广西苦树群落类型划分及其物种多样性

采用样地调查法调查苦树Picrasmaquassioides群落，以分析其生境特征、物种组成、区系成分、群落类型和物种多样性。结果表明，苦树群落物种组成丰富，10个样地共有维管植物85科207属255种，主要优势科为大戟科、豆科、禾本科、桑科等。苦树群落种子植物分为14个区系类型，以泛热带和热带亚洲成分为主，热带成分占总属数的72.73%，具明显的热带区系特点；群落划分为4个类型，苦树在群落Ⅰ和群落Ⅳ中生长旺盛且为优势种，是苦树的理想生境。调查样地内Margalef指数、Shannon-wiener指数、Pielou指数均表现为灌木层>乔木层；群落Ⅱ乔木层和灌木层的3个多样性指数均最高，群落Ⅳ乔木层Margalef物种丰富度指数较高而Shannon-wiener多样性指数最低。苦树根系萌芽力强，封禁措施对苦树居群恢复具有积极意义。     

广西元宝山植被种子植物区系初步研究

组成元宝山植被的种子植物共有118科337属732种,区系统计分析表明:(1)科级和属级的区系成分都表现为热带性质稍强于温带性质,亚热带区系性质明显。在元宝山植被区系中,热带亚热带成分与温带成分相互交融,这正是亚热带山地植物区系的一个基本特征。(2)泛热带分布、热带亚洲分布、北温带分布、东亚和北美洲间断分布和东亚分布的属为该植被区系主要构成成分。(3)元宝山植被中存在许多区系上孑遗、古老、孤立的植物类群,并且特有成分丰富,具有重要的保护价值。(4)裸子植物丰富,针叶林群落类型多样,是元宝山植被组成的突出特点。     

广东石门台自然保护区广东松群落的基本特征

应用样方法研究了广东英德石门台自然保护区的广东松群落的物种多样性、区系地理成分和年龄结构。结果表明,在2 000 m2样方中,有维管植物68种,隶属于38科57属,其中有广东松、白豆杉和福建柏3种国家Ⅱ级保护植物。群落的Simpson和Shannon-Wiener多样性指数分别为0.880 7和3.977 3。群落优势科为山茶科、樟科、壳斗科、木兰科和杜鹃花科等,植物科属的地理成分以泛热带和北温带分布型等占优势,体现了南亚热带向中亚热带过渡的特点。种群的立木结构表明广东松无更新幼苗,属于衰退种群,将来可能被阔叶树种群取代。对广东松群落的保护,将有利于群落中多个濒危植物的生存和发展。     

赤水桫椤国家级自然保护区桫椤群落特征及物种多样性研究

桫椤(Alsophila spinulosa),为中生代古老孑遗物种,国家二级保护植物。贵州赤水桫椤国家级自然保护区是以桫椤及其生存环境为保护对象的自然保护区,是拥有世界上数量最多、面积最广的桫椤林区之一。该文采用植物生态学、区系学等方法,对保护区内群落及物种多样性、伴生物种区系成分、生活型谱、群落结构等进行研究。结果表明:(1)群落内维管植物共计60科96属122种,其中蕨类植物12科14属17种,裸子植物2科2属2种,被子植物46科80属103种。(2)群落内植物的科、属区系成分类型多样,热带成分占优势,温带成分次之,表现出从热带区系向温带区系过渡的特征。(3)生活型谱以高位芽植物为主(占57.38%),反映出中亚热带森林以高位芽植物为优势的特点。(4)群落垂直分层显著,乔木层树高在4~12m的比例最大为76.64%;灌木层树高在2~3m的比例最大为69.78%;草本层各区间分布较为均匀,但以0~0.2 m的比例较大,群落层次明显。(5)毛竹(Phyllostachys heterocycla cv.pubescens)和桫椤在该地乔木组成中占主导地位;灌木层中,桫椤为最优物种;草本层主要以红盖鳞毛蕨(Dryopteris erythrosora)、翠云草(Selaginella uncinata)为主;物种丰富度分析显示,乔木层灌木层草本层;多样性指数、均匀度指数分析表明,乔木层为聚集分布、组成较简单,灌木层和草本层为均匀分布,但数量较少。     

