陕南蔬菜根结线虫种类的同工酶酶谱鉴定

在形态学鉴定的基础上,运用同工酶电泳技术,对采自陕南3市18县区的37个为害蔬菜的根结线虫种群进行鉴定。结果表明:在所鉴定的种群中,32个种群为南方根结线虫(Meloidogyne incognita),2个种群为花生根结线虫(M.arenaria),1个种群为北方根结线虫(M.hapla),1个种群为南方根结线虫和花生根结线虫的混合群体,1个种群为南方根结线虫和北方根结线虫的混合群体;其中南方根结线虫是陕南为害蔬菜的主要根结线虫。     

西班牙根结线虫rDNA特性及其检测方法

通过对rDNA的ITS区和IGS2区进行PCR扩增并对产物测序,比较分析了西班牙根结线虫与中国4种常见的南方根结线虫、爪哇根结线虫、花生根结线虫和北方根结线虫群体rDNA的ITS区和IGS2区的序列差异,选择限制性内切酶TaqⅠ对IGS2区的PCR扩增产物进行酶切,获得了西班牙根结线虫的554 bp的特异性条带.表明用此方法可以明显将西班牙根结线虫与其他4种常见的根结线虫群体区分开,其灵敏度可达到单条根结线虫二龄幼虫.     

西班牙根结线虫rDNA特性及其检测方法

通过对rDNA的ITS区和IGS2区进行PCR扩增并对产物测序,比较分析了西班牙根结线虫与中国4种常见的南方根结线虫、爪哇根结线虫、花生根结线虫和北方根结线虫群体rDNA的ITS区和IGS2区的序列差异,选择限制性内切酶TaqⅠ对IGS2区的PCR扩增产物进行酶切,获得了西班牙根结线虫的554 bp的特异性条带.表明用此方法可以明显将西班牙根结线虫与其他4种常见的根结线虫群体区分开,其灵敏度可达到单条根结线虫二龄幼虫.     

陕南蔬菜根结线虫群体的mtDNA-PCR-RFLP快速种类鉴定

[目的]运用mtDNA-PCR-RFLP技术快速鉴定陕南蔬菜根结线虫,为根结线虫的有效防治提供参考。[方法]在形态学、同工酶鉴定的基础上,运用mtDNA-PCR-RFLP电泳技术,对采自陕南3市18县区的37个为害蔬菜的根结线虫种群进行了鉴定。[结果]在所鉴定的种群中,32个种群为南方根结线虫（Meloidogyne incognita）,2个种群为花生根结线虫（M.arenaria）,1个种群为北方根结线虫（M.hapla）,1个种群为南方根结线虫和花生根结线虫的混合群体,1个种群为南方根结线虫和北方根结线虫的混合群体;其中南方根结线虫是陕南为害蔬菜的主要根结线虫。[结论]形态学方法应仅作为辅助鉴定手段,而同工酶表型和mtDNA-PCR-RFLP分析均可作为快速而可靠地鉴定中国常见根结线虫种类的方法。     

野生樱桃李对北方根结线虫和花生根结线虫的抗性

为探明野生樱桃李抗根结线虫种质资源的价值,以实生钵苗为试材,采用人工接种等方法,研究其对北方根结线虫和花生根结线虫的抗性.结果表明:接种后30 d,野生樱桃李根系中北方根结线虫、花生根结线虫的雌成虫数量分别占2龄线虫接种量的0.16％和0.03％,依据抗性评价标准判定其高抗北方根结线虫和花生根结线虫;接种北方根结线虫的群体中包含免疫、高抗和中抗3种类型,分别占群体总数的46％、48％和6％;接种花生根结线虫的包含免疫和高抗2种类型,分别占群体总数的56％和44％;接种北方根结线虫和花生根结线虫的植株未被侵染率分别为46％和52％,所有供试植株根系表面均未发现线虫卵块.野生樱桃李高抗北方根结线虫和花生根结线虫,其对北方根结线虫、花生根结线虫的抗性均存在显著的株间分离现象;抗侵入、抗发育和抗繁殖是其对北方根结线虫和花生根结线虫的主要抗性机制;野生樱桃李是抗根结线虫核果类果树砧木种质资源树种.     

