广西木荷林的分类和演替

木荷（ＳｃｈｉｍａｓｕｐｅｒｂａＧａｒｄｎ．ｅｔＣｈａｍｐ．）林是原来的常绿阔叶林遭受破坏以后,在保护较好的情况下,从演替系列群落顺向演替恢复为常绿阔叶林的一个早期类型。本文对广西木荷林进行分类,划分和论述７个群丛的种类组成特点和演替方向,可供进一步研究和规划退化生态系统的恢复和重建参考     

井冈山自然保护区栲属群落植物区系分析

井冈山自然保护区栲属群落的维管植物75科132属214种,其中蕨类植物有14科19属34种,裸子植物3科4属4种,被子植物58科109属186种。区系分析显示该植物区系起源石老,保留有大量第四纪冰前期区系万分;地理成分复杂,以热带亚热带成分为主,温带成分占有一定比例;珍稀涉危植物和特有植物丰富。植被组成中以壳斗科栲属的植物为优势种,乔木层的主要伴生种有木兰科、樟科、山茶科等科的常绿树种;主要灌木有柃木、杜茎山、草珊瑚、多花山竹子等;草本以淡竹叶、苔草、贯众、鳞毛蕨、狗脊蕨等为主。     

广西大穗鹅耳枥林的分类和演替趋向

大穗鹅耳枥林是广西东北部黄壤山地常绿阔叶林遭受砍伐后,在保护较好的情况下迅速发展起来的一个演替阶段。本文通过群落分类的研究,从不同群丛的外貌、结构和种类组成的变化,论证其向常绿阔叶林恢复过程的演替趋向。     

缙云山风灾迹地恢复群落主要乔木树种种间联结性

应用方差比率法,并通过2×2列联表χ2检验法及利用联结系数AC指数测定法研究了缙云山自然保护区风灾迹地恢复群落自然恢复样地和人工恢复样地中主要乔木树种的种间联结性。结果表明:(1)自然恢复样地主要乔木种群间在总体上呈一定的正关联;而人工恢复样地种群间在总体上呈负关联;(2)2×2列联表的χ2检验共有5个(3)种对为显著正关联(括号内为人工恢复群落的种对数,下同),2个(1)种对为显著负关联;(3)联结系数(AC)指数标量出了自然恢复和人工恢复样地中种对间的联结程度和相伴随出现的机率,两种恢复方式中的多数乔木种群间的联结性不显著且联结程度较低,绝大多数乔木树种之间无显著关联,而且人工恢复比自然恢复无关联性更强;(4)种对间的正关联,主要是由于它们具有相近的生物学特性以及对生境具有相似的生态适应性所致,种对间的负关联主要是由于物种间的空间排斥,适应不同的微环境的结果;(5)人工恢复和自然恢复所在的群落处于演替的不稳定阶段。     

Species composition and correlation of understory woody plants in Chinese fir plantation in the lower subtropical area

There are 71 species in the shrub layer of the Cunninghamia lanceolata plantation after natural succession.The species richness and diversity have increased with slight anthropogenic disturbance.The status and function of tmderstory woody species were judged by the analysis of the important value (IV).X2 statistics and r test were used for testing the significance of interspecific association and correlation among 25 main understory woody plants selected from the woody population.The results clearly showed their interspecific relationships and their differences in resource utilization.Species-pairs of positive association were in the majority.Most species were accommodated in the shady habitat.There was a positive correlation between the IV of the species and the interspecific association.The higher the IV of the species,the closer and more significant was the interspecific association.Based on analytical results of interspecitic association and correlation,25 woody plants in the shrub layer could be divided into four ecological species groups:I.Ficus hispida +Antidesma bunius+Mallotus barbatus+Ficus cunia+Saurauia tristyla+Mallotus philippinensis+Maesa japonica +Ficus hirta+Alchornea rugosa+Ficus fulva+Mallotus apelta;II.Cudrania tricuspidata+Schefflera octopylla;III.Cunninghamia lanceolata+Clerodendron cytophyllum +Millettia semicastrata+Randia spinosa+Litsea cubeba +Litsea pungens;IV.Ardisia japonica+Psychotria rubra +Vitex quinata+Cephalanthus occidentalis+ Pithecellobium lucidum+Mycetia sinensis.If species group III or II is the advantaged species in the shrub layer,the community would change from a coniferous forest to a sparse evergreen broad-leaved forest.For group IV,the community would be relatively stable.For group I,the coniferous forest would be mixed with coniferous-broad leaved forest.The classification of ecological species groups would provide a theoretical basis on judging its ecological function,adjusting the stand structure of the plantation and directing the suitable natural vegetation type through the close-natural restoration process.     

