两类豆科植物：锦鸡儿和野大豆的分子生态学研究

野大豆和锦鸡儿，同属豆科植物。前者是一年生自交植物，后者是多年生异交植物;一个是大豆的种质资源，另一个是固沙植物;一个具有耐盐适应，另一个能够抗旱。本文首先结合同工酶分析结果，通过随机扩增多态性DNA（RAPD]标记研究了锦鸡儿和野大豆群体的分子生态学特征。然后用限制性内切酶消化了单态的野大豆群体扩增产物以提高RAPD标记检测野大豆DNA多态性的能力。并且根据锦鸡儿群体的RAPD谱估算了每位点上的等位基因频率，分别用Shannon信息指数和Nei指数估测了各群体的遗传变异。最后，在以上研究的基础上结合我们实验室有关锦鸡儿和野大豆的形态，种子蛋白或同工酶方面的分析得到以下结论： 1]在本文的实验条件下，RAPD标记的重复性很好，使有关锦鸡儿和野大豆群体分子生态学的研究结果有了可靠的基础。 2]RAPD标记的显性特征使实验中确定显、隐性等位基因频率困难较大。用估测的显、隐性等位基因频率通过Shannon信息指数估算群体遗传多样性可能更适合于异交植物。 3）用限制性内切酶消化随机扩增产物后，能够提高RAPD标记检测野大豆群体DNA多态性的能力。4]按RAPD多态位点比率排列毛乌素沙地锦鸡儿各群体为：硬粱群体<沙丘群体<硬粱覆沙群体<毛条群体<滩地覆沙群体<软梁覆沙群体。按遗传多样性排列各群体为：硬粱群体<硬梁覆沙群体<沙丘群体<软梁覆沙群体<毛条群体<滩地覆沙群体。反映了RAPD多态位点比率与遗传多样性在检测群体DNA多态性能力上的异同。 5]毛乌素沙地锦鸡儿群体间 存在着强大的基因流，其高度异交性与生态过渡带可能是一致的。 6]根据同工酶、种子蛋白的分析结果，硬粱覆沙群体的基因多样性在毛鸟素沙地锦鸡儿各群体中是最高的。然而，根据DNA多态性的研究结果，硬粱覆沙群体的基因多样性在各个群体中仅大于硬梁群体。反映了锦鸡尔表型分化与基因型分化的差异。7]就本文的研究结果来看，野大豆群体以其高水平的遗传多样性和发育变通性适应着多变的盐环境。8]无论从DNA多态位点比率还是群体的基因多样性来看，异交植物锦鸡儿群体都具有比自交植物野大豆群体较高的水平。除了盐适应的野大豆群体外，一般来讲，锦鸡儿群体间的基因流要明显地大干野大豆的群体间的基因流。

High Altitude Adaptation and Phylogenetic Analysis of Tibetan Horse Based on the Mitochondrial Genome

研究测定了西藏那曲(4,500 m)、云南中甸(3,300 m)、云南德钦(3,300 m)地区3匹藏马线粒体全基因组序列.3个地区的藏马线粒体基因组全长以及结构均与韩国济州岛的马类似,但比瑞典马线粒体基因组短.藏马基因组在DNA序列上的两两相似性达99.3%.通过对线粒体蛋白编码区的分析发现,NADH6基因的蛋白序列在三匹藏马中均表现快速进化的现象.这表明NADH6基因在藏马高原适应进化过程中扮演着重要角色.此外,利用7匹藏马的D-loop区域序列以及与其亲缘关系较近的马的序列首次构建的藏马的系统发育树显示,那曲藏马与中甸、德钦藏马属于不同的分支,且存在较大的遗传多样性,表明藏马可能为多地区起源.