福建猕猴桃根结线虫病病原鉴定

对从福建省建宁县中华猕猴桃(Actinidia chinensis)根部采集的30个根结线虫群体进行鉴定,结果表明侵染猕猴桃的线虫群体是由爪哇根结线虫(Meloidogyne javanica)和南方根结线虫(M.incognita)组成的混合种群,爪哇根线虫为优势种。     

侵染江苏猕猴桃的北方根结线虫(Meloidogyne hapla)形态学描述和分子特征分析

根结线虫病长期以来对猕猴桃安全生产造成了严重威胁.调查发现江苏省连云港市部分猕猴桃种植园根结线虫病发生普遍,组织切片可见根部出现根结线虫诱导的特异的巨细胞.形态学观察和分子检测结果显示,尽管与其他群体存在一定差异,但仍确定本次分离自猕猴桃的根结线虫(种群编号:CN43)为北方根结线虫(Meloidogyne hapla).基于内转录间隔区(ITS)和COⅡ-16S序列构建的遗传进化树显示,CN43分离群体与已知的北方根结线虫位于同一进化分支,而与其他种类的根结线虫明显区分开来.以ITS序列构建的中接网络将34个北方根结线虫分离群体划分为10个单倍型,其中CN43属于最大的单倍型群组;然而,单倍型分析不能确定各分离群体在地理分布上的关联性.综上,本研究首次报道了北方根结线虫在中国猕猴桃上的侵染和发生,其分离群体的形态学描述和分子特征分析可为揭示猕猴桃根结线虫的种群多样性和种间变异提供参考.     

根结线虫rDNA-ITS片段的克隆与序列分析

用PCR方法扩增了16个不同地区和不同作物上根结线虫群体的ITS片段,并进行了克隆、序列测定分析和比对。结果表明:采自北京密云苦瓜和豇豆、北京通州月季以及山东胶州、烟台、潍坊花生上的6个根结线虫群体为北方根结线虫(Meloidogyne hapla),其ITS片段大小为772 bp;来自云南番茄、成都黄瓜和海南石榴上的3个根结线虫群体为爪哇根结线虫(M.javanica),其ITS片段大小为767 bp;来自河北廊坊番茄、北京海淀番茄和浙江黄瓜上的3个根结线虫则属于花生根结线虫(M.arenaria),其ITS片段大小为768 bp;而安徽和县、宿州的番茄以及太和桔梗上的3个根结线虫则属于南方根结线虫(M.incognita),其ITS片段大小为766 bp;海南胡椒上的根结线虫群体为番禺根结线虫(M.panyuensis),ITS片段大小为869 bp。     

海南省番石榴根结线虫病病原的种类鉴定及其寄主范围的测试

对源自海南省3地侵染番石榴的9个根结线虫群体进行了形态观察和同工酶分析,对4个代表性群体在10种常见经济作物15个品种上的繁殖力进行了测试.同工酶鉴定结果表明,病原线虫为象耳豆根结线虫(Meloidogyne enterolobii).生物测试发现或证实:携带Mi基因的抗性番茄以及菜豆、豇豆、茄子、黄瓜、西瓜、辣椒、烟草为供试象耳豆根结线虫群体的高度适宜寄主,大豆为低度适宜寄主,棉花为非寄主.寄主范围的测试结果提示,象耳豆根结线虫可潜在地对农业生产造成巨大的经济损失.     

深圳市蔬菜基地根结线虫的种类和分布

为明确深圳市威胁蔬菜生产的根结线虫种类和种群分布,对其主要蔬菜基地的根结线虫进行调查,并采用传统形态学与分子生物学结合的方法进行种类鉴定。结果表明:在深圳市13个蔬菜基地的121个调查采样点中,有11个蔬菜基地的74个采样点发现根结线虫Meloidogyne spp.,蔬菜根结线虫发生率为61.16%;从采集的样本中纯化得到76个根结线虫种群,并鉴定出4种根结线虫,其中69个种群为南方根结线虫M.incognita,3个种群为爪哇根结线虫M.javanica,1个种群为花生根结线虫M.arenaria,3个种群为象耳豆根结线虫M.enterolobii;同时发现2个采样点有南方根结线虫和象耳豆根结线虫的复合种群。     

High incidence of "leapfrog" pattern of geographic variation in andean birds: implications for the speciation process

Many species of birds in the humid forests of the Andes show a pattern of geographic variation in color that is virtually unknown in other regions of the world. This pattern, here termed "leapfrog," is one in which two populations very similar in appearance are geographically separated from each other by very different, intervening populations of the same species. Approximately 21 percent of all Andean bird species and superspecies with three or more differentiated populations show the leapfrog pattern, and several of these show multiple cases of leapfrogging color patterns. Lack of concordance in the geographic distribution of taxa showing the leapfrog pattern suggests that there is a strongly random component in phenotypic differentiation with respect to direction, geography, and timing.     

