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1.
Data are presented on allozyme variation between 15 populations of the stenophagous capitulum weevil, Larinus cynarae , and three populations of its congener, L. latus , that had been collected throughout the northern mediterranean range of these species. A phenetic analysis of these data revealed no direct relationship between genetic variation and host-plant association within L. cynarae , but there was a strong geographical structuring of allozyme patterns. Most of the genetic variation was due to differences between geographical regions and variation within these was small. Wright's F ST values showed that Italian and Greek populations of L. cynarae were most distinct from L. latus , with southern Iberian, northern Spanish and French populations increasingly less so. This pattern was associated with a cline in the frequencies of certain alleles along this geographical arc from France to Greece. A phenogram of Nei's genetic distances indicated the close genetic relationship between the two species of Larinus and separated the populations of L. cynarae into three allopatric groups. These groups have different host-plant spectra - dominated by Cynara cardunculus in Italy and Greece, Cynara humilis/Onopordum in southern Iberia and Onopordum spp. in France/Northern Spain - and can be considered to be host biotypes of L. cynarae. L. latus , which occurs in Greece and further east is also an Onopordum specialist. An analysis of the phylogeny of this group of Larinus indicates a primary separation into eastern ( L. latus ) and western ( L. cynarae ) taxa, with further branching of the L. cynarae lineage into the putative host-biotypes. An hypothesis for the evolution of these taxa is given, based on the evolutionary history of host-plant taxa and geographical constraints.  相似文献   

2.
We examined data for 11 allozyme loci in 14 populations that represent the distribution of the endangered Lotus kunkelii, the narrowly distributed L. arinagensis (both endemic to Gran Canaria), and the broad-ranging L. lancerottensis (endemic to the easternmost Canary Islands, Fuerteventura and Lanzarote) to explore and construe patterns of genetic variation and use this data to assess the controversial taxonomic status of L. kunkelii relative to L. lancerottensis. While L. kunkelii maintains low levels of variation, presumably as a consequence of prolonged inbreeding due to very low population size and sharp geographic isolation, the other two taxa have much higher indicators of polymorphism than those reported for other oceanic island endemics. Lotus arinagensis has the highest genetic polymorphism and the lowest interpopulation differentiation, presumably because of its considerable antiquity and habitat stability, despite recent fragmentation. The high interpopulation differentiation in L. lancerottensis is attributed to the Atlantic acting as a barrier, reducing gene flow within islands. Evolutionary analysis of the allozyme evidence indicates that L. kunkelii is genetically closer to L. arinagensis than to L. lancerottensis, thereby dispelling the taxonomic uncertainty and supporting L. kunkelii as a distinct species, warranting legal protection in the forthcoming catalog of threatened Canarian species.  相似文献   

3.
Urbanelli S 《Heredity》2002,88(5):333-341
The reproductive isolation in hydrenid beetles of the Ochthebius complex was studied by analysing gene exchange in natural populations of O. quadricollis, Ochthebius sp. A and O. brevicollis steinbuehleri collected along the Mediterranean coasts. The ranges of these three species are largely allopatric, but sympatric areas were detected between contiguous taxa, ie, O. quadricollis and Ochthebius sp. A; Ochthebius sp. A and O. b. steinbuehleri. Three levels of reproductive isolation and genetic divergence were observed. One level involves extensive intraspecific genetic divergence within the biological species O. quadricollis, Ochthebius sp. A and O. brevicollis, associated with both physical barriers (eg, sea and sand stretches) and the low dispersal capacity of larvae and adults. The finding of transitional samples between the most differentiated population groups should indicate, however, that there is still some gene flow between the populations of the three taxa. Another level is found between Ochthebius sp. A and O. b. steinbuehleri, whose gene pools appear to be fairly distinct in spite of the fact that reproductive isolation is still incomplete: in their few syntopic sites, some F1 hybrids appeared indeed to have lower fitness, since backcrosses or recombinant genotypes were never observed. The final level in the evolution of reproductive isolation (full reproductive isolation) has been achieved by the species O. quadricollis and Ochthebius sp. A. No F1 or F(n) hybrids, nor backcrosses were found in their sympatric areas. The relative importance of ecological factors and evolutionary forces in the prevention of gene exchange between taxa are discussed.  相似文献   