长苞铁杉林乔木层优势种群种间关联及尺度效应研究

通过设定不同尺度的样方面积,根据2×2联列表,运用方差分析、联结系数AC、2统计量度量、 Ochiai指数系列技术,测定天宝岩国家级自然保护区长苞铁杉群落乔木层10个优势种群间的总体联结关系、 种对间联结显著性和关联系数。结果表明:长苞铁杉群落乔木层10个优势种群的总体种间关联性均呈正关 联,反映该群落处于稳定的顶极阶段;10个优势种群的种间联结关系中,有26个种对在不同尺度样方设计中 均未达到一般显著水平,种对间的相互独立性较强;样方设计为100 m2时,各项指标上规律性比较明显,它的 研究结果与实际情况相吻合。群落虽处于比较稳定的顶极阶段,但应适当调整群落结构,为长苞铁杉的生长 更新提供良好的生态环境。     

米槁群落主要物种资源利用特征分析

开展米槁群落物种生态位研究,可了解米槁群落物种对资源的利用特征,为米槁的保护与管理提供科学依据。基于贵州省米槁天然林群落的实际调查数据,通过生态位宽度、生态位重叠指数,分析该群落主要物种的资源利用特征。群落中米槁(Cinnamomum migao)、杜茎山(Maesa japonica)、菝葜(Smilax china)的生态位宽度最大,在群落中处于明显优势地位,具有较强竞争力和资源利用能力;生态位宽度越大的物种间生态位重叠越大,但在相同或相似环境条件下,生态位宽度值小的种对也会拥有较高的生态位重叠;米槁群落主要物种间的生态位重叠指数偏低,说明物种间对资源利用的相似性较低,物种的生态位分化明显,竞争不激烈,群落结构较为稳定,物种间能够较好地相互共存。     

山西五鹿山白皮松群落乔木层的种间关联性分析

根据2×2联列表,运用方差分析、χ2检验、AC指数、Ochiai指数等技术,对山西五鹿山白皮松群落50个样方内的26种乔木的种间总体联结关系以及各种对间关联显著性和关联系数进行分析与测定。结果表明:该地区26种乔木的总体联结关系以正关联为主,表明白皮松林与其外环境是相适应的;种对间以正、负关联两种形式存在,成对物种之间正负关联的出现,是该群落内环境的表现,也是由群落内环境异质性所致。     

山西历山国家级自然保护区千金榆群落种间分离研究

对山西历山国家级自然保护区普通沟和西峡的千金榆(Carpinus cordata)群落进行野外调查,共记录了40个样方,44个物种,组成946个种对.利用最近邻体法构造N×N最近邻体列联表,以x2检验和种间分离指数S作为区分指标,研究了千金榆群落的种间分离情况.结果表明:(1)946个种对中呈现随机毗邻的最多,有507个种对,占总数的53.59％;呈现正分离的有349个种对,占总数的36.89％;而呈现负分离种对最少,只有90对,占总数的9.52％.(2)群落的建群种或优势种因为有较强的生存能力和竞争能力,往往表现出正分离,例如千金榆、小叶鹅耳枥(Carpinus turczaninowii)、五角枫(Acer mono)、葛罗槭(Acer grosseri)等有较强生存能力的物种与大多数的物种发生正分离;而六道木(Abelia biflora)、东北茶镳子(Ribes mandshuricum)、小花溲疏(Deutziaparviflora),美蔷薇(Rosa bella)和紫花卫矛(Euonymus porphyries)等群落中的伴生种或小灌木,与部分物种形成负分离.其余物种之间发生随机毗邻的较多.(3)对千金榆群落44×44列联表进行全面分离,结果表明群落内的44个物种相互交错分布,不是全面分离.此外,种间分离的结果也揭示该群落处于演替初期,受岩石风化崩塌的影响较严重,人为干扰因素较轻.     

