古田山常绿阔叶林物种生境关联及其对物种共存的贡献

物种共存机制一直是群落生态学研究的核心内容。解释物种共存的假说很多，近年来最引人注目的是生态位分化假说和群落中性理论。这两种理论对群落内物种共存的相对重要性是目前群落生态学研究的热点。国际上这方面的研究基本集中在热带森林大样地内，而针对亚热带森林大样地的相关研究却非常少见。本文以浙江古田山24公顷常绿阔叶林永久固定监测样地第一次调查数据为基础，研究样地内木本植物与生境关联和与地形因子梯度相关，目的在于探讨物种生境生态位分化在亚热带常绿阔叶林内物种多样性维持中的作用，也为了解决当前物种生境关联相关研究中的一些不足之处。 本研究首先采用Torus转换检验分析古田山样地内90种常见木本植物与5类生境关联，结果表明有75种（83.3%）至少与一类生境类型显著相关，说明大部分亚热带森林群落内物种具有生境特化的特性。与CTFS全球大样地类似研究结果相比，古田山样地内生境特化的物种比例更高，这与古田山样地复杂的地形条件密切相关。通过本研究，证明地形条件越复杂，物种特化比例越高的趋势确实存在。在古田山样地，虽然83.3%的物种有生境特化的特性，但生境特化没有排他性，即并不完全排斥其他生境，在非最适生境也能稳定与其他物种共存。根据本研究与生境负相关的平均物种数与被检测的物种比例估算，古田山样地内生境异质性对物种多样性维持的贡献率约为19.6%，说明物种生境特化对于物种共存有一定的作用，但贡献并不大，除了生境异质性，仍有其他因素决定物种共存。 目前有关物种生境关联的研究都假设同一物种的个体对于生境偏好一致，不管胸径大小是否相同，很少有人研究不同生长阶段生境偏好的变化。本研究利用Torus转换检验比较样地内60种常见木本植物在3个生活史阶段（幼苗阶段、小树阶段和成熟阶段）与5类生境关联的变化，结果表明大部分物种在其幼苗和小树阶段的生境偏好比较一致，但成熟阶段与前两个阶段差别比较大，说明物种在生活史不同阶段的生境偏好可能发生改变。 由于生境划分没有统一的标准，不同学者用不同的方法划分生境类型和数量，主观性很大，造成不同研究地点、不同研究者之间的研究结果可比性差。本研究尝试利用直接梯度分析方法重新分析物种空间分布与地形梯度相关，用以代替生境关联分析。利用CCA分析检验样地内90种常见木本植物与4种地形因子梯度（海拔、凹凸度、坡度和坡向）的相关情况，发现有76个（84%）物种的空间分布与地形梯度相关，说明大部分物种具有沿地形因子梯度分布的特性。4种地形因子梯度变化对90个物种空间分布的解释量约为20%，说明地形异质性对于物种共存有一定作用，但贡献并不大。对生境关联分析和直接梯度法分析结果进行比较，两种方法分析结果一致，得到的结论也一致。直接梯度分析方法可以避免生境划分对研究结果的影响，是今后类似研究中值得采纳的方法。 本研究的结果表明地形异质性引起的生态位分化在古田山样地群落内物种多样性维持中起一定的作用，但贡献不大，因此需要更深入地研究其他环境因素引起的生态位分化在物种多样性维持中的作用，同时也需要进一步研究中性过程在物种多样性维持中的作用，以更全面地探讨生态位分化假说和中性理论在亚热带常绿阔叶林内物种共存的相对重要性。

Characterization of three fibrinogenolytic enzymes from Chinese green tree viper (Trimeresurus stejnegeri) venom