4.
大别山山核桃天然群体遗传结构的初步分析   总被引:1,自引:0,他引:1  
利用RAPD分子标记技术检测了大别山山核桃3个天然居群的遗传多样性和遗传结构。20条10 bp随机引物共检测到238个扩增位点,其中多态性位点162个,多态位点百分率(PPB)为68.1%。居群水平Shannon’s多态性信息指数(I)介于0.2651~0.2801之间;居群水平Ne i’s基因多样性指数(H)介于0.1789~0.1890之间。遗传变异计算显示大别山山核桃居群间基因分化系数(Gst)为0.4063,分子方差分析(AMOVA)表明居群间基因分化水平为0.4177,居群间基因流(Nm)为0.7306,说明大别山山核桃大部分变异存在于居群内,居群间基因交流相对较少。这一结果符合大别山山核桃风媒、异交的繁育系统特点,但其居群间基因分化程度明显高于异交植物的平均水平(Gst=0.1930)。地理隔离、居群内近交及居群间基因流受阻可能是形成目前大别山山核桃天然群体遗传结构的主要因素。  相似文献   

5.
The genetic diversity and genetic structure of a population of isolates of Sclerotinia sclerotiorum (Lib.) de Bary from different regions and host plants were investigated using the random amplified polymorphic DNA (RAPD) method with 20 random decamer primer pairs in order to provide some information on the phylogenetic taxa and breeding for resistance to sclerotinia stem rot. A minimum of three and a maximum of 15 unambiguously amplified bands were generated, furnishing a total of 170 bands ranging in size from 100to 3 200 bp, corresponding to an average of 8.5 bands per primer pair. One hundred and four of these 170bands (61.2%) were polymorphic, the percentage of polymorphic bands for each primer pair ranging from 0.0% to 86.7%. The genetic relationships among the isolates, based on the results of RAPD analysis, were examined. The genetic similarity of all selected isolates was quite high. At the species level, the genetic diversity estimated by Nei's gene diversity (h) was 0.197 and S hannon's index of diversity (I) was 0.300. The unweighted pair-group mean analysis (UPGMA) cluster analysis showed that most isolates from the same regions were grouped in the same cluster or a close cluster. The population of isolates from Hefei (Anhui Province, China) was more uniform and relatively distant to other populations. The Canadian population collected from carrot (Daucus carota var. sativa DC.) was relatively close to the Polish population collected from oilseed rape (Brassica napus L.) plants. There was no relationship between isolates from the same host plants. An analysis of molecular variance (AMOVA) revealed that the percentage of variance attributable to variation among and within populations was 50.62% and 49.38%, respectively. When accessions from China, Europe, and Canada were treated as three separate groups, the variance components among groups,among populations within groups, and within populations were -0.96%, 51.48%, and 49.47%, respectively.The genetic differentiations among and within populations were highly significant (P < 0.001). Similarly, the coefficient of gene differentiation (Gst) in total populations calculated by population genetic analysis was 0.229 4, which indicated that the genetic variation among populations was 22.94%. The gene flow (Nm)was 1.68, which indicated that the gene permutation and interaction among populations was relatively high.  相似文献   

6.
The rare and endangered Hieracium wiesbaurianum species group shows a scattered relictual distribution in Bavaria. Recently, a couple of populations were discovered which clearly differ from all other populations. If these must be considered as taxonomically independent units, they would be of crucial conservation interest, because of the sole responsibility that Bavaria has for these worldwide endemics. We therefore analysed the genetic structure of H. wiesbaurianum in a comparative approach. Our analysis comprised 37 populations of 13 taxa of H. wiesbaurianum, H. bifidum and H. laevigatum, including three potentially new taxa. We applied amplified fragment length polymorphism (AFLP) analysis and observed only limited genetic variation within populations and taxa. Nevertheless, each studied individual exhibited a unique genotype. An analysis of molecular variance revealed high levels of genetic variation between taxa, but populations were genetically less different. The clear genetic differentiation between the studied taxa was supported by neighbor‐joining cluster analyses and principal coordinate analyses in which every individual was clearly assigned to its respective taxon. The three potentially new taxa were genetically as well differentiated as the other taxa included in our study. This supports the assumption that they should be treated as taxonomically independent units of high conservation interest. Therefore, the genetic analysis confirmed the morphologically based classification of the studied Hieracium taxa. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 112–123.  相似文献   

