta (total N = 322 individuals). Using a hierarchical analysis of molecular variance (amova ), we test the hypothesis of genetic isolation among disjunct mountain areas. We use a standard coalescence model to estimate genealogical relationship among populations, investigating the potential role of the regional relief as a factor influencing historic gene exchange among Scots pine populations. Results Population haplotypic diversity was high among Scots pine populations (He = 0.978), greater than values reported for other more thermophilic pine species in the Iberian Peninsula. The amova revealed low (but significant) differentiation among populations (ΦST = 0.031, P = 0.010), showed that the disjoint montane distribution could not account for the genetic divergence among areas (ΦCT = 0.012, P = 0.253), and that there was non‐trivial subdivision among populations within the same mountain region (ΦSC = 0.021, P = 0.012). The genealogical relationships among populations showed that Scots pine isolates growing on disjoint mountain blocks, but on slopes flowing to the same basin, were genetically closer than populations growing on different slopes of the same mountain chain, flowing to different basins. Main conclusions The observed genetic structure for Scots pine is consistent with its population history, inferred from the palaeobotanical record, with vertical migrations throughout climatic pulses and with the drainage basins and large long‐term population sizes connecting different mountain blocks during the cooler glacial periods. Overall, the results suggest that, despite periodic interstadial fragmentation episodes, Scots pine biology provides for the long‐term maintenance of high within‐population and low among‐population genetic diversity at neutral genetic markers.  相似文献   

14.
Effective population size, levels of genetic diversity, gene flow, and genetic structuring were assessed in 205 colonial Roseate spoonbills from 11 breeding colonies from north, central west, and south Brazil. Colonies and regions exhibited similar moderate levels of diversity at five microsatellite loci (mean expected heterozygosity range 0.50–0.62; allelic richness range 3.17–3.21). The central west region had the highest Ne (59). F ST values revealed low but significant genetic structuring among colonies within the north and within the south regions. Significant global genetic structuring was found between the northern and central western populations as well as between the northern and southern populations. An individual-based Bayesian clustering method inferred three population clusters. Assignment tests correctly allocated up to 64% of individuals to their source regions. Collectively, results revealed complex demographic dynamics, with ongoing gene flow on a local scale, but genetic differentiation on a broader scale. Populations in the three regions may all be conserved, but special concern should be given to central western ones, which can significantly contribute to the species’ gene pool in Brazil.  相似文献   

15.
Analysis of isozyme variation was carried out for 27 natural populations ofCeratopteris thalictroides in Japan. Of fifteen enzyme loci examined, eight loci were genetically polymorphic. At six loci,Lap, Pgi-2, Pgm-3, Pgm-4, Idh-2, and Skd-2, a marked genetic differentiation was observed between populations to the south of Okinawa Island and those to the north of the island. Okinawa Island contained a mixture of both southern and northern variants. Thus, two genetically distinct types (the south type and the north type) ofC. thalictroides occur allopatrically in Japan. Nei's genetic identity (I) between the two was 0.64, which was within the range of the I values between congeneric pteridophyte species. Regional fixation of a null allele was detected for one duplicated PGI locus in the north type ofC. thalictroides. This finding supports the recent hypothesis of genetic diploidization of polyploids through gene silencing.  相似文献   

16.
In South America, 94% of dry‐temperate lands present some degree of environmental degradation, highlighting the need for ecological restoration. We analyzed geographic patterns of genetic variation in Austrocedrus chilensis, a dominant conifer of the steppe‐forest ecotone in the eastern Andes, to examine its potential for restoration. We sampled 67 locations in Argentina and estimated genetic parameters to determine the effects of historical factors affecting diversity, together with inbreeding and gene flow, using 12 allozyme loci. Genetic diversity decreased southwards in eastern populations, which are marginal for the range of the species and patchily distributed, while high genetic admixture was detected in continuous western populations, possibly reflecting postglacial migrations from northern and eastern sources. Higher inbreeding (FIS > 0.14) was recorded in northern compared with southern populations, attributed to the impact of recent bottlenecks resulting from anthropogenic fires. Gene flow was found to be moderate overall (FST = 0.12). The implications of these results for restoration actions focusing on Austrocedrus were explored. Relatively small, inbred yet genetically diverse northern populations should be the subject of passive restoration efforts, while experimental common gardens should be established toward the south, to support active restoration approaches. This illustrates how ahead of time information on patterns of genetic variation can support restoration efforts for dryland tree species.  相似文献   