皖西大别山多枝尖山区主要乔木树种种间联结特征

为探讨皖西大别山多枝尖山区植物群落中乔木树种间的相互关系,采用X2检验、联结系数(AC)和共同出现百分率(PC)对出现频率大于5%的30个主要乔木树种间的种间联结特性进行了分析。X2检验结果显示:在30个主要乔木树种组成的435个种对中,种间联结性显著(P<0.05)或极显著(P<0.01)的种对有23个,其中,正联结种对有15个,负联结种对有8个。AC值分析结果显示:具有明显正联结性(AC≥0.4)的种对有20个,仅占种对总数的4.6%;而具有明显负联结性(AC<-0.6)的种对有113个,占种对总数的26.0%。PC值分析结果显示:PC值在0.6以上(PC≥0.6)的种对有22个,占种对总数的5.1%;PC值低于0.2(PC<0.2)的种对有271个,占种对总数的62.3%。3个指标的分析结果均表明:该区域植物群落主要乔木树种间具有明显正联结性的种对较少,大多数树种的种间联结较松散;物种生态习性、群落演替阶段和人为活动等因素是造成这一特性的主要原因。     

The extent of linkage disequilibrium in rice (Oryza sativa L.)

Despite its status as one of the world's major crops, linkage disequilibrium (LD) patterns have not been systematically characterized across the genome of Asian rice (Oryza sativa). Such information is critical to fully exploit the genome sequence for mapping complex traits using association techniques. Here we characterize LD in five 500-kb regions of the rice genome in three major cultivated rice varieties (indica, tropical japonica, and temperate japonica) and in the wild ancestor of Asian rice, Oryza rufipogon. Using unlinked SNPs to determine the amount of background linkage disequilibrium in each population, we find that the extent of LD is greatest in temperate japonica (probably >500 kb), followed by tropical japonica (approximately 150 kb) and indica (approximately 75 kb). LD extends over a shorter distance in O. rufipogon (<40 kb) than in any of the O. sativa groups assayed here. The differences in the extent of LD among these groups are consistent with differences in outcrossing and recombination rate estimates. As well as heterogeneity between groups, our results suggest variation in LD patterns among genomic regions. We demonstrate the feasibility of genomewide association mapping in cultivated Asian rice using a modest number of SNPs.     

甘肃省小陇山濒危珍稀植物白皮松群落种间关联

通过野外调查,选取小陇山白皮松群落50个样方的20个常见物种,运用多物种方差比值(VR),χ2检验,OI、DI、JI指数,AC、PC值以及Pearson相关系数和Spearman秩相关系数对其进行了种间关联分析。VR分析表明,白皮松林主要组成成分间的关系以正关联为主,说明白皮松群落的性质与其生存环境特征是一致的,白皮松林适应群落外环境;20个常见种种对关系表现出了不同的性质,是群落内环境的表现,也是由群落内环境异质性所致;综合植物的生态特征,划分出3个生态种组,发现白皮松群落的高负关联性是由林下喜阴灌木引起的,而群落较高的独立性则是由林缘植物引起的。种间关联的研究可以反映出由物种生态特征所形成的有机联系,研究结果对白皮松群落的保护与恢复有一定的指导意义。     

栽培稻种子含氮量的基因型差异

采用田间试验研究了421个常规籼稻、63个常规粳稻和82个籼型杂交稻品种种子含氮量的基因型差异。结果表明,栽培稻种子含氮量变幅在0.85%~2.55%,平均为1.39%。种子平均含氮量最高的是籼型杂交稻,高达1.46%,显著高于常规粳稻(1.39%)和常规籼稻(1.37%)。不同类型的栽培稻种子含氮量呈正态分布,但频数分布最高的区间存在一定的差异。以50%品种的种子含氮量(累积百分数从25%~75%)为依据,常规籼稻、常规粳稻、籼型杂交稻分别集中在1.21%~1.52%、1.21%~1.51%、1.36%~1.53%。LSR测验表明,籼型杂交稻极差显著小于常规籼稻和常规粳稻,但常规粳稻与常规籼稻的差异未达显著水平,即籼型杂交稻种子含氮量比常规籼稻和常规粳稻的分布更加集中。不同类型栽培稻内的种子含氮量极差较大,可分为若干组,且各组间达极显著差异。     