Rong Gao, Yun Zhang, Qing-Xiong Meng, Wen-Hui Lee, Dong-Sheng Li, Yu-liang Xiong and Wan-Yu Wang. Characterization of three fibrinogenolytic enzymes from Chinese green tree viper (Trimeresurus stejneger ) venom. Toxicon 36, 457-467, 1998.-From the venom of Chinese green tree viper (Trimeresurus stejnegeri), three distinct fibrinogenolytic enzymes: stejnefibrase-l, stejnefibrase-2 and stejnefibrase-3, were purified by gel filtration, ion-exchange chromatography and reverse-phase high-performance chromatograghy (HPLC). SDS-PAGE analysis of those three enzymes showed that they consisted of a single polypeptide chain with mel. wt of -50 000, 31 000 and 32 000, respectively. Like TSV-PA (a specific plasminogen activator) and stejnobin (a fibrinogen-clotting enzyme) purified from the same venom, stejnfibrase-1, -2 and -3 were able to hydrolyze several chromogenic substrate. On the other hand, different from TSV-PA. and stejnobin, stejnefibrase-l, -2 and -3 did not activate plasminogen and did not possess fibrinogen-clotting activity. The three purified enzymes directly degraded fibrinogen to small fragments and rendered it unclottable by thrombin. Stejnefibrase-2 degraded preferentially BE-chain while stejnefibrase-l and -3 cleaved concomitantly Ax and B beta-chains of fibrinogen. None of these proteases degraded the gamma-chain of fibrinogen. When correlated with the loss of clottability of fibrinogen, the most active enzyme was stejnefibrase-l. The activities of the three enzymes were inhibited by phenylmethylsulfonyl fluoride (PMSF) and p-nitrophenyl-p-guanidinobenzoate (NPGB), indicating that like TSV-PA and stejnobin, they are venom serine proteases. (C) 1998 Elsevier Science Ltd. All rights reserved.

A novel antimicrobial peptide from salivary glands of the hard tick, Ixodes sinensis

A novel antimicrobial peptide named as ixosin was isolated from the salivary glands of the hard tick, Ixodes sinensis, by gel filtration, ion exchange chromatography and reverse-phase high-performance liquid chromatography (RP-HPLC). Its amino acid sequen

Molecular Phylogeny of Geographical Isolates of Bursaphelenchus xylophilus: Implications on the Origin and Spread of this Species in China and Worldwide

The genetic diversity and phylogeny of 26 isolates of Bursaphelenchus xlophilus from China, Japan, Portugal and North America were investigated based on the D2/3 domain of 28S rDNA, nuclear ribosomal Internal Transcribed Spacer (ITS) sequences, and random amplified polymorphic DNA (RAPD) analysis. The genetic diversity analysis showed that the D2/3 domain of 28S rDNA of isolates of B. xlophilus from China, Portugal, Japan and the US were identical and differed at one to three nucleotides compared to those from Canada. ITS sequences of isolates from China and Portugal were the same; they differed at one or two nucleotides compared to those of Japanese isolates and at four and 23 nucleotides compared to those front the US and Canada, respectively. The phylogenetic analysis indicated that Chinese isolates share a common ancestor with one of the two Japanese clades and that the Canadian isolates form a sister group of the clade comprised of isolates from China, Portugal,Japan, and the US. The relationship between Japanese isolates and those from China was closer than with the American isolates. The Canadian isolates were the basal group of B. xylophilus. This suggests that B. xlophilus originated in North America and that the B. xylphilus that occurs in China could have been first introduced from Japan. Further analysis based on RAPD analysis revealed that the relationship among isolates from Guangdong, Zhejiang, Shandong, Anhui provinces and Nanjing was the closest, which suggests that pine wilt disease in these Chinese locales was probably dispersed from Nanjing, where this disease first occurred in China.

Novel cathelicidin-derived antimicrobial peptides from Equus asinus

In the present study, EA-CATH1 and EA-CATH2 were identified from a constructed lung cDNA library of donkey (Equus asinus) as members of cathelicidin-derived antimicrobial peptides, using a nested PCR-based cloning strategy. Composed of 25 and 26 residues, respectively, EA-CATH1 and EA-CATH2 are smaller than most other cathelicidins and have no sequence homology to other cathelicidins identified to date. Chemically synthesized EA-CATH1 exerted potent antimicrobial activity against most of the 32 strains of bacteria and fungi tested, especially the clinically isolated drug-resistant strains, and minimal inhibitory concentration values against Gram-positive bacteria were mostly in the range of 0.3-2.4 mu g center dot mL-1. EA-CATH1 showed an extraordinary serum stability and no haemolytic activity against human erythrocytes in a dose up to 20 mu g center dot mL-1. CD spectra showed that EA-CATH1 mainly adopts an alpha-helical conformation in a 50% trifluoroethanol/water solution, but a random coil in aqueous solution. Scanning electron microscope observations of Staphylococcus aureus (ATCC2592) treated with EA-CATH1 demonstrated that EA-CATH could cause rapid disruption of the bacterial membrane, and in turn lead to cell lysis. This might explain the much faster killing kinetics of EA-CATH1 than conventional antibiotics revealed by killing kinetics data. In the presence of CaCl2, EA-CATH1 exerted haemagglutination activity, which might potentiate an inhibition against the bacterial polyprotein interaction with the host erythrocyte surface, thereby possibly restricting bacterial colonization and spread.

