生物多样性与传染病风险

近半个世纪以来,新发传染病(多为涉及多宿主的人兽共患病)正在以前所未有的速度不断增加,不仅严重威胁人类健康,还影响着农业生产和野生动物保护。因不同宿主对病原的传播能力具有种间差异,宿主群落结构能够显著地影响病原的传播动态和传染病风险。多样性,作为表征群落结构的重要指标之一,其和传染病风险间的关系(即多样性-疾病关系)是传染病生态学研究的核心问题之一。尤其是“稀释效应”(即提高宿主多样性能够降低疾病风险)的提出引发了广泛的关注。虽然稀释效应得到了众多实证研究的支持,但其普适性仍然存在争议。笔者围绕多样性-疾病关系,介绍稀释效应的生态学机制、普适性及其产生的前提条件。并就3个方向总结了稀释效应的研究进展:①稀释效应的尺度依赖性;②宿主局部灭绝风险和其病原传播能力间的关系;③多样性对疾病风险的身份效应。此外,还分析了近期关于多样性-疾病关系研究框架的拓展,即从物种多样性拓展到谱系多样性;从单一疾病风险拓展到疾病总负担。最后,就未来可能的研究方向提出展望,认为未来研究需探讨分析生境破碎化、非宿主以及群落功能多样性在多样性-疾病关系中的作用。     

Morphologische Indizien für das unmittelbare Schwestergruppenverhältnis der Schizophora mit den Syrphoidea (‘Aschiza’) in der phylogenetischen Systematik der Cyclorrhapha (Diptera: Brachycera)

The phylogenetic relationships of the Schizophora with the families of the Aschiza were investigated on the basis of synapomorphies. Depending on the family, the sensory epithelium of the retinae of the compound eyes of flies consists either of populations of two ommatidial elements or of uniform ommatidia: duotype and monotype respectively. Within the Cyclorrhapha, the monotype occurs exclusively in the Schizophora and Syrphoidea (= Syrphidae + Pipunculidae), whereas the duotype occurs in the remaining Aschiza. These two types form a plesio-apomorphous pair: on the basis of character state analysis the duotype was regarded as plesiomorphous and the monotype proved to be a synapomorphy of the Schizophora and Syrphoidea. The retinal pair was accorded a high relevance as an indicator of the phylogenetic relationships in Cyclorrhapha owing to its special morphology and the very low probability of a parallel development of the apomorphous monotype.

In this paper the hypothesis (Hennig, 1976) that the dorsobasal arista on the antennal flagellum in the Schizophora and Syrphoidea is a synapomorphy compared to the original apical arista was confirmed on the basis of literature studies.

The monophyly of these two groups together, and their sister group relationship, were demonstrated in an argumentation scheme. Three alterations of the conventional systematics of the Cyclorrhapha were undertaken: (a) the term ‘Eumuscomorpha’ was introduced to designate a new monophyletic taxon of the Schizophora and Syrphoidea. (b) The remaining groups of the Aschiza were temporarily subsumed in a ‘superfamily Platypezoidea’ owing to their manifestation of complementary symplesiomorphous characteristics. Until its phylogenetic character (monophyly or paraphyly) is unequivocally clarified, it remains an ‘artifical’ entity. (c) The term ‘Aschiza’ is for a taxon of the genealogical system no longer applicable.     

应用ITS序列分析葱属植物发育关系

用克隆测序法检测葱属14个种的ITS序列,共获得17条不同的ITS序列.结果表明:大葱和洋葱正反交杂种一代测定出分别来自大葱和洋葱两个不同的ITS序列;楼葱也具有两个不同的ITS序列.从ITS序列分析、简约信息位点、GC含量及位点数差异看出,ITS序列比5.8SrDNA序列变异程度高,且ITS1序列比ITS2序列变异丰富.种间遗传距离表明:洋葱、分蘖洋葱和胡葱亲缘关系最近,大葱、鸡腿葱和阿尔泰葱之间也非常近.MP和NJ系统树显示:14种葱属物种分为两大支,薤、韭菜、韭葱和大蒜被分在一支;其余的为另一支.由此推测出:楼葱起源于两葱属物种的种间杂种;胡葱与洋葱源于共同祖先;大葱是由阿尔泰葱进化而来.     

红藻门仙菜科Ceramiaceae的分类现状与展望

仙菜科Ceramiaceae海藻作为红藻门中的一个重要类群,具有较高的研究价值.但由于科级以下分类系统、系统演化和物种数目在不同历史时期的变化比较大,仙菜科的分类研究还存在着许多争议.本文梳理目前国际与国内仙菜科分类学上的各种变动与争议,总结该科分类系统存在的问题,概述分子标记在仙菜科系统发育分析中存在的问题.同时,为...     

