孑遗植物桫椤种群遗传变异的RAPD分析

应用 RAPD标记分析了桫椤分布在海南尖峰岭及霸王岭 ,广东塘朗山、黑石顶及大西山孑遗种群的遗传变异。 2 8个引物共检测到 1 1 8个位点 ,其中多态位点 33个 ,多态位点比率 2 7.97%。Shannon多样性、Nei遗传分化和分子方差分析 ( AMOVA)结果一致显示尖峰岭种群遗传多样性最大 ,霸王岭种群次之、塘郎山种群第三 ,黑石顶种群第四 ,而大西山种群最小。种群的遗传变异主要发生在种群间 ;Shannon指数测出的种群间遗传多样性所占比率为 79.1 0 % (基于表型频率 )和 77.85 % (基于基因频率 ) ,Nei基因分化系数 ( Gst)达 80 .69% ,分子方差分析也表明种群分化极为显著 ( Φst=0 .82 86,P<0 .0 0 1 )。桫椤的种内遗传多样性水平很低 ,种内 Shannon多样性仅为 0 .0 641 (基于表型频率 )和 0 .1 1 2 4 (基于基因频率 ) ,总基因多样性只有 0 .0 770。另外 ,Jaccard相似性系数的 UPGMA分析结果显示 5个种群分为两个分支 :尖峰岭种群和霸王岭种群组成一分支 ;黑石顶、塘郎山和大西山种群组成另一分支 ,并且三者中前两者的遗传关系更为密切。聚类分析结果还得到主成分分析的支持。根据桫椤种群的遗传变异特点 ,初步探讨了保护策略。     

观光木种群遗传多样性研究

 应用随机扩增多态DNA（RAPD）标记方法检测了广东南昆山和车八岭、广西靖西和海南霸王岭等4个观光木种群的遗传多样性。利用45个10聚寡核苷酸引物共检测出224个位点,其中多态位点175个,占78.13%,4个种群的遗传多态位点百分率分别为47.89％（海南）、53.96%（靖西）、55.00%（车八岭）和56.35％（南昆山）。观光木的遗传多样性分析结果显示,Shannon 指数为0.3565,其中36.58％来自种群间, 63.42％来自种群内; Nei指数为0.2597,种群间的遗传分化系数(GST     

Genetic differentiation of relictual populations of Alsophila spinulosa in southern China inferred from cpDNA trnL-F noncoding sequences

The genetic differentiation and phylogeographical pattern of 11 relictual populations of Alsophila spinulosa distributed across Hainan, Guangdong, and Guangxi in southern China were inferred from sequence variations of trnL-F noncoding regions of chloroplast DNA (cpDNA). The length of trnL-F noncoding sequences varied from 863 to 940 bp. The A + T content was 62.23-63.36%. Sequences were neutral in terms of evolution (Tajima's criterion D=-0.62417, P>0.10 and Fu and Li's test D*=-1.45455, P>0.10; F*=-1.32798, P>0.10). Thirty-four haplotypes were identified based on nucleotide variation. Relatively high levels of haplotype diversity (h=0.929) and nucleotide diversity (Dij=0.022263) were detected in A. spinulosa, probably associated with its long evolutionary history which allowed the accumulation of genetic variation within lineages. Both the minimum spanning network and the strict consensus tree of the most parsimonious trees generated for haplotypes demonstrated that the investigated populations of A. spinulosa were subdivided into two geographical groups: Hainan and Guangdong-Guangxi. An analysis of molecular variance (AMOVA) indicated that most of the genetic variation (87.48%, P<0.001) was partitioned among regions. Spatial structure measurements revealed that population genetic structure was not related to geographical distance. This research suggests that blocked gene flow by Qiongzhou strait and an inbreeding system might result in the geographical subdivision between Hainan and Guangdong-Guangxi (F(ST)=0.92, Nm=0.09). Within each region, the "star like" pattern of phylogeography of haplotypes implied a population expansion process during evolutionary history. Gene genealogies together with coalescent theory were useful tools for uncovering the phylogeography of A. spinulosa.     