浙江苍南南部沿岸海域主要游泳动物生态位及种间联结性

根据2014年苍南南部沿岸海域春季(5月)和秋季(11月)的渔业资源调查资料,采用生态位测度、方差比率法、基于2×2列联表的χ²检验和联结系数(AC)等方法分析群落物种间的相互关系.结果表明： 该海域主要游泳动物按生态位宽度值可划分为广生态位种、中生态位种和窄生态位种3大类,其中广生态位种包括龙头鱼、三疣梭子蟹、口虾蛄等5种,中生态位种包括棘头梅童鱼、哈氏仿对虾和细巧仿对虾等8种,窄生态位种包括日本蟳、六丝钝尾鰕虎鱼和葛氏长臂虾等10种;种对间生态位重叠值差异较大,最大值和最小值分别为0.93和0, 部分游泳动物间可能存在资源利用性竞争.方差比率法分析表明,主要游泳动物总体呈显著正关联,其中有78个种对间的联结性达到显著水平(χ²≥3.841),联结系数(AC)中正显著联结的种对多于负显著联结.     

Screening for new hydroxynitrilases from plants

We established a simple HPLC method to determine the activity and stereochemistry of the chiral mandelonitrile synthesized from benzaldehyde and cyanide, and applied it to screen for hydroxynitrile lyase (HNL) activity of plant origin. A total of 163 species of plants among 74 families were examined for (R)- and (S)-HNL activities using the method. We discovered that homogenate of leaves of Baliospermum montanum shows (S)-HNL activity, while leaves and seeds from Passiflora edulis, and seeds from Eriobotrya japonica, Chaenomles sinensis, Sorbus aucuparia, Prunus mume, and Prunus persica show (R)-HNL activity. Partially purified (R)-HNLs from Passiflora edulis and Eriobotrya japonica acted not only on benzaldehyde but also on aliphatic ketone. The enantiomeric excess of (R)-methylpropylketone cyanohydrin synthesized from 2-pentanone using homogenate from leaves of Passiflora edulis was 87.0%, and that of (R)-mandelonitrile synthesized by homogenate from seeds of Eriobotrya japonica was 85.0%.     

Contrasting patterns of DNA variation in natural populations of two related conifers, Cryptomeria japonica and Taxodium distichum (Cupressaceae sensu lato)

We investigated DNA variation within and between two closely related conifers, Cryptomeria japonica and Taxodium distichum, at nuclear loci encoding ferredoxin, glutamyl-tRNA reductase, lycopene beta cyclase, and phosphoribosylanthranilate transferase. Average nucleotide diversity at silent sites was estimated to be 0.0035 (SE 0.0012) in C. japonica and 0.0058 (SE 0.0006) in T. distichum. One population in C. japonica was differentiated from the others but generally there was not much differentiation among populations or varieties within the two species. However, the two species seemed to differ in frequency spectra of DNA polymorphisms. Excesses of intermediate-frequency variants were found in C. japonica, whereas excesses of both rare and high-frequency variants were found in T. distichum, which suggested different histories of population structures in the two species. Deviations from the standard neutral expectations in DNA polymorphisms were found by applications of neutrality tests. The results show that actions of selection to respective loci seem to differ between the two species, indicating differences of interaction among evolutionary factors.     

Genotypic and phenotypic characterization of genetic differentiation and diversity in the USDA rice mini-core collection

A rice mini-core collection consisting of 217 accessions has been developed to represent the USDA core and whole collections that include 1,794 and 18,709 accessions, respectively. To improve the efficiency of mining valuable genes and broadening the genetic diversity in breeding, genetic structure and diversity were analyzed using both genotypic (128 molecular markers) and phenotypic (14 numerical traits) data. This mini-core had 13.5 alleles per locus, which is the most among the reported germplasm collections of rice. Similarly, polymorphic information content (PIC) value was 0.71 in the mini-core which is the highest with one exception. The high genetic diversity in the mini-core suggests there is a good possibility of mining genes of interest and selecting parents which will improve food production and quality. A model-based clustering analysis resulted in lowland rice including three groups, aus (39 accessions), indica (71) and their admixtures (5), upland rice including temperate japonica (32), tropical japonica (40), aromatic (6) and their admixtures (12) and wild rice (12) including glaberrima and four other species of Oryza. Group differentiation was analyzed using both genotypic distance Fst from 128 molecular markers and phenotypic (Mahalanobis) distance D(2) from 14 traits. Both dendrograms built by Fst and D(2) reached similar-differentiative relationship among these genetic groups, and the correlation coefficient showed high value 0.85 between Fst matrix and D(2) matrix. The information of genetic and phenotypic differentiation could be helpful for the association mapping of genes of interest. Analysis of genotypic and phenotypic diversity based on genetic structure would facilitate parent selection for broadening genetic base of modern rice cultivars via breeding effort.     