17.
Aim Phylogeographical studies in the Brazilian Atlantic Forest (BAF) have mostly included species associated with forest habitats, whereas taxa associated with grassland and sand‐dune plant communities have so far been largely overlooked. This study examines the phylogeography of the orchid Epidendrum fulgens, which occurs on coastal sand dunes and granitic outcrops, in order to identify major genetic divergences or disjunctions across the range of the species and to investigate the genetic signatures of past range contractions and expansions. Location Southern and south‐eastern seashore vegetation along the BAF biome, and granitic and arenitic outcrops that occur in the subtropical grassland plant communities located south of the BAF. Methods Nine nuclear and four plastid microsatellite loci were used to genotype 424 individuals from 16 populations across the distributional range of E. fulgens. For both sets of markers, we estimated genetic diversity and population differentiation, testing for a north–south gradient of genetic diversity. The plastid haplotype network and a Bayesian assignment analysis of nuclear markers were used to infer population structure. Past demographic changes were investigated using a coalescence approach. Results A deep disjunction was found between northern populations within the BAF and southern populations outside the BAF that occur on granitic and arenitic outcrops. Recent demographic reductions were detected in northern populations on coastal sands. Such demographic changes were not expected for those populations, as previous studies with forest species had found evidence of population expansion in the same areas. Higher genetic diversity was found in southern populations on granite, in contrast to patterns observed in previous studies of forest species. Main conclusions The results are consistent with the long‐term persistence of E. fulgens. Bottlenecks were detected in populations from areas where population expansion events have been detected in other plant (and animal) species, suggesting that forest expansion after the Last Glacial Maximum played a role in the population fragmentation and decrease in genetic diversity in E. fulgens. A substantial genetic division in E. fulgens corresponds to the ‘Portal de Torres’, a region that demarcates the northern limits of subtropical grassland plant communities and the southern limits of the BAF.  相似文献   

18.
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   

19.
Marginal populations are expected to provide the frontiers for adaptation, evolution and range shifts of plant species under the anticipated climate change conditions. Marginal populations are predicted to show genetic divergence from central populations due to their isolation, and divergent natural selection and genetic drift operating therein. Marginal populations are also expected to have lower genetic diversity and effective population size (N e) and higher genetic differentiation than central populations. We tested these hypotheses using eastern white pine (Pinus strobus) as a model for keystone, long-lived widely-distributed plants. All 614 eastern white pine trees, in a complete census of two populations each of marginal old-growth, central old-growth, and central second-growth, were genotyped at 11 microsatellite loci. The central populations had significantly higher allelic and genotypic diversity, latent genetic potential (LGP) and N e than the marginal populations. However, heterozygosity and fixation index were similar between them. The marginal populations were genetically diverged from the central populations. Model testing suggested predominant north to south gene flow in the study area with curtailed gene flow to northern marginal populations. Signatures of natural selection were detected at three loci in the marginal populations; two showing divergent selection with directional change in allele frequencies, and one balancing selection. Contrary to the general belief, no significant differences were observed in genetic diversity, differentiation, LGP, and N e between old-growth and second-growth populations. Our study provides information on the dynamics of migration, genetic drift and selection in central versus marginal populations of a keystone long-lived plant species and has broad evolutionary, conservation and adaptation significance.  相似文献   

20.
There is an ongoing debate about the glacial history of non‐arctic species in central and northern Europe. The two main hypotheses are: (1) postglacial colonization from refugia outside this region; (2) glacial survival in microclimatically favourable sites within the periglacial areas. In order to clarify the glacial history of a boreo‐montane tall forb, we analysed AFLPs from populations of Cicerbita alpina through most of its range (Scandinavia, the mountains of central Europe, the Alps, the Pyrenees and the Balkan Peninsula). We found a major differentiation between the Pyrenean population and all others, supported by principal coordinate, neighbour joining and STRUCTURE analyses. Furthermore, three populations from the central and north‐eastern Alps were genetically distinct from the bulk of populations from Scandinavia, central Europe, the Alps and the Balkan Peninsula. Most populations, including those from central and northern Europe, had moderate to high levels of genetic diversity (mean Shannon index HSh = 0.292, mean percentage of polymorphic loci P = 54.1%, mean Nei's gene diversity H = 0.195). The results indicate separate glacial refugia in the Pyrenean region and the Italian Alps. Furthermore, they provide evidence of glacial persistence in cryptic refugia north of the Alps, from where Scandinavia and most of the Alps are likely to have been colonized following deglaciation. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 142–154.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号