珍稀濒危树种陆均松天然种群结构与空间分布格局

为研究陆均松(Dacrydium pectinatum)种群生存现状及分布格局,对BWL、DLS、JFL三种不同分布区域的陆均松天然种群进行了调查,分析了其天然群落乔木层物种多样性及优势种组成、龄级结构及分布格局三个方面的空间异质性,结果表明:(1)三种陆均松天然群落乔木层物种丰富度及多样性指数均较高,基本表现为BWLJFLDLS,且远高于中高纬度温带及亚热带森林群落;群落内多为小密度种群,少有占绝对优势地位的树种,符合热带山地雨林物种组成的一般规律。(2)龄级结构有所差异,BWL和JFL种群呈衰退趋势,共同特点是幼年树数量较少,成年和老年树比例较高;DLS种群幼年树数量在所有个体中比例最高,属于增长型种群。(3)BWL和DLS种群整体呈聚集分布,幼年至老年阶段由聚集分布转变为均匀分布,JFL种群整体及不同发育阶段均呈均匀分布状态;聚集强度表现为DLSBWLJFL,幼年树成年树老年树。陆均松是热带山地雨林的关键种和建群种,对研究海南热带雨林的起源及其区系特征具有重要意义,针对其生存现状,可根据实际情况,利用人工辅助措施如开辟林窗、合理疏伐等方式进行保护及更新复壮。     

Evaluation of genetic diversity in Piper spp using RAPD and SRAP markers

Random amplified polymorphic DNA (RAPD) and sequence-related amplified polymorphism (SRAP) analysis were applied to 74 individual plants of Piper spp in Hainan Island. The results showed that the SRAP technique may be more informative and more efficient and effective for studying genetic diversity of Piper spp than the RAPD technique. The overall level of genetic diversity among Piper spp in Hainan was relatively high, with the mean Shannon diversity index being 0.2822 and 0.2909, and the mean Nei's genetic diversity being 0.1880 and 0.1947, calculated with RAPD and SRAP data, respectively. The ranges of the genetic similarity coefficient were 0.486-0.991 and 0.520-1.000 for 74 individual plants of Piper spp (the mean genetic distance was 0.505 and 0.480) and the within-species genetic distance ranged from 0.063 to 0.291 and from 0.096 to 0.234, estimated with RAPD and SRAP data, respectively. These genetic indices indicated that these species are closely related genetically. The dendrogram generated with the RAPD markers was topologically different from the dendrogram based on SRAP markers, but the SRAP technique clearly distinguished all Piper spp from each other. Evaluation of genetic variation levels of six populations showed that the effective number of alleles, Nei's gene diversity and the Shannon information index within Jianfengling and Diaoluoshan populations are higher than those elsewhere; consequently conservation of wild resources of Piper in these two regions should have priority.     

Genetic structure and phylogeography of a relict tree fern,Sphaeropteris brunoniana (Cyatheaceae) from China and Laos inferred from cpDNA sequence variations: Implications for conservation

In this study, we analyzed the genetic structure and phylogeography of Sphaeropteris brunoniana from China and Laos. Combining cpDNA trnL-trnF and atpB-rbcL sequence variations, five haplotypes were identified from the 10 investigated populations. Moderate haplotype diversity (h= 0.66580) and low nucleotide diversity (π= 0.23 × 10⁻³) were detected. The S. brunoniana in Yunnan region had much higher genetic diversity (h= 0.60195, π= 0.35 × 10⁻³) than that of Hainan–Laos (h= 0.00000, π= 0.00). A high level of genetic differentiation (94.74%) between the two regions was revealed by amova. Nested clade analysis identified two major clusters of the five haplotypes, one clade in the Yunnan region and the other in Hainan–Laos. The analysis indicated that restricted gene flow with isolation by distance and allopatric fragmentation were likely the major processes that shaped the spatial distribution of the haplotypes. The isolated distribution of clades implied the emergence of independent refugia of this species in each region during Quaternary glaciations. The Yunnan populations frequently contained an ancestral haplotype, and most of them harbored other descendent haplotypes. Based on the distribution pattern of haplotypes and the nested clade analysis results, the Yunnan region potentially had several refugia of this species during glacial periods, whereas the Hainan populations were probable new colonizations.     

