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.

水生生物中化学踪迹的水动力学问题

化学踪迹调控着水生生物的许多关键生命过程,如摄食、繁殖和海底沉淀等.随着流体流速和流态的不同,水生生物所释放的化学物质在被生物体接收之前会经历扩散、层流或湍流对流等输运过程.综述了各种流态中的输运机制及生态效应.从浓度梯度、浓度涨落和空间分布模式的角度讨论了化学踪迹的结构,从中总结出水生动物获取信息的策略.在一些情况下,化学物质的输运是通过多种机制联合作用而实现的,需要引入多尺度分析,而流态和尺度问题则是最近研究中显现出的主要议题.尤其是,组合了生物变量和物理变量的无量纲参数揭示了生物体对化学踪迹反应的一般原则,也促进了对水生生物行为模态的区分和定义.

Dynamics of intraseasonal sea level and thermocline variability in the equatorial Atlantic during 2002-03

Satellite and in situ observations in the equatorial Atlantic Ocean during 2002-03 show dominant spectral peaks at 40-60 days and secondary peaks at 10-40 days in sea level and thermocline within the intraseasonal period band (10-80 days). A detailed investigation of the dynamics of the intraseasonal variations is carried out using an ocean general circulation model, namely, the Hybrid Coordinate Ocean Model (HYCOM). Two parallel experiments are performed in the tropical Atlantic Ocean basin for the period 2000-03: one is forced by daily scatterometer winds from the Quick Scatterometer (QuikSCAT) satellite together with other forcing fields, and the other is forced by the low-passed 80-day version of the above fields. To help in understanding the role played by the wind-driven equatorial waves, a linear continuously stratified ocean model is also used. Within 3 degrees S-3 degrees N of the equatorial region, the strong 40-60-day sea surface height anomaly (SSHA) and thermocline variability result mainly from the first and second baroclinic modes equatorial Kelvin waves that are forced by intraseasonal zonal winds, with the second baroclinic mode playing a more important role. Sharp 40-50-day peaks of zonal and meridional winds appear in both the QuikSCAT and Pilot Research Moored Array in the Tropical Atlantic (PIRATA) data for the period 2002-03, and they are especially strong in 2002. Zonal wind anomaly in the central-western equatorial basin for the period 2000-06 is significantly correlated with SSHA across the equatorial basin, with simultaneous/ lag correlation ranging from-0.62 to 0.74 above 95% significance. Away from the equator (3 degrees-5 degrees N), however, sea level and thermocline variations in the 40-60-day band are caused largely by tropical instability waves (TIWs). On 10-40-day time scales and west of 10 degrees W, the spectral power of sea level and thermocline appears to be dominated by TIWs within 5 degrees S-5 degrees N of the equatorial region. The wind-driven circulation, however, also provides a significant contribution. Interestingly, east of 10 W, SSHA and thermocline variations at 10 40- day periods result almost entirely from wind-driven equatorial waves. During the boreal spring of 2002 when TIWs are weak, Kelvin waves dominate the SSHA across the equatorial basin (2 degrees S-2 degrees N). The observed quasi-biweekly Yanai waves are excited mainly by the quasi-biweekly meridional winds, and they contribute significantly to the SSHA and thermocline variations in 1 degrees-5 degrees N and 1 degrees-5 degrees S regions.