7.
我国北回归线区域普通野生稻遗传多样性和遗传结构研究   总被引:8,自引:1,他引:8  
选择分布于水稻染色体组的26对SSR引物,对集中分布于广西来宾市北回归线附近的13个普通野生稻居群的342份材料进行遗传多样性和遗传结构研究。结果表明,该地区的野生稻无论在种内(A=9.154,Ae=4.446,I=1.547,He=0.671)还是居群水平上(P=95%,A=4.219,Ae=2.394,I=0.905,He=0.476)遗传多样性都十分丰富,高于同类研究水平。供试居群的遗传分化系数Gst为0.30,表明30%的遗传变异存在于居群间,大部分遗传变异存在于居群内。居群间的遗传一致度变化范围为0.332~0.903,且居群间地理距离越近,遗传一致度越高,说明北回归线附近的普通野生稻居群符合"隔离-距离"模型。综合上述研究结果和我国野生稻保护现状,建议对居群G13和G06实施优先保护。  相似文献   

8.
The tribe Genisteae includes genera of great ecological importance in Mediterranean countries because they are dominant elements of many plant communities. Genetic variation and diversification patterns in Stauracanthus (Genisteae) provide information relevant for the study of the processes of diversification in relation to the environmental history of the western Mediterranean. Nineteen populations of S. boivinii and S. genistoides were assessed by 11 chloroplast microsatellite markers, revealing 44 haplotypes. Both species had different haplotypes and contrasting patterns of karyological, morphological, and genetic variation. In the minimum spanning tree of the haplotypes, AMOVA analysis, and nested clade analysis, S. boivinii had high levels of differentiation and restricted gene flow among populations. Allopatric differentiation occurred between the Moroccan and Iberian populations of S. genistoides, although S. genistoides subsp. spectabilis and subsp. vicentinus had high levels of differentiation among populations (F(ST)), whereas S. genistoides subsp. genistoides had a low F(ST). Genetic patterns are discussed in relation to the Messinian salinity crisis (MSC): hard conditions drove plants to refuge habitats along the Atlantic coast and higher altitude areas in the Moroccan mountains (S. genistoides subsp. spectabilis and S. boivinii). After the MSC, S. boivinii underwent polyploidization and expansion, whereas S. genistoides expanded and continued diversifying into S. genistoides subspp. genistoides and vicentinus.  相似文献   

9.
Swordtail fish have been studied extensively in relation to diverse aspects of biology; however, little attention has been paid to the patterns of genetic variation within and among populations of swordtails. In this study, we sequenced the mtDNA control region from 65 individuals and 10 populations of Xiphophorus cortezi to investigate the genetic variation within and among populations, including tests for correlations between genetic and geographic distances and tests for species monophyly. We found low gene and nucleotide diversity within populations and high degrees of genetic differentiation among populations. Significant and positive correlations between genetic distance and both river and straight-line geographic distance indicate that genetic differentiation among X. cortezi populations can be explained, to some extent, by an isolation-by-distance model and provide evidence of stream capture. Phylogenetic analyses suggest that X. cortezi is paraphyletic relative to X. malinche, raising questions concerning the status of these taxa as separate species.  相似文献   

10.
We used sequences of the mitochondria control region to assess the distribution of genetic variation within and among populations of the poeciliid fish species Xiphophorus birchmanni . We collected 122 X. birchmanni samples from 11 sites in three drainage systems comprising the distribution of the species. We found low levels of polymorphism among aligned sequences and low levels of genetic variation within populations but high levels of genetic differentiation among populations. Haplotypes are exclusive to three river drainages (Los Hules, Calabozo and San Pedro). Mantel tests revealed correlations between geographical (both straight-line and river distances) and genetic distance, consistent with an isolation by distance scenario, while nested clade analysis suggested allopatric fragmentation between haplotypes from two of the major drainages, and isolation by distance with restricted gene flow within those drainages. Finally, monophyly of X. birchmanni is strongly supported while the previous hypothesis of the evolutionary origin of this species from X. malinche is not.  相似文献   