Population genetic structure and phylogeographical pattern of a relict tree fern,Alsophila spinulosa (Cyatheaceae), inferred from cpDNA atpB–rbcL intergenic spacers

Sequences of chloroplast DNA (cpDNA) atpB–rbcL intergenic spacers of individuals of a tree fern species, Alsophila spinulosa, collected from ten relict populations distributed in the Hainan and Guangdong provinces, and the Guangxi Zhuang region in southern China, were determined. Sequence length varied from 724 bp to 731 bp, showing length polymorphism, and base composition was with high A+T content between 63.17% and 63.95%. Sequences were neutral in terms of evolution (Tajimas criterion D=–1.01899, P>0.10 and Fu and Lis test D*=–1.39008, P>0.10; F*=–1.49775, P>0.10). A total of 19 haplotypes were identified based on nucleotide variation. High levels of haplotype diversity (h=0.744) and nucleotide diversity (D_ij=0.01130) were detected in A. spinulosa, probably associated with its long evolutionary history, which has allowed the accumulation of genetic variation within lineages. Both the minimum spanning network and neighbor-joining trees generated for haplotypes demonstrated that current populations of A. spinulosa existing in Hainan, Guangdong, and Guangxi were subdivided into two geographical groups. An analysis of molecular variance indicated that most of the genetic variation (93.49%, P<0.001) was partitioned among regions. Wrights isolation by distance model was not supported across extant populations. Reduced gene flow by the Qiongzhou Strait and inbreeding may result in the geographical subdivision between the Hainan and Guangdong + Guangxi populations (F_ST=0.95, Nm=0.03). Within each region, the star-like pattern of phylogeography of haplotypes implied a population expansion process during evolutionary history. Gene genealogies together with coalescent theory provided significant information for uncovering phylogeography of A. spinulosa.     

海南岛热带原始森林主要分布区土壤有机碳密度及影响因素

以海南尖峰岭、霸王岭、五指山、吊罗山、鹦哥岭5个热带原始森林土壤为研究对象, 分层采集0-100 cm的土壤样品并分析有机碳含量, 用纵向拟合法和分层估算法分别估算其土壤有机碳密度。结果显示: (1)纵向拟合法计算的5个热带原始森林土壤有机碳密度分别为14.98、18.46、16.48、18.81、16.66 kg·m^-2, 分层估算法分别为14.73、16.24、15.50、16.91、15.03 kg·m^-2, 前者显著高于后者(p < 0.05); 未经扰动的原始森林土壤, 宜采用纵向拟合法计算土壤有机碳密度。(2) 5个热带原始森林0-30 cm表层土壤有机碳含量分别占0-100 cm的50.50%、48.56%、43.49%、47.37、42.88%。(3)土壤有机碳密度与森林群落Shannon-Wiener指数(p < 0.01)、Simpson指数(p < 0.05)、物种丰富度(p < 0.01)、土壤容重(p < 0.001)存在极显著或显著的负相关关系; 与海拔(p < 0.05)、土壤孔隙度(p < 0.001)、土壤全氮含量(p < 0.001)存在极显著或显著的正相关关系; 与坡向、林分生物量、平均胸径、平均树高无显著相关关系(p > 0.05)。(4)由于海南地处低纬度地区, 其丰富的降水和持续高温条件加速了有机质的分解和物质的再循环, 导致海南森林土壤碳密度远低于全国平均水平。     

Soil organic carbon density and influencing factors in tropical virgin forests of Hainan Island,China

Aims
Estimating soil organic carbon (SOC) density and influence factors of tropical virgin forests in Hainan Island provide new insight in basic data for SOC pool estimation and its dynamics study.
Methods
The main distribution areas of tropical virgin forests in Jianfengling (JFL), Bawangling (BWL), Wu- zhishan (WZS), Diaoluoshan (DLS), Yinggeling (YGL) of Hainan Island were selected, and soil samples (0-100 cm) were sampled and analyzed. SOC density was estimated by soil vertical fitting method and soil stratification method to discover the distribution characteristics of soil organic carbon in tropical virgin forests of Hainan Island.
Important findings
Results showed that: (1) The average SOC density using soil vertical fitting method in JFL, BWL, WZS, DLS and YGL was 14.98, 18.46, 16.48, 18.81, 16.66 kg·m^-2, respectively, which was significantly higher (p < 0.05) than the estimated average SOC density using soil stratification method in these areas (14.73, 16.24, 15.50, 16.91, 15.03 kg·m^-2, respectively). It is better to use soil vertical fitting method for SOC density estimation when the soil was natural without disturbance. (2) The proportion of SOC content in the first 0-30 cm depth interval out of SOC in the whole 0-100 cm soil profiles in JFL, BWL, WZS, DLS and YGL was 50.50%, 48.56%, 43.49%, 47.37%, 42.88%, respectively. (3) SOC density was significantly negative correlated with Shannon-Wiener index, Simpson index, species richness, and soil bulk density; and was significantly positive correlated with altitude, soil porosity, and soil nitrogen. However, SOC density was not significantly correlated to slope, biomass, average diameter at breast height, or average height. (4) Our study area Hainan was located in low latitude area with high rainfall and high temperature, which accelerated the decomposition of organic matter and nutrient recycling, resulting in significantly lower SOC densities in this tropical virgin forests of Hainan Island than the average value in China.     