Mitochondrial genome evidence reveals successful Late Paleolithic settlement on the Tibetan Plateau

Due to its numerous environmental extremes, the Tibetan Plateau -the world's highest plateau-is one of the most challenging areas of modern human settlement. Archaeological evidence dates the earliest settlement on the plateau to the Late Paleolithic, whi

Mutation analysis of a large Chinese pedigree with congenital preaxial polydactyly

Mutations in the long-range limb-specific cis-regulator (ZRS) could cause ectopic shh gene expression and are responsible for preaxial polydactyly (PPD). In this study, we analyzed a large Chinese isolated autosomal dominant PPD pedigree. By fine mapping

Origin and dispersal of atypical aldehyde dehydrogenase ALDH2*487Lys

The East Asian respond with a marked facial flushing and mild to moderate symptoms of intoxication after drinking the amounts of alcohol that has no detectable effect on European. The alcohol sensitivity in Orientals is due to a delayed oxidation of aceta

Phylogeny of the Asian spiny frog tribe Paini (Family Dicroglossidae) sensu Dubois

The anuran tribe Paini, family Dicroglossidae, is known in this group only from Asia. The phylogenetic relationships and often the taxonomic recognition of species are controversial. In order to stabilize the classification, we used approximately 2100bp o

Singing Behavior and Singing Functions of Black-Crested Gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang, Central Yunnan, China

We used data on loud duetted and solo songs collected from one habituated polygynous group of black-crested gibbons (Nomascus concolor jingdongensis) on Mt. Wuliang, Yunnan, to test several hypotheses about the functions of these songs. The major function

A New Species of the Genus Garra from Nujiang River Basin, Yunnan, China (Teleostei: Cyprinidae)

2003年4月,于怒江二级支流镇康县境内的大叉河中采获一批墨头鱼属(Garra)鱼类标本,经鉴定为一新种,命名为怒江墨头鱼(G.nujiangensis Chen and Yang,sp.nov.).该新种主要鉴别特征:围尾柄鳞12～14:侧线鳞48～50:在小个体中有一对微小的吻须;背鳍分支鳍条8～9;侧线上鳞5～6,侧线下鳞3～4;体高小于头长;臀鳍起点处的小于眼后至吻端的距离;腹鳍前长为体长的50.0%～53.7%;肛门前长为体长的58.9%～63.9%:体宽为体长的16.7%～19.6%:体高为体长的19.2%～22.6%.本研究证实,在缺须的墨头鱼属的一些物种中,如高体墨头鱼(G.alticorpora)和怒江墨头鱼(G.nujiangensis),其幼体中往往具有一对很小的吻须.

A new species of sisorid catfish genus Glyptothorax (Teleostei: Sisoridae) from Salween drainage of Yunnan, China

A new species of the genus Glyptothorax, Glyptothorax obliquimaculatus sp. nov. is described from the Xiaohei River, a tributary of the Nanting River, Salween drainage, in southwestern Yunnan province, China. This new species can be distinguished from its congeners by the following combination of characteristics: unculiferous ridges of the thoracic adhesive apparatus extending anteriorly onto the gular region; body with irregular dark blotches scattered along lateral surface (blotches mostly oblique); skin smooth on head and body; dorsal spine smooth without serrations on its posterior margin; lips smooth; posterior margin of pectoral spine with 7-8 serrations; dorsal-fin base 11.0-13.2% SL; pectoral-fin length 15.6-19.6% SL; depth of caudal peduncle 8.6-9.8% SL; head width 19.1-24.0% SL; nasal barbel length 23.3-33.3% HL.