11.
Random amplified polymorphic DNA (RAPD) markers were used to provide estimates of the comparative genetic variation within and among four native populations of Schizachyrium scoparium . Genotypes were collected from high- and low-fertility sites in both New Jersey (forest biome) and in Oklahoma (grassland biome), USA, and propagated in the greenhouse. Four oligonucleotide primers, 10 bp in length, produced a total of 60 RAPD markers, with the minimum marker difference between any two individuals being 14 markers. Euclidean metric distances were calculated among all individuals, and the analysis of molecular variance ( AMOVA ) technique was used to apportion the total genetic variation among individuals within populations, populations within fertility levels, populations within biomes, fertility levels, and biomes. Even though most genetic variation resided within populations, statistically significant differences were detected between populations within each biome. Furthermore, genetic distances between high and low fertility levels within biomes were equal to or greater than biome distances. Therefore, in this wide-ranging and highly variable species, RAPD analysis suggests that local site differences in fertility and ecological history can promote genetic differentiation equal to or greater than geographical differentiation.  相似文献   

12.
Levels of neutral genetic diversity within and between populations were compared between outcrossing (self-incompatible) and inbreeding populations in the annual plant genus Leavenworthia. Two taxonomically independent comparisons are possible, since self-incompatibility has been lost twice in the group of species studied. Within inbred populations of L.uniflora and L.crassa, no DNA sequence variants were seen among the alleles sampled, but high diversity was seen in alleles from populations of the outcrosser L. stylosa, and in self-incompatible L. crassa populations. Diversity between populations was seen in all species. Although total diversity values were lower in the sets of inbreeding populations, between-population values were as high or higher, than those in the outcrossing taxa. Possible reasons for these diversity patterns are discussed. As the effect of inbreeding appears to be a greater than twofold reduction in diversity, we argue that some process such as selection for advantageous mutations, or against deleterious mutations, or bottlenecks occurring predominantly in the inbreeders, appears necessary to account for the findings. If selection for advantageous mutations is responsible, it appears that it must be some form of local adaptive selection, rather than substitution of alleles that are advantageous throughout the species. This is consistent with the finding of high between-population diversity in the inbreeding taxa.  相似文献   

13.
The genetic population structure of coastal cutthroat trout ( Oncorhynchus clarki clarki ) in Washington state was investigated by analysis of variation in allele frequencies at six highly polymorphic microsatellite loci for 13 anadromous populations, along with one outgroup population from the Yellowstone subspecies ( O. clarki bouvieri) (mean heterozygosity = 67%; average number of alleles per locus = 24). Tests for genetic differentiation revealed highly significant differences in genotypic frequencies for pairwise comparisons between all populations within geographical regions and overall population subdivision was substantial ( F ST = 0.121, R ST = 0.093), with 44.6% and 55.4% of the among-population diversity being attributable to differences between streams ( F SR = 0.054) and between regions ( F RT = 0.067), respectively. Analysis of genetic distances and geographical distances did not support a simple model of isolation by distance for these populations. With one exception, neighbour-joining dendrograms from the Cavalli-Sforza and Edwards' chord distances and maximum likelihood algorithms clustered populations by physiogeographic region, although overall bootstrap support was relatively low (53%). Our results suggest that coastal cutthroat trout populations are ultimately structured genetically at the level of individual streams. It appears that the dynamic balance between gene flow and genetic drift in the subspecies favours a high degree of genetic differentiation and population subdivision with the simultaneous maintenance of high heterozygosity levels within local populations. Results are discussed in terms of coastal cutthroat trout ecology along with implications for the designation of evolutionarily significant units pursuant to the US Endangered Species Act of 1973 and analogous conservation units.  相似文献   