岩浆－热液过渡阶段体系中不相容元素地球化学行为及其机制－以新疆阿尔泰3号伟晶岩脉研究为例

伟晶岩形成和演化中岩浆-热液过渡阶段物理化学性质、过铝质富挥发分岩浆体系岩浆液相不混溶、流体相出溶事件的相对时间尺度以及在岩浆-热液过渡阶段体系中稀土和其它微量元素地球化学行为(稀土“四重效应”机制和微量元素分异及控制因素等)是目前过铝质岩浆体系研究的焦点问题。对上述问题的研究和探讨，将有助于了解伟晶岩形成和演化的全过程，有助于了解挥发分(H_20、F、B、P)对过铝质岩浆体系物理性质以及对REE和其它微量元素地球化学行为影响，这对于理解过铝质岩浆体系成岩、成矿作用过程具有重大的理论和实际意义。本论文选择著名的新疆阿尔泰3号伟晶岩脉为研究对象，由于它具有完美的分带特征，使我们有可能通过各结构带矿物学、地球化学的研究揭示伟晶岩成因和演化过程以及讨论岩浆-热液过渡阶段体系中的稀土和微量元素地球化学行为。由于LCT型伟晶岩具有明显的分带性、矿物颗粒大小不均匀性等特点，因此利用全岩样品研究伟晶岩往往因取样没有代表性而被大多数岩石学家和地球化学家所否定。考虑到这点，本文系统采集阿尔泰3号伟晶岩脉各结构带磷灰石、电气石、碱性长石、石英矿物，部分结构带的石榴石、绿柱石、锂辉石矿物以及伟晶岩冷凝边和蚀变围岩的全岩样品，通过各结构带磷灰石矿物化学组成和~(87)Sr／~(86)Sr比值测定，电气石矿物的化学组成和硼同位素组成分析，碱性长石中磷含量的电子探针分析和碱性长石-石英矿物对的氧同位素体系研究以及蚀变围岩和冷凝边的化学组成分析，本文较为详尽系统地探讨以上所有的问题。通过本次多年的研究，我们获得了以下几点新的认识：f1) 富挥发分过铝质岩浆体系的样品存在稀土“四重效应”和Y-Ho、Zr-Hf、Nb-Ta、Sr-Eu元素对的显著分异，表明在过铝质岩浆演化过程中含氟流体相起着重要的作用；目前，稀土“四重效应”机制被认为是含水流体相与过铝质岩浆熔体相互作用的结果(Irber 1999；Bau 1997)，而不是独居石、磷钇矿、石榴石矿物等矿物的早期结晶引起的残余熔体稀土含量的异常变化。由于阿尔泰3号伟晶岩脉各带磷灰石以及与其共生的石榴石、绿柱石、碱性长石、锂辉石矿物均存存明显的稀土“四重效应”以及相同电价、相似离子半径的不相容元素间存在显著的分异，并结合最近赵振华等(1999)和Sba and Chappell(1999)报道S型花岗岩全岩和单矿物(磷灰石、独居石、长石、黄玉等)均存在稀土“四重效应”这一现象，本文研究提出，稀土“四重效应”是富挥发分过铝质岩浆体系的一个基本特征，其机制既不可能由含稀土的副矿物早期结晶引起残余熔体相中REE含量变化的结果，也不能定性地归因于流体相与熔体相相互作用过程中稀土元素在流体／熔体之间分异的结果，而很可能与伟晶岩岩浆形成之前某些过程密切相关，S型花岗岩岩浆在液相线以上存在硅酸盐熔体与高盐熔体(或卤水相)的不混溶液相分离有可能是过铝质岩浆体系产生稀土“四重效应”的主要原因。(2) 由于Sr~(2+)与Eu~(2+)具有相同的电价、相似的离子半径，根据经典的地球化学原理，它们具有相似的地球化学行为，在各种地质过程中其它们具有紧密的一致性。阿尔泰3号伟晶岩磷灰石中Sr／Eu比值具有二歧变化现象，其中I、Il、III和IV带磷灰石具有低的Sr／Eu比值(16:0～111.2)，而V、VI、VII带、核部带和IV带中的一个磷灰石则显示较大的Sr／Eu比值(主要在246．6～514:9范围，其中IV带的一个磷灰石该比值在10000以上)。对世界范围内的过铝质花岗岩统计表明，过铝质岩浆岩的全岩样品中的Sr／Eu也呈现二歧变化，由此本文提出Sr／Eu比值是指示过铝质岩浆体系中岩浆流体相出溶的有效地球化学参数，大于300的Sr／Eu比值是Eu~(2+)强烈分配进入流体相的地球化学标志。(3) 阿尔泰3号伟晶岩I、II、III带电气石矿物的硼同位素组成(δ~(11)B)分布在-41.11‰～-30.90‰之间，V、VI、VII带电气石矿物硼同位素组成(δ~(11)B)在-15.23‰～-9.20‰范围，IV带电气石硼同位素分布于-39.19～13.10‰范围，如此大的硼同位素分馏无法根据实验研究获得的熔体／流体相间的分馏系数进行合理解释。我们的研究表明岩浆成因电气石的B同位素组成与电气石化学组成具相关性，随电气石Y位上AI、Li阳离子数的增大，δ~(11)B值显示明显增大的趋势。阿尔泰3号伟晶岩最初形成的结构带中电气石的B同位素组成是目前所发现的最低值之一(-41.1l～39.01‰)，指示形成伟晶岩脉的初始岩浆可能由含非海相蒸发岩的泥质岩经变质深熔作用形成，或是伟晶岩岩浆在上侵定位过程中同化了含非海相蒸发岩地层的结果。本次研究利用电气石-白云母和电气石-四硼酸盐矿物间的同位索分馏以及熔体相-流体相间的同位索分馏，合理解释了阿尔泰3号伟晶岩脉电气石B同位素分馏过程，并首次获得伟晶岩形成、演化过程中B同位素组成演化的全程图谱。(4)伟晶岩岩浆形成和演化过程是否存在由过磷引起的液相不混溶现象未见确凿的岩石学和实验地球化学证据。阿尔泰3号伟晶岩脉糖粒状钠长石带(II带)明显由两种不同组构的岩性组成，而且该带是3号脉主要的Be矿化带，也是P、REE最重要的沉淀场所。阿尔泰3号伟晶岩脉梳状结构带和I带的碱性长石具较高P含量(平均值分别为0.42 wt％和0.22 wt％)，随着岩浆的演化进行，从III带到核部带，碱性长石中P含量逐渐增大(平均值由0.21 wt％增至0.50 wt％)，而II带碱性长石中异常低的P含量(平均值为0.08、wt％)是该带大量磷灰石矿物饱和结晶，导致残余熔体相中P极度亏损所造成的，而不是晚期出溶的岩浆热液交代形成的。根据Watson (1978)、Ryerson and Hess(1980)在液相线以上温度下实验研究获得的微量元素在不混溶的基性和酸性液相中分配特征，以及Webster et a1．(1997）对德国Ehrenfriedersdorf矿区伟晶岩石英中熔体包裹体的研究成果，我们推断在富磷岩浆体系中，在其演化的早期将出现由磷引起的液相不混溶作用，它对伟晶岩成岩和Be的成矿具有重大的影响。