江西官山自然保护区巴东木莲群落特征

对江西省官山国家级自然保护区内巴东木莲(Manglietia patungensis)群落特征进行调查和分析,结果表明,保护区内巴东木莲群落物种组成丰富,区系成分复杂,热带分布属明显多于温带分布属。群落组成以高位芽植物为主,地上芽植物次之,植物叶的性质以中小型叶、单叶、革质、非全缘为主。群落地上成层现象明显,下木层物种多样性高于乔木层。巴东木莲种群结构稳定,呈集群分布。     

湖南八大公山黄杉种群结构和群落特征研究

利用样方法对湖南八大公山黄杉(Pseudotsuga sinensis Dode)群落进行调查,分析黄杉群落的物种组成、区系特征、径级结构和物种多样性。结果显示,群落内共有维管植物132种,隶属于48科89属。群落垂直结构明显,分为乔木层、灌木层和草本层,黄杉是乔木层的优势种,另有檵木(Loropetalum chinense(R.Br.)Oliver)、马尾松(Pinus massoniana Lamb)和油桐(Vernicia fordii(Hemsl.)Airy Shaw)等主要伴生种,檵木为灌木层优势种,两色鳞毛蕨(Dryopteris setosa(Thunb.)Akasawa)为草本层优势种。群落区系组成以泛热带分布和北温带分布为主,具有明显的亚热带向温带过渡的性质。种群年龄结构可分为稳定型向衰退型过渡和衰退型2个类型,样方中幼苗和幼树极度缺失,中龄和老龄个体居多。黄杉、钩栲针阔混交林的物种多样性高于黄杉纯林,其中灌木层的多样性指数最高,乔木层的物种多样性指数最低。群落冠层郁闭度高造成的幼苗缺失可能是影响其濒危的主要原因,建议采取人为干扰创造林窗、加快繁殖技术研究等措施扩大其种群数量。     

粤北南方红豆杉植物群落的物种多样性和种群格局

在用样方法取样的基础上 ,分析粤北南方红豆杉生长地植物群落的物种多样性和种群分布格局 ,结果表明 :在调查地南方红豆杉出现于 5种类型的群落中 ;从物种多样性指数的平均值来看 ,灌木层的物种多样性大于乔木层 ,但乔木层和灌木层之间的 Shannon指数和群落均匀度无明显的差异 ;从乔木层和灌木层的变异系数看 ,丰富度、Shannon指数和群落均匀度均表现为乔木层 >灌木层。所调查的南方红豆杉生长地的植物群落的多样性指数和均匀度高于其他类群的南亚热带常绿阔叶林 ,但低于海南岛的热带雨林类群。南方红豆杉生长地植物群落中各优势种群均呈集群分布 ,且集群强度也都较高。南方红豆杉种群在大多数样地中亦呈集群分布     

江西中南部观光木种群及所在群落特征研究

采用样地调查法,对赣中南观光木种群及群落特征进行了研究。结果表明:观光木种群分布格局呈集群分布,径级结构为衰退型。观光木所在群落有维管植物60科94属112种,植物生活型以高位芽植物为主,占总种数的69.64%。植物区系起源古老,成分复杂,具有明显的热带性质。群落除Pielou指数较高外,其它各种多样性指数偏低,各样地间多样性指数有一定的差异;测度观光木所在群落物种多样性时,4种多样性指数未表现出相同的趋势,Simpson指数和Pielou指数在群落不同层次的变化规律为:灌木层>草本层>乔木层,Shannon-wiener指数和物种丰富度指数在群落不同层次的变化规律为:灌木层>乔木层>草本层。观光木本身的生物学特性和人类掠夺式的破坏是导致观光木种群濒危的主要原因。     

浙江丽水太山山地常绿阔叶林的物种多样性

通过样方调查,应用物种多样性指数和群落均匀度等指标对分布在浙江丽水太山山地的常绿阔叶林的物种多样性进行了研究。结果表明,常绿阔叶林群落乔木种类较为单一,物种多样性和均匀性在群落不同层次中差别较大,灌木层的物种数量和物种多样性指数最大,乔木层次之,草本层最小,灌木层-乔木层-草本层的物种多样性依此递减。根据分布生境,群落结构和种类组成,可将该山地常绿阔叶林分为3个类型(群系),即木荷甜槠林、青冈石栎林和褐叶青冈林。     