14.
We analyzed genetic differentiation of Rosa rubiginosa by RAPD from populations growing in two Argentinean ecoregions, Chaco Serrano and Patagonian Steppe. Leaf material was collected during the spring and summer of 2006. UPGMA dendrogram and PCoA clearly suggest a geographical differentiation of the provenances of R. rubiginosa populations. AMOVA analyses revealed high genetic variation within populations (71%) and low variation between populations (29%), in agreement with values estimated by the Shannon–Weaver index. Genetic differentiation between populations estimated by AMOVA was ?PT = 0.29 (P < 0.001). Nei’s Gst (0.2205) was lower for interpopulation variation. The low interpopulation value obtained suggests genetic homogeneity between the populations. The presence of specific monomorphic bands accounts for the genetic differentiation between populations. The high percentage of within-population genetic diversity suggests the introduction of genetic variation into both ecoregions. From the present results we can conclude that we observed two independently established populations with high similarity between them and a strong intrapopulation differentiation. The empty niche hypothesis for explainging invasion success might explain the invasiveness of R. rubiginosa in Argentinean ecoregions.  相似文献   

15.
In the present paper we tested the hypothesis that differences in the acoustic communication system of diploid and tetraploid green toads ( Bufo viridis complex) might be due to selection for reproductive character displacement. We recorded two acoustic signals of the toad repertoire − the advertisement call (a long range mate-attracting signal) and the release call (a short-range signal mediating male–male interactions) − from six sympatric Central Asian populations (three diploid and three tetraploid populations) as well as from three allopatric diploid populations from Italy, and compared their patterns of variation with the pattern of among-population genetic distances. Although release and advertisement calls share the same morpho-physiological constraints, they show significantly different patterns of variation. Release calls vary congruently with the pattern of genetic distances, suggesting that mutation and genetic drift have been the major forces responsible for their change both in time and space. By contrast, the pattern of advertisement-call variation is not consistent with the phylogeny of the group, because the advertisement calls of Asian diploid and tetraploid populations differ from each other more than their genetic distances would predict. These results strongly support the hypothesis that selection acted on the advertisement calls of either or both Asian taxa , possibly, to favour reproductive isolation.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77, 379–391.  相似文献   

16.
对云南地区栽培的大叶茶(Camellia sinensis var. assamica)9个居群和大理茶(C.taliensis)3个居群的遗传多样性和居群遗传结构进行了比较研究。通过对94条叶绿体DNA RPL32-TRNL序列的核苷酸序列变异进行分析,共发现了7个单倍型。研究结果表明,大叶茶(h=0.728,π=0.00469)比大理茶(h=0.610,π=0.00225)拥有更为丰富的遗传变异,但其居群遗传分化水平(Gst=0.580,FST=0.612)却低于大理茶(Gst=0.696,FST=0.773)。AMOVA分析进一步证实了它们的遗传变异主要存在于居群间,且大叶茶(61.21%)低于大理茶(77.34%)。相对于大理茶,遗传多样性水平在本研究所取的大叶茶居群间存在着较大的差异,单倍型多态性水平变化范围为0~0.809,核苷酸多态性水平变化范围为0~0.00487。最后,讨论并提出了科学有效地保护我国古茶园茶种资源的建议和对策。  相似文献   

17.
In order to assess genetic diversity and population structure, nine Camellia sinensis var.assamica and three C.taliensis populations from Yunnan, China were evaluated. Based on nucleotide variation of 94 cpDNA RPL32-TRNL sequences, a total of seven distinct haplotypes were detected in the studied populations. It was apparent that C.sinensis var.assamica (h=0.728,π =0.00469) possessed higher levels of genetic diversity than C.taliensis (h =0.610, π =0.00225). However, genetic differentiation among populations of C.sinensis varassamica (Gst=0.580, FST=0.612) was lower than that among C.taliensis populations (Gst=0.696, FST=0.773). Our AMOVA analysis further revealed that the majority of variation was partitioned among populations of the two taxa, while C.sinensis var.assamica (6121%) showed lower level of genetic differentiation than C.taliensis (77.34%). In comparisons to C.taliensis, genetic diversity within C.sinensis var.assamica largely varied among populations, ranging from 0 to 0.809 and from 0 to 0.00487 for haplotype and nucleotide diversity, respectively. Conservation strategies were finally discussed and proposed to efficiently protect ancient tea plantations in China.  相似文献   