Genome-wide searching of single-nucleotide polymorphisms among eight distantly and closely related rice cultivars (Oryza sativa L.) and a wild accession (Oryza rufipogon Griff.).

We searched the genomes of eight rice cultivars (Oryza sativa L. ssp. japonica and ssp. indica) and a wild rice accession (Oryza rufipogon Griffith) for nucleotide polymorphisms, and identified 7805 polymorphic loci, including single-nucleotide polymorphisms (SNPs) and insertions/deletions (InDels), in predicted intergenic regions. Polymorphisms are useful as DNA markers for genetic analysis or positional cloning with segregating populations of crosses. Pairwise comparison between cultivars and a neighbor-joining tree calculated from SNPs agreed very well with relationships between rice strains predicted from pedigree data or calculated with other DNA markers such as p-SINE1 and simple sequence repeats (SSRs), suggesting that whole-genome SNP information can be used for analysis of evolutionary relationships. Using multiple SNPs to identify alleles, we drew a map to illustrate the alleles shared among the eight cultivars and the accession. The map revealed that most of the genome is mono- or di-allelic among japonica cultivars, whereas alleles well conserved among modern japonica paddy rice cultivars were often shared with indica cultivars or wild rice, suggesting that the genome structure of modern cultivars is composed of chromosomal segments from various genetic backgrounds. Use of allele-sharing analysis and association analysis were also tested and are discussed.     

Genetic differentiation among Hemarthria compressa populations in south China and its genetic relationship with H. japonica

Within and among populations genetic variance of twelve Hemarthria compressa populations and one Hemarthria japonica population from China were analyzed using inter simple sequence repeat (ISSR). Twelve primers amplified a total of 165 genomic DNA fragments across a total of 148 individuals of which 156 were polymorphic (94.55%). 75.76% of the bands were unique to each species, while the average genetic distance (GD) between one population of H. japonica and twelve populations of H. compressa was 0.44, which suggest that there was distinct differentiation between these two species. In H. compressa, twelve primers produced 145 bands across 145 individuals. High genetic diversity was observed at species level. The percentage of polymorphic loci (P) was 86.21% and Shannon's information index of diversity (I) was 0.357. In contrast, there were relatively low levels of genetic diversity within population (P=32.93%, I=0.174). Analysis of molecular variance (AMOVA) showed that a considerable proportion of genetic variation (48.02%) resided among populations. The coefficient of gene differentiation (G(ST)=48.6%) also suggested that there was strong genetic differentiation among H. compressa populations in southern China. An indirect estimate of the number of migrants per generation (N(m)=0.264) indicated that gene flow was low among populations of this species. Relative high clonal diversity was found, and all local genotypes were found.     

滇西北云南红豆杉群落物种生态位与种间联结

在对滇西北云南红豆杉(Taxus yunnanensis)群落的野外调查基础上,采用生态位宽度、生态位重叠和基于2× 2联列表的χ²检验、联结系数(AC)的方法,分析了群落种群间的相互关系。结果表明:物种的重要值与相对应的生态位宽度存在着极显著正相关;云南红豆杉、丽江铁杉(Tsuga forrestii)与青荚叶(Helwingia japonica)的生态位宽度大于其它种群;在1225个种对中有48.16%的生态位重叠值为0,同时χ²统计量中有4%为中性联结,说明群落中木本植物种群间资源利用性竞争较强。生态位宽度较大的种群间往往生态位重叠也较大;云南红豆杉与丽江铁杉之间的生态位重叠值要明显高于与其它种群的,Schoener指数为0.875。χ²检验表明云南红豆杉与其它种群之间表现为无联结。联结系数中显著负联结的种对要多于显著正联结,群落物种受到较大的外来干扰。联结系数与生态位重叠值之间存在极显著正相关,并能用Cubic指数建立回归方程模型。