伊犁郁金香和阿尔泰郁金香不同居群的物候特点

对分布于新疆的伊犁郁金香和阿尔泰郁金香不同居群的物候特征进行了连续两年的详细观察，结果表明；两种植物的所有居群均具有萌动及结实早、生长发育快、年生长期在70-90d，且生殖生长在年生长期中所占比例较大等物候特点；同一居群内植株开花比较集中，年际间物候期无明显波动，但不同居群在年生长期及萌动、始花等主要物候期上存在差异，且这种差异在营养生长阶段不明显，进入生殖生长后逐渐增大；伊犁郁金香不同居群物候期的早晚与海拔因素有关。     

Morphology and Taxonomy of Xiphinema(Nematoda:Longidoridae) Occurring in Arkansas,USA

In a survey, primarily from the rhizosphere of hardwood trees growing on sandy stream banks, for longidorids, 828 soil samples were collected from 37 Arkansas counties in 1999-2001. One hundred twenty-seven populations of Xiphinema were recovered from 452 of the 828 soil samples (54.6%), including 71 populations of X. americanum sensu lato, 33 populations of X. bakeri, 23 populations of X. chambersi and one population of X. krugi. The morphological and morphometric characteristics of these Arkansas species are presented. Morphological and morphometric characteristics are also given for two populations of X. krugi from Hawaii and North Carolina.     

韩国Ophiostomatoid真菌与棘胫小囊树皮甲虫的互作研究

棘胫小囊树皮甲虫(Coleopterla:Scolytidae)是一种与树木或新鲜木材兰染真菌相关的昆虫。本研究用不同种的松树制备的圆木诱捕、采集棘胫小囊树皮甲虫，并对其种类进行了比较。自4月至7月，从Pinus．rigida和Pinus．korniensis诱捕圆木上收集昆虫，共获得了10种树皮甲虫，其中Hylurgops interstitialis是P．koraiensi上最常见的甲虫，而Tomicus piniperda则在P．rigida上最常见。5月是H．interstitialis出现的高峰期，T.piniperda出现的高峰期是在4月。在6月上旬，新的成虫自蛹中孵化而出。为了研究树皮甲虫的种群与树木兰染真菌分离获得的频率的相关性，采用选择性培养基自成虫、卵／幼虫和树皮甲虫的虫道分离真菌。研究发现在越冬成虫和虫道上兰染真菌出现的频率分别是100％和94％，但在孵化的卵或刚孵出的幼虫上出现的频率相对较低。从兰染真菌分离出现的频率上看，收集的时间与树皮甲虫的种群没有显著的相关性。于4月20日可以首次观察到在虫道的下面出现变色现象，2周内，木材变色迅速增长，100％变色。对这些分离获得真菌进行鉴定，发现Leptographium spp出现频率高于Ophiostoma spp．。     

Modern human ancestry at the peripheries: a test of the replacement theory

The replacement theory of modern human origins stipulates that populations outside of Africa were replaced by a new African species of modern humans. Here we test the replacement theory in two peripheral areas far from Africa by examining the ancestry of early modern Australians and Central Europeans. Analysis of pairwise differences was used to determine if dual ancestry in local archaic populations and earlier modern populations from the Levant and/or Africa could be rejected. The data imply that both have a dual ancestry. The diversity of recent humans cannot result exclusively from a single Late Pleistocene dispersal.     

Genetic evidence for two species of elephant in Africa

Elephants from the tropical forests of Africa are morphologically distinct from savannah or bush elephants. Dart-biopsy samples from 195 free-ranging African elephants in 21 populations were examined for DNA sequence variation in four nuclear genes (1732 base pairs). Phylogenetic distinctions between African forest elephant and savannah elephant populations corresponded to 58% of the difference in the same genes between elephant genera Loxodonta (African) and Elephas (Asian). Large genetic distance, multiple genetically fixed nucleotide site differences, morphological and habitat distinctions, and extremely limited hybridization of gene flow between forest and savannah elephants support the recognition and conservation management of two African species: Loxodonta africana and Loxodonta cyclotis.     