Effect of a feeding stimulant on feeding adaptation of gibel carp Carassius auratus gibelio (Bloch), fed diets with replacement of fish meal by meat and bone meal

The objectives of the study were to investigate the effect of a feeding stimulant on feeding adaptation of gibel carp (Carassius auratus gibelio Bloch) fed diets with replacement of fish meal by meat and bone meal (MBM), and whether or not the juvenile gibel carp could adapt to higher MBM level in the diet. Juvenile and adult gibel carp were tested. Two and one replacement levels were used for juvenile and adult fish respectively. Each group of diets was set as two types with or without a unique rare earth oxide: Y2O3, Yb2O3, La2O3, Sm2O3, Nd2O3 or Gd2O3 (only the first four rare earth oxides were used in adult diets) for four adaptation periods of 3, 7, 14 and 28 days respectively. After mixing, an equal mixture of all six diets for juvenile or four diets for adult was offered in excess for 2 days. During the last 2 days of each experiment, no feed was offered and faeces from each tank were collected. Feeding preference was expressed as relative feed intake of each diet, which was estimated based on the relative concentration of each marker in the faeces. Given some adaptation period, such as 3-28 days, the effects of MBM and squid extract inclusion on the preference to each diet were reduced. After 28 days adaptation, the preferences between groups were not significantly different.

Independent adaptation to riverine habitats allowed survival of ancient cetacean lineages

The four species of "river dolphins" are associated with six separate great river systems on three subcontinents and have been grouped for more than a century into a single taxon based on their similar appearance. However, several morphologists recently questioned the monophyly of that group. By using phylogenetic analyses of nucleotide sequences from three mitochondrial and two nuclear genes, we demonstrate with statistical significance that extant river dolphins are not monophyletic and suggest that they are relict species whose adaptation to riverine habitats incidentally insured their survival against major environmental changes in the marine ecosystem or the emergence of Delphinidae.

A VSLMS Style Tap-length Learning Algorithm for Structure Adaptation

Compared with the ordinary adaptive filter, the variable-length adaptive filter is more efficient (including smaller., lower power consumption and higher computational complexity output SNR) because of its tap-length learning algorithm, which is able to dynamically adapt its tap-length to the optimal tap-length that best balances the complexity and the performance of the adaptive filter. Among existing tap-length algorithms, the LMS-style Variable Tap-Length Algorithm (also called Fractional Tap-Length Algorithm or FT Algorithm) proposed by Y.Gong has the best performance because it has the fastest convergence rates and best stability. However, in some cases its performance deteriorates dramatically. To solve this problem, we first analyze the FT algorithm and point out some of its defects. Second, we propose a new FT algorithm called 'VSLMS' (Variable Step-size LMS) Style Tap-Length Learning Algorithm, which not only uses the concept of FT but also introduces a new concept of adaptive convergence slope. With this improvement the new FT algorithm has even faster convergence rates and better stability. Finally, we offer computer simulations to verify this improvement.

Kinetic spectra of light-adaptation dark-adaptation and M-intermediate of BR-D96N

BR-D96N is a kind of genetically site-specific mutants of bacteriorhodopsin (BR) with obvious photochromic effect. Compared to the wild type BR, the lifetime of M state of BR-D96N is prolonged to several minutes so that the photochromic kinetics and the intermediates formation can be studied by the conventional spectra analysis. In the experiment, the absorption spectra of the sample at different time after light illumination are measured with spectrophotometer. By fitting and analyzing the variation of the spectra, we suppose that there are three main states in the, photochromic process, i.e., B state (light-adapted state), M state and D state (dark-adapted state). The absorption spectra of the B state, M state and D state are extracted from the experimental data based on this three-state model and the spectra at various time are fitted with the least-square method. So, the variations of population percentages of the M state, B state and D state are obtained and the M state and B state lifetimes are estimated. In another way, from the measurement of the absorption dynamics at 407 and 568 nm, the M state and B state lifetimes are also obtained by two exponential data fitting, which give coincident results with those of the spectra analysis. (C) 2003 Elsevier Science B.V. All rights reserved.