18.
中国特有植物卧龙沙棘自然群体的RAPD分析   总被引:1,自引:0,他引:1  
陈纹  孙坤  张辉  苏雪  陈学林  马瑞君   《广西植物》2007,27(2):152-155,145
应用12个随机引物对卧龙沙棘全部2居群共28个个体进行了RAPD分析。结果表明,卧龙沙棘具有较丰富的遗传多样性,多态位点百分率为78.05%,Nei’s基因多样性h=0.2553,Shannon’s多态性信息指数Ι=0.3841。分布范围狭窄的卧龙沙棘在亚种水平的遗传多样性明显高于分布较广的中国沙棘。在居群水平上,卧龙沙棘同样具有很高的遗传多样性,平均多态位点百分率为63.42%,Nei’s基因多样性h=0.2193,Shannon’s多态性信息指数I=0.3287。卧龙沙棘的基因分化系数Gst=0.1425,表明遗传变异主要存在于居群内。AMOVA的结果也表明,在全部的遗传变异中,19.18%的遗传变异存在于居群之间,与Gst值基本一致。这一结果符合卧龙沙棘风媒、异交的繁育系统特点。  相似文献   

19.
The Ostracoda (Crustacea; Class Ostracoda) is a diverse, frequently abundant, and ecologically important component of the marine zooplankton assemblage. There are more than 200 described species of marine planktonic ostracods, many of which (especially conspecific species) can be identified only by microscopic examination and dissection of fragile morphological characters. Given the complexity of species identification and increasing lack of expert taxonomists, DNA barcodes (short DNA sequences for species discrimination and identification) are particularly useful and necessary. Results are reported from analysis of 210 specimens of 78 species of marine planktonic ostracods, including two novel species, and 51 species for which barcodes have not been previously published. Specimens were collected during 2006 to 2008 from the Atlantic, Indian, and Southern Oceans, Greenland Sea and Gulf of Alaska. Samples were collected from surface to 5,000 m using various collection devices. DNA sequence variation was analyzed for a 598 base-pair region of the mitochondrial cytochrome oxidase subunit I (COI) gene. Kimura-2-Parameter (K2P) genetic distances within described species (mean = 0.010 ± 0.017 SD) were significantly smaller than between species (0.260 + 0.080), excluding eight taxa hypothesized to comprise cryptic species due to morphological variation (especially different size forms) and/or collection from different geographic regions. These taxa showed similar K2P distance values within (0.014 + 0.026) and between (0.221 ± 0.068) species. All K2P distances > 0.1 resulted from comparisons between identified or cryptic species, with no overlap between intra- and interspecific genetic distances. A Neighbor Joining tree resolved nearly all described species analyzed, with multiple sequences forming monophyletic clusters with high bootstrap values (typically 99%). Based on taxonomically and geographically extensive sampling and analysis (albeit with small sample sizes), the COI barcode region was shown to be a valuable character for discrimination, recognition, identification, and discovery of species of marine planktonic ostracods.  相似文献   

20.
卷叶凤尾藓(Fissidens dubius P.Beauv.)是凤尾藓科凤尾藓属植物,该种分布广泛,形态变异强烈。为了解其遗传多样性及种群遗传结构特点,本研究利用ISSR分子标记对采集于浙江、福建、广西、四川、辽宁5个省区的卷叶凤尾藓14个自然种群的遗传多样性进行了评价。结果显示:筛选出的12对引物共扩增出259条清晰、重复性高的条带,其中多态性位点有248个,多态位点百分率为95.75%;种群总的Nei's基因多样性指数为0.2327,Shannon's信息指数为0.3701,说明卷叶凤尾藓遗传多样性水平较高;14个种群的遗传分化系数(Gst)为0.7078,种群间的基因流(Nm)为0.1864,表明大部分遗传变异(72.01%)存在于种群间,27.99%的遗传变异存在于种群内,即卷叶凤尾藓种群间遗传分化明显。基于ISSR数据的聚类分析表明,在遗传距离50为分组阈值处,14个种群可被分为6组(G1~G6):G1为来自于浙江省不同采集地点的8个种群(JHBS除外);G2由浙江金华北山种群(JHBS)组成;G3包括福建武夷山(WYS)和天宝岩种群(TBY);G4、G5、G6分别由广西龙胜县花坪种群(GX)、四川龙池种群(LC)、辽宁白石砬子保护区种群(BSLZ)组成,表明卷叶凤尾藓种群间的遗传分化主要由地理距离造成,种群内的遗传分化可能与其生境的异质性有关。  相似文献   

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