贵州习水杜鹃群落结构和种群动态分析

为了探究贵州习水国家级自然保护区特有植物习水杜鹃(Rhododendron xishuiense)种群现状,揭示该种群动态及濒危原因,加强对该种群的保护,在该保护区设置了13条样线,调查习水杜鹃在保护区的分布情况。对现存习水杜鹃分布地开展样地调查,采用4个多样性指数和Raunkiear生活型系统分析习水杜鹃分布群落的结构,通过空间代替时间得到种群年龄结构,据此编制静态生命表,并绘制存活曲线及4个生存函数曲线分析习水杜鹃种群的动态特征。结果表明,共有维管植物27科42属65种,其中种子植物24科39属62种,蕨类植物3科3属3种。以高位芽的物种数最多,有56种,占物种总数的86.15%,其次是地上芽植物、地面芽植物、地下芽植物。群落的多样性指数均表现为乔木层>灌木层>草本层,乔木层占有绝对的优势地位。种群年龄结构呈“金字塔”型,种群幼苗个体相对于整个种群数量较多;种群存活曲线属于DeeveyⅡ型,个体数量随着年龄的增加而不断减少;种群生存率持续下降,尤以中后期减少速度较快,种群衰退。习水杜鹃种群分布范围狭窄,分布群落物种多样性高,幼苗相对较多表现为增长型,但种群总量极少,且遭...     

澳门青洲山翻白叶树群落特征及物种多样性研究

根据样方调查结果,对澳门青洲山翻白叶树(Pterospermum heterophyllum)群落的种类组成、外貌、结构特征与动态及物种多样性进行分析.结果表明:(1)在1 600 m2样地中,有维管束植物47种,隶属于29科44属;对乔木层和灌木层主要物种的重要值以及频度分析结果显示,该群落是以翻白叶树为主的单优种群落,群落种类组成多样性和水平分布不均匀,其外貌终年常绿;对优势种种群的年龄结构分析显示,该种群处于增长状态;(2)整个群落的物种丰富度Margalef指数为13.72,Shannon-Wiener指数为1.15,Simpson指数为0.875,均匀度指数为0.34,该群落的层次格局为:灌木层>藤本层>乔木层>草本层;(3) 与其他5个不同类型地区森林群的物种多样性比较结果显示,澳门翻白叶树群落的物种多样性明显低于其他5个森林群落.     

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BWL>JFL>DLS,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DLS>BWL>JFL,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...     

特有珍稀植物宝华玉兰种群分布格局和群落特征

采用相邻格子样方法和典型样地法研究镇江宝华山国家森林公园珍稀植物宝华玉兰的种群分布格局和群落物种多样性。从分布格局看,宝华玉兰种群在半自然样地Q1中为聚集分布,但聚集强度不高,而在另外3个样地中均为随机分布。从群落特征看,4个样地共有维管植物89种,隶属于43科74属;群落分层明显,但宝华玉兰为亚优势种;半自然林中各层次的物种多样性Shannon-Wiener指数为草本层>灌木层>乔木层,而在自然样地中,则为草本层>乔木层>灌木层。     

草海国家级自然保护区华山松群落特征及物种多样性研究

为探讨喀斯特地区森林群落的演替动态和生物多样性维持机制,采用样地调查法对草海国家级自然保护区的华山松(Pinusarmandii)群落的物种组成、植物区系特征、种群结构和物种多样性等进行了分析。结果表明,样地内共有种子植物37科69属81种,其中乔木11种、灌木32种、草本38种;群落内植物的科、属区系成分类型多样,以温带成分为主;生活型谱主要以高位芽植物(46.91%)和地面芽植物(27.16%)为主;乔木层华山松的重要值达58%,为群落的单优势种;径级结构呈左偏正态型分布,树高分布集中在12～21 m,冠幅分布呈V型;乔木层与灌木层、草本层间的多样性差异显著(P0.05),物种丰富度指数S和D_M、多样性指数H和D_S均为草本层灌木层乔木层,物种均匀度指数J为灌木层草本层乔木层。因此,草海国家级自然保护区内的华山松群落特征和物种多样性具有明显的地域特点。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.