黑线仓鼠KiSS-1基因的生物信息学与系统进化研究

采用RT-PCR技术克隆得到黑线仓鼠(Cricetulus barabensis)KiSS-1基因的部分序列,并进行生物信息学分析。结果表明:该段序列共429bp,包含部分5’非翻译区、转录起始位点、信号肽序列以及主要的活性区域。黑线仓鼠KiSS-1编码的蛋白质是一种胞外分泌的亲水性蛋白质,N端含有19个氨基酸组成的信号肽序列,67、121-122位各有一个水解位点,68、69处的磷酸化位点可能与蛋白质活性的获得有关。二级结构预测含有较多的α螺旋和自由卷曲,115-119位的α螺旋在与受体结合中有重要作用。系统进化分析证实该序列与其他物种有较高的同源性,说明该基因在进化中相对保守。通过生物信息学与系统进化分析,有助于进一步揭示KiSS-1的转运加工途径及作用机制。     

New ancient DNA sequences suggest high genetic diversity for the woolly mammoth (Mammuthus primigenius)

Partial DNA sequences of cytochrome b gene (mtDNA) were successfully retrieved from Late Pleistocene fossil bone of Mammuthus primigenius collected from the Xiguitu County ( Yakeshi), Inner Mongolia Autonomous Region and from Zhaodong, Harbin of Heilongjiang Province in northern China. Two ancient DNA fragments (109 bp and 124 bp) were authenticated by reproducible experiments in two different laboratories and by phylogenetic analysis with other Elephantidae taxa. Phylogenetic analysis using these sequences and published data in either separate or combined datasets indicate unstable relationship among the woolly mammoth and the two living elephants, Elephas and Loxodonta . In addition to the short sequences used to attempt the long independent evolution of Elephantidae terminal taxa, we suggest that a high intra-specific diversity existed in Mammuthus primigenius crossing both spatial and temporal ranges, resulting in a complex and divergent genetic background for DNA sequences so far recovered. The high genetic diversity in the extinct woolly mammoth can explain the apparent instability of Elephantidae taxa on the molecular phylogenetic trees and can reconcile the apparent paradox regarding the unresolved Elephantidae trichotomy.     

Phylogenetic relationship of organisms obtained by ribosomal protein comparison

The evolutionary relationships of ribosomal proteins from eubacteria, archaea, eukaryotes, chloroplasts and mitochondria were examined by their degree of conservation, their structural and functional properties and by the occurrence of conserved structural elements. The structural domains formed by the different protein families were studied. The occurrence of monophyletic groups was investigated for each protein family within the archaea. Phylogenetic trees were constructed between these organisms and together with the homologous sequences of the other phylogenetic domains. All organisms belonging to the archaea clearly formed a monophyletic group. The conserved sequence motifs were checked for the potential to form similar secondary structural elements. Received 24 October 1996; accepted 30 October 1996     

烤烟品种NC297内生细菌中拮抗烟草黑胫病的生防菌筛选及种群组成分析

 从来自烤烟品种NC297的970株内生细菌中,以烟草黑胫病菌(Phytophthora parasitica var. nicotianae) 为靶标,共筛选出165株拮抗菌,这些内生细菌对黑胫病菌的抑菌率在9.55%~55.96%之间.内生细菌的生物量在苗期、团棵期、开花期和成熟期中无显著差异,但拮抗菌数量呈上升趋势.对165株拮抗菌的16S rRNA基因序列进行RFLP分析共产生12种带型.根据RFLP带型选取41株进行16S rRNA基因序列测定和系统发育分析.结果表明这165株生防内生细菌归于3大类群:Proteobacteria,Actinobacteria和Firmicutes.Firmicutes类群中的芽孢杆菌属(Bacillus)是优势属,共6种RFLP带型,159个菌株,包括Bacillus amyloliquefaciens subsp.plantarum,Bacillus methylotrophicus,Bacillus tequilensis,Bacillus aryabhattai,Bacillus cereus和Bacillus mycoide.Bacillus amyloliquefaciens subsp.plantarum和Bacillus.methylotrophicus是Bacillus中分离频率最高的2种内生拮抗菌,共149株,占该属菌株数的90.30%.其余6个菌株分别属于6个种:Brevibacillus reuszeri,Streptomyces finlayi,Streptomyces atroolivaceus,Erwinia rhapontici,Enhydrobacter aerosaccus和Stenotrophomonas rhizophila.     

基于18S rDNA的全变态类昆虫系统发育分析

 为了揭示全变态类昆虫的系统发育关系,选择准新翅群3目3种昆虫作为外群,基于18S rDNA序列对全变态类11个目21科21种昆虫的系统发育关系进行研究。通过对18S rDNA序列进行多重序列比对,用似然比检验进行碱基替代模型的选择,分别利用ML法和贝叶斯法构建系统发育树。结果表明,全变态类昆虫聚为3个分支：双翅目+捻翅目、鞘翅目+(广翅目+(蛇蛉目+脉翅目))和膜翅目+(蚤目+长翅目)+(鳞翅目+毛翅目)。长翅类的单系性未得到支持。     

基于ITS、atpB-rbcL序列的醉翁榆(Ulmus gaussenii)与相近榆属植物的亲缘关系

濒危植物保护生物学研究已成为生态学领域的研究热点之一.为了廓清我国特有濒危植物醉翁榆(Ulmus gaussenii)与相近榆属植物的系统地位,用分子标记ITS和atpB-rbcL手段分析醉翁榆与其他榆属相关种的亲缘关系,结果表明:24种榆属植物atpB-rbcL扩增片段长度为735～834 bp,G+C的含量在29.3%～31.6%之间,并没有发生很大的偏差;基于ITS(包括5.8 s)扩增片段,醉翁榆与黑榆系的毛果旱榆、栓枝春榆以及榆系中的大果榆、脱皮榆(U.lamellosa)相近;基于atpB-rbcL扩增片段,醉翁榆与榆系中的大果榆、脱皮榆以及明陵榆的关系比较近,两种标记都表现出醉翁榆与黑榆系中变种毛果旱榆、栓枝春榆的关系比较近;atpB-rbcL的NJ和Bayesian树完全支持榆属组下的分类以及榆属系统的演化关系.