Uniform genetic diversity, low differentiation, and neutral evolution characterize contemporary refuge populations of Taiwan fir (Abies kawakamii, Pinaceae)

Based on fossil pollen, the distribution range of Taiwan fir [Abies kawakamii (Hay.) Ito] (Pinaceae) is smaller than it was 50?000 years ago. To characterize the present refuge populations of A. kawakamii, which survive only in subalpine forests in Taiwan, we surveyed nuclear genes and chloroplast intergenic spacers to assess the genetic diversity of Taiwan fir. Populations maintain high genetic diversity and contain similar numbers of haplotypes for the GapC (cytosolic glyceraldehyde 3-phosphate dehydrogenase) fragment. Haplotypes for GapC are generally widespread, and population-specific haplotypes accounted for 2.5% of the total. Differentiation among populations is very low (G(ST) = 0.01). Only three haplotypes were detected for the cpDNA marker, and every population had one or two haplotypes. In a neutrality test, the variation in nucleotides did not deviate from that expected with neutral evolution for either marker. A retreat route to higher elevations was not evident from either the GapC or cpDNA markers. Hsuehshan was the site of the most divergent population in Taiwan. We concluded that uniform genetic diversity, low differentiation, low numbers of population-specific haplotypes, and neutral evolution characterize contemporary refuge populations of Taiwan fir.     

Phylogeographic study reveals the origin and evolutionary history of a Rhododendron species complex in Taiwan

This study infers a single origin and a once-widespread distribution of the Rhododendron pseudochrysanthum species complex in Taiwan based on chloroplast DNA (cpDNA) variation. In total, 124 individuals from five endemic Rhododendron species were used for amplifications of two chloroplast intergenic spacers: trnL-trnF and atpB-rbcL. The haplotype and nucleotide diversities were much lower for the R. pseudochrysanthum complex, comprised of the species R. pseudochrysanthum, R. morii, Rhododendron rubropunctatum, and Rhododendron hyperythrum, than for Rhododendron formosanum. Two measures of pairwise population differentiation, N(ST) and F(ST), consistently revealed mostly non-significant levels of genetic divergence between populations of the R. pseudochrysanthum complex. No genetic difference was found among the four species of the R. pseudochrysanthum complex by analysis of molecular variance (AMOVA), which is concordant with the parsimonious topology of cpDNA haplotypes for the complex. Nested clade analysis (NCA) of the cpDNA haplotypes indicated that restricted gene flow with isolation-by-distance characterized the recolonization pattern of the R. pseudochrysanthum complex. In contrast, the NCA analysis indicated a contiguous range expansion for cpDNA haplotypes of R. formosanum. This research suggests a once-widespread distribution of the R. pseudochrysanthum complex probably via north-to-south colonization of mid-elevations during low-temperature periods of the Pleistocene. Population fragmentation followed the warmer climate which began in the Holocene and resulted in the present-day range contraction into high elevations.     

拟环纹豹蛛种群遗传多样性与其生境的关系

对分布于我国中南、西南和海南岛8个不同生境的拟环纹豹蛛种群进行RAPD分析.筛选出10对引物扩增出清晰稳定的200～2 500 bp片段84条,其中多态性片段62条(占73.8%).表明种群存在明显多态现象.Shannon指数、相似系数和遗传距离测定以及聚类分析的结果表明：拟环纹豹蛛种群总的遗传多样性指数为0.5177,而且种群内遗传变异（64.24%)大于种群间（35.76%）;8个狼蛛种群平均遗传距离为0.2426,变异范围为0.0753～0.3725,表明8个种群由于所处生境条件不同而产生了一定的适应性变异.多元回归统计结果表明,制约拟环纹豹蛛成为稻田优势种的主要因子是年平均气温和农药的长期施用.     

Molecular phylogeography and conservation genetics of Sladenia celastrifolia inferred from chloroplast DNA sequence variation

The genetic variation and structure of Sladenia celastrifolia Kurz, a species of conservation concern, were investigated. Analyses of two chloroplast DNA loci (trnS-trnGand atpB-rbcL intergenic regions) were carried out for 24 populations of S. celastrifolia and five haplotypes were identified. High levels of genetic differentiation (G_ST = 1, F_ST = 1) were detected, which may be a result of limited gene flow caused by geographic isolation. Analysis of molecular variance suggests that the existence of marked phylogeographical structure within the haplotype distribution is probably due to geographic barriers among populations. The haplotype network and mismatch distribution analyses did not detect any signals for recent population expansions in S. celastrifolia. Thus, it can be inferred that the species likely persistedin situ during climatic oscillations. Considering its genetic diversity and uniqueness, conservation strategies are further discussed for this species.     

不同居群龙须草RAPD分析及其分类研究

利用RAPD分子标记和形态特征观察,分析研究了中国12个龙须草居群的遗传差异,16个寡聚核苷酸引物扩增共得到124条带,其中110条为多态性带,占88.7%.Shannon多样性指数(I)为0.359 0,物种水平N e i s基因多样性(H)为0.224 1.12个龙须草居群的遗传相似系数在0.48~0.99之间.聚类结果结合形态学特征分析,12个龙须草居群可划分为4类,其中河南、湖北、陕西山阳的9个居群聚为1类,陕西洋县居群、广东星子山居群、广西百色居群各代表1类.     

斑节对虾两个野生亲虾种群遗传多样性

采用RAPD和mtDNA 16S rRNA基因序列分析方法对海南和马来西亚斑节对虾(Penaeus monodon)种群进行了遗传多样性和遗传分化研究.结果表明:15个RAPD随机引物共检测到82个位点,海南和马来西亚种群的多态位点比例分别为75.90％和76.83％,杂合度分别为0.199和0.218,遗传多样性指数分别为0.276和0.288,种群间的遗传距离为0.015;16S rRNA基因检测的种内遗传变异较低,马来西亚和海南种群的核苷酸多样性分别为0.011和0,种群之间的遗传距离为0.008;马来西亚种群比海南种群的遗传变异水平要高得多,且海南种群可能起源于马来西亚种群;进行遗传选育时可考虑引进马来西亚亲虾作为奠基群体.     

High RAPD but no cpDNA sequence variation in the endemic and endangered plant, Heptacodium miconioides Rehd. (Caprifoliaceae)

Heptacodium miconioides Rehd. is an endangered species endemic to China and has suffered rapid decrease of distribution range and population size. This species has been disappeared in central China where the modal specimen was collected. We analyzed the genetic variation of the remaining populations to reveal whether the genetic diversity also suffered decrease and to provide some suggestions for conservation. All the nine known remaining populations were sampled. Genetic variation was analyzed based on RAPD markers and two fragments of cpDNA sequence, intergenic spacers of petG-trnP and trnS-trnG. No variation was observed in the two fragments of cpDNA sequence. However, the species exhibited high level of RAPD variation compared to other threatened or rare plants. Measures of genetic diversity within populations were strongly related to the log of estimated population size, indicating that large populations usually have more genetic diversity than that of small ones. About 25% of the variation was partitioned among populations. Significant relationship was observed between differentiation and geographical distance, indicating a pattern of isolation-by-distance. Given for few populations remaining, all the populations should be protected and urgent efforts be paid on the small populations to avoid their local extinction.     