Demographic characteristics and population dynamical patterns of solitary birds

In birds and many other animals, there are large interspecific differences in the magnitude of annual variation in population size. Using time-series data on populations of solitary bird species, we found that fluctuations in population size of solitary birds were affected by the deterministic characteristics of the population dynamics as well as the stochastic factors. In species with highly variable populations, annual variation in recruitment was positively related to the return rate of adults between successive breeding seasons. In stable populations, more recruits were found in years with low return rates of breeding adults. This identifies a gradient, associated with the position of the species along a "slow-fast" continuum of life history variation, from highly variable populations with a recruitment-driven demography to stable, strongly density-regulated populations with a survival-restricted demography. These results suggest that patterns in avian population fluctuations can be predicted from a knowledge of life-history characteristics and/or temporal variation in certain demographic traits.     

Homoploid hybrid speciation in an extreme habitat

According to theory, homoploid hybrid speciation, which is hybrid speciation without a change in chromosome number, is facilitated by adaptation to a novel or extreme habitat. Using molecular and ecological data, we found that the alpine-adapted butterflies in the genus Lycaeides are the product of hybrid speciation. The alpine populations possess a mosaic genome derived from both L. melissa and L. idas and are differentiated from and younger than their putative parental species. As predicted, adaptive traits may allow for persistence in the environmentally extreme alpine habitat and reproductively isolate these populations from their parental species.     

Competition between Species: Frequency Dependence

Whether two species competing for the same limited resources can stably coexist has been subject to controversy for several decades. The relative fitnesses of two species of Drosophila under competition in laboratory populations are shown to be inversely related to the relative frequencies of these species. This frequency-dependent fitness leads to a stable coexistence of the two species in spite of their competition for limited resources.     

Ecology of insect host-parasitoid communities

Although conclusive evidence is lacking for its establishment, the thesis that complexity adds stability to communities is probably accepted by the majority of ecologists. I believe this attitude found its origins in the indisputable fact that there are latitudinal and altitudinal changes in community complexity. As one progresses northward or southward from the equator, or higher in altitude in most parts of the world, one cannot help but notice that communities tend to become simpler, that is, there are fewer species per community. At the same time, these communities appear to become less stable. But perhaps this change in stability is in appearance only; they appear to be less stable because of the relatively greater number of individuals comprising each species population in temperate areas. Each population, because of its greater numbers, is therefore conspicuous, and changes in these numbers are noticed. We are particularly aware of such changes because populations in these areas of the world have been comparatively well studied. Many of the most studied populations include species of economic importance where changes in population numbers are vital to agricultural or forestry practices. Equatorial populations, on the other hand, contain smaller numbers of individuals of each species because of the greater number of species present. Number changes are simply not as noticeable because the population itself is not as obvious among the other populations. It may be that when (if ever) we have as much data on equatorial populations as we have on those of temperate climates, we will find fluctuations of equal relative magnitude (but not of equal numbers, of course). If, on the other hand, we really do find a correlation between complexity and stability, the suggestion by May (12) that stability permits complexity may be well worth investigating. Because of its organization and physical setting, the Rhopalomyia community I have studied might be expected to have considerable stability. In fact, however, it does not. Each of the populations in the community fluctuates greatly and irregularly in both percentages and numbers, and these populations apparently become locally extinct occasionally, because they sometimes cannot be found even in extensive collections. After studying several of the more important parasitoid species, it is evident to me that there is little or nothing about their interactions that might induce greater community stability. Each species seems to have evolved into the community with no higher purpose than simply to usurp what it can from some other member, and it does this by concentrating its energies on better competitive mechanisms rather than higher reproductive capacities. There are never empty niches to be filled by organisms having the "correct specifications" because new niches are created out of parts of older, broader niches which were occupied by other, more r-selected organisms. Thus, perhaps we have read too much into community organization. Perhaps the "ifiling of niches" is essentially nothing more than the haphazard result of competitive jostling among species; and that as communities develop, they are not necessarily programmed for such things as greater stability or better energy utilizationthe species merely become more closely packed.