西双版纳鸡血藤次生群落的特征分析

本文对西双版纳热带雨林刀耕火种撩荒后形成的鸡血藤次生群落进行了研究和分析,结果表明：在９００ｍ２的固定样地上,计有维管束植物６２种,隶属于３６科５５属,ｓｈａｎｎｏｎ－ｗｉｅｎｎｅｒ指数为４．２５;区系地理成分可分为９种类型,以热带区系成分为主,占９２．７３％。群落结构可分为乔木层（Ⅰ、Ⅱ、Ⅲ）、灌木层、草木层及层间植物,群落的外貌以高位芽、小叶型、单叶、纸质为主组成。与先锋阶段的植物群落相比,该群落正向湿润性的热带森林方向发展。     

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。     

不同程度人为干扰对古田山森林群落谱系结构的影响

群落谱系结构包含群落发育的历史信息,能从新的角度反映群落形成的生态过程.作者在浙江古田山自然保护区亚热带常绿阔叶林中选择了人为干扰强度不同的4种群落类型,以20 m×20 m为研究尺度探讨了不同干扰程度对群落谱系结构的影响.结果表明,人工林(类型Ⅰ)谱系结构发散;但间伐林(类型Ⅱ)、自然恢复林(类型Ⅲ)以及自然老龄林(类型Ⅳ)谱系结构聚集,且以类型Ⅱ和Ⅳ聚集度最高.进一步分析不同径级谱系结构发现,在中小径级(DBH≤5 cm和5 cm10 cm时,除了类型Ⅳ,其他3种群落都是谱系结构发散,这反映了在恢复早期种子扩散对这些林型群落构建影响较大:而皆伐后的演替和间伐增加了群落生境异质性,生境过滤作用增强,使类型Ⅱ、Ⅲ群落中小径级谱系结构表现为聚集;类型Ⅳ群落不同径级谱系结构均表现为聚集,可能与其稳定的生境过滤作用有关.     

江西九连山常绿阔叶林群落区系特征分析

采用群落生态学的方法对九连山常绿阔叶林的区系组成进行了分析。样地调查结果表明,群落内种类丰富,种子植物共有144科379属647种,其中裸子植物有6科8属9种,单子叶植物21科77属116种,双子叶植物117科294属522种。九连山常绿阔叶林群落的主要表征科为壳斗科、樟科、冬青科、蔷薇科、厚皮香科、山茶科、茜草科、桑科、大戟科等,且多为热带或亚热带科。从样地科的分布型统计看,热带、亚热带与温带成分属的比例为100∶62.8。从属的分布型统计看,有205属热带、亚热带地理分布类型;131属温带地理分布类型,35属世界广布类型和8属中国特有分布类型;热带、亚热带与温带成分的属比例为100∶63.9。九连山常绿阔叶林群落的标志种及其区系组成均较好地反映了本地区热带、亚热带区系成分的组合特征,对于九连山自然保护区天然常绿阔叶林的保护与发展具有重要的参考价值。     

四川卧龙地区珙桐群落特征的初步研究

珙桐是我国特产的第三纪古热带区系的孑遗植物。本文通过对珙桐群落的区系组成、地理成分和林木层的优势度分析,说明该群落是一种种类丰富,古老成分较多,并以珙桐为优势的具有残遗性质的混交林。通过生活型、叶级谱、叶型与叶质的分析,珙桐林是一种中亚热带亚高山垂直带谱上的典型的常绿、落叶阔叶混交林植被。此外,对群落结构和动态也作了一些分析。     

广东郁南同乐大山自然保护区种子植物区系研究

通过野外调查与查阅资料,广东郁南同乐大山自然保护区共有野牛种子植物149科542属1 002种.种子植物区系组成丰富,区系地理成分复杂,以南亚热带和热带北缘植物区系地理成分为主.区内珍稀濒危植物多,特有现象较明显,植物区系起源古老.与其它邻近地区植物区系相比较,同乐大山自然保护区种子植物区系与广西龙虎山自然保护区、广东黑石顶自然保护区的相似性较高,与湖南武陵源的相似性较低.     

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.