Genetic variability of Triatoma rubrovaria (Reduviidae: Triatominae) from Brazil, Argentina and Uruguay as revealed by two different molecular markers

Randomly amplified polymorphic DNA (RAPD) and nuclear ribosomal DNA sequence analyses were used to assess the genetic population structure of the South American triatomine species Triatomo rubrovario throughout its geographical distribution. To investigate the genetic variability at both intraspecific and intrapopulational levels the RAPD profiles and the nucleotide sequences of the rDNA intergenic spacers, ITS-1 and ITS-2, were analysed and compared. The phenetic analysis based on RAPD profiles show three distinct clusters diverging by similarity coefficients ranging from 0.62 to 0.96. The ITS-1 and ITS-2 sequence variability detected may be considered very high, suggesting reproductive isolation between populations. A total of seven composite haplotypes (CH) were found, among which three are specific for Brazil, other three for Uruguay, and the last one common for the three countries studied. The population studied in Argentina does not represent an independent CH. Sequence analyses proved that the five populations studied are easily differentiable and that there is heterogeneity within each one. True mutations and indels are the responsible of sequence differences between haplotypes and populations, suggesting that divergence processes may presently go on within this species. The large intraspecific variability detected may underlie the known plasticity of T. rubrovaria, making it a potential intradomiciliary invader and consequently an appropriate vector for Chagas disease transmission. Therefore, this triatomine species must be continuously monitored throughout.     

濒危灌木长叶红砂遗传多样性的RAPD分析

应用RAPD分子标记对濒危灌木长叶红砂(Reaumuria trigyna)种群遗传多样性进行了分析.应用18条随机引物对长叶红砂5个种群的95个个体进行扩增,检测到118个位点,其中多态位点105个.结果表明:长叶红砂种群的多态位点比率(P)为88.98%,显示出长叶红砂种群存在较高的遗传多样性.Shannon多样性指数(0.4966)、Nei基因多样性指数(0.3303)和基因分化系数(Gst=0.1425)的分析结果显示,长叶红砂种群遗传变异大多存在于种群内,种群间的遗传分化占14.25%.聚类分析表明,长叶红砂种群遗传距离与地理距离之间无直接相关关系.遗传多样性水平与物种特性和所处不同群落有关,濒危植物并不一定表现为遗传变异水平的降低.     

Evolution of Synthyris sect. Dissecta (Plantaginaceae) on sky islands in the Northern Rocky Mountains

We examined the phylogeography of Synthyris sect. Dissecta (Plantaginaceae), which is restricted to the Olympic (S. lanuginosa) and Northern Rocky Mountains (S. dissecta and S. canbyi), to infer effects of sky islands and modes of speciation. Sequences of cpDNA trnT-trnL and psbA-trnH intergenic spacers resolved 22 haplotypes among 185 individuals sampled from 16 populations of the three species. Gene flow in the ancestral lineage and random capture of haplotypes in species lineages of sect. Dissecta have resulted in haplotype clades that are not exclusive to species. Nested clade analysis (NCA) indicates that allopatric fragmentation separated Olympic and Northern Rocky Mountain populations, giving rise to the Olympic endemic S. lanuginosa, which is characterized by unique haplotypes consistent with long temporal isolation. Low haplotype and nucleotide diversity in S. canbyi are consistent with newly founded populations experiencing a bottleneck. Furthermore, we infer S. canbyi evolved as a peripheral isolate of S. dissecta. NCA indicated limited migration in S. dissecta with possible isolation by distance. Both isolation on interglacial sky islands and valley glaciers during at least the last glaciation limited gene flow among populations of S. dissecta in different ranges of the Northern Rocky Mountains.     

Assessing Genetic Diversity of Ginkgo biloba L. (Ginkgoaceae) Populations from China by RAPD Markers

Genetic diversity and differentiation of nine populations of Ginkgo biloba L. (Ginkgoaceae)from China were evaluated using RAPD. Of 47 clear and repeatable RAPD bands, 46 were polymorphic (overall polymorphism = 97.9%). A ranged from 1.57 to 1.83 with a mean of 1.75. Mean He was 0.3159 (0.2429-0.3603). The Shannon index ranged from 0.3432 to 0.5119 with a mean of 0.4489. The GST was 0.1609 and AMOVA analysis indicated 89% of the variation within populations. UPGMA clustered the 9 populations into two groups: one containing only population JF and the other including 8 populations. Genetic diversity and differentiation of Chinese populations were higher than those of Korean and North American populations, which are ultimately descended